xref: /openbmc/linux/arch/x86/kernel/unwind_guess.c (revision 5d0e4d78)
1 #include <linux/sched.h>
2 #include <linux/ftrace.h>
3 #include <asm/ptrace.h>
4 #include <asm/bitops.h>
5 #include <asm/stacktrace.h>
6 #include <asm/unwind.h>
7 
8 unsigned long unwind_get_return_address(struct unwind_state *state)
9 {
10 	unsigned long addr;
11 
12 	if (unwind_done(state))
13 		return 0;
14 
15 	addr = READ_ONCE_NOCHECK(*state->sp);
16 
17 	return ftrace_graph_ret_addr(state->task, &state->graph_idx,
18 				     addr, state->sp);
19 }
20 EXPORT_SYMBOL_GPL(unwind_get_return_address);
21 
22 bool unwind_next_frame(struct unwind_state *state)
23 {
24 	struct stack_info *info = &state->stack_info;
25 
26 	if (unwind_done(state))
27 		return false;
28 
29 	do {
30 		for (state->sp++; state->sp < info->end; state->sp++) {
31 			unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
32 
33 			if (__kernel_text_address(addr))
34 				return true;
35 		}
36 
37 		state->sp = PTR_ALIGN(info->next_sp, sizeof(long));
38 
39 	} while (!get_stack_info(state->sp, state->task, info,
40 				 &state->stack_mask));
41 
42 	return false;
43 }
44 EXPORT_SYMBOL_GPL(unwind_next_frame);
45 
46 void __unwind_start(struct unwind_state *state, struct task_struct *task,
47 		    struct pt_regs *regs, unsigned long *first_frame)
48 {
49 	memset(state, 0, sizeof(*state));
50 
51 	state->task = task;
52 	state->sp   = PTR_ALIGN(first_frame, sizeof(long));
53 
54 	get_stack_info(first_frame, state->task, &state->stack_info,
55 		       &state->stack_mask);
56 
57 	/*
58 	 * The caller can provide the address of the first frame directly
59 	 * (first_frame) or indirectly (regs->sp) to indicate which stack frame
60 	 * to start unwinding at.  Skip ahead until we reach it.
61 	 */
62 	if (!unwind_done(state) &&
63 	    (!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
64 	    !__kernel_text_address(*first_frame)))
65 		unwind_next_frame(state);
66 }
67 EXPORT_SYMBOL_GPL(__unwind_start);
68