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x86: Fix get_wchan() to support the ORC unwinder

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Currently, the kernel CONFIG_UNWINDER_ORC option is enabled by default
on x86, but the implementation of get_wchan() is still based on the frame
pointer unwinder, so the /proc/<pid>/wchan usually returned 0 regardless
of whether the task <pid> is running.

Reimplement get_wchan() by calling stack_trace_save_tsk(), which is
adapted to the ORC and frame pointer unwinders.

Fixes: ee9f8fce99 ("x86/unwind: Add the ORC unwinder")
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20211008111626.271115116@infradead.org
This commit is contained in:
Qi Zheng 2021-09-29 15:02:17 -07:00 committed by Peter Zijlstra
parent 4e04615679
commit bc9bbb8173
1 changed files with 3 additions and 48 deletions
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51
arch/x86/kernel/process.c
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@ -944,58 +944,13 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
*/
unsigned long get_wchan(struct task_struct *p)
{
unsigned long start, bottom, top, sp, fp, ip, ret = 0;
int count = 0;
unsigned long entry = 0;
if (p == current || task_is_running(p))
return 0;
if (!try_get_task_stack(p))
return 0;
start = (unsigned long)task_stack_page(p);
if (!start)
goto out;
/*
* Layout of the stack page:
*
* ----------- topmax = start + THREAD_SIZE - sizeof(unsigned long)
* PADDING
* ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING
* stack
* ----------- bottom = start
*
* The tasks stack pointer points at the location where the
* framepointer is stored. The data on the stack is:
* ... IP FP ... IP FP
*
* We need to read FP and IP, so we need to adjust the upper
* bound by another unsigned long.
*/
top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
top -= 2 * sizeof(unsigned long);
bottom = start;
sp = READ_ONCE(p->thread.sp);
if (sp < bottom || sp > top)
goto out;
fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
do {
if (fp < bottom || fp > top)
goto out;
ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
if (!in_sched_functions(ip)) {
ret = ip;
goto out;
}
fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
} while (count++ < 16 && !task_is_running(p));
out:
put_task_stack(p);
return ret;
stack_trace_save_tsk(p, &entry, 1, 0);
return entry;
}
long do_arch_prctl_common(struct task_struct *task, int option,