netdev - Re: [PATCH 2/2] x86/cfi,bpf: Fix BPF JIT call

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Message-ID: <CABCJKufBiJjUdmnuy=HkV+dDnZ=xne-OBwPSfJ21RX9c0AzCZw@mail.gmail.com>
Date: Fri, 1 Dec 2023 15:54:13 -0800
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, paul.walmsley@...ive.com, 
	palmer@...belt.com, aou@...s.berkeley.edu, tglx@...utronix.de, 
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org, 
	hpa@...or.com, davem@...emloft.net, dsahern@...nel.org, ast@...nel.org, 
	daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev, 
	song@...nel.org, yonghong.song@...ux.dev, john.fastabend@...il.com, 
	kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org, 
	Arnd Bergmann <arnd@...db.de>, keescook@...omium.org, nathan@...nel.org, 
	ndesaulniers@...gle.com, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, bpf@...r.kernel.org, 
	linux-arch@...r.kernel.org, llvm@...ts.linux.dev, jpoimboe@...nel.org, 
	joao@...rdrivepizza.com, mark.rutland@....com
Subject: Re: [PATCH 2/2] x86/cfi,bpf: Fix BPF JIT call

On Wed, Nov 22, 2023 at 3:15 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> So the kCFI thing is 'new' but readily inspected by objdump or godbolt:
>
>   https://godbolt.org/z/sGe18z3ca
>
> (@Sami, that .Ltmp15 thing, I don't see that in the kernel, what
> compiler flag makes that go away?)

Hmm, that looks like that's what we emit to .kcfi_traps. I suppose
Godbolt just doesn't show the section directives?

https://github.com/llvm/llvm-project/blob/main/llvm/test/CodeGen/X86/kcfi.ll#L30

Sami