Replace a pipeline of echo and sed with printf to decrease process forks.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
In 22f26f2177 awk was added to deduplicate *.mod files. The awk
invocation passes -v RS='( |\n)' to match a space or newline character
as the record separator. Unfortunately, POSIX states[1]
> If RS contains more than one character, the results are unspecified.
Some implementations (such as the One True Awk[2] used by the BSDs) do
not treat RS as a regular expression. When awk does not support regex
RS, build failures such as the following are produced (first error using
allmodconfig):
CC [M] arch/x86/events/intel/uncore.o
CC [M] arch/x86/events/intel/uncore_nhmex.o
CC [M] arch/x86/events/intel/uncore_snb.o
CC [M] arch/x86/events/intel/uncore_snbep.o
CC [M] arch/x86/events/intel/uncore_discovery.o
LD [M] arch/x86/events/intel/intel-uncore.o
ld: cannot find uncore_nhmex.o: No such file or directory
ld: cannot find uncore_snb.o: No such file or directory
ld: cannot find uncore_snbep.o: No such file or directory
ld: cannot find uncore_discovery.o: No such file or directory
make[3]: *** [scripts/Makefile.build:422: arch/x86/events/intel/intel-uncore.o] Error 1
make[2]: *** [scripts/Makefile.build:487: arch/x86/events/intel] Error 2
make[1]: *** [scripts/Makefile.build:487: arch/x86/events] Error 2
make: *** [Makefile:1839: arch/x86] Error 2
To avoid this, use printf(1) to produce a newline between each object
path, instead of the space produced by echo(1), so that the default RS
can be used by awk.
[1]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/awk.html
[2]: https://github.com/onetrueawk/awk
Fixes: 22f26f2177 ("kbuild: get rid of duplication in *.mod files")
Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
scripts/Makefile.build and scripts/link-vmlinux.sh have similar setups
for the objtool arguments.
It was difficult to factor out them because all the vmlinux build rules
were written in a shell script. It is somewhat tedious to touch the two
files every time a new objtool option is supported.
To reduce the code duplication, move the objtool for vmlinux.o into
scripts/Makefile.vmlinux_o. Then, move the common macros to Makefile.lib
so they are shared between Makefile.build and Makefile.vmlinux_o.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
When CONFIG_LTO_CLANG or CONFIG_X86_KERNEL_IBT is enabled, objtool for
multi-object modules is postponed until the objects are linked together.
Make sure to re-run objtool and re-link multi-object modules when
objtool is updated.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Like built-in.a, the command length of the *.mod rule scales with
the depth of the directory times the number of objects in the Makefile.
Add $(obj)/ by the shell command (awk) instead of by Make's builtin
function.
In-tree modules still have some room to the limit (ARG_MAX=2097152),
but this is more future-proof for big modules in a deep directory.
For example, you can build i915 as a module (CONFIG_DRM_I915=m) and
compare drivers/gpu/drm/i915/.i915.mod.cmd with/without this commit.
The issue is more critical for external modules because the M= path
can be very long as Jeff Johnson reported before [1].
[1] https://lore.kernel.org/linux-kbuild/4c02050c4e95e4cb8cc04282695f8404@codeaurora.org/
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Kbuild runs at the top of objtree instead of changing the working
directory to subdirectories. I think this design is nice overall but
some commands have a scalability issue.
The build command of built-in.a is one of them whose length scales with:
O(D * N)
Here, D is the length of the directory path (i.e. $(obj)/ prefix),
N is the number of objects in the Makefile, O() is the big O notation.
The deeper directory the Makefile directory is located, the more easily
it will hit the too long argument error.
We can make it better. Trim the $(obj)/ by Make's builtin function, and
restore it by a shell command (sed).
With this, the command length scales with:
O(D + N)
In-tree modules still have some room to the limit (ARG_MAX=2097152),
but this is more future-proof for big modules in a deep directory.
