On 06/01/2017, 07:44 AM, Josh Poimboeuf wrote:
> --- /dev/null
> +++ b/arch/x86/kernel/unwind_undwarf.c
> @@ -0,0 +1,402 @@
...
> +void __unwind_start(struct unwind_state *state, struct task_struct *task,
> + struct pt_regs *regs, unsigned long *first_frame)
> +{
> + memset(state, 0, sizeof(*state));
> + state->task = task;
> +
> + if (regs) {
> + if (user_mode(regs)) {
> + state->stack_info.type = STACK_TYPE_UNKNOWN;
> + return;
> + }
> +
> + state->ip = regs->ip;
> + state->sp = kernel_stack_pointer(regs);
> + state->bp = regs->bp;
> + state->regs = regs;
> +
> + } else if (task == current) {
> + register void *__sp asm(_ASM_SP);
> +
> + asm volatile("lea (%%rip), %0\n\t"
> + "mov %%rsp, %1\n\t"
> + "mov %%rbp, %2\n\t"
> + : "=r" (state->ip), "=r" (state->sp),
> + "=r" (state->bp), "+r" (__sp));
Maybe I don't understand this completely, but what is __sp used for here?
> + state->regs = NULL;
> +
> + } else {
In DWARF unwinder, we also used to do here:
+#ifdef CONFIG_SMP
+ } else if (task->on_cpu) {
+ return;
+#endif
} else {
> + struct inactive_task_frame *frame = (void *)task->thread.sp;
Since there is no inactive_task_frame for tasks currently running (on
other CPUs). At least this always held in the past.
Though, the test is indeed racy.
> + state->ip = frame->ret_addr;
> + state->sp = task->thread.sp;
> + state->bp = frame->bp;
> + state->regs = NULL;
> + }
thanks,
--
js
suse labs
