From mboxrd@z Thu Jan 1 00:00:00 1970 From: lauraa@codeaurora.org (Laura Abbott) Date: Wed, 24 Aug 2011 13:58:18 -0700 (PDT) Subject: [PATCH 2/2] process: change from __backtrace to dump_stack_regs in show_regs In-Reply-To: References: <1314206507-6487-1-git-send-email-lauraa@codeaurora.org> <1314206507-6487-3-git-send-email-lauraa@codeaurora.org> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, August 24, 2011 11:57 am, Nicolas Pitre wrote: > On Wed, 24 Aug 2011, Laura Abbott wrote: > >> Currently, show_regs calls __backtrace which does >> nothing if CONIFG_FRAME_POINTER is not set. Switch to > > s/CONIFG/CONFIG/ > >> dump_stack_regs to show the backtrace from a given >> set of registers. >> >> Signed-off-by: Laura Abbott >> --- >> arch/arm/kernel/process.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c >> index 1a347f4..6f11213 100644 >> --- a/arch/arm/kernel/process.c >> +++ b/arch/arm/kernel/process.c >> @@ -319,7 +319,7 @@ void show_regs(struct pt_regs * regs) >> printk("\n"); >> printk("Pid: %d, comm: %20s\n", task_pid_nr(current), current->comm); >> __show_regs(regs); >> - __backtrace(); >> + dump_stack_regs(regs); > > This is not equivalent. A call to __backtrace() will display a call > trace leading to this show_regs(). Given that you defined > dump_stack_regs(regs) as dump_backtrace(regs, NULL), the trace will > instead contain calls leading up to the point where those regs were > saved. > Do other architectures show the call stack to show_regs? From my reading of other code (x86, ppc) it seems like if show_regs generates a call stack it generates a call stack based off of the saved registers unless I'm drastically misunderstanding the code. Generating a call stack based off of not saved registers seems inconsistent with the rest of show_regs which shows saved state. > A better way to achieve what you want would be: > > - remove the __backtrace entry point from lib/backtrace.S > > - define __backtrace() in kernel/traps.c as a call to > dump_backtrace(NULL, NULL) which will have the same effect as the > assembly code for __backtrace(). > > - realize that dump_stack() is already doing exactly that, therefore... > > - use dump_stack() in show_regs() which is the only caller of > __backtrace and get rid of __backtrace entirely. > > Obviously the above can be collapsed in one patch. > > > Nicolas > Laura -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.