For example, you can build i915 as builtin (CONFIG_DRM_I915=y) and
compare drivers/gpu/drm/i915/.built-in.a.cmd with/without this commit.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
The 'static' specifier and EXPORT_SYMBOL() are an odd combination.
Commit 15bfc2348d ("modpost: check for static EXPORT_SYMBOL*
functions") tried to detect it, but this check has false negatives.
Here is the sample code.
Makefile:
obj-y += foo1.o foo2.o
foo1.c:
#include <linux/export.h>
static void foo(void) {}
EXPORT_SYMBOL(foo);
foo2.c:
void foo(void) {}
foo1.c exports the static symbol 'foo', but modpost cannot catch it
because it is fooled by foo2.c, which has a global symbol with the
same name.
s->is_static is cleared if a global symbol with the same name is found
somewhere, but EXPORT_SYMBOL() and the global symbol do not necessarily
belong to the same compilation unit.
This check should be done per compilation unit, but I do not know how
to do it in modpost. modpost runs against vmlinux.o or modules, which
merges multiple objects, then forgets their origin.
modpost cannot parse individual objects because they may not be ELF but
LLVM IR when CONFIG_LTO_CLANG=y.
Add a simple bash script to parse the output from ${NM}. This works for
CONFIG_LTO_CLANG=y because llvm-nm can dump symbols of LLVM IR files.
Revert 15bfc2348d.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
When CONFIG_LTO_CLANG=y, additional intermediate *.prelink.o is created
for each module. Also, objtool is postponed until LLVM IR is converted
to ELF.
CONFIG_X86_KERNEL_IBT works in a similar way to postpone objtool until
objects are merged together.
This commit stops generating *.prelink.o, so the build flow will look
similar with/without LTO.
The following figures show how the LTO build currently works, and
how this commit is changing it.
Current build flow
==================
[1] single-object module
$(LD)
$(CC) +objtool $(LD)
foo.c --------------------> foo.o -----> foo.prelink.o -----> foo.ko
(LLVM IR) (ELF) | (ELF)
|
foo.mod.o --/
(LLVM IR)
[2] multi-object module
$(LD)
$(CC) $(AR) +objtool $(LD)
foo1.c -----> foo1.o -----> foo.o -----> foo.prelink.o -----> foo.ko
| (archive) (ELF) | (ELF)
foo2.c -----> foo2.o --/ |
(LLVM IR) foo.mod.o --/
(LLVM IR)
One confusion is that foo.o in multi-object module is an archive
despite of its suffix.
New build flow
==============
[1] single-object module
Since there is only one object, there is no need to keep the LLVM IR.
Use $(CC)+$(LD) to generate an ELF object in one build rule. When LTO
is disabled, $(LD) is unneeded because $(CC) produces an ELF object.
$(CC)+$(LD)+objtool $(LD)
foo.c ----------------------------> foo.o ---------> foo.ko
(ELF) | (ELF)
|
foo.mod.o --/
(LLVM IR)
[2] multi-object module
Previously, $(AR) was used to combine LLVM IR files into an archive,
but there was no technical reason to do so. Use $(LD) to merge them
into a single ELF object.
$(LD)
$(CC) +objtool $(LD)
foo1.c ---------> foo1.o ---------> foo.o ---------> foo.ko
| (ELF) | (ELF)
foo2.c ---------> foo2.o ----/ |
(LLVM IR) foo.mod.o --/
(LLVM IR)
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
*.prelink.o is created when CONFIG_LTO_CLANG or CONFIG_X86_KERNEL_IBT
is enabled.
Replace $(linked-object) with $(CONFIG_LTO_CLANG)$(CONFIG_X86_KERNEL_IBT)
so you will get a quick idea of when the --link option is passed.
