gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
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/*
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* Copyright 2012-2016 by the PaX Team <pageexec@freemail.hu>
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* Copyright 2016 by Emese Revfy <re.emese@gmail.com>
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* Licensed under the GPL v2
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*
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* Note: the choice of the license means that the compilation process is
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* NOT 'eligible' as defined by gcc's library exception to the GPL v3,
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* but for the kernel it doesn't matter since it doesn't link against
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* any of the gcc libraries
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*
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* This gcc plugin helps generate a little bit of entropy from program state,
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* used throughout the uptime of the kernel. Here is an instrumentation example:
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*
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* before:
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* void __latent_entropy test(int argc, char *argv[])
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* {
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* if (argc <= 1)
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* printf("%s: no command arguments :(\n", *argv);
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* else
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* printf("%s: %d command arguments!\n", *argv, args - 1);
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* }
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*
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* after:
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* void __latent_entropy test(int argc, char *argv[])
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* {
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* // latent_entropy_execute() 1.
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* unsigned long local_entropy;
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* // init_local_entropy() 1.
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* void *local_entropy_frameaddr;
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* // init_local_entropy() 3.
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* unsigned long tmp_latent_entropy;
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*
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* // init_local_entropy() 2.
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* local_entropy_frameaddr = __builtin_frame_address(0);
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* local_entropy = (unsigned long) local_entropy_frameaddr;
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*
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* // init_local_entropy() 4.
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* tmp_latent_entropy = latent_entropy;
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* // init_local_entropy() 5.
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* local_entropy ^= tmp_latent_entropy;
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*
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* // latent_entropy_execute() 3.
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* if (argc <= 1) {
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* // perturb_local_entropy()
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* local_entropy += 4623067384293424948;
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* printf("%s: no command arguments :(\n", *argv);
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* // perturb_local_entropy()
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* } else {
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* local_entropy ^= 3896280633962944730;
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* printf("%s: %d command arguments!\n", *argv, args - 1);
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* }
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*
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* // latent_entropy_execute() 4.
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* tmp_latent_entropy = rol(tmp_latent_entropy, local_entropy);
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* latent_entropy = tmp_latent_entropy;
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* }
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*
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* TODO:
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* - add ipa pass to identify not explicitly marked candidate functions
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* - mix in more program state (function arguments/return values,
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* loop variables, etc)
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* - more instrumentation control via attribute parameters
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*
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* BUGS:
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* - none known
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*
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* Options:
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* -fplugin-arg-latent_entropy_plugin-disable
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*
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* Attribute: __attribute__((latent_entropy))
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* The latent_entropy gcc attribute can be only on functions and variables.
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* If it is on a function then the plugin will instrument it. If the attribute
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* is on a variable then the plugin will initialize it with a random value.
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* The variable must be an integer, an integer array type or a structure
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* with integer fields.
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*/
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#include "gcc-common.h"
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2016-11-01 01:40:13 +08:00
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__visible int plugin_is_GPL_compatible;
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gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
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static GTY(()) tree latent_entropy_decl;
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static struct plugin_info latent_entropy_plugin_info = {
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2022-05-24 21:55:41 +08:00
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.version = PLUGIN_VERSION,
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gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
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.help = "disable\tturn off latent entropy instrumentation\n",
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};
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gcc-plugins: latent_entropy: use /dev/urandom
While the latent entropy plugin mostly doesn't derive entropy from
get_random_const() for measuring the call graph, when __latent_entropy is
applied to a constant, then it's initialized statically to output from
get_random_const(). In that case, this data is derived from a 64-bit
seed, which means a buffer of 512 bits doesn't really have that amount
of compile-time entropy.
This patch fixes that shortcoming by just buffering chunks of
/dev/urandom output and doling it out as requested.
At the same time, it's important that we don't break the use of
-frandom-seed, for people who want the runtime benefits of the latent
entropy plugin, while still having compile-time determinism. In that
case, we detect whether gcc's set_random_seed() has been called by
making a call to get_random_seed(noinit=true) in the plugin init
function, which is called after set_random_seed() is called but before
anything that calls get_random_seed(noinit=false), and seeing if it's
zero or not. If it's not zero, we're in deterministic mode, and so we
just generate numbers with a basic xorshift prng.
