From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758063Ab2GMToS (ORCPT ); Fri, 13 Jul 2012 15:44:18 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:2048 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753190Ab2GMToQ (ORCPT ); Fri, 13 Jul 2012 15:44:16 -0400 X-Authority-Analysis: v=2.0 cv=AtpsLZBP c=1 sm=0 a=s5Htg7xnQOKvHEu9STBOug==:17 a=OpT9cpI26MMA:10 a=m_VzdanGAVkA:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=meVymXHHAAAA:8 a=ayC55rCoAAAA:8 a=PSFjnz9KlFBXcQplrC8A:9 a=PUjeQqilurYA:10 a=jeBq3FmKZ4MA:10 a=s5Htg7xnQOKvHEu9STBOug==:117 X-Cloudmark-Score: 0 X-Originating-IP: 72.230.195.127 Message-ID: <1342208654.30075.22.camel@gandalf.stny.rr.com> Subject: [RFC][PATCH] x86_32: Return actual stack when requesting sp from regs From: Steven Rostedt To: LKML Cc: Masami Hiramatsu , Ingo Molnar , Andrew Morton , "H. Peter Anvin" , stable Date: Fri, 13 Jul 2012 15:44:14 -0400 Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.4.3 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As x86_32 traps do not save sp when taken in kernel mode, we need to accommodate the sp when requesting to get the register. This affects kprobes. Before: # echo 'p:ftrace sys_read+4 s=%sp' > /debug/tracing/kprobe_events # echo 1 > /debug/tracing/events/kprobes/enable # cat trace sshd-1345 [000] d... 489.117168: ftrace: (sys_read+0x4/0x70) s=b7e96768 sshd-1345 [000] d... 489.117191: ftrace: (sys_read+0x4/0x70) s=b7e96768 cat-1447 [000] d... 489.117392: ftrace: (sys_read+0x4/0x70) s=5a7 cat-1447 [001] d... 489.118023: ftrace: (sys_read+0x4/0x70) s=b77ad05f less-1448 [000] d... 489.118079: ftrace: (sys_read+0x4/0x70) s=b7762e06 less-1448 [000] d... 489.118117: ftrace: (sys_read+0x4/0x70) s=b7764970 After: sshd-1352 [000] d... 362.348016: ftrace: (sys_read+0x4/0x70) s=f3febfa8 sshd-1352 [000] d... 362.348048: ftrace: (sys_read+0x4/0x70) s=f3febfa8 bash-1355 [001] d... 362.348081: ftrace: (sys_read+0x4/0x70) s=f5075fa8 sshd-1352 [000] d... 362.348082: ftrace: (sys_read+0x4/0x70) s=f3febfa8 sshd-1352 [000] d... 362.690950: ftrace: (sys_read+0x4/0x70) s=f3febfa8 bash-1355 [001] d... 362.691033: ftrace: (sys_read+0x4/0x70) s=f5075fa8 [ I wonder if this should also go to stable? ] Signed-off-by: Steven Rostedt Index: linux-trace.git/arch/x86/include/asm/ptrace.h =================================================================== --- linux-trace.git.orig/arch/x86/include/asm/ptrace.h +++ linux-trace.git/arch/x86/include/asm/ptrace.h @@ -246,6 +246,15 @@ static inline unsigned long regs_get_reg { if (unlikely(offset > MAX_REG_OFFSET)) return 0; +#ifdef CONFIG_X86_32 + /* + * Traps from the kernel do not save sp and ss. + * Use the helper function to retrieve sp. + */ + if (offset == offsetof(struct pt_regs, sp) && + regs->cs == __KERNEL_CS) + return kernel_stack_pointer(regs); +#endif return *(unsigned long *)((unsigned long)regs + offset); }