From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759659AbcB2EYb (ORCPT ); Sun, 28 Feb 2016 23:24:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41886 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755246AbcB2EY2 (ORCPT ); Sun, 28 Feb 2016 23:24:28 -0500 From: Josh Poimboeuf To: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org Cc: linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, Michal Marek , Peter Zijlstra , Andy Lutomirski , Borislav Petkov , Linus Torvalds , Andi Kleen , Pedro Alves , Namhyung Kim , Bernd Petrovitsch , Chris J Arges , Andrew Morton , Jiri Slaby , Arnaldo Carvalho de Melo , Daniel Borkmann , Alexei Starovoitov , netdev@vger.kernel.org Subject: [PATCH v19 04/10] bpf: Mark __bpf_prog_run() stack frame as non-standard Date: Sun, 28 Feb 2016 22:22:37 -0600 Message-Id: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org objtool reports the following false positive warnings: kernel/bpf/core.o: warning: objtool: __bpf_prog_run()+0x5c: sibling call from callable instruction with changed frame pointer kernel/bpf/core.o: warning: objtool: __bpf_prog_run()+0x60: function has unreachable instruction kernel/bpf/core.o: warning: objtool: __bpf_prog_run()+0x64: function has unreachable instruction [...] It's confused by the following dynamic jump instruction in __bpf_prog_run():: jmp *(%r12,%rax,8) which corresponds to the following line in the C code: goto *jumptable[insn->code]; There's no way for objtool to deterministically find all possible branch targets for a dynamic jump, so it can't verify this code. In this case the jumps all stay within the function, and there's nothing unusual going on related to the stack, so we can whitelist the function. Signed-off-by: Josh Poimboeuf Acked-by: Daniel Borkmann Acked-by: Alexei Starovoitov Cc: netdev@vger.kernel.org --- kernel/bpf/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 972d9a8..be0abf6 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -27,6 +27,7 @@ #include #include #include +#include #include @@ -649,6 +650,7 @@ load_byte: WARN_RATELIMIT(1, "unknown opcode %02x\n", insn->code); return 0; } +STACK_FRAME_NON_STANDARD(__bpf_prog_run); /* jump table */ bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp) -- 2.4.3