Note that we don't detect if -frandom-seed is being used using the
documented local_tick variable, because it's assigned via:
local_tick = (unsigned) tv.tv_sec * 1000 + tv.tv_usec / 1000;
which may well overflow and become -1 on its own, and so isn't
reliable: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105171
[kees: The 256 byte rnd_buf size was chosen based on average (250),
median (64), and std deviation (575) bytes of used entropy for a
defconfig x86_64 build]
Fixes: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin")
Cc: stable@vger.kernel.org
Cc: PaX Team <pageexec@freemail.hu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220405222815.21155-1-Jason@zx2c4.com
2022-04-06 06:28:15 +08:00
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static unsigned HOST_WIDE_INT deterministic_seed;
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static unsigned HOST_WIDE_INT rnd_buf[32];
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static size_t rnd_idx = ARRAY_SIZE(rnd_buf);
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static int urandom_fd = -1;
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gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
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static unsigned HOST_WIDE_INT get_random_const(void)
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{
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gcc-plugins: latent_entropy: use /dev/urandom
While the latent entropy plugin mostly doesn't derive entropy from
get_random_const() for measuring the call graph, when __latent_entropy is
applied to a constant, then it's initialized statically to output from
get_random_const(). In that case, this data is derived from a 64-bit
seed, which means a buffer of 512 bits doesn't really have that amount
of compile-time entropy.
This patch fixes that shortcoming by just buffering chunks of
/dev/urandom output and doling it out as requested.
At the same time, it's important that we don't break the use of
-frandom-seed, for people who want the runtime benefits of the latent
entropy plugin, while still having compile-time determinism. In that
case, we detect whether gcc's set_random_seed() has been called by
making a call to get_random_seed(noinit=true) in the plugin init
function, which is called after set_random_seed() is called but before
anything that calls get_random_seed(noinit=false), and seeing if it's
zero or not. If it's not zero, we're in deterministic mode, and so we
just generate numbers with a basic xorshift prng.
Note that we don't detect if -frandom-seed is being used using the
documented local_tick variable, because it's assigned via:
local_tick = (unsigned) tv.tv_sec * 1000 + tv.tv_usec / 1000;
which may well overflow and become -1 on its own, and so isn't
reliable: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105171
[kees: The 256 byte rnd_buf size was chosen based on average (250),
median (64), and std deviation (575) bytes of used entropy for a
defconfig x86_64 build]
Fixes: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin")
Cc: stable@vger.kernel.org
Cc: PaX Team <pageexec@freemail.hu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220405222815.21155-1-Jason@zx2c4.com
2022-04-06 06:28:15 +08:00
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if (deterministic_seed) {
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unsigned HOST_WIDE_INT w = deterministic_seed;
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w ^= w << 13;
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w ^= w >> 7;
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w ^= w << 17;
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deterministic_seed = w;
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return deterministic_seed;
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gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
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}
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gcc-plugins: latent_entropy: use /dev/urandom
While the latent entropy plugin mostly doesn't derive entropy from
get_random_const() for measuring the call graph, when __latent_entropy is
applied to a constant, then it's initialized statically to output from
get_random_const(). In that case, this data is derived from a 64-bit
seed, which means a buffer of 512 bits doesn't really have that amount
of compile-time entropy.
This patch fixes that shortcoming by just buffering chunks of
/dev/urandom output and doling it out as requested.
At the same time, it's important that we don't break the use of
-frandom-seed, for people who want the runtime benefits of the latent
entropy plugin, while still having compile-time determinism. In that
case, we detect whether gcc's set_random_seed() has been called by
making a call to get_random_seed(noinit=true) in the plugin init
function, which is called after set_random_seed() is called but before
anything that calls get_random_seed(noinit=false), and seeing if it's
zero or not. If it's not zero, we're in deterministic mode, and so we
just generate numbers with a basic xorshift prng.
