From: Michael Ellerman <mpe@ellerman.id.au>
To: Naveen N Rao <naveen@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org, Joel Stanley <joel@jms.id.au>,
Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH] powerpc: Fail build if using recordmcount with binutils v2.37
Date: Tue, 30 May 2023 10:00:57 +1000 [thread overview]
Message-ID: <877csqu1qe.fsf@mail.lhotse> (raw)
In-Reply-To: <20230529134512.51749-1-naveen@kernel.org>
Naveen N Rao <naveen@kernel.org> writes:
> 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/
cheers
next prev parent reply other threads:[~2023-05-30 0:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-29 13:45 [PATCH] powerpc: Fail build if using recordmcount with binutils v2.37 Naveen N Rao
2023-05-30 0:00 ` Michael Ellerman [this message]
2023-05-30 6:18 ` Naveen N Rao
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