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Message-ID: <20201021090817.GU2651@hirez.programming.kicks-ass.net>
Date: Wed, 21 Oct 2020 11:08:17 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>, Jann Horn <jannh@...gle.com>,
the arch/x86 maintainers <x86@...nel.org>,
Masahiro Yamada <masahiroy@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>, Will Deacon <will@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Kees Cook <keescook@...omium.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
clang-built-linux <clang-built-linux@...glegroups.com>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
linux-arch <linux-arch@...r.kernel.org>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
linux-kbuild <linux-kbuild@...r.kernel.org>,
kernel list <linux-kernel@...r.kernel.org>,
linux-pci@...r.kernel.org
Subject: Re: [PATCH v6 22/25] x86/asm: annotate indirect jumps
On Wed, Oct 21, 2020 at 10:56:06AM +0200, Peter Zijlstra wrote:
> The "falls through to next function" seems to be limited to things like:
>
> warning: objtool: setup_vq() falls through to next function setup_vq.cold()
> warning: objtool: e1000_xmit_frame() falls through to next function e1000_xmit_frame.cold()
>
> So something's weird with the .cold thing on vmlinux.o runs.
Shiny, check this:
$ nm defconfig-build/vmlinux.o | grep setup_vq
00000000004d33a0 t setup_vq
00000000004d4c20 t setup_vq
000000000001edcc t setup_vq.cold
000000000001ee31 t setup_vq.cold
00000000004d3dc0 t vp_setup_vq
$ nm defconfig-build/vmlinux.o | grep e1000_xmit_frame
0000000000741490 t e1000_xmit_frame
0000000000763620 t e1000_xmit_frame
000000000002f579 t e1000_xmit_frame.cold
0000000000032b6e t e1000_xmit_frame.cold
$ nm defconfig-build/vmlinux.o | grep e1000_diag_test
000000000074c220 t e1000_diag_test
000000000075eb70 t e1000_diag_test
000000000002fc2a t e1000_diag_test.cold
0000000000030880 t e1000_diag_test.cold
I guess objtool goes sideways when there's multiple symbols with the
same name in a single object file. This obvously never happens on single
TU .o files.
Not sure what to do about that.
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