linux-kernel - [tip:x86/debug] bpf: Fix ORC unwinding in non-JIT BPF code

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Message-ID: <tip-e55a73251da335873a6e87d68fb17e5aabb8978e@git.kernel.org>
Date:   Tue, 9 Jul 2019 05:02:05 -0700
From:   tip-bot for Josh Poimboeuf <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     ast@...nel.org, hpa@...or.com, rostedt@...dmis.org,
        jpoimboe@...hat.com, kasong@...hat.com, mingo@...nel.org,
        peterz@...radead.org, bp@...en8.de, songliubraving@...com,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        daniel@...earbox.net
Subject: [tip:x86/debug] bpf: Fix ORC unwinding in non-JIT BPF code

Commit-ID:  e55a73251da335873a6e87d68fb17e5aabb8978e
Gitweb:     https://git.kernel.org/tip/e55a73251da335873a6e87d68fb17e5aabb8978e
Author:     Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Thu, 27 Jun 2019 20:50:47 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 9 Jul 2019 13:55:57 +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@...com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Alexei Starovoitov <ast@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Kairui Song <kasong@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Daniel Borkmann <daniel@...earbox.net>
Link: https://lkml.kernel.org/r/881939122b88f32be4c374d248c09d7527a87e35.1561685471.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/bpf/core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 080e2bb644cc..1e12ac382a90 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1299,7 +1299,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack)
 {
 #define BPF_INSN_2_LBL(x, y)    [BPF_##x | BPF_##y] = &&x##_##y
 #define BPF_INSN_3_LBL(x, y, z) [BPF_##x | BPF_##y | BPF_##z] = &&x##_##y##_##z
-	static const void *jumptable[256] = {
+	static const void * const jumptable[256] __annotate_jump_table = {
 		[0 ... 255] = &&default_label,
 		/* Now overwrite non-defaults ... */
 		BPF_INSN_MAP(BPF_INSN_2_LBL, BPF_INSN_3_LBL),
@@ -1558,7 +1558,6 @@ out:
 		BUG_ON(1);
 		return 0;
 }
-STACK_FRAME_NON_STANDARD(___bpf_prog_run); /* jump table */
 
 #define PROG_NAME(stack_size) __bpf_prog_run##stack_size
 #define DEFINE_BPF_PROG_RUN(stack_size) \