Summary:
Quote from http://eel.is/c++draft/expr.add#4:
```
4 When an expression J that has integral type is added to or subtracted
from an expression P of pointer type, the result has the type of P.
(4.1) If P evaluates to a null pointer value and J evaluates to 0,
the result is a null pointer value.
(4.2) Otherwise, if P points to an array element i of an array object x with n
elements ([dcl.array]), the expressions P + J and J + P
(where J has the value j) point to the (possibly-hypothetical) array
element i+j of x if 0≤i+j≤n and the expression P - J points to the
(possibly-hypothetical) array element i−j of x if 0≤i−j≤n.
(4.3) Otherwise, the behavior is undefined.
```
Therefore, as per the standard, applying non-zero offset to `nullptr`
(or making non-`nullptr` a `nullptr`, by subtracting pointer's integral value
from the pointer itself) is undefined behavior. (*if* `nullptr` is not defined,
i.e. e.g. `-fno-delete-null-pointer-checks` was *not* specified.)
To make things more fun, in C (6.5.6p8), applying *any* offset to null pointer
is undefined, although Clang front-end pessimizes the code by not lowering
that info, so this UB is "harmless".
Since rL369789 (D66608 `[InstCombine] icmp eq/ne (gep inbounds P, Idx..), null -> icmp eq/ne P, null`)
LLVM middle-end uses those guarantees for transformations.
If the source contains such UB's, said code may now be miscompiled.
Such miscompilations were already observed:
* https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20190826/687838.html
* https://github.com/google/filament/pull/1566
Surprisingly, UBSan does not catch those issues
... until now. This diff teaches UBSan about these UB's.
`getelementpointer inbounds` is a pretty frequent instruction,
so this does have a measurable impact on performance;
I've addressed most of the obvious missing folds (and thus decreased the performance impact by ~5%),
and then re-performed some performance measurements using my [[ https://github.com/darktable-org/rawspeed | RawSpeed ]] benchmark:
(all measurements done with LLVM ToT, the sanitizer never fired.)
* no sanitization vs. existing check: average `+21.62%` slowdown
* existing check vs. check after this patch: average `22.04%` slowdown
* no sanitization vs. this patch: average `48.42%` slowdown
Reviewers: vsk, filcab, rsmith, aaron.ballman, vitalybuka, rjmccall, #sanitizers
Reviewed By: rsmith
Subscribers: kristof.beyls, nickdesaulniers, nikic, ychen, dtzWill, xbolva00, dberris, arphaman, rupprecht, reames, regehr, llvm-commits, cfe-commits
Tags: #clang, #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D67122
llvm-svn: 374293
Unlike asan, which isn't supported yet on 64-bit Solaris/x86, there's no reason to disable
ubsan. This patch does that, but keeps the 64-bit ubsan-with-asan tests disabled.
Tested on x86_64-pc-solaris2.11.
Differential Revision: https://reviews.llvm.org/D63982
llvm-svn: 365302
These lit configuration files are really Python source code. Using the
.py file extension helps editors and tools use the correct language
mode. LLVM and Clang already use this convention for lit configuration,
this change simply applies it to all of compiler-rt.
Reviewers: vitalybuka, dberris
Differential Revision: https://reviews.llvm.org/D63658
llvm-svn: 364591
Summary:
This is the compiler-rt part.
The clang part is D54589.
This is a second commit, the original one was r351106,
which was mass-reverted in r351159 because 2 compiler-rt tests were failing.
Now, i have fundamentally changed the testing approach:
i malloc a few bytes, intentionally mis-align the pointer
(increment it by one), and check that. Also, i have decreased
the expected alignment. This hopefully should be enough to pacify
all the bots. If not, i guess i might just drop the two 'bad' tests.
Reviewers: filcab, vsk, #sanitizers, vitalybuka, rsmith, morehouse
Reviewed By: morehouse
Subscribers: rjmccall, krytarowski, rsmith, kcc, srhines, kubamracek, dberris, llvm-commits
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D54590
llvm-svn: 351178
OpenBSD needs lld linker for sanitisers.
Disabling lint checking as some symbols cannot be defined and block the proper unit tests launch.