No functional change is intended.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14
- Add HOSTPKG_CONFIG env variable to allow users to override pkg-config
- Support W=e as a shorthand for KCFLAGS=-Werror
- Fix CONFIG_IKHEADERS build to support toybox cpio
- Add scripts/dummy-tools/pahole to ease distro packagers' life
- Suppress false-positive warnings from checksyscalls.sh for W=2 build
- Factor out the common code of arch/*/boot/install.sh into
scripts/install.sh
- Support 'kernel-install' tool in scripts/prune-kernel
- Refactor module-versioning to link the symbol versions at the final
link of vmlinux and modules
- Remove CONFIG_MODULE_REL_CRCS because module-versioning now works in
an arch-agnostic way
- Refactor modpost, Makefiles
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Merge tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- Add HOSTPKG_CONFIG env variable to allow users to override pkg-config
- Support W=e as a shorthand for KCFLAGS=-Werror
- Fix CONFIG_IKHEADERS build to support toybox cpio
- Add scripts/dummy-tools/pahole to ease distro packagers' life
- Suppress false-positive warnings from checksyscalls.sh for W=2 build
- Factor out the common code of arch/*/boot/install.sh into
scripts/install.sh
- Support 'kernel-install' tool in scripts/prune-kernel
- Refactor module-versioning to link the symbol versions at the final
link of vmlinux and modules
- Remove CONFIG_MODULE_REL_CRCS because module-versioning now works in
an arch-agnostic way
- Refactor modpost, Makefiles
* tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (56 commits)
genksyms: adjust the output format to modpost
kbuild: stop merging *.symversions
kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS
modpost: extract symbol versions from *.cmd files
modpost: add sym_find_with_module() helper
modpost: change the license of EXPORT_SYMBOL to bool type
modpost: remove left-over cross_compile declaration
kbuild: record symbol versions in *.cmd files
kbuild: generate a list of objects in vmlinux
modpost: move *.mod.c generation to write_mod_c_files()
modpost: merge add_{intree_flag,retpoline,staging_flag} to add_header
scripts/prune-kernel: Use kernel-install if available
kbuild: factor out the common installation code into scripts/install.sh
modpost: split new_symbol() to symbol allocation and hash table addition
modpost: make sym_add_exported() always allocate a new symbol
modpost: make multiple export error
modpost: dump Module.symvers in the same order of modules.order
modpost: traverse the namespace_list in order
modpost: use doubly linked list for dump_lists
modpost: traverse unresolved symbols in order
...
- Comprehensive interface overhaul:
=================================
Objtool's interface has some issues:
- Several features are done unconditionally, without any way to turn
them off. Some of them might be surprising. This makes objtool
tricky to use, and prevents porting individual features to other
arches.
- The config dependencies are too coarse-grained. Objtool enablement is
tied to CONFIG_STACK_VALIDATION, but it has several other features
independent of that.
- The objtool subcmds ("check" and "orc") are clumsy: "check" is really
a subset of "orc", so it has all the same options. The subcmd model
has never really worked for objtool, as it only has a single purpose:
"do some combination of things on an object file".
- The '--lto' and '--vmlinux' options are nonsensical and have
surprising behavior.
Overhaul the interface:
- get rid of subcmds
- make all features individually selectable
- remove and/or clarify confusing/obsolete options
- update the documentation
- fix some bugs found along the way
- Fix x32 regression
- Fix Kbuild cleanup bugs
- Add scripts/objdump-func helper script to disassemble a single function from an object file.
- Rewrite scripts/faddr2line to be section-aware, by basing it on 'readelf',
moving it away from 'nm', which doesn't handle multiple sections well,
which can result in decoding failure.
- Rewrite & fix symbol handling - which had a number of bugs wrt. object files
that don't have global symbols - which is rare but possible. Also fix a
bunch of symbol handling bugs found along the way.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'objtool-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull objtool updates from Ingo Molnar:
- Comprehensive interface overhaul:
=================================
Objtool's interface has some issues:
- Several features are done unconditionally, without any way to
turn them off. Some of them might be surprising. This makes
objtool tricky to use, and prevents porting individual features
to other arches.