Note that we don't detect if -frandom-seed is being used using the
documented local_tick variable, because it's assigned via:
local_tick = (unsigned) tv.tv_sec * 1000 + tv.tv_usec / 1000;
which may well overflow and become -1 on its own, and so isn't
reliable: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105171
[kees: The 256 byte rnd_buf size was chosen based on average (250),
median (64), and std deviation (575) bytes of used entropy for a
defconfig x86_64 build]
Fixes: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin")
Cc: stable@vger.kernel.org
Cc: PaX Team <pageexec@freemail.hu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220405222815.21155-1-Jason@zx2c4.com
2022-04-06 06:28:15 +08:00
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if (urandom_fd < 0) {
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urandom_fd = open("/dev/urandom", O_RDONLY);
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gcc_assert(urandom_fd >= 0);
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}
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if (rnd_idx >= ARRAY_SIZE(rnd_buf)) {
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gcc_assert(read(urandom_fd, rnd_buf, sizeof(rnd_buf)) == sizeof(rnd_buf));
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rnd_idx = 0;
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}
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return rnd_buf[rnd_idx++];
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gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
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}
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static tree tree_get_random_const(tree type)
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{
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unsigned long long mask;
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mask = 1ULL << (TREE_INT_CST_LOW(TYPE_SIZE(type)) - 1);
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|
|
mask = 2 * (mask - 1) + 1;
|
|
|
|
|
|
|
|
|
|
if (TYPE_UNSIGNED(type))
|
|
|
|
|
return build_int_cstu(type, mask & get_random_const());
|
|
|
|
|
return build_int_cst(type, mask & get_random_const());
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static tree handle_latent_entropy_attribute(tree *node, tree name,
|
|
|
|
|
tree args __unused,
|
|
|
|
|
int flags __unused,
|
|
|
|
|
bool *no_add_attrs)
|
|
|
|
|
{
|
|
|
|
|
tree type;
|
|
|
|
|
vec<constructor_elt, va_gc> *vals;
|
|
|
|
|
|
|
|
|
|
switch (TREE_CODE(*node)) {
|
|
|
|
|
default:
|
|
|
|
|
*no_add_attrs = true;
|
|
|
|
|
error("%qE attribute only applies to functions and variables",
|
|
|
|
|
name);
|
|
|
|
|
break;
|
|
|
|
|
|
|
|
|
|
case VAR_DECL:
|
|
|
|
|
if (DECL_INITIAL(*node)) {
|
|
|
|
|
*no_add_attrs = true;
|
|
|
|
|
error("variable %qD with %qE attribute must not be initialized",
|
|
|
|
|
*node, name);
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
if (!TREE_STATIC(*node)) {
|
|
|
|
|
*no_add_attrs = true;
|
|
|
|
|
error("variable %qD with %qE attribute must not be local",
|
|
|
|
|
*node, name);
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
type = TREE_TYPE(*node);
|
|
|
|
|
switch (TREE_CODE(type)) {
|
|
|
|
|
default:
|
|
|
|
|
*no_add_attrs = true;
|
|
|
|
|
error("variable %qD with %qE attribute must be an integer or a fixed length integer array type or a fixed sized structure with integer fields",
|
|
|
|
|
*node, name);
|
|
|
|
|
break;
|
|
|
|
|
|
|
|
|
|
case RECORD_TYPE: {
|
|
|
|
|
tree fld, lst = TYPE_FIELDS(type);
|
|
|
|
|
unsigned int nelt = 0;
|
|
|
|
|
|
|
|
|
|
for (fld = lst; fld; nelt++, fld = TREE_CHAIN(fld)) {
|
|
|
|
|
tree fieldtype;
|
|
|
|
|
|
|
|
|
|
fieldtype = TREE_TYPE(fld);
|
|
|
|
|
if (TREE_CODE(fieldtype) == INTEGER_TYPE)
|
|
|
|
|
continue;
|
|
|
|
|
|
|
|
|
|
*no_add_attrs = true;
|
|
|
|
|
error("structure variable %qD with %qE attribute has a non-integer field %qE",
|
|
|
|
|
*node, name, fld);
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
if (fld)
|
|
|
|
|
break;
|
|
|
|
|
|
|
|
|
|
vec_alloc(vals, nelt);
|
|
|
|
|
|
|
|
|
|
for (fld = lst; fld; fld = TREE_CHAIN(fld)) {
|
|
|
|
|
