Re: [PATCH] powerpc: Fail build if using recordmcount with binutils v2.37
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2023-05-30 00:02:04
Naveen N Rao [off-list ref] writes:
quoted hunk ↗ jump to hunk
binutils v2.37 drops unused section symbols, which prevents recordmcount from capturing mcount locations in sections that have no non-weak symbols. This results in a build failure with a message such as: Cannot find symbol for section 12: .text.perf_callchain_kernel. kernel/events/callchain.o: failed The change to binutils was reverted for v2.38, so this behavior is specific to binutils v2.37: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=c09c8b42021180eee9495bd50d8b35e683d3901b Objtool is able to cope with such sections, so this issue is specific to recordmcount. Fail the build and print a warning if binutils v2.37 is detected and if we are using recordmcount. Cc: stable@vger.kernel.org Suggested-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Naveen N Rao <naveen@kernel.org> --- arch/powerpc/Makefile | 8 ++++++++ 1 file changed, 8 insertions(+)diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile index dca73f673d7046..f0540c1f1377c8 100644 --- a/arch/powerpc/Makefile +++ b/arch/powerpc/Makefile@@ -409,3 +409,11 @@ checkbin: echo -n '*** Please use a different binutils version.' ; \ false ; \ fi + @if test "x${CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT}" = "xy" -a \ + "x${CONFIG_LD_IS_BFD}" = "xy" -a \ + "x$(call ld-ifversion, -eq, 23700, y)" = "xy" ; then \ + echo -n '*** binutils 2.37 drops unused section symbols, which recordmcount ' ; \ + echo 'is unable to handle.' ; \ + echo '*** Please use a different binutils version.' ; \ + false ; \ + fi
Thanks for doing this. Masahiro wanted to remove ld-ifversion, he suggested to just check CONFIG_LD_VERSION directly instead. Mind doing a v2 with that change? https://lore.kernel.org/all/CAK7LNAQWtDHOs=K+qznt5U1WiDv86tChkj4zOer4wtVRB974OA@mail.gmail.com/ (local) cheers