1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Stack trace management functions
4  *
5  * Copyright (C) 2022 Loongson Technology Corporation Limited
6  */
7 #include <linux/sched.h>
8 #include <linux/stacktrace.h>
9 #include <linux/uaccess.h>
10 
11 #include <asm/stacktrace.h>
12 #include <asm/unwind.h>
13 
14 void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
15 		     struct task_struct *task, struct pt_regs *regs)
16 {
17 	unsigned long addr;
18 	struct pt_regs dummyregs;
19 	struct unwind_state state;
20 
21 	regs = &dummyregs;
22 
23 	if (task == current) {
24 		regs->regs[3] = (unsigned long)__builtin_frame_address(0);
25 		regs->csr_era = (unsigned long)__builtin_return_address(0);
26 	} else {
27 		regs->regs[3] = thread_saved_fp(task);
28 		regs->csr_era = thread_saved_ra(task);
29 	}
30 
31 	regs->regs[1] = 0;
32 	for (unwind_start(&state, task, regs);
33 	      !unwind_done(&state); unwind_next_frame(&state)) {
34 		addr = unwind_get_return_address(&state);
35 		if (!addr || !consume_entry(cookie, addr))
36 			break;
37 	}
38 }
39 
40 static int
41 copy_stack_frame(unsigned long fp, struct stack_frame *frame)
42 {
43 	int ret = 1;
44 	unsigned long err;
45 	unsigned long __user *user_frame_tail;
46 
47 	user_frame_tail = (unsigned long *)(fp - sizeof(struct stack_frame));
48 	if (!access_ok(user_frame_tail, sizeof(*frame)))
49 		return 0;
50 
51 	pagefault_disable();
52 	err = (__copy_from_user_inatomic(frame, user_frame_tail, sizeof(*frame)));
53 	if (err || (unsigned long)user_frame_tail >= frame->fp)
54 		ret = 0;
55 	pagefault_enable();
56 
57 	return ret;
58 }
59 
60 void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
61 			  const struct pt_regs *regs)
62 {
63 	unsigned long fp = regs->regs[22];
64 
65 	while (fp && !((unsigned long)fp & 0xf)) {
66 		struct stack_frame frame;
67 
68 		frame.fp = 0;
69 		frame.ra = 0;
70 		if (!copy_stack_frame(fp, &frame))
71 			break;
72 		if (!frame.ra)
73 			break;
74 		if (!consume_entry(cookie, frame.ra))
75 			break;
76 		fp = frame.fp;
77 	}
78 }
79