tree random_const, fld_t = TREE_TYPE(fld);
|
|
|
|
|
|
|
|
|
|
random_const = tree_get_random_const(fld_t);
|
|
|
|
|
CONSTRUCTOR_APPEND_ELT(vals, fld, random_const);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/* Initialize the fields with random constants */
|
|
|
|
|
DECL_INITIAL(*node) = build_constructor(type, vals);
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/* Initialize the variable with a random constant */
|
|
|
|
|
case INTEGER_TYPE:
|
|
|
|
|
DECL_INITIAL(*node) = tree_get_random_const(type);
|
|
|
|
|
break;
|
|
|
|
|
|
|
|
|
|
case ARRAY_TYPE: {
|
|
|
|
|
tree elt_type, array_size, elt_size;
|
|
|
|
|
unsigned int i, nelt;
|
|
|
|
|
HOST_WIDE_INT array_size_int, elt_size_int;
|
|
|
|
|
|
|
|
|
|
elt_type = TREE_TYPE(type);
|
|
|
|
|
elt_size = TYPE_SIZE_UNIT(TREE_TYPE(type));
|
|
|
|
|
array_size = TYPE_SIZE_UNIT(type);
|
|
|
|
|
|
|
|
|
|
if (TREE_CODE(elt_type) != INTEGER_TYPE || !array_size
|
|
|
|
|
|| TREE_CODE(array_size) != INTEGER_CST) {
|
|
|
|
|
*no_add_attrs = true;
|
|
|
|
|
error("array variable %qD with %qE attribute must be a fixed length integer array type",
|
|
|
|
|
*node, name);
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
array_size_int = TREE_INT_CST_LOW(array_size);
|
|
|
|
|
elt_size_int = TREE_INT_CST_LOW(elt_size);
|
|
|
|
|
nelt = array_size_int / elt_size_int;
|
|
|
|
|
|
|
|
|
|
vec_alloc(vals, nelt);
|
|
|
|
|
|
|
|
|
|
for (i = 0; i < nelt; i++) {
|
|
|
|
|
tree cst = size_int(i);
|
|
|
|
|
tree rand_cst = tree_get_random_const(elt_type);
|
|
|
|
|
|
|
|
|
|
CONSTRUCTOR_APPEND_ELT(vals, cst, rand_cst);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Initialize the elements of the array with random
|
|
|
|
|
* constants
|
|
|
|
|
*/
|
|
|
|
|
DECL_INITIAL(*node) = build_constructor(type, vals);
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
break;
|
|
|
|
|
|
|
|
|
|
case FUNCTION_DECL:
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
return NULL_TREE;
|
|
|
|
|
}
|
|
|
|
|
|
2018-02-06 09:27:46 +08:00
|
|
|
static struct attribute_spec latent_entropy_attr = { };
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
|
|
|
|
|
static void register_attributes(void *event_data __unused, void *data __unused)
|
|
|
|
|
{
|
2018-02-06 09:27:46 +08:00
|
|
|
latent_entropy_attr.name = "latent_entropy";
|
|
|
|
|
latent_entropy_attr.decl_required = true;
|
|
|
|
|
latent_entropy_attr.handler = handle_latent_entropy_attribute;
|
|
|
|
|
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
register_attribute(&latent_entropy_attr);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static bool latent_entropy_gate(void)
|
|
|
|
|
{
|
|
|
|
|
tree list;
|
|
|
|
|
|
|
|
|
|
/* don't bother with noreturn functions for now */
|
|
|
|
|
if (TREE_THIS_VOLATILE(current_function_decl))
|
|
|
|
|
return false;
|
|
|
|
|
|
|
|
|
|
/* gcc-4.5 doesn't discover some trivial noreturn functions */
|
|
|
|
|
if (EDGE_COUNT(EXIT_BLOCK_PTR_FOR_FN(cfun)->preds) == 0)
|
|
|
|
|
return false;
|
|
|
|
|
|
|
|
|
|
list = DECL_ATTRIBUTES(current_function_decl);
|
|
|
|
|
return lookup_attribute("latent_entropy", list) != NULL_TREE;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static tree create_var(tree type, const char *name)
|
|
|
|
|
{
|
|
|
|
|
tree var;
|
|
|
|
|
|
|
|
|
|
var = create_tmp_var(type, name);
|
|
|
|
|
add_referenced_var(var);
|
|
|
|
|
mark_sym_for_renaming(var);
|
|
|
|
|
return var;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Set up the next operation and its constant operand to use in the latent
|
|
|
|
|
* entropy PRNG. When RHS is specified, the request is for perturbing the
|
|
|
|
|
* local latent entropy variable, otherwise it is for perturbing the global
|
|
|
|
|
* latent entropy variable where the two operands are already given by the
|
|
|
|
|
* local and global latent entropy variables themselves.
|
|
|
|
|
*
|
|
|
|
|
* The operation is one of add/xor/rol when instrumenting the local entropy
|
|
|
|
|
* variable and one of add/xor when perturbing the global entropy variable.
|
|
|
|
|
* Rotation is not used for the latter case because it would transmit less
|
|
|
|
|
* entropy to the global variable than the other two operations.
