1/*
2 * Stack trace management functions
3 *
4 *  Copyright (C) 2006-2009 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
5 */
6#include <linux/sched.h>
7#include <linux/sched/debug.h>
8#include <linux/sched/task_stack.h>
9#include <linux/stacktrace.h>
10#include <linux/export.h>
11#include <linux/uaccess.h>
12#include <asm/stacktrace.h>
13#include <asm/unwind.h>
14
15void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
16		     struct task_struct *task, struct pt_regs *regs)
17{
18	struct unwind_state state;
19	unsigned long addr;
20
21	if (regs && !consume_entry(cookie, regs->ip))
22		return;
23
24	for (unwind_start(&state, task, regs, NULL); !unwind_done(&state);
25	     unwind_next_frame(&state)) {
26		addr = unwind_get_return_address(&state);
27		if (!addr || !consume_entry(cookie, addr))
28			break;
29	}
30}
31
32int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
33			     void *cookie, struct task_struct *task)
34{
35	struct unwind_state state;
36	struct pt_regs *regs;
37	unsigned long addr;
38
39	for (unwind_start(&state, task, NULL, NULL);
40	     !unwind_done(&state) && !unwind_error(&state);
41	     unwind_next_frame(&state)) {
42
43		regs = unwind_get_entry_regs(&state, NULL);
44		if (regs) {
45			/* Success path for user tasks */
46			if (user_mode(regs))
47				return 0;
48
49			/*
50			 * Kernel mode registers on the stack indicate an
51			 * in-kernel interrupt or exception (e.g., preemption
52			 * or a page fault), which can make frame pointers
53			 * unreliable.
54			 */
55			if (IS_ENABLED(CONFIG_FRAME_POINTER))
56				return -EINVAL;
57		}
58
59		addr = unwind_get_return_address(&state);
60
61		/*
62		 * A NULL or invalid return address probably means there's some
63		 * generated code which __kernel_text_address() doesn't know
64		 * about.
65		 */
66		if (!addr)
67			return -EINVAL;
68
69		if (!consume_entry(cookie, addr))
70			return -EINVAL;
71	}
72
73	/* Check for stack corruption */
74	if (unwind_error(&state))
75		return -EINVAL;
76
77	return 0;
78}
79
80/* Userspace stacktrace - based on kernel/trace/trace_sysprof.c */
81
82struct stack_frame_user {
83	const void __user	*next_fp;
84	unsigned long		ret_addr;
85};
86
87static int
88copy_stack_frame(const struct stack_frame_user __user *fp,
89		 struct stack_frame_user *frame)
90{
91	int ret;
92
93	if (!__access_ok(fp, sizeof(*frame)))
94		return 0;
95
96	ret = 1;
97	pagefault_disable();
98	if (__get_user(frame->next_fp, &fp->next_fp) ||
99	    __get_user(frame->ret_addr, &fp->ret_addr))
100		ret = 0;
101	pagefault_enable();
102
103	return ret;
104}
105
106void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
107			  const struct pt_regs *regs)
108{
109	const void __user *fp = (const void __user *)regs->bp;
110
111	if (!consume_entry(cookie, regs->ip))
112		return;
113
114	while (1) {
115		struct stack_frame_user frame;
116
117		frame.next_fp = NULL;
118		frame.ret_addr = 0;
119		if (!copy_stack_frame(fp, &frame))
120			break;
121		if ((unsigned long)fp < regs->sp)
122			break;
123		if (!frame.ret_addr)
124			break;
125		if (!consume_entry(cookie, frame.ret_addr))
126			break;
127		fp = frame.next_fp;
128	}
129}
130
131