Messages in this thread Patch in this message | | | From | Johannes Weiner <> | Subject | [patch 1/5] xtensa: always use correct stack pointer for stack traces | Date | Mon, 11 May 2009 15:43:33 +0200 |
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Commit '28a0ce7 xtensa: use correct stack pointer for stack traces' changed the stack tracer from always reading the stack pointer register to always using the saved value in the task descriptor.
The author was too dense to consider the fact that the saved stack value is stale for a running process und thus unusable for 'current'.
What we do now is to use the stack pointer register (a1) for when the task is unknown - we can't help it then - or when the task is 'current'. For everything else use the saved stack pointer value contained in the task descriptor.
Signed-off-by: Johannes Weiner <jw@emlix.com> --- arch/xtensa/kernel/traps.c | 16 ++++++++++++++-- 1 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c index 9f0b711..ba9ab93 100644 --- a/arch/xtensa/kernel/traps.c +++ b/arch/xtensa/kernel/traps.c @@ -369,6 +369,18 @@ void show_regs(struct pt_regs * regs) regs->syscall); } +static __always_inline unsigned long *stack_pointer(struct task_struct *task) +{ + unsigned long *sp; + + if (!task || task == current) + __asm__ __volatile__ ("mov %0, a1\n" : "=a"(sp)); + else + sp = (unsigned long *)task->thread.sp; + + return sp; +} + void show_trace(struct task_struct *task, unsigned long *sp) { unsigned long a0, a1, pc; @@ -377,7 +389,7 @@ void show_trace(struct task_struct *task, unsigned long *sp) if (sp) a1 = (unsigned long)sp; else - a1 = task->thread.sp; + a1 = (unsigned long)stack_pointer(task); sp_start = a1 & ~(THREAD_SIZE-1); sp_end = sp_start + THREAD_SIZE; @@ -420,7 +432,7 @@ void show_stack(struct task_struct *task, unsigned long *sp) unsigned long *stack; if (!sp) - sp = (unsigned long *)task->thread.sp; + sp = stack_pointer(task); stack = sp; printk("\nStack: "); -- 1.6.3.rc3
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