|
|
|
|
|
*/
|
|
|
|
|
static enum tree_code get_op(tree *rhs)
|
|
|
|
|
{
|
|
|
|
|
static enum tree_code op;
|
|
|
|
|
unsigned HOST_WIDE_INT random_const;
|
|
|
|
|
|
|
|
|
|
random_const = get_random_const();
|
|
|
|
|
|
|
|
|
|
switch (op) {
|
|
|
|
|
case BIT_XOR_EXPR:
|
|
|
|
|
op = PLUS_EXPR;
|
|
|
|
|
break;
|
|
|
|
|
|
|
|
|
|
case PLUS_EXPR:
|
|
|
|
|
if (rhs) {
|
|
|
|
|
op = LROTATE_EXPR;
|
|
|
|
|
/*
|
|
|
|
|
* This code limits the value of random_const to
|
2016-12-17 04:59:31 +08:00
|
|
|
* the size of a long for the rotation
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
*/
|
2016-12-17 04:59:31 +08:00
|
|
|
random_const %= TYPE_PRECISION(long_unsigned_type_node);
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
case LROTATE_EXPR:
|
|
|
|
|
default:
|
|
|
|
|
op = BIT_XOR_EXPR;
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
if (rhs)
|
2016-10-19 06:08:04 +08:00
|
|
|
*rhs = build_int_cstu(long_unsigned_type_node, random_const);
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
return op;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static gimple create_assign(enum tree_code code, tree lhs, tree op1,
|
|
|
|
|
tree op2)
|
|
|
|
|
{
|
|
|
|
|
return gimple_build_assign_with_ops(code, lhs, op1, op2);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static void perturb_local_entropy(basic_block bb, tree local_entropy)
|
|
|
|
|
{
|
|
|
|
|
gimple_stmt_iterator gsi;
|
|
|
|
|
gimple assign;
|
|
|
|
|
tree rhs;
|
|
|
|
|
enum tree_code op;
|
|
|
|
|
|
|
|
|
|
op = get_op(&rhs);
|
|
|
|
|
assign = create_assign(op, local_entropy, local_entropy, rhs);
|
|
|
|
|
gsi = gsi_after_labels(bb);
|
|
|
|
|
gsi_insert_before(&gsi, assign, GSI_NEW_STMT);
|
|
|
|
|
update_stmt(assign);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static void __perturb_latent_entropy(gimple_stmt_iterator *gsi,
|
|
|
|
|
tree local_entropy)
|
|
|
|
|
{
|
|
|
|
|
gimple assign;
|
|
|
|
|
tree temp;
|
|
|
|
|
enum tree_code op;
|
|
|
|
|
|
|
|
|
|
/* 1. create temporary copy of latent_entropy */
|
2016-10-19 06:08:04 +08:00
|
|
|
temp = create_var(long_unsigned_type_node, "temp_latent_entropy");
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
|
|
|
|
|
/* 2. read... */
|
|
|
|
|
add_referenced_var(latent_entropy_decl);
|
|
|
|
|
mark_sym_for_renaming(latent_entropy_decl);
|
|
|
|
|
assign = gimple_build_assign(temp, latent_entropy_decl);
|
|
|
|
|
gsi_insert_before(gsi, assign, GSI_NEW_STMT);
|
|
|
|
|
update_stmt(assign);
|
|
|
|
|
|
|
|
|
|
/* 3. ...modify... */
|
|
|
|
|
op = get_op(NULL);
|
|
|
|
|
assign = create_assign(op, temp, temp, local_entropy);
|
|
|
|
|
gsi_insert_after(gsi, assign, GSI_NEW_STMT);
|
|
|
|
|
update_stmt(assign);
|
|
|
|
|
|
|
|
|
|
/* 4. ...write latent_entropy */
|
|
|
|
|
assign = gimple_build_assign(latent_entropy_decl, temp);
|
|
|
|
|
gsi_insert_after(gsi, assign, GSI_NEW_STMT);
|
|
|
|
|
update_stmt(assign);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static bool handle_tail_calls(basic_block bb, tree local_entropy)
|
|
|
|
|
{
|
|
|
|
|
gimple_stmt_iterator gsi;
|
|
|
|
|
|
|
|
|
|
for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
|
|
|
|
|
gcall *call;
|
|
|
|
|
gimple stmt = gsi_stmt(gsi);
|
|
|
|
|
|
|
|
|
|
if (!is_gimple_call(stmt))
|
|
|
|
|
continue;
|
|
|
|
|
|
|
|
|
|
call = as_a_gcall(stmt);
|
|
|
|
|
if (!gimple_call_tail_p(call))
|
|
|
|
|
continue;
|
|
|
|
|
|
|
|
|
|
__perturb_latent_entropy(&gsi, local_entropy);
|
|
|
|
|
return true;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
return false;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static void perturb_latent_entropy(tree local_entropy)
|
|
|
|
|
{
|
|
|
|
|
edge_iterator ei;
|
|
|
|
|
edge e, last_bb_e;
|
|
|
|
|
basic_block last_bb;
|
|
|
|
|
|
|
|
|
|
gcc_assert(single_pred_p(EXIT_BLOCK_PTR_FOR_FN(cfun)));
|
|
|
|
|
last_bb_e = single_pred_edge(EXIT_BLOCK_PTR_FOR_FN(cfun));
|
|
|
|
|
|
|
|
|
|
FOR_EACH_EDGE(e, ei, last_bb_e->src->preds) {
|
|
|
|
|
if (ENTRY_BLOCK_PTR_FOR_FN(cfun) == e->src)
|
|
|
|
