linux-kernel - Re: [PATCH 2/2] objtool: Improve call destination function detection

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Message-ID: <20200218195838.GA8061@ubuntu-m2-xlarge-x86>
Date:   Tue, 18 Feb 2020 12:58:38 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH 2/2] objtool: Improve call destination function detection

On Mon, Feb 17, 2020 at 09:41:54PM -0600, Josh Poimboeuf wrote:
> A recent clang change, combined with a binutils bug, can trigger a
> situation where a ".Lprintk$local" STT_NOTYPE symbol gets created at the
> same offset as the "printk" STT_FUNC symbol.  This confuses objtool:
> 
>   kernel/printk/printk.o: warning: objtool: ignore_loglevel_setup()+0x10: can't find call dest symbol at .text+0xc67
> 
> Improve the call destination detection by looking specifically for an
> STT_FUNC symbol.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/872
> Link: https://sourceware.org/bugzilla/show_bug.cgi?id=25551
> Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>

Tested with clang-11 and binutils 2.34, a combo that was previously
broken and I no longer see these warnings on either defconfig or
allyesconfig.

Tested-by: Nathan Chancellor <natechancellor@...il.com>