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
14void 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	if (!regs) {
22		regs = &dummyregs;
23
24		if (task == current) {
25			regs->regs[3] = (unsigned long)__builtin_frame_address(0);
26			regs->csr_era = (unsigned long)__builtin_return_address(0);
27		} else {
28			regs->regs[3] = thread_saved_fp(task);
29			regs->csr_era = thread_saved_ra(task);
30		}
31		regs->regs[1] = 0;
32		regs->regs[22] = 0;
33	}
34
35	for (unwind_start(&state, task, regs);
36	     !unwind_done(&state); unwind_next_frame(&state)) {
37		addr = unwind_get_return_address(&state);
38		if (!addr || !consume_entry(cookie, addr))
39			break;
40	}
41}
42
43int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
44			     void *cookie, struct task_struct *task)
45{
46	unsigned long addr;
47	struct pt_regs dummyregs;
48	struct pt_regs *regs = &dummyregs;
49	struct unwind_state state;
50
51	if (task == current) {
52		regs->regs[3] = (unsigned long)__builtin_frame_address(0);
53		regs->csr_era = (unsigned long)__builtin_return_address(0);
54	} else {
55		regs->regs[3] = thread_saved_fp(task);
56		regs->csr_era = thread_saved_ra(task);
57	}
58	regs->regs[1] = 0;
59	regs->regs[22] = 0;
60
61	for (unwind_start(&state, task, regs);
62	     !unwind_done(&state) && !unwind_error(&state); unwind_next_frame(&state)) {
63		addr = unwind_get_return_address(&state);
64
65		/*
66		 * A NULL or invalid return address probably means there's some
67		 * generated code which __kernel_text_address() doesn't know about.
68		 */
69		if (!addr)
70			return -EINVAL;
71
72		if (!consume_entry(cookie, addr))
73			return -EINVAL;
74	}
75
76	/* Check for stack corruption */
77	if (unwind_error(&state))
78		return -EINVAL;
79
80	return 0;
81}
82
83static int
84copy_stack_frame(unsigned long fp, struct stack_frame *frame)
85{
86	int ret = 1;
87	unsigned long err;
88	unsigned long __user *user_frame_tail;
89
90	user_frame_tail = (unsigned long *)(fp - sizeof(struct stack_frame));
91	if (!access_ok(user_frame_tail, sizeof(*frame)))
92		return 0;
93
94	pagefault_disable();
95	err = (__copy_from_user_inatomic(frame, user_frame_tail, sizeof(*frame)));
96	if (err || (unsigned long)user_frame_tail >= frame->fp)
97		ret = 0;
98	pagefault_enable();
99
100	return ret;
101}
102
103void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
104			  const struct pt_regs *regs)
105{
106	unsigned long fp = regs->regs[22];
107
108	while (fp && !((unsigned long)fp & 0xf)) {
109		struct stack_frame frame;
110
111		frame.fp = 0;
112		frame.ra = 0;
113		if (!copy_stack_frame(fp, &frame))
114			break;
115		if (!frame.ra)
116			break;
117		if (!consume_entry(cookie, frame.ra))
118			break;
119		fp = frame.fp;
120	}
121}
122