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Subject[tip:x86/urgent] bpf: Fix ORC unwinding in non-JIT BPF code
Commit-ID:  b22cf36c189f31883ad0238a69ccf82aa1f3b16b
Gitweb: https://git.kernel.org/tip/b22cf36c189f31883ad0238a69ccf82aa1f3b16b
Author: Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Thu, 27 Jun 2019 20:50:47 -0500
Committer: Thomas Gleixner <tglx@linutronix.de>
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@fb.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kairui Song <kasong@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lkml.kernel.org/r/881939122b88f32be4c374d248c09d7527a87e35.1561685471.git.jpoimboe@redhat.com

---
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 7c473f208a10..45456a796d7f 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) \
\
 
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