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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] objtool: support '-mtune=atom' stack frame setup instruction
Date: Mon, 10 Oct 2016 20:53:07 -0500	[thread overview]
Message-ID: <20161011015307.su5oe4ki4otddrb6@treble> (raw)
In-Reply-To: <20161010125709.1870563-1-arnd@arndb.de>


>From 60c982d4d04014adb3bde1ebee6ca95320ffb213 Mon Sep 17 00:00:00 2001
Message-Id: <60c982d4d04014adb3bde1ebee6ca95320ffb213.1476150736.git.jpoimboe@redhat.com>
From: Josh Poimboeuf <jpoimboe@redhat.com>
Date: Mon, 10 Oct 2016 15:24:01 -0500
Subject: [PATCH] objtool: support '-mtune=atom' stack frame setup instruction

Arnd reported that enabling CONFIG_MATOM results in a bunch of objtool
false positive frame pointer warnings:

  arch/x86/events/intel/ds.o: warning: objtool: intel_pmu_pebs_del()+0x43: call without frame pointer save/setup
  security/keys/keyring.o: warning: objtool: keyring_read()+0x59: call without frame pointer save/setup
  kernel/signal.o: warning: objtool: __dequeue_signal()+0xd8: call without frame pointer save/setup
  ...

objtool gets confused by the fact that the '-mtune=atom' gcc option
sometimes uses 'lea (%rsp),%rbp' instead of 'mov %rsp,%rbp'.  The
instructions are effectively the same, but objtool doesn't know about
the 'lea' variant.

Fix the false warnings by adding support for 'lea (%rsp),%rbp' in the
objtool decoder.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 tools/objtool/arch/x86/decode.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index c0c0b26..b63a31b 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -98,6 +98,15 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
 			*type = INSN_FP_SETUP;
 		break;
 
+	case 0x8d:
+		if (insn.rex_prefix.bytes &&
+		    insn.rex_prefix.bytes[0] == 0x48 &&
+		    insn.modrm.nbytes && insn.modrm.bytes[0] == 0x2c &&
+		    insn.sib.nbytes && insn.sib.bytes[0] == 0x24)
+			/* lea %(rsp), %rbp */
+			*type = INSN_FP_SETUP;
+		break;
+
 	case 0x90:
 		*type = INSN_NOP;
 		break;
-- 
2.7.4

      parent reply	other threads:[~2016-10-11  1:53 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-10 12:56 [PATCH] [RFC] x86: avoid -mtune=atom for objtool warnings Arnd Bergmann
2016-10-10 20:23 ` Josh Poimboeuf
2016-10-11  8:08   ` Arnd Bergmann
2016-10-11 12:20     ` Josh Poimboeuf
2016-10-11 13:30       ` Arnd Bergmann
2016-10-11 15:05         ` Josh Poimboeuf
2016-10-11 15:51           ` Josh Poimboeuf
2016-10-11 20:38             ` Arnd Bergmann
2016-10-12 13:01               ` Josh Poimboeuf
2016-10-13 12:46               ` Another gcc corruption bug (was Re: [PATCH] [RFC] x86: avoid -mtune=atom for objtool warnings) Josh Poimboeuf
2016-10-13 17:57                 ` Denys Vlasenko
2016-10-13 20:15                   ` Josh Poimboeuf
2017-03-01  9:34               ` [PATCH] [RFC] x86: avoid -mtune=atom for objtool warnings Arnd Bergmann
2017-03-01  9:45                 ` Arnd Bergmann
2017-03-01 14:40                   ` Josh Poimboeuf
2017-03-01 15:27                     ` Arnd Bergmann
2017-03-01 16:53                       ` Josh Poimboeuf
2017-03-01 22:05                         ` Arnd Bergmann
2017-03-01 22:42                         ` Arnd Bergmann
2017-03-02  1:03                           ` Josh Poimboeuf
2017-03-02  6:31                             ` Ingo Molnar
2017-03-02 12:49                               ` Josh Poimboeuf
2017-03-02 13:46                                 ` Ingo Molnar
2017-03-02 14:08                                   ` Josh Poimboeuf
2017-03-02 14:46                                     ` Ingo Molnar
2017-03-02 22:49                             ` Arnd Bergmann
2017-03-02 23:05                               ` Josh Poimboeuf
2017-03-03  8:58                                 ` Arnd Bergmann
2017-03-03 11:27                                   ` Arnd Bergmann
2017-03-01 14:31                 ` Josh Poimboeuf
2017-03-01 15:21                   ` Arnd Bergmann
2017-03-02 18:25                     ` Josh Poimboeuf
2017-03-02 22:43                       ` Arnd Bergmann
2017-03-02 22:57                         ` [PATCH] objtool: fix another gcc jump table detection issue Josh Poimboeuf
2017-03-02 23:01                           ` Arnd Bergmann
2016-10-11  1:53 ` Josh Poimboeuf [this message]

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