From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: x86@kernel.org, Alexei Starovoitov <ast@kernel.org>,
linux-kernel@vger.kernel.org,
Daniel Borkmann <daniel@iogearbox.net>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Song Liu <songliubraving@fb.com>, Kairui Song <kasong@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
David Laight <David.Laight@ACULAB.COM>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v2 2/5] objtool: Fix ORC unwinding in non-JIT BPF generated code
Date: Fri, 14 Jun 2019 13:58:42 -0700 [thread overview]
Message-ID: <20190614205841.s4utbpurntpr6aiq@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <c0add777a2e0207c1474ce99baa492a7ce3502d6.1560534694.git.jpoimboe@redhat.com>
On Fri, Jun 14, 2019 at 12:56:41PM -0500, Josh Poimboeuf wrote:
> Objtool currently ignores ___bpf_prog_run() because it doesn't
> understand the jump table. This results in the ORC unwinder not being
> able to unwind through non-JIT BPF code.
>
> Luckily, the BPF jump table resembles a GCC switch jump table, which
> objtool already knows how to read.
>
> Add generic support for reading any static local jump table array named
> "jump_table", and rename the BPF variable accordingly, so objtool can
> generate ORC data for ___bpf_prog_run().
>
> 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>
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> kernel/bpf/core.c | 5 ++---
> tools/objtool/check.c | 16 ++++++++++++++--
> 2 files changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 7c473f208a10..aa546ef7dbdc 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 *jump_table[256] = {
> [0 ... 255] = &&default_label,
> /* Now overwrite non-defaults ... */
> BPF_INSN_MAP(BPF_INSN_2_LBL, BPF_INSN_3_LBL),
> @@ -1315,7 +1315,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack)
> #define CONT_JMP ({ insn++; goto select_insn; })
>
> select_insn:
> - goto *jumptable[insn->code];
> + goto *jump_table[insn->code];
>
> /* ALU */
> #define ALU(OPCODE, OP) \
> @@ -1558,7 +1558,6 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack)
> 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) \
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 172f99195726..8341c2fff14f 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -18,6 +18,8 @@
>
> #define FAKE_JUMP_OFFSET -1
>
> +#define JUMP_TABLE_SYM_PREFIX "jump_table."
since external tool will be looking at it should it be named
"bpf_jump_table." to avoid potential name conflicts?
Or even more unique name?
Like "bpf_interpreter_jump_table." ?
next prev parent reply other threads:[~2019-06-14 20:58 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-14 17:56 [PATCH v2 0/5] x86/bpf: unwinder fixes Josh Poimboeuf
2019-06-14 17:56 ` [PATCH v2 1/5] perf/x86: Always store regs->ip in perf_callchain_kernel() Josh Poimboeuf
2019-06-14 20:56 ` Alexei Starovoitov
2019-06-14 21:06 ` Josh Poimboeuf
2019-06-14 21:16 ` Steven Rostedt
2019-06-14 21:20 ` Song Liu
2019-06-14 17:56 ` [PATCH v2 2/5] objtool: Fix ORC unwinding in non-JIT BPF generated code Josh Poimboeuf
2019-06-14 20:58 ` Alexei Starovoitov [this message]
2019-06-14 21:07 ` Josh Poimboeuf
2019-06-14 21:09 ` Alexei Starovoitov
2019-06-14 21:19 ` Josh Poimboeuf
2019-06-14 21:22 ` Alexei Starovoitov
2019-06-14 23:17 ` Josh Poimboeuf
2019-06-14 23:30 ` Alexei Starovoitov
2019-06-15 0:02 ` Josh Poimboeuf
2019-06-15 0:06 ` abhja kaanlani
2019-06-15 0:07 ` Alexei Starovoitov
2019-06-17 14:57 ` David Laight
2019-06-14 17:56 ` [PATCH v2 3/5] x86/bpf: Move epilogue generation to a dedicated function Josh Poimboeuf
2019-06-14 17:56 ` [PATCH v2 4/5] x86/bpf: Fix 64-bit JIT frame pointer usage Josh Poimboeuf
2019-06-14 21:05 ` Alexei Starovoitov
2019-06-14 21:19 ` Josh Poimboeuf
2019-06-14 21:27 ` Alexei Starovoitov
2019-06-14 23:13 ` Josh Poimboeuf
2019-06-14 23:23 ` Alexei Starovoitov
2019-06-14 23:54 ` Josh Poimboeuf
2019-06-15 0:02 ` Alexei Starovoitov
2019-06-15 4:27 ` Josh Poimboeuf
2019-06-15 5:16 ` Alexei Starovoitov
2019-06-15 12:57 ` Josh Poimboeuf
2019-06-14 17:56 ` [PATCH v2 5/5] x86/unwind/orc: Fall back to using frame pointers for generated code Josh Poimboeuf
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