|
continue;
|
|
|
|
|
if (EXIT_BLOCK_PTR_FOR_FN(cfun) == e->src)
|
|
|
|
|
continue;
|
|
|
|
|
|
|
|
|
|
handle_tail_calls(e->src, local_entropy);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
last_bb = single_pred(EXIT_BLOCK_PTR_FOR_FN(cfun));
|
|
|
|
|
if (!handle_tail_calls(last_bb, local_entropy)) {
|
|
|
|
|
gimple_stmt_iterator gsi = gsi_last_bb(last_bb);
|
|
|
|
|
|
|
|
|
|
__perturb_latent_entropy(&gsi, local_entropy);
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static void init_local_entropy(basic_block bb, tree local_entropy)
|
|
|
|
|
{
|
|
|
|
|
gimple assign, call;
|
|
|
|
|
tree frame_addr, rand_const, tmp, fndecl, udi_frame_addr;
|
|
|
|
|
enum tree_code op;
|
|
|
|
|
unsigned HOST_WIDE_INT rand_cst;
|
|
|
|
|
gimple_stmt_iterator gsi = gsi_after_labels(bb);
|
|
|
|
|
|
|
|
|
|
/* 1. create local_entropy_frameaddr */
|
|
|
|
|
frame_addr = create_var(ptr_type_node, "local_entropy_frameaddr");
|
|
|
|
|
|
|
|
|
|
/* 2. local_entropy_frameaddr = __builtin_frame_address() */
|
|
|
|
|
fndecl = builtin_decl_implicit(BUILT_IN_FRAME_ADDRESS);
|
|
|
|
|
call = gimple_build_call(fndecl, 1, integer_zero_node);
|
|
|
|
|
gimple_call_set_lhs(call, frame_addr);
|
|
|
|
|
gsi_insert_before(&gsi, call, GSI_NEW_STMT);
|
|
|
|
|
update_stmt(call);
|
|
|
|
|
|
2016-10-19 06:08:04 +08:00
|
|
|
udi_frame_addr = fold_convert(long_unsigned_type_node, frame_addr);
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
assign = gimple_build_assign(local_entropy, udi_frame_addr);
|
|
|
|
|
gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
|
|
|
|
|
update_stmt(assign);
|
|
|
|
|
|
|
|
|
|
/* 3. create temporary copy of latent_entropy */
|
2016-10-19 06:08:04 +08:00
|
|
|
tmp = create_var(long_unsigned_type_node, "temp_latent_entropy");
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
|
|
|
|
|
/* 4. read the global entropy variable into local entropy */
|
|
|
|
|
add_referenced_var(latent_entropy_decl);
|
|
|
|
|
mark_sym_for_renaming(latent_entropy_decl);
|
|
|
|
|
assign = gimple_build_assign(tmp, latent_entropy_decl);
|
|
|
|
|
gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
|
|
|
|
|
update_stmt(assign);
|
|
|
|
|
|
|
|
|
|
/* 5. mix local_entropy_frameaddr into local entropy */
|
|
|
|
|
assign = create_assign(BIT_XOR_EXPR, local_entropy, local_entropy, tmp);
|
|
|
|
|
gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
|
|
|
|
|
update_stmt(assign);
|
|
|
|
|
|
|
|
|
|
rand_cst = get_random_const();
|
2016-10-19 06:08:04 +08:00
|
|
|
rand_const = build_int_cstu(long_unsigned_type_node, rand_cst);
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
op = get_op(NULL);
|
|
|
|
|
assign = create_assign(op, local_entropy, local_entropy, rand_const);
|
|
|
|
|
gsi_insert_after(&gsi, assign, GSI_NEW_STMT);
|
|
|
|
|
update_stmt(assign);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static bool create_latent_entropy_decl(void)
|
|
|
|
|
{
|
|
|
|
|
varpool_node_ptr node;
|
|
|
|
|
|
|
|
|
|
if (latent_entropy_decl != NULL_TREE)
|
|
|
|
|
return true;
|
|
|
|
|
|
|
|
|
|
FOR_EACH_VARIABLE(node) {
|
|
|
|
|
tree name, var = NODE_DECL(node);
|
|
|
|
|
|
|
|
|
|
if (DECL_NAME_LENGTH(var) < sizeof("latent_entropy") - 1)
|
|
|
|
|
continue;
|
|
|
|
|
|
|
|
|
|
name = DECL_NAME(var);
|
|
|
|
|
if (strcmp(IDENTIFIER_POINTER(name), "latent_entropy"))
|
|
|
|
|
continue;
|
|
|
|
|
|
|
|
|
|
latent_entropy_decl = var;
|
|
|
|
|
break;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
return latent_entropy_decl != NULL_TREE;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static unsigned int latent_entropy_execute(void)
|
|
|
|
|
{
|
|
|
|
|
basic_block bb;
|
|
|
|
|
tree local_entropy;
|
|
|
|
|
|
|
|
|
|
if (!create_latent_entropy_decl())
|
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
|
|
/* prepare for step 2 below */
|
|
|
|
|
gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
|
|
|
|
|
bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
|
|
|
|
|
if (!single_pred_p(bb)) {
|
|
|
|
|
split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