Reviewers: lebedev.ri, vitalybuka
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D48528
llvm-svn: 335524
Summary:
This patch (on top of the previous two (https://reviews.llvm.org/D40898 and
https://reviews.llvm.org/D40899) complete the compiler-rt side of the the Solaris
sanitizer port.
It contains the following sets of changes:
* For the time being, the port is for 32-bit x86 only, so reject the various tests on
x86_64.
* When compiling as C++, <setjmp.h> resp. <iso/setjmp_iso.h> only declares
_setjmp and _longjmp inside namespace std.
* MAP_FILE is a Windows feature. While e.g. Linux <sys/mman.h> provides a
no-op compat define, Solaris does not.
* test/asan/TestCases/Posix/coverage.cc was initially failing like this:
/vol/gcc/src/llvm/llvm/local/projects/compiler-rt/lib/sanitizer_common/scripts/sancov.py: 4 files merged; 2 PCs total
rm: cannot remove '/var/gcc/llvm/local/projects/compiler-rt/test/asan/I386SunOSConfig/TestCases/Posix/Output/coverage': Invalid argument
Further digging revealed that the rm was trying to remove the running test's working
directory which failed as observed. cd'ing out of the dir before let the test pass.
* Two tests needed a declaration of alloca. I've now copied the existing code from
test/asan/TestCases/alloca_constant_size.cc, but it may be more profitable and
maintainable to have a common testsuite header where such code is collected.
* Similarly, Solaris' printf %p format doesn't include the leading 0x.
* In test/asan/TestCases/malloc-no-intercept.c, I had to undef __EXTENSIONS__
(predefined by clang for no apparent reason) to avoid conflicting declarations
for memalign.
* test/ubsan/TestCases/Float/cast-overflow.cpp has different platform dependent
ways to define BYTE_ORDER and friends. Why not just use __BYTE_ORDER__ and
friends as predefined by clang and gcc?
Patch by Rainer Orth.
Reviewers: kcc, alekseyshl
Reviewed By: alekseyshl
Subscribers: srhines, kubamracek, mgorny, krytarowski, fedor.sergeev, JDevlieghere, llvm-commits, #sanitizers
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D40900
llvm-svn: 322635
Summary:
As discussed in https://github.com/google/oss-fuzz/issues/933,
it would be really awesome to be able to use ThinLTO for fuzzing.
However, as @kcc has pointed out, it is currently undefined (untested)
whether the sanitizers actually function properly with LLD and/or LTO.
This patch is inspired by the cfi test, which already do test with LTO
(and/or LLD), since LTO is required for CFI to function.
I started with UBSan, because it's cmakelists / lit.* files appeared
to be the cleanest. This patch adds the infrastructure to easily add
LLD and/or LTO sub-variants of the existing lit test configurations.
Also, this patch adds the LLD flavor, that explicitly does use LLD to link.
The check-ubsan does pass on my machine. And to minimize the [initial]
potential buildbot breakage i have put some restrictions on this flavour.
Please review carefully, i have not worked with lit/sanitizer tests before.
The original attempt, r319525 was reverted in r319526 due
to the failures in compiler-rt standalone builds.
Reviewers: eugenis, vitalybuka
Reviewed By: eugenis
Subscribers: #sanitizers, pcc, kubamracek, mgorny, llvm-commits, mehdi_amini, inglorion, kcc
Differential Revision: https://reviews.llvm.org/D39508
llvm-svn: 319575
This reverts commit r319525.
