I wonder if clang folks have seen this and perhaps have a comment as to
why the volatile gets ingored... Added.
On Wed, Dec 22, 2021 at 09:10:30AM -0000, tip-bot2 for Josh Poimboeuf wrote:
> The following commit has been merged into the objtool/urgent branch of tip:
>
> Commit-ID: dcce50e6cc4d86a63dc0a9a6ee7d4f948ccd53a1
> Gitweb: https://git.kernel.org/tip/dcce50e6cc4d86a63dc0a9a6ee7d4f948ccd53a1
> Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> AuthorDate: Mon, 08 Nov 2021 14:35:59 -08:00
> Committer: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> CommitterDate: Tue, 21 Dec 2021 15:09:46 -08:00
>
> compiler.h: Fix annotation macro misplacement with Clang
>
> When building with Clang and CONFIG_TRACE_BRANCH_PROFILING, there are a
> lot of unreachable warnings, like:
>
> arch/x86/kernel/traps.o: warning: objtool: handle_xfd_event()+0x134: unreachable instruction
>
> Without an input to the inline asm, 'volatile' is ignored for some
> reason and Clang feels free to move the reachable() annotation away from
> its intended location.
>
> Fix that by re-adding the counter value to the inputs.
>
> Fixes: f1069a8756b9 ("compiler.h: Avoid using inline asm operand modifiers")
> Fixes: c199f64ff93c ("instrumentation.h: Avoid using inline asm operand modifiers")
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/0417e96909b97a406323409210de7bf13df0b170.1636410380.git.jpoimboe@xxxxxxxxxx
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: x86@xxxxxxxxxx
> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
> Cc: Miroslav Benes <mbenes@xxxxxxx>
> ---
> include/linux/compiler.h | 4 ++--
> include/linux/instrumentation.h | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 3d5af56..429dceb 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -121,7 +121,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
> asm volatile(__stringify_label(c) ":\n\t" \
> ".pushsection .discard.reachable\n\t" \
> ".long " __stringify_label(c) "b - .\n\t" \
> - ".popsection\n\t"); \
> + ".popsection\n\t" : : "i" (c)); \
> })
> #define annotate_reachable() __annotate_reachable(__COUNTER__)
>
> @@ -129,7 +129,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
> asm volatile(__stringify_label(c) ":\n\t" \
> ".pushsection .discard.unreachable\n\t" \
> ".long " __stringify_label(c) "b - .\n\t" \
> - ".popsection\n\t"); \
> + ".popsection\n\t" : : "i" (c)); \
> })
> #define annotate_unreachable() __annotate_unreachable(__COUNTER__)
>
> diff --git a/include/linux/instrumentation.h b/include/linux/instrumentation.h
> index fa2cd8c..24359b4 100644
> --- a/include/linux/instrumentation.h
> +++ b/include/linux/instrumentation.h
> @@ -11,7 +11,7 @@
> asm volatile(__stringify(c) ": nop\n\t" \
> ".pushsection .discard.instr_begin\n\t" \
> ".long " __stringify(c) "b - .\n\t" \
> - ".popsection\n\t"); \
> + ".popsection\n\t" : : "i" (c)); \
> })
> #define instrumentation_begin() __instrumentation_begin(__COUNTER__)
>
> @@ -50,7 +50,7 @@
> asm volatile(__stringify(c) ": nop\n\t" \
> ".pushsection .discard.instr_end\n\t" \
> ".long " __stringify(c) "b - .\n\t" \
> - ".popsection\n\t"); \
> + ".popsection\n\t" : : "i" (c)); \
> })
> #define instrumentation_end() __instrumentation_end(__COUNTER__)
> #else
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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