From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760654AbZELLXY (ORCPT ); Tue, 12 May 2009 07:23:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758158AbZELLXF (ORCPT ); Tue, 12 May 2009 07:23:05 -0400 Received: from relay1.sgi.com ([192.48.179.29]:58149 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756431AbZELLXB (ORCPT ); Tue, 12 May 2009 07:23:01 -0400 Date: Tue, 12 May 2009 06:23:00 -0500 From: Robin Holt To: Linus Torvalds Cc: Masami Hiramatsu , LKML , systemtap@sources.redhat.com, Harvey Harrison , Ingo Molnar , Thomas Gleixner , Jan Blunck , Christoph Hellwig Subject: Re: [PATCH -rc] [BUGFIX] x86: fix kernel_trap_sp() Message-ID: <20090512112300.GL7601@sgi.com> References: <20090511210300.17332.67549.stgit@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 11, 2009 at 03:24:07PM -0700, Linus Torvalds wrote: > > > On Mon, 11 May 2009, Masami Hiramatsu wrote: > > > > Use ®s->sp instead of regs for getting the top of stack in kernel mode. > > (on x86-64, regs->sp always points the top of stack) > > Ack. > > That said, we have only _one_ use of this "kernel_trap_sp()" in the whole > kernel, and that use is actually fairly odd too, in that it does it > _before_ checking that it's in kernel mode. > > Admittedly it will then only _use_ the value after it has checked that > things are in kernel mode, but it all boils down to "ok, that's pretty > odd". > > So how about fixing that, and also fixing the naming of the function. Call > it "kernel_stack_pointer()" to match its more widely used sibling function > "user_stack_pointer()". > > IOW, something like this? > > Linus > > --- > arch/x86/include/asm/ptrace.h | 7 ++++--- > arch/x86/oprofile/backtrace.c | 2 +- > 2 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h > index e304b66..624f133 100644 > --- a/arch/x86/include/asm/ptrace.h > +++ b/arch/x86/include/asm/ptrace.h > @@ -187,14 +187,15 @@ static inline int v8086_mode(struct pt_regs *regs) > > /* > * X86_32 CPUs don't save ss and esp if the CPU is already in kernel mode > - * when it traps. So regs will be the current sp. > + * when it traps. The previous stack will be directly underneath the saved > + * registers, and 'sp/ss' won't even have been saved. Thus the '®s->sp'. > * > * This is valid only for kernel mode traps. > */ > -static inline unsigned long kernel_trap_sp(struct pt_regs *regs) > +static inline unsigned long kernel_stack_pointer(struct pt_regs *regs) Why not have it return an unsigned long *? > { > #ifdef CONFIG_X86_32 > - return (unsigned long)regs; > + return (unsigned long)(®s->sp); > #else > return regs->sp; > #endif > diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c > index 04df67f..044897b 100644 > --- a/arch/x86/oprofile/backtrace.c > +++ b/arch/x86/oprofile/backtrace.c > @@ -76,9 +76,9 @@ void > x86_backtrace(struct pt_regs * const regs, unsigned int depth) > { > struct frame_head *head = (struct frame_head *)frame_pointer(regs); > - unsigned long stack = kernel_trap_sp(regs); > > if (!user_mode_vm(regs)) { > + unsigned long stack = kernel_stack_pointer(regs); Make this an unsigned long *? > if (depth) > dump_trace(NULL, regs, (unsigned long *)stack, 0, Then get rid of the cast? Robin