- The config dependencies are too coarse-grained. Objtool
enablement is tied to CONFIG_STACK_VALIDATION, but it has several
other features independent of that.
- The objtool subcmds ("check" and "orc") are clumsy: "check" is
really a subset of "orc", so it has all the same options.
The subcmd model has never really worked for objtool, as it only
has a single purpose: "do some combination of things on an object
file".
- The '--lto' and '--vmlinux' options are nonsensical and have
surprising behavior.
Overhaul the interface:
- get rid of subcmds
- make all features individually selectable
- remove and/or clarify confusing/obsolete options
- update the documentation
- fix some bugs found along the way
- Fix x32 regression
- Fix Kbuild cleanup bugs
- Add scripts/objdump-func helper script to disassemble a single
function from an object file.
- Rewrite scripts/faddr2line to be section-aware, by basing it on
'readelf', moving it away from 'nm', which doesn't handle multiple
sections well, which can result in decoding failure.
- Rewrite & fix symbol handling - which had a number of bugs wrt.
object files that don't have global symbols - which is rare but
possible. Also fix a bunch of symbol handling bugs found along the
way.
* tag 'objtool-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (23 commits)
objtool: Fix objtool regression on x32 systems
objtool: Fix symbol creation
scripts/faddr2line: Fix overlapping text section failures
scripts: Create objdump-func helper script
objtool: Remove libsubcmd.a when make clean
objtool: Remove inat-tables.c when make clean
objtool: Update documentation
objtool: Remove --lto and --vmlinux in favor of --link
objtool: Add HAVE_NOINSTR_VALIDATION
objtool: Rename "VMLINUX_VALIDATION" -> "NOINSTR_VALIDATION"
objtool: Make noinstr hacks optional
objtool: Make jump label hack optional
objtool: Make static call annotation optional
objtool: Make stack validation frame-pointer-specific
objtool: Add CONFIG_OBJTOOL
objtool: Extricate sls from stack validation
objtool: Rework ibt and extricate from stack validation
objtool: Make stack validation optional
objtool: Add option to print section addresses
objtool: Don't print parentheses in function addresses
...
Make genksyms output symbol versions in the format modpost expects,
so the 'sed' is unneeded.
This commit makes *.symversions completely unneeded.
I will keep *.symversions in .gitignore and 'make clean' for a while.
Otherwise, 'git status' might be surprising.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
Now modpost reads symbol versions from .*.cmd files.
The merged *.symversions are no longer needed.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
include/{linux,asm-generic}/export.h defines a weak symbol, __crc_*
as a placeholder.
Genksyms writes the version CRCs into the linker script, which will be
used for filling the __crc_* symbols. The linker script format depends
on CONFIG_MODULE_REL_CRCS. If it is enabled, __crc_* holds the offset
to the reference of CRC.
It is time to get rid of this complexity.
Now that modpost parses text files (.*.cmd) to collect all the CRCs,
it can generate C code that will be linked to the vmlinux or modules.
Generate a new C file, .vmlinux.export.c, which contains the CRCs of
symbols exported by vmlinux. It is compiled and linked to vmlinux in
scripts/link-vmlinux.sh.
Put the CRCs of symbols exported by modules into the existing *.mod.c
files. No additional build step is needed for modules. As before,
*.mod.c are compiled and linked to *.ko in scripts/Makefile.modfinal.
No linker magic is used here. The new C implementation works in the
same way, whether CONFIG_RELOCATABLE is enabled or not.
CONFIG_MODULE_REL_CRCS is no longer needed.
