From: Qi Zheng zhengqi.arch@bytedance.com
[ Upstream commit bc9bbb81730ea667c31c5b284f95ee312bab466f ]
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: ee9f8fce9964 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/process.c | 51 +++------------------------------------ 1 file changed, 3 insertions(+), 48 deletions(-)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index f2f733bcb2b95..cd426c3283ee1 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -945,58 +945,13 @@ 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,