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Date: Wed, 21 Oct 2020 11:51:33 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Sami Tolvanen <samitolvanen@...gle.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 Tue, Oct 20, 2020 at 01:52:17PM -0500, Josh Poimboeuf wrote:
> > arch/x86/lib/retpoline.S:
> > __x86_retpoline_rdi()+0x10: return with modified stack frame
> > __x86_retpoline_rdi()+0x0: stack state mismatch: cfa1=7+32 cfa2=7+8
> > __x86_retpoline_rdi()+0x0: stack state mismatch: cfa1=7+32 cfa2=-1+0
>
> Is this with upstream? I thought we fixed that with
> UNWIND_HINT_RET_OFFSET.
I can't reproduce this one either; but I do get different warnings:
gcc (Debian 10.2.0-13) 10.2.0, x86_64-defconfig:
defconfig-build/vmlinux.o: warning: objtool: __x86_indirect_thunk_rax() falls through to next function __x86_retpoline_rax()
defconfig-build/vmlinux.o: warning: objtool: .altinstr_replacement+0x1063: (branch)
defconfig-build/vmlinux.o: warning: objtool: __x86_indirect_thunk_rax()+0x0: (alt)
defconfig-build/vmlinux.o: warning: objtool: __x86_indirect_thunk_rax()+0x0: <=== (sym)
(for every single register, not just rax)
Which is daft as well, because the retpoline.o run is clean. It also
doesn't make sense because __x86_retpoline_rax isn't in fact STT_FUNC,
so WTH ?!
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