Previously, Kbuild invoked additional $(LD) to update the CRCs in
objects, but this step is unneeded too.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM-14 (x86-64)
are not really needed anymore
- Misc fixes and cleanups
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Merge tag 'x86_cpu_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 CPU feature updates from Borislav Petkov:
- Remove a bunch of chicken bit options to turn off CPU features which
are not really needed anymore
- Misc fixes and cleanups
* tag 'x86_cpu_for_v5.19_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/speculation: Add missing prototype for unpriv_ebpf_notify()
x86/pm: Fix false positive kmemleak report in msr_build_context()
x86/speculation/srbds: Do not try to turn mitigation off when not supported
x86/cpu: Remove "noclflush"
x86/cpu: Remove "noexec"
x86/cpu: Remove "nosmep"
x86/cpu: Remove CONFIG_X86_SMAP and "nosmap"
x86/cpu: Remove "nosep"
x86/cpu: Allow feature bit names from /proc/cpuinfo in clearcpuid=
When CONFIG_MODVERSIONS=y, the output from genksyms is saved in
separate *.symversions files, and will be used much later when
CONFIG_LTO_CLANG=y because it is impossible to update LLVM bit code
here.
This approach is not robust because:
- *.symversions may or may not exist. If *.symversions does not
exist, we never know if it is missing for legitimate reason
(i.e. no EXPORT_SYMBOL) or something bad has happened (for
example, the user accidentally deleted it). Once it occurs,
it is not self-healing because *.symversions is generated
as a side effect.
- stale (i.e. invalid) *.symversions might be picked up if an
object is generated in a non-ordinary way, and corresponding
*.symversions (, which was generated by old builds) just happen
to exist.
A more robust approach is to save symbol versions in *.cmd files
because:
- *.cmd always exists (if the object is generated by if_changed
rule or friends). Even if the user accidentally deletes it,
it will be regenerated in the next build.
- *.cmd is always re-generated when the object is updated. This
avoid stale version information being picked up.
I will remove *.symversions later.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Tested-by: Nathan Chancellor <nathan@kernel.org>
ld and ar support @file, which command-line options are read from.
Now that *.mod lists the member objects in the correct order, without
duplication, it is ready to be passed to ld and ar.
By using the @file syntax, people will not be worried about the pitfall
described in the NOTE.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
The dependency
$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o
... exists because *.mod files previously contained undefined symbols,
which are computed from *.o files when CONFIG_TRIM_UNUSED_KSYMS=y.
Now that the undefined symbols are put into separate *.usyms files,
there is no reason to make *.mod depend on *.o files.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
It is allowed to add the same objects multiple times to obj-y / obj-m:
obj-y += foo.o foo.o foo.o
obj-m += bar.o bar.o bar.o
It is also allowed to add the same objects multiple times to a composite
module:
obj-m += foo.o
foo-y := foo1.o foo2.o foo2.o foo1.o
This flexibility is useful because the same object might be selected by
different CONFIG options, like this:
obj-m += foo.o
foo-y := foo1.o
foo-$(CONFIG_FOO_X) += foo2.o
foo-$(CONFIG_FOO_Y) += foo2.o
The duplicated objects are omitted at link time. It works naturally in
Makefiles because GNU Make removes duplication in $^ without changing
the order.
It is working well, almost...
A small flaw I notice is, *.mod contains duplication in such a case.
This is probably not a big deal. As far as I know, the only small
problem is scripts/mod/sumversion.c parses the same file multiple
times.
I am fixing this because I plan to reuse *.mod for other purposes,
where the duplication can be problematic.
The code change is quite simple. We already use awk to drop duplicated
lines in modules.order (see cmd_modules_order in the same file).
I copied the code, but changed RS to use spaces as record separators.
I also changed the file format to list one object per line.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
The *.mod files have two lines; the first line lists the member objects
of the module, and the second line, if CONFIG_TRIM_UNUSED_KSYMS=y, lists
the undefined symbols.
Currently, we generate *.mod after constructing composite modules,
otherwise, we cannot compute the second line. No prerequisite is
required to print the first line.
They are orthogonal. Splitting them into separate commands will ease
further cleanups.
This commit splits the list of undefined symbols out to *.usyms files.
Previously, the list of undefined symbols ended up with a very long
line, but now it has one symbol per line.
Use sed like we did before commit 7d32358be8 ("kbuild: avoid split
lines in .mod files").
