With LTO, the compiler doesn't necessarily obey the link order for
initcalls, and initcall variables need globally unique names to avoid
collisions at link time.
This change exports __KBUILD_MODNAME and adds the initcall_id() macro,
which uses it together with __COUNTER__ and __LINE__ to help ensure
these variables have unique names, and moves each variable to its own
section when LTO is enabled, so the correct order can be specified using
a linker script.
The generate_initcall_ordering.pl script uses nm to find initcalls from
the object files passed to the linker, and generates a linker script
that specifies the same order for initcalls that we would have without
LTO. With LTO enabled, the script is called in link-vmlinux.sh through
jobserver-exec to limit the number of jobs spawned.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-8-samitolvanen@google.com
With CONFIG_MODVERSIONS, version information is linked into each
compilation unit that exports symbols. With LTO, we cannot use this
method as all C code is compiled into LLVM bitcode instead. This
change collects symbol versions into .symversions files and merges
them in link-vmlinux.sh where they are all linked into vmlinux.o at
the same time.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-4-samitolvanen@google.com
This change adds build system support for Clang's Link Time
Optimization (LTO). With -flto, instead of ELF object files, Clang
produces LLVM bitcode, which is compiled into native code at link
time, allowing the final binary to be optimized globally. For more
details, see:
https://llvm.org/docs/LinkTimeOptimization.html
The Kconfig option CONFIG_LTO_CLANG is implemented as a choice,
which defaults to LTO being disabled. To use LTO, the architecture
must select ARCH_SUPPORTS_LTO_CLANG and support:
- compiling with Clang,
- compiling all assembly code with Clang's integrated assembler,
- and linking with LLD.
While using CONFIG_LTO_CLANG_FULL results in the best runtime
performance, the compilation is not scalable in time or
memory. CONFIG_LTO_CLANG_THIN enables ThinLTO, which allows
parallel optimization and faster incremental builds. ThinLTO is
used by default if the architecture also selects
ARCH_SUPPORTS_LTO_CLANG_THIN:
https://clang.llvm.org/docs/ThinLTO.html
To enable LTO, LLVM tools must be used to handle bitcode files, by
passing LLVM=1 and LLVM_IAS=1 options to make:
$ make LLVM=1 LLVM_IAS=1 defconfig
$ scripts/config -e LTO_CLANG_THIN
$ make LLVM=1 LLVM_IAS=1
To prepare for LTO support with other compilers, common parts are
gated behind the CONFIG_LTO option, and LTO can be disabled for
specific files by filtering out CC_FLAGS_LTO.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-3-samitolvanen@google.com
Move function tracer options to Kconfig to make it easier to add
new methods for generating __mcount_loc, and to make the options
available also when building kernel modules.
Note that FTRACE_MCOUNT_USE_* options are updated on rebuild and
therefore, work even if the .config was generated in a different
environment.
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201211184633.3213045-2-samitolvanen@google.com
Commit 436e980e2e ("kbuild: don't hardcode depmod path") stopped
hard-coding the path of depmod, but in the process caused trouble for
distributions that had that /sbin location, but didn't have it in the
PATH (generally because /sbin is limited to the super-user path).
Work around it for now by just adding /sbin to the end of PATH in the
depmod.sh script.
Reported-and-tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull coccinelle updates from Julia Lawall.
* 'for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/jlawall/linux:
scripts: coccicheck: Correct usage of make coccicheck
coccinelle: update expiring email addresses
coccinnelle: Remove ptr_ret script
kbuild: do not use scripts/ld-version.sh for checking spatch version
remove boolinit.cocci
The command "make coccicheck C=1 CHECK=scripts/coccicheck" results in the
error:
./scripts/coccicheck: line 65: -1: shift count out of range
This happens because every time the C variable is specified,
the shell arguments need to be "shifted" in order to take only
the last argument, which is the C file to test. These shell arguments
mostly comprise flags that have been set in the Makefile. However,
when coccicheck is specified in the make command as a rule, the
number of shell arguments is zero, thus passing the invalid value -1
to the shift command, resulting in an error.
Modify coccicheck to print correct usage of make coccicheck so as to
avoid the error.
Signed-off-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Pull Kconfig updates from Masahiro Yamada:
- Support only Qt5 for qconf
- Validate signal/slot connection at compile time of qconf
- Sanitize header includes
* tag 'kconfig-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
kconfig: doc: fix $(fileno) to $(filename)
kconfig: fix return value of do_error_if()
kconfig: clean up header inclusion
kconfig: qconf: show Qt version in the About dialog
kconfig: make lkc.h self-sufficient #include-wise
kconfig: qconf: convert to Qt5 new signal/slot connection syntax
kconfig: qconf: use a variable to pass packages to pkg-config
kconfig: qconf: drop Qt4 support
Pull Kbuild updates from Masahiro Yamada:
- Use /usr/bin/env for shebang lines in scripts
- Remove useless -Wnested-externs warning flag
- Update documents
- Refactor log handling in modpost
- Stop building modules without MODULE_LICENSE() tag
- Make the insane combination of 'static' and EXPORT_SYMBOL an error
- Improve genksyms to handle _Static_assert()
* tag 'kbuild-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
Documentation/kbuild: Document platform dependency practises
Documentation/kbuild: Document COMPILE_TEST dependencies
genksyms: Ignore module scoped _Static_assert()
modpost: turn static exports into error
modpost: turn section mismatches to error from fatal()
modpost: change license incompatibility to error() from fatal()
modpost: turn missing MODULE_LICENSE() into error
modpost: refactor error handling and clarify error/fatal difference
modpost: rename merror() to error()
kbuild: don't hardcode depmod path
kbuild: doc: document subdir-y syntax
kbuild: doc: clarify the difference between extra-y and always-y
kbuild: doc: split if_changed explanation to a separate section
kbuild: doc: merge 'Special Rules' and 'Custom kbuild commands' sections
kbuild: doc: fix 'List directories to visit when descending' section
kbuild: doc: replace arch/$(ARCH)/ with arch/$(SRCARCH)/
kbuild: doc: update the description about kbuild Makefiles
Makefile.extrawarn: remove -Wnested-externs warning
tweewide: Fix most Shebang lines
$(error-if,...) is expanded to an empty string. Currently, it relies on
eval_clause() returning xstrdup("") when all attempts for expansion fail,
but the correct implementation is to make do_error_if() return xstrdup("").