|
|
|
|
|
gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
|
|
|
|
|
bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/* 1. create the local entropy variable */
|
2016-10-19 06:08:04 +08:00
|
|
|
local_entropy = create_var(long_unsigned_type_node, "local_entropy");
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
|
|
|
|
|
/* 2. initialize the local entropy variable */
|
|
|
|
|
init_local_entropy(bb, local_entropy);
|
|
|
|
|
|
|
|
|
|
bb = bb->next_bb;
|
|
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* 3. instrument each BB with an operation on the
|
|
|
|
|
* local entropy variable
|
|
|
|
|
*/
|
|
|
|
|
while (bb != EXIT_BLOCK_PTR_FOR_FN(cfun)) {
|
|
|
|
|
perturb_local_entropy(bb, local_entropy);
|
|
|
|
|
bb = bb->next_bb;
|
2020-04-18 15:05:21 +08:00
|
|
|
}
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
|
|
|
|
|
/* 4. mix local entropy into the global entropy variable */
|
|
|
|
|
perturb_latent_entropy(local_entropy);
|
|
|
|
|
return 0;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
static void latent_entropy_start_unit(void *gcc_data __unused,
|
|
|
|
|
void *user_data __unused)
|
|
|
|
|
{
|
|
|
|
|
tree type, id;
|
|
|
|
|
int quals;
|
|
|
|
|
|
|
|
|
|
if (in_lto_p)
|
|
|
|
|
return;
|
|
|
|
|
|
2016-10-19 06:08:04 +08:00
|
|
|
/* extern volatile unsigned long latent_entropy */
|
|
|
|
|
quals = TYPE_QUALS(long_unsigned_type_node) | TYPE_QUAL_VOLATILE;
|
|
|
|
|
type = build_qualified_type(long_unsigned_type_node, quals);
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
id = get_identifier("latent_entropy");
|
|
|
|
|
latent_entropy_decl = build_decl(UNKNOWN_LOCATION, VAR_DECL, id, type);
|
|
|
|
|
|
|
|
|
|
TREE_STATIC(latent_entropy_decl) = 1;
|
|
|
|
|
TREE_PUBLIC(latent_entropy_decl) = 1;
|
|
|
|
|
TREE_USED(latent_entropy_decl) = 1;
|
|
|
|
|
DECL_PRESERVE_P(latent_entropy_decl) = 1;
|
|
|
|
|
TREE_THIS_VOLATILE(latent_entropy_decl) = 1;
|
|
|
|
|
DECL_EXTERNAL(latent_entropy_decl) = 1;
|
|
|
|
|
DECL_ARTIFICIAL(latent_entropy_decl) = 1;
|
|
|
|
|
lang_hooks.decls.pushdecl(latent_entropy_decl);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
#define PASS_NAME latent_entropy
|
|
|
|
|
#define PROPERTIES_REQUIRED PROP_gimple_leh | PROP_cfg
|
|
|
|
|
#define TODO_FLAGS_FINISH TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func \
|
|
|
|
|
| TODO_update_ssa
|
|
|
|
|
#include "gcc-generate-gimple-pass.h"
|
|
|
|
|
|
2016-11-01 01:40:13 +08:00
|
|
|
__visible int plugin_init(struct plugin_name_args *plugin_info,
|
|
|
|
|
struct plugin_gcc_version *version)
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
{
|
|
|
|
|
bool enabled = true;
|
|
|
|
|
const char * const plugin_name = plugin_info->base_name;
|
|
|
|
|
const int argc = plugin_info->argc;
|
|
|
|
|
const struct plugin_argument * const argv = plugin_info->argv;
|
|
|
|
|
int i;
|
|
|
|
|
|
gcc-plugins: latent_entropy: use /dev/urandom
While the latent entropy plugin mostly doesn't derive entropy from
get_random_const() for measuring the call graph, when __latent_entropy is
applied to a constant, then it's initialized statically to output from
get_random_const(). In that case, this data is derived from a 64-bit
seed, which means a buffer of 512 bits doesn't really have that amount
of compile-time entropy.
This patch fixes that shortcoming by just buffering chunks of
/dev/urandom output and doling it out as requested.
At the same time, it's important that we don't break the use of
-frandom-seed, for people who want the runtime benefits of the latent
entropy plugin, while still having compile-time determinism. In that
case, we detect whether gcc's set_random_seed() has been called by
making a call to get_random_seed(noinit=true) in the plugin init
function, which is called after set_random_seed() is called but before
anything that calls get_random_seed(noinit=false), and seeing if it's
zero or not. If it's not zero, we're in deterministic mode, and so we
just generate numbers with a basic xorshift prng.