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
The first command in cmd_mod is similar to the real-search macro.
Reuse it.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Split the code into two macros, cmd_gen_symversions_S for running
genksyms, and cmd_modversions for running $(LD) to update the object
with CRCs.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
cmd_modversions_c implements two parts; run genksyms to calculate CRCs
of exported symbols, run $(LD) to update the object with the CRCs. The
latter is not executed for CONFIG_LTO_CLANG=y since the object is not
ELF but LLVM bit code at this point.
The first part can be unified because we can always use $(NM) instead
of "$(OBJDUMP) -h" to dump the symbols.
Split the code into the two macros, cmd_gen_symversions_c and
cmd_modversions.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
The '--lto' option is a confusing way of telling objtool to do stack
validation despite it being a linked object. It's no longer needed now
that an explicit '--stackval' option exists. The '--vmlinux' option is
also redundant.
Remove both options in favor of a straightforward '--link' option which
identifies a linked object.
Also, implicitly set '--link' with a warning if the user forgets to do
so and we can tell that it's a linked object. This makes it easier for
manual vmlinux runs.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/dcd3ceffd15a54822c6183e5766d21ad06082b45.1650300597.git.jpoimboe@redhat.com
Objtool has some hacks in place to workaround toolchain limitations
which otherwise would break no-instrumentation rules. Make the hacks
explicit (and optional for other arches) by turning it into a cmdline
option and kernel config option.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/b326eeb9c33231b9dfbb925f194ed7ee40edcd7c.1650300597.git.jpoimboe@redhat.com
Objtool secretly does a jump label hack to overcome the limitations of
the toolchain. Make the hack explicit (and optional for other arches)
by turning it into a cmdline option and kernel config option.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/3bdcbfdd27ecb01ddec13c04bdf756a583b13d24.1650300597.git.jpoimboe@redhat.com
Now that CONFIG_STACK_VALIDATION is frame-pointer specific, do the same
for the '--stackval' option. Now the '--no-fp' option is redundant and
can be removed.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/f563fa064b3b63d528de250c72012d49e14742a3.1650300597.git.jpoimboe@redhat.com
Now that stack validation is an optional feature of objtool, add
CONFIG_OBJTOOL and replace most usages of CONFIG_STACK_VALIDATION with
it.
CONFIG_STACK_VALIDATION can now be considered to be frame-pointer
specific. CONFIG_UNWINDER_ORC is already inherently valid for live
patching, so no need to "validate" it.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/939bf3d85604b2a126412bf11af6e3bd3b872bcb.1650300597.git.jpoimboe@redhat.com
Objtool has a fairly singular focus. It runs on object files and does
validations and transformations which can be combined in various ways.
The subcommand model has never been a good fit, making it awkward to
combine and remove options.
Remove the "check" and "orc" subcommands in favor of a more traditional
cmdline option model. This makes it much more flexible to use, and
easier to port individual features to other arches.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/5c61ebf805e90aefc5fa62bc63468ffae53b9df6.1650300597.git.jpoimboe@redhat.com
Split the existing options into two groups: actions, which actually do
something; and options, which modify the actions in some way.
Also there's no need to have short flags for all the non-action options.
Reserve short flags for the more important actions.
While at it:
- change a few of the short flags to be more intuitive
- make option descriptions more consistently descriptive
- sort options in the source like they are when printed
- move options to a global struct
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/9dcaa752f83aca24b1b21f0b0eeb28a0c181c0b0.1650300597.git.jpoimboe@redhat.com
With IBT support in, objtool is now fully capable of following vmlinux
code flow in LTO mode. Start reporting unreachable warnings for Clang
LTO as well.
Fixes: ed53a0d971 ("x86/alternative: Use .ibt_endbr_seal to seal indirect calls")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/7b12df54bceeb0761fe9fc8269ea0c00501214a9.1650300597.git.jpoimboe@redhat.com
Presumably, 'test -s $@ || rm -f $@' intends to remove the output when
the genksyms command fails.