Fixes: 1d6272e6fe ("kconfig: add 'info', 'warning-if', and 'error-if' built-in functions")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
The C11 _Static_assert() keyword may be used at module scope, and we
need to teach genksyms about it to not abort with an error. We currently
have a growing number of static_assert() (but also direct usage of
_Static_assert()) users at module scope:
git grep -E '^_Static_assert\(|^static_assert\(' | grep -v '^tools' | wc -l
135
More recently, when enabling CONFIG_MODVERSIONS with CONFIG_KCSAN, we
observe a number of warnings:
WARNING: modpost: EXPORT symbol "<..all kcsan symbols..>" [vmlinux] [...]
When running a preprocessed source through 'genksyms -w' a number of
syntax errors point at usage of static_assert()s. In the case of
kernel/kcsan/encoding.h, new static_assert()s had been introduced which
used expressions that appear to cause genksyms to not even be able to
recover from the syntax error gracefully (as it appears was the case
previously).
Therefore, make genksyms ignore all _Static_assert() and the contained
expression. With the fix, usage of _Static_assert() no longer cause
"syntax error" all over the kernel, and the above modpost warnings for
KCSAN are gone, too.
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Using EXPORT_SYMBOL*() on static functions is fundamentally wrong.
Modpost currently reports that as a warning, but clearly this is not a
pattern we should allow, and all in-tree occurences should have been
fixed by now. So, promote the warn() message to error() to make sure
this never happens again.
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Matthias Maennich <maennich@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
There is code that reports static EXPORT_SYMBOL a few lines below.
It is not a good idea to bail out here.
I renamed sec_mismatch_fatal to sec_mismatch_warn_only (with logical
inversion) to match to CONFIG_SECTION_MISMATCH_WARN_ONLY.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Change fatal() to error() to continue running to report more possible
issues.
There is no difference in the fact that modpost will fail anyway.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
We have 3 log functions. fatal() is special because it lets modpost bail
out immediately. The difference between warn() and error() is the only
prefix parts ("WARNING:" vs "ERROR:").
In my understanding, the expected handling of error() is to propagate
the return code of the function to the exit code of modpost, as
check_exports() etc. already does. This is a good manner in general
because we should display as many error messages as possible in a
single run of modpost.
What is annoying about fatal() is that it kills modpost at the first
error. People would need to run Kbuild again and again until they fix
all errors.
But, unfortunately, people tend to do:
"This case should not be allowed. Let's replace warn() with fatal()."
One of the reasons is probably it is tedious to manually hoist the error
code to the main() function.
This commit refactors error() so any single call for it automatically
makes modpost return the error code.
I also added comments in modpost.h for warn(), error(), and fatal().
Please use fatal() only when you have a strong reason to do so.
For example:
- Memory shortage (i.e. malloc() etc. has failed)
- The ELF file is broken, and there is no point to continue parsing
- Something really odd has happened
For general coding errors, please use error().
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Quentin Perret <qperret@google.com>
The log function names, warn(), merror(), fatal() are inconsistent.
Commit 2a11665945 ("kbuild: distinguish between errors and warnings
in modpost") intentionally chose merror() to avoid the conflict with
the library function error(). See man page of error(3).
But, we are already causing the conflict with warn() because it is also
a library function. See man page of warn(3). err() would be a problem
for the same reason.
The common technique to work around name conflicts is to use macros.
For example:
/* in a header */
#define error(fmt, ...) __error(fmt, ##__VA_ARGS__)
#define warn(fmt, ...) __warn(fmt, ##__VA_ARGS__)
/* function definition */
void __error(const char *fmt, ...)
{
<our implementation>
}
void __warn(const char *fmt, ...)
{
<our implementation>
}
In this way, we can implement our own warn() and error(), still we can
include <error.h> and <err.h> with no problem.
And, commit 93c95e526a ("modpost: rework and consolidate logging
interface") already did that.
Since the log functions are all macros, we can use error() without
causing "conflicting types" errors.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Pull gcc-plugins updates from Kees Cook:
- Clean up gcc plugin builds now that GCC must be 4.9+ (Masahiro
Yamada)
- Update MAINTAINERS (Kees Cook)
* tag 'gcc-plugins-v5.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
MAINTAINERS: Drop inactive gcc-plugins maintainer
gcc-plugins: simplify GCC plugin-dev capability test
gcc-plugins: remove code for GCC versions older than 4.9
