From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756170AbcCCAlF (ORCPT ); Wed, 2 Mar 2016 19:41:05 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33968 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755469AbcCCAlC (ORCPT ); Wed, 2 Mar 2016 19:41:02 -0500 From: Josh Poimboeuf To: Ingo Molnar Cc: x86@kernel.org, linux-kernel@vger.kernel.org, Stephen Rothwell , Masami Hiramatsu , Adrian Hunter , Michael Ellerman , Peter Zijlstra , Thomas Gleixner , "H. Peter Anvin" Subject: [PATCH 1/2] x86/asm/decoder: Use explicitly signed chars Date: Wed, 2 Mar 2016 18:39:36 -0600 Message-Id: <9dd4161719b20e6def9564646d68bfbe498c549f.1456962210.git.jpoimboe@redhat.com> In-Reply-To: References: <20160303092134.7c750589@canb.auug.org.au> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 03 Mar 2016 00:41:01 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When running objtool on a ppc64le host to analyze x86 binaries, it reports a lot of false warnings like: ipc/compat_mq.o: warning: objtool: compat_SyS_mq_open()+0x91: can't find jump dest instruction at .text+0x3a5 The warnings are caused by the x86 instruction decoder setting the wrong value for the jump instruction's immediate field because it assumes that "char == signed char", which isn't true for all architectures. When converting char to int, gcc sign-extends on x86 but doesn't sign-extend on ppc64le. According to the gcc man page, that's a feature, not a bug: > Each kind of machine has a default for what "char" should be. It is > either like "unsigned char" by default or like "signed char" by > default. > > Ideally, a portable program should always use "signed char" or > "unsigned char" when it depends on the signedness of an object. Conform to the "standards" by changing the "char" casts to "signed char". This results in no actual changes to the object code on x86. Note: the x86 decoder now lives in three different locations in the kernel tree, which are all kept in sync via makefile checks and warnings: in-kernel, perf, and objtool. This fixes all three locations. Eventually we should probably try to at least converge the two separate "tools" locations into a single shared location. Signed-off-by: Josh Poimboeuf --- arch/x86/lib/insn.c | 6 +++--- tools/objtool/arch/x86/insn/insn.c | 6 +++--- tools/perf/util/intel-pt-decoder/insn.c | 6 +++--- 3 files changed, 9 insertions(+), 9 deletions(-) diff --git a/arch/x86/lib/insn.c b/arch/x86/lib/insn.c index 8f72b33..1a41693 100644 --- a/arch/x86/lib/insn.c +++ b/arch/x86/lib/insn.c @@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn) if (mod == 3) goto out; if (mod == 1) { - insn->displacement.value = get_next(char, insn); + insn->displacement.value = get_next(signed char, insn); insn->displacement.nbytes = 1; } else if (insn->addr_bytes == 2) { if ((mod == 0 && rm == 6) || mod == 2) { @@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn) switch (inat_immediate_size(insn->attr)) { case INAT_IMM_BYTE: - insn->immediate.value = get_next(char, insn); + insn->immediate.value = get_next(signed char, insn); insn->immediate.nbytes = 1; break; case INAT_IMM_WORD: @@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn) goto err_out; } if (inat_has_second_immediate(insn->attr)) { - insn->immediate2.value = get_next(char, insn); + insn->immediate2.value = get_next(signed char, insn); insn->immediate2.nbytes = 1; } done: diff --git a/tools/objtool/arch/x86/insn/insn.c b/tools/objtool/arch/x86/insn/insn.c index 47314a6..9f26eae 100644 --- a/tools/objtool/arch/x86/insn/insn.c +++ b/tools/objtool/arch/x86/insn/insn.c @@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn) if (mod == 3) goto out; if (mod == 1) { - insn->displacement.value = get_next(char, insn); + insn->displacement.value = get_next(signed char, insn); insn->displacement.nbytes = 1; } else if (insn->addr_bytes == 2) { if ((mod == 0 && rm == 6) || mod == 2) { @@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn) switch (inat_immediate_size(insn->attr)) { case INAT_IMM_BYTE: - insn->immediate.value = get_next(char, insn); + insn->immediate.value = get_next(signed char, insn); insn->immediate.nbytes = 1; break; case INAT_IMM_WORD: @@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn) goto err_out; } if (inat_has_second_immediate(insn->attr)) { - insn->immediate2.value = get_next(char, insn); + insn->immediate2.value = get_next(signed char, insn); insn->immediate2.nbytes = 1; } done: diff --git a/tools/perf/util/intel-pt-decoder/insn.c b/tools/perf/util/intel-pt-decoder/insn.c index 47314a6..9f26eae 100644 --- a/tools/perf/util/intel-pt-decoder/insn.c +++ b/tools/perf/util/intel-pt-decoder/insn.c @@ -374,7 +374,7 @@ void insn_get_displacement(struct insn *insn) if (mod == 3) goto out; if (mod == 1) { - insn->displacement.value = get_next(char, insn); + insn->displacement.value = get_next(signed char, insn); insn->displacement.nbytes = 1; } else if (insn->addr_bytes == 2) { if ((mod == 0 && rm == 6) || mod == 2) { @@ -532,7 +532,7 @@ void insn_get_immediate(struct insn *insn) switch (inat_immediate_size(insn->attr)) { case INAT_IMM_BYTE: - insn->immediate.value = get_next(char, insn); + insn->immediate.value = get_next(signed char, insn); insn->immediate.nbytes = 1; break; case INAT_IMM_WORD: @@ -566,7 +566,7 @@ void insn_get_immediate(struct insn *insn) goto err_out; } if (inat_has_second_immediate(insn->attr)) { - insn->immediate2.value = get_next(char, insn); + insn->immediate2.value = get_next(signed char, insn); insn->immediate2.nbytes = 1; } done: -- 2.4.3