void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
{
struct stackframe frame;
unsigned long irq_stack_ptr;
int skip;
pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
tsk = current;
if (!try_get_task_stack(tsk))
return;
/*
* Switching between stacks is valid when tracing current and in
* non-preemptible context.
*/
if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
else
irq_stack_ptr = 0;
if (tsk == current) {
frame.fp = (unsigned long)__builtin_frame_address(0);
frame.sp = current_stack_pointer;
frame.pc = (unsigned long)dump_backtrace;
} else {
/*
* task blocked in __switch_to
*/
frame.fp = thread_saved_fp(tsk);
frame.sp = thread_saved_sp(tsk);
frame.pc = thread_saved_pc(tsk);
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
frame.graph = tsk->curr_ret_stack;
#endif
skip = !!regs;
printk("Call trace:\n");
while (1) {
unsigned long where = frame.pc;
unsigned long stack;
int ret;
/* skip until specified stack frame */
if (!skip) {
dump_backtrace_entry(where);
} else if (frame.fp == regs->regs[29]) {
skip = 0;
/*
* Mostly, this is the case where this function is
* called in panic/abort. As exception handler's
* stack frame does not contain the corresponding pc
* at which an exception has taken place, use regs->pc
* instead.
*/
dump_backtrace_entry(regs->pc);
}
ret = unwind_frame(tsk, &frame);
if (ret < 0)
break;
stack = frame.sp;
if (in_exception_text(where)) {
/*
* If we switched to the irq_stack before calling this
* exception handler, then the pt_regs will be on the
* task stack. The easiest way to tell is if the large
* pt_regs would overlap with the end of the irq_stack.
*/
if (stack < irq_stack_ptr &&
(stack + sizeof(struct pt_regs)) > irq_stack_ptr)
stack = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
dump_mem("", "Exception stack", stack,
stack + sizeof(struct pt_regs));
}
}
put_task_stack(tsk);
}
/*
* AArch64 PCS assigns the frame pointer to x29.
*
* A simple function prologue looks like this:
* sub sp, sp, #0x10
* stp x29, x30, [sp]
* mov x29, sp
*
* A simple function epilogue looks like this:
* mov sp, x29
* ldp x29, x30, [sp]
* add sp, sp, #0x10
*/
int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
{
unsigned long high, low;
unsigned long fp = frame->fp;
unsigned long irq_stack_ptr;
/*
* Switching between stacks is valid when tracing current and in
* non-preemptible context.
*/
if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
else
irq_stack_ptr = 0;
low = frame->sp;
/* irq stacks are not THREAD_SIZE aligned */
if (on_irq_stack(frame->sp, raw_smp_processor_id()))
high = irq_stack_ptr;
else
high = ALIGN(low, THREAD_SIZE) - 0x20;
if (fp < low || fp > high || fp & 0xf)
return -EINVAL;
frame->sp = fp + 0x10;
frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp));
frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
if (tsk && tsk->ret_stack &&
(frame->pc == (unsigned long)return_to_handler)) {
/*
* This is a case where function graph tracer has
* modified a return address (LR) in a stack frame
* to hook a function return.
* So replace it to an original value.
*/
frame->pc = tsk->ret_stack[frame->graph--].ret;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
/*
* Check whether we are going to walk through from interrupt stack
* to task stack.
* If we reach the end of the stack - and its an interrupt stack,
* unpack the dummy frame to find the original elr.
*
* Check the frame->fp we read from the bottom of the irq_stack,
* and the original task stack pointer are both in current->stack.
*/
if (frame->sp == irq_stack_ptr) {
struct pt_regs *irq_args;
unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
if (object_starts_on_stack((void *)orig_sp) &&
object_starts_on_stack((void *)frame->fp)) {
frame->sp = orig_sp;
/* orig_sp is the saved pt_regs, find the elr */
irq_args = (struct pt_regs *)orig_sp;
frame->pc = irq_args->pc;
} else {
/*
* This frame has a non-standard format, and we
* didn't fix it, because the data looked wrong.
* Refuse to output this frame.
*/
return -EINVAL;
}
}
return 0;
}