Note that we don't detect if -frandom-seed is being used using the
documented local_tick variable, because it's assigned via:
local_tick = (unsigned) tv.tv_sec * 1000 + tv.tv_usec / 1000;
which may well overflow and become -1 on its own, and so isn't
reliable: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105171
[kees: The 256 byte rnd_buf size was chosen based on average (250),
median (64), and std deviation (575) bytes of used entropy for a
defconfig x86_64 build]
Fixes: 38addce8b600 ("gcc-plugins: Add latent_entropy plugin")
Cc: stable@vger.kernel.org
Cc: PaX Team <pageexec@freemail.hu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220405222815.21155-1-Jason@zx2c4.com
2022-04-06 06:28:15 +08:00
|
|
|
/*
|
|
|
|
|
* Call get_random_seed() with noinit=true, so that this returns
|
|
|
|
|
* 0 in the case where no seed has been passed via -frandom-seed.
|
|
|
|
|
*/
|
|
|
|
|
deterministic_seed = get_random_seed(true);
|
|
|
|
|
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
static const struct ggc_root_tab gt_ggc_r_gt_latent_entropy[] = {
|
|
|
|
|
{
|
|
|
|
|
.base = &latent_entropy_decl,
|
|
|
|
|
.nelt = 1,
|
|
|
|
|
.stride = sizeof(latent_entropy_decl),
|
|
|
|
|
.cb = >_ggc_mx_tree_node,
|
|
|
|
|
.pchw = >_pch_nx_tree_node
|
|
|
|
|
},
|
|
|
|
|
LAST_GGC_ROOT_TAB
|
|
|
|
|
};
|
|
|
|
|
|
2017-01-14 06:09:35 +08:00
|
|
|
PASS_INFO(latent_entropy, "optimized", 1, PASS_POS_INSERT_BEFORE);
|
|
|
|
|
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
if (!plugin_default_version_check(version, &gcc_version)) {
|
|
|
|
|
error(G_("incompatible gcc/plugin versions"));
|
|
|
|
|
return 1;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
for (i = 0; i < argc; ++i) {
|
|
|
|
|
if (!(strcmp(argv[i].key, "disable"))) {
|
|
|
|
|
enabled = false;
|
|
|
|
|
continue;
|
|
|
|
|
}
|
2016-09-17 22:44:17 +08:00
|
|
|
error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
|
gcc-plugins: Add latent_entropy plugin
This adds a new gcc plugin named "latent_entropy". It is designed to
extract as much possible uncertainty from a running system at boot time as
possible, hoping to capitalize on any possible variation in CPU operation
(due to runtime data differences, hardware differences, SMP ordering,
thermal timing variation, cache behavior, etc).
At the very least, this plugin is a much more comprehensive example for
how to manipulate kernel code using the gcc plugin internals.
The need for very-early boot entropy tends to be very architecture or
system design specific, so this plugin is more suited for those sorts
of special cases. The existing kernel RNG already attempts to extract
entropy from reliable runtime variation, but this plugin takes the idea to
a logical extreme by permuting a global variable based on any variation
in code execution (e.g. a different value (and permutation function)
is used to permute the global based on loop count, case statement,
if/then/else branching, etc).
To do this, the plugin starts by inserting a local variable in every
marked function. The plugin then adds logic so that the value of this
variable is modified by randomly chosen operations (add, xor and rol) and
random values (gcc generates separate static values for each location at
compile time and also injects the stack pointer at runtime). The resulting
value depends on the control flow path (e.g., loops and branches taken).
Before the function returns, the plugin mixes this local variable into
the latent_entropy global variable. The value of this global variable
is added to the kernel entropy pool in do_one_initcall() and _do_fork(),
though it does not credit any bytes of entropy to the pool; the contents
of the global are just used to mix the pool.
Additionally, the plugin can pre-initialize arrays with build-time
random contents, so that two different kernel builds running on identical
hardware will not have the same starting values.
Signed-off-by: Emese Revfy <re.emese@gmail.com>
[kees: expanded commit message and code comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
2016-06-21 02:41:19 +08:00
|
|
|
}
|
|
|
|
|
|
|
|
|
|
register_callback(plugin_name, PLUGIN_INFO, NULL,
|
|
|
|
|
&latent_entropy_plugin_info);
|
|
|
|
|
if (enabled) {
|
|
|
|
|
register_callback(plugin_name, PLUGIN_START_UNIT,
|
|
|
|
|
&latent_entropy_start_unit, NULL);
|
|
|
|
|
register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS,
|
|
|
|
|
NULL, (void *)>_ggc_r_gt_latent_entropy);
|
|
|
|
|
register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
|
|
|
|
|
&latent_entropy_pass_info);
|
|
|
|
|
}
|
|
|
|
|
register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes,
|
|
|
|
|
NULL);
|
|
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
|
}
|