linux-kernel - Re: [PATCH v4 2/2] bpf: Fix ORC unwinding in non-JIT BPF code

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Message-ID: <CAADnVQ+tMk9B3S=OfsaNiKNpMv0x-AmqMTxdh=Av+DN8_ZEo7w@mail.gmail.com>
Date:   Fri, 28 Jun 2019 08:37:01 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Song Liu <songliubraving@...com>,
        Kairui Song <kasong@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH v4 2/2] bpf: Fix ORC unwinding in non-JIT BPF code

On Thu, Jun 27, 2019 at 6:51 PM Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> Objtool previously ignored ___bpf_prog_run() because it didn't
> understand the jump table.  This resulted in the ORC unwinder not being
> able to unwind through non-JIT BPF code.
>
> Now that objtool knows how to read jump tables, remove the whitelist and
> annotate the jump table so objtool can recognize it.
>
> Also add an additional "const" to the jump table definition to clarify
> that the text pointers are constant.  Otherwise GCC sets the section
> writable flag and the assembler spits out warnings.
>
> Fixes: d15d356887e7 ("perf/x86: Make perf callchains work without CONFIG_FRAME_POINTER")
> Reported-by: Song Liu <songliubraving@...com>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>

I'm traveling atm, but the set looks good.
Acked-by: Alexei Starovoitov <ast@...nel.org>

If tip maintainers can route it to Linus quickly then
please send the whole thing via tip tree.
Or we can send these two patches via bpf tree early next week.