It is unneeded because .DELETE_ON_ERROR automatically removes the output
on failure.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
The genksyms command part in cmd_gensymtypes_{c,S} is duplicated.
Factor it out into the 'genksyms' macro.
For the readability, I slightly refactor the arguments to genksyms.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Those were added as part of the SMAP enablement but SMAP is currently
an integral part of kernel proper and there's no need to disable it
anymore.
Rip out that functionality. Leave --uaccess default on for objtool as
this is what objtool should do by default anyway.
If still needed - clearcpuid=smap.
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220127115626.14179-4-bp@alien8.de
- Add new environment variables, USERCFLAGS and USERLDFLAGS to allow
additional flags to be passed to user-space programs.
- Fix missing fflush() bugs in Kconfig and fixdep
- Fix a minor bug in the comment format of the .config file
- Make kallsyms ignore llvm's local labels, .L*
- Fix UAPI compile-test for cross-compiling with Clang
- Extend the LLVM= syntax to support LLVM=<suffix> form for using a
particular version of LLVm, and LLVM=<prefix> form for using custom
LLVM in a particular directory path.
- Clean up Makefiles
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Merge tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- Add new environment variables, USERCFLAGS and USERLDFLAGS to allow
additional flags to be passed to user-space programs.
- Fix missing fflush() bugs in Kconfig and fixdep
- Fix a minor bug in the comment format of the .config file
- Make kallsyms ignore llvm's local labels, .L*
- Fix UAPI compile-test for cross-compiling with Clang
- Extend the LLVM= syntax to support LLVM=<suffix> form for using a
particular version of LLVm, and LLVM=<prefix> form for using custom
LLVM in a particular directory path.
- Clean up Makefiles
* tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
kbuild: Make $(LLVM) more flexible
kbuild: add --target to correctly cross-compile UAPI headers with Clang
fixdep: use fflush() and ferror() to ensure successful write to files
arch: syscalls: simplify uapi/kapi directory creation
usr/include: replace extra-y with always-y
certs: simplify empty certs creation in certs/Makefile
certs: include certs/signing_key.x509 unconditionally
kallsyms: ignore all local labels prefixed by '.L'
kconfig: fix missing '# end of' for empty menu
kconfig: add fflush() before ferror() check
kbuild: replace $(if A,A,B) with $(or A,B)
kbuild: Add environment variables for userprogs flags
kbuild: unify cmd_copy and cmd_shipped
Objtool's --ibt option generates .ibt_endbr_seal which lists
superfluous ENDBR instructions. That is those instructions for which
the function is never indirectly called.
Overwrite these ENDBR instructions with a NOP4 such that these
function can never be indirect called, reducing the number of viable
ENDBR targets in the kernel.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154319.822545231@infradead.org
$(or ...) is available since GNU Make 3.81, and useful to shorten the
code in some places.
Covert as follows:
$(if A,A,B) --> $(or A,B)
This patch also converts:
$(if A, A, B) --> $(or A, B)
Strictly speaking, the latter is not an equivalent conversion because
GNU Make keeps spaces after commas; if A is not empty, $(if A, A, B)
expands to " A", while $(or A, B) expands to "A".
Anyway, preceding spaces are not significant in the code hunks I touched.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
For CONFIG_LTO_CLANG=y, the objtool processing is not possible at the
compilation, hence postponed by the link time.
Reuse $(cmd_objtool) for CONFIG_LTO_CLANG=y by defining objtool-enabled
properly.
For CONFIG_LTO_CLANG=y:
objtool-enabled is off for %.o compilation
objtool-enabled is on for %.lto link
For CONFIG_LTO_CLANG=n:
objtool-enabled is on for %.o compilation
(but, it depends on OBJECT_FILE_NON_STANDARD)
Set part-of-module := y for %.lto.o to avoid repeating --module.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Redo commit 8852c55240 ("kbuild: Fix objtool dependency for
'OBJECT_FILES_NON_STANDARD_<obj> := n'") to add the objtool
dependency in a cleaner way.
