FROMGIT: module: Ignore _GLOBAL_OFFSET_TABLE_ when warning for undefined symbols
clang-12 -fno-pic (since
https://github.com/llvm/llvm-project/commit/a084c0388e2a59b9556f2de0083333232da3f1d6)
can emit `call __stack_chk_fail@PLT` instead of `call __stack_chk_fail`
on x86. The two forms should have identical behaviors on x86-64 but the
former causes GNU as<2.37 to produce an unreferenced undefined symbol
_GLOBAL_OFFSET_TABLE_.
(On x86-32, there is an R_386_PC32 vs R_386_PLT32 difference but the
linker behavior is identical as far as Linux kernel is concerned.)
Simply ignore _GLOBAL_OFFSET_TABLE_ for now, like what
scripts/mod/modpost.c:ignore_undef_symbol does. This also fixes the
problem for gcc/clang -fpie and -fpic, which may emit `call foo@PLT` for
external function calls on x86.
Note: ld -z defs and dynamic loaders do not error for unreferenced
undefined symbols so the module loader is reading too much. If we ever
need to ignore more symbols, the code should be refactored to ignore
unreferenced symbols.
Cc: <stable@vger.kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/1250
Link: https://sourceware.org/bugzilla/show_bug.cgi?id=27178
Reported-by: Marco Elver <elver@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Tested-by: Marco Elver <elver@google.com>
Signed-off-by: Fangrui Song <maskray@google.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
(cherry picked from commit ebfac7b778fac8b0e8e92ec91d0b055f046b4604 https://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux.git modules-next)
BUG=chromium:1171076
TEST=amd64-generic 4.14 vm boots
Signed-off-by: Manoj Gupta <manojgupta@google.com>
Change-Id: I5510947f9fc2c53736caecaae1cff30aff9d1fb5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2660767
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
Auto-Submit: Manoj Gupta <manojgupta@chromium.org>
Commit-Queue: Guenter Roeck <groeck@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2665098
Reviewed-by: Tomasz Jeznach <tjeznach@chromium.org>
Commit-Queue: Tomasz Jeznach <tjeznach@chromium.org>
1 file changed
