Re: [tip:x86/urgent] bpf: Fix ORC unwinding in non-JIT BPF code

[Ingo Molnar]

* tip-bot for Josh Poimboeuf <tipbot@xxxxxxxxx> wrote:

> Commit-ID:  b22cf36c189f31883ad0238a69ccf82aa1f3b16b
> Gitweb:     https://git.kernel.org/tip/b22cf36c189f31883ad0238a69ccf82aa1f3b16b
> Author:     Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> AuthorDate: Thu, 27 Jun 2019 20:50:47 -0500
> Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> CommitDate: Sat, 29 Jun 2019 07:55:14 +0200
> 
> bpf: Fix ORC unwinding in non-JIT BPF code
> 
> 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@xxxxxx>
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Acked-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Kairui Song <kasong@xxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Link: https://lkml.kernel.org/r/881939122b88f32be4c374d248c09d7527a87e35.1561685471.git.jpoimboe@xxxxxxxxxx
> 
> ---
>  kernel/bpf/core.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)

Hm, I get this new build warning on x86-64 defconfig-ish kernels plus 
these enabled:

 CONFIG_BPF=y
 CONFIG_BPF_JIT=y

kernel/bpf/core.o: warning: objtool: ___bpf_prog_run()+0x8da: sibling call from callable instruction with modified stack frame

Thanks,

	Ingo