From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752708AbcAUWxZ (ORCPT ); Thu, 21 Jan 2016 17:53:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59999 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752342AbcAUWvl (ORCPT ); Thu, 21 Jan 2016 17:51:41 -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 , Alexei Starovoitov , netdev@vger.kernel.org Subject: [PATCH 31/33] bpf: Add __bpf_prog_run() to stacktool whitelist Date: Thu, 21 Jan 2016 16:49:35 -0600 Message-Id: <8ee01c195432e4c1ebaa79c20e91525c7af22384.1453405861.git.jpoimboe@redhat.com> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org stacktool reports the following false positive warnings: stacktool: kernel/bpf/core.o: __bpf_prog_run()+0x5c: sibling call from callable instruction with changed frame pointer stacktool: kernel/bpf/core.o: __bpf_prog_run()+0x60: function has unreachable instruction stacktool: kernel/bpf/core.o: __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 stacktool 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 Cc: 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..7108a96 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; } +STACKTOOL_IGNORE_FUNC(__bpf_prog_run); bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp) -- 2.4.3