| Message ID | 20190111190538.6744-1-paul.burton@mips.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] kbuild: Disable LD_DEAD_CODE_DATA_ELIMINATION with ftrace & GCC <= 4.7 | expand |
On Sat, Jan 12, 2019 at 6:00 AM Paul Burton <paul.burton@mips.com> wrote: > > When building using GCC 4.7 or older, -ffunction-sections & the -pg flag > used by ftrace are incompatible. This causes warnings or build failures > (where -Werror applies) such as the following: > > arch/mips/generic/init.c: > error: -ffunction-sections disabled; it makes profiling impossible > > This used to be taken into account by the ordering of calls to cc-option > from within the top-level Makefile, which was introduced by commit > 90ad4052e85c ("kbuild: avoid conflict between -ffunction-sections and > -pg on gcc-4.7"). Unfortunately this was broken when the > CONFIG_LD_DEAD_CODE_DATA_ELIMINATION cc-option check was moved to > Kconfig in commit e85d1d65cd8a ("kbuild: test dead code/data elimination > support in Kconfig"), because the flags used by this check no longer > include -pg. > > Fix this by not allowing CONFIG_LD_DEAD_CODE_DATA_ELIMINATION to be > enabled at the same time as ftrace/CONFIG_FUNCTION_TRACER when building > using GCC 4.7 or older. > > Signed-off-by: Paul Burton <paul.burton@mips.com> > Fixes: e85d1d65cd8a ("kbuild: test dead code/data elimination support in Kconfig") > Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> > Cc: Masahiro Yamada <yamada.masahiro@socionext.com> > Cc: Nicholas Piggin <npiggin@gmail.com> > Cc: stable@vger.kernel.org # v4.19+ > Cc: linux-kbuild@vger.kernel.org > Cc: linux-mips@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > --- > Changes in v2: > - Invert the dependency as Masahiro suggested. Applied to linux-kbuild/fixes. Thanks!
diff --git a/init/Kconfig b/init/Kconfig index d47cb77a220e..513fa544a134 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1124,6 +1124,7 @@ config LD_DEAD_CODE_DATA_ELIMINATION bool "Dead code and data elimination (EXPERIMENTAL)" depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION depends on EXPERT + depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800) depends on $(cc-option,-ffunction-sections -fdata-sections) depends on $(ld-option,--gc-sections) help
When building using GCC 4.7 or older, -ffunction-sections & the -pg flag used by ftrace are incompatible. This causes warnings or build failures (where -Werror applies) such as the following: arch/mips/generic/init.c: error: -ffunction-sections disabled; it makes profiling impossible This used to be taken into account by the ordering of calls to cc-option from within the top-level Makefile, which was introduced by commit 90ad4052e85c ("kbuild: avoid conflict between -ffunction-sections and -pg on gcc-4.7"). Unfortunately this was broken when the CONFIG_LD_DEAD_CODE_DATA_ELIMINATION cc-option check was moved to Kconfig in commit e85d1d65cd8a ("kbuild: test dead code/data elimination support in Kconfig"), because the flags used by this check no longer include -pg. Fix this by not allowing CONFIG_LD_DEAD_CODE_DATA_ELIMINATION to be enabled at the same time as ftrace/CONFIG_FUNCTION_TRACER when building using GCC 4.7 or older. Signed-off-by: Paul Burton <paul.burton@mips.com> Fixes: e85d1d65cd8a ("kbuild: test dead code/data elimination support in Kconfig") Reported-by: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: stable@vger.kernel.org # v4.19+ Cc: linux-kbuild@vger.kernel.org Cc: linux-mips@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- Changes in v2: - Invert the dependency as Masahiro suggested. --- init/Kconfig | 1 + 1 file changed, 1 insertion(+)