Using .SECONDEXPANSION ends up with unreadable code due to escaped
dollars. Also, it is not efficient because the second half of
Makefile.build is parsed twice every time.
Append the objtool dependency to the *.cmd files at the build time.
This is what fixdep and gen_ksymdeps.sh already do. So, following the
same pattern seems a natural solution.
This allows us to drop $$(objtool_dep) entirely.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
The OBJECT_FILES_NON_STANDARD check is quite long.
Factor it out into a new macro, objtool-enabled, to not repeat it.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
objtool_dep includes include/config/{ORC_UNWINDER,STACK_VALIDATION}
so that all the objects are rebuilt when CONFIG_ORC_UNWINDER or
CONFIG_STACK_VALIDATION is toggled.
BTW, the correct option name is not CONFIG_ORC_UNWINDER, but
CONFIG_UNWINDER_ORC. Commit 11af847446 ("x86/unwind: Rename
unwinder config options to 'CONFIG_UNWINDER_*'") missed to
adjust this part. So, this dependency has been broken for a
long time.
As you can see in 'objtool_args', there are more CONFIG options
that affect the objtool command line.
Adding more and more include/config/* is ugly and unmaintainable.
Another issue is that non-standard objects are needlessly rebuilt.
Objects specified as OBJECT_FILES_NON_STANDARD is not processed by
objtool, but they are rebuilt anyway when CONFIG_STACK_VALIDATION
is toggled. This is not a big deal, but better to fix.
A cleaner and more precise fix is to include the objtool command in
*.cmd files so any command change is naturally detected by if_change.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Rename __objtool_obj to objtool, and move it out of the
'ifndef CONFIG_LTO_CLANG' conditional, so it can be used for
cmd_cc_lto_link_modules as well.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Commit b1a1a1a09b ("kbuild: lto: postpone objtool") moved objtool_args
to Makefile.lib, so the arguments can be used in Makefile.modfinal as
well as Makefile.build.
With commit 850ded46c6 ("kbuild: Fix TRIM_UNUSED_KSYMS with
LTO_CLANG"), module LTO linking came back to scripts/Makefile.build
again.
So, there is no more reason to keep objtool_args in a separate file.
Get it back to the original place, close to the objtool command.
Remove the stale comment too.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
cmd_update_lto_symversions merges all the existing *.symversions, but
some of them might be stale.
If the last EXPORT_SYMBOL is removed from a C file, the *.symversions
file is not deleted or updated. It contains stale CRCs, but still they
will be used for linking the vmlinux or modules.
It is not a big deal when the EXPORT_SYMBOL is really removed. However,
when the EXPORT_SYMBOL is moved to another file, the same __crc_<symbol>
will appear twice in the merged *.symversions, possibly with different
CRCs if the function argument is changed at the same time. It would
confuse module versioning.
If no EXPORT_SYMBOL is found, let's remove *.symversions explicitly.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
This is not used anywhere because the short log is displayed when
it is used through a $(call cmd,...) invocation.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
With CONFIG_LTO_CLANG, we currently link modules into native
code just before modpost, which means with TRIM_UNUSED_KSYMS
enabled, we still look at the LLVM bitcode in the .o files when
generating the list of used symbols. As the bitcode doesn't
yet have calls to compiler intrinsics and llvm-nm doesn't see
function references that only exist in function-level inline
assembly, we currently need a whitelist for TRIM_UNUSED_KSYMS to
work with LTO.
This change moves module LTO linking to happen earlier, and
thus avoids the issue with LLVM bitcode and TRIM_UNUSED_KSYMS
entirely, allowing us to also drop the whitelist from
gen_autoksyms.sh.
Link: https://github.com/ClangBuiltLinux/linux/issues/1369
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Alexander Lobakin <alobakin@pm.me>
Tested-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Masahiro Yamada