This change has introduced a problem with the Lit tests build for compiler-rt using Gold: http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux/builds/6047/steps/test%20standalone%20compiler-rt/logs/stdio
llvm-lit: /b/sanitizer-x86_64-linux/build/llvm/utils/lit/lit/TestingConfig.py:101: fatal: unable to parse config file '/b/sanitizer-x86_64-linux/build/llvm/projects/compiler-rt/test/profile/Linux/lit.local.cfg', traceback: Traceback (most recent call last):
File "/b/sanitizer-x86_64-linux/build/llvm/utils/lit/lit/TestingConfig.py", line 88, in load_from_path
exec(compile(data, path, 'exec'), cfg_globals, None)
File "/b/sanitizer-x86_64-linux/build/llvm/projects/compiler-rt/test/profile/Linux/lit.local.cfg", line 37, in <module>
if root.host_os not in ['Linux'] or not is_gold_linker_available():
File "/b/sanitizer-x86_64-linux/build/llvm/projects/compiler-rt/test/profile/Linux/lit.local.cfg", line 27, in is_gold_linker_available
stderr = subprocess.PIPE)
File "/usr/lib/python2.7/subprocess.py", line 390, in __init__
errread, errwrite)
File "/usr/lib/python2.7/subprocess.py", line 1024, in _execute_child
raise child_exception
OSError: [Errno 2] No such file or directory
llvm-svn: 319529
Summary:
As discussed in https://github.com/google/oss-fuzz/issues/933,
it would be really awesome to be able to use ThinLTO for fuzzing.
However, as @kcc has pointed out, it is currently undefined (untested)
whether the sanitizers actually function properly with LLD and/or LTO.
This patch is inspired by the cfi test, which already do test with LTO
(and/or LLD), since LTO is required for CFI to function.
I started with UBSan, because it's cmakelists / lit.* files appeared
to be the cleanest. This patch adds the infrastructure to easily add
LLD and/or LTO sub-variants of the existing lit test configurations.
Also, this patch adds the LLD flavor, that explicitly does use LLD to link.
The check-ubsan does pass on my machine. And to minimize the [initial]
potential buildbot breakage i have put some restrictions on this flavour.
Please review carefully, i have not worked with lit/sanitizer tests before.
Reviewers: eugenis, vitalybuka
Reviewed By: eugenis
Subscribers: #sanitizers, pcc, kubamracek, mgorny, llvm-commits, mehdi_amini, inglorion, kcc
Differential Revision: https://reviews.llvm.org/D39508
llvm-svn: 319525
Check that the symbol sets exported by the minimal runtime and the full
runtime match (making exceptions for special cases as needed).
This test uses some possibly non-standard nm options, and needs to
inspect the symbols in runtime dylibs. I haven't found a portable way to
do this, so it's limited to x86-64/Darwin for now.
llvm-svn: 313615
This eliminates a few inconsistencies between the symbol sets exported
by RTUBSan and RTUBSan_minimal:
* Handlers for nonnull_return were missing from the minimal RT, and
are now added in.
* The minimal runtime exported recoverable handlers for
builtin_unreachable and missing_return. These are not supposed to
exist, and are now removed.
llvm-svn: 313614
We're seeing strange issues on the public GreenDragon Darwin bots which
we don't understand. x86_64h tests are still being run on pre-Haswell
bots despite the added checks in test/ubsan_minimal/lit.common.cfg,
which were verified on our internal bots.
I'm unable to ssh into the affected public bot, so for now am trying a
more aggressive check which disables all x86_64h testing for
ubsan-minimal on Darwin.
rdar://problem/34409349
llvm-svn: 313189
Checking if config.target_arch is x86_64h doesn't work (the 'h' suffix
is dropped here, and I didn't account for that). Instead, check to see
if '-arch x86_64h' is in the cflags.
Tested on a pre-Haswell bot.
rdar://problem/34378605
llvm-svn: 313053
Summary:
An implementation of ubsan runtime library suitable for use in production.
Minimal attack surface.
* No stack traces.
* Definitely no C++ demangling.
* No UBSAN_OPTIONS=log_file=/path (very suid-unfriendly). And no UBSAN_OPTIONS in general.
* as simple as possible
Minimal CPU and RAM overhead.
* Source locations unnecessary in the presence of (split) debug info.
* Values and types (as in A+B overflows T) can be reconstructed from register/stack dumps, once you know what type of error you are looking at.
* above two items save 3% binary size.
When UBSan is used with -ftrap-function=abort, sometimes it is hard to reason about failures. This library replaces abort with a slightly more informative message without much extra overhead. Since ubsan interface in not stable, this code must reside in compiler-rt.
Reviewers: pcc, kcc
Subscribers: srhines, mgorny, aprantl, krytarowski, llvm-commits
Differential Revision: https://reviews.llvm.org/D36810
llvm-svn: 312029
Roman Lebedev