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Date: Wed, 21 Oct 2020 11:51:33 +0200
From: Peter Zijlstra <>
To: Josh Poimboeuf <>
Cc: Sami Tolvanen <>, Jann Horn <>,
	the arch/x86 maintainers <>,
	Masahiro Yamada <>,
	Steven Rostedt <>, Will Deacon <>,
	Greg Kroah-Hartman <>,
	"Paul E. McKenney" <>,
	Kees Cook <>,
	Nick Desaulniers <>,
	clang-built-linux <>,
	Kernel Hardening <>,
	linux-arch <>,
	Linux ARM <>,
	linux-kbuild <>,
	kernel list <>,
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

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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