1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Stack trace management functions
4 *
5 * Copyright IBM Corp. 2006
6 */
7
8 #include <linux/perf_event.h>
9 #include <linux/stacktrace.h>
10 #include <linux/uaccess.h>
11 #include <linux/compat.h>
12 #include <asm/stacktrace.h>
13 #include <asm/unwind.h>
14 #include <asm/kprobes.h>
15 #include <asm/ptrace.h>
16
17 void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
18 struct task_struct *task, struct pt_regs *regs)
19 {
20 struct unwind_state state;
21 unsigned long addr;
22
23 unwind_for_each_frame(&state, task, regs, 0) {
24 addr = unwind_get_return_address(&state);
25 if (!addr || !consume_entry(cookie, addr))
26 break;
27 }
28 }
29
30 int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
31 void *cookie, struct task_struct *task)
32 {
33 struct unwind_state state;
34 unsigned long addr;
35
36 unwind_for_each_frame(&state, task, NULL, 0) {
37 if (state.stack_info.type != STACK_TYPE_TASK)
38 return -EINVAL;
39
40 if (state.regs)
41 return -EINVAL;
42
43 addr = unwind_get_return_address(&state);
44 if (!addr)
45 return -EINVAL;
46
47 #ifdef CONFIG_RETHOOK
48 /*
49 * Mark stacktraces with krethook functions on them
50 * as unreliable.
51 */
52 if (state.ip == (unsigned long)arch_rethook_trampoline)
53 return -EINVAL;
54 #endif
55
56 if (!consume_entry(cookie, addr))
57 return -EINVAL;
58 }
59
60 /* Check for stack corruption */
61 if (unwind_error(&state))
62 return -EINVAL;
63 return 0;
64 }
65
66 static inline bool store_ip(stack_trace_consume_fn consume_entry, void *cookie,
67 struct perf_callchain_entry_ctx *entry, bool perf,
68 unsigned long ip)
69 {
70 #ifdef CONFIG_PERF_EVENTS
71 if (perf) {
72 if (perf_callchain_store(entry, ip))
73 return false;
74 return true;
75 }
76 #endif
77 return consume_entry(cookie, ip);
78 }
79
80 static inline bool ip_invalid(unsigned long ip)
81 {
82 /*
83 * Perform some basic checks if an instruction address taken
84 * from unreliable source is invalid.
85 */
86 if (ip & 1)
87 return true;
88 if (ip < mmap_min_addr)
89 return true;
90 if (ip >= current->mm->context.asce_limit)
91 return true;
92 return false;
93 }
94
95 static inline bool ip_within_vdso(unsigned long ip)
96 {
97 return in_range(ip, current->mm->context.vdso_base, vdso_text_size());
98 }
99
100 void arch_stack_walk_user_common(stack_trace_consume_fn consume_entry, void *cookie,
101 struct perf_callchain_entry_ctx *entry,
102 const struct pt_regs *regs, bool perf)
103 {
104 struct stack_frame_vdso_wrapper __user *sf_vdso;
105 struct stack_frame_user __user *sf;
106 unsigned long ip, sp;
107 bool first = true;
108
109 if (is_compat_task())
110 return;
111 if (!current->mm)
112 return;
113 ip = instruction_pointer(regs);
114 if (!store_ip(consume_entry, cookie, entry, perf, ip))
115 return;
116 sf = (void __user *)user_stack_pointer(regs);
117 pagefault_disable();
118 while (1) {
119 if (__get_user(sp, &sf->back_chain))
120 break;
121 /*
122 * VDSO entry code has a non-standard stack frame layout.
123 * See VDSO user wrapper code for details.
124 */
125 if (!sp && ip_within_vdso(ip)) {
126 sf_vdso = (void __user *)sf;
127 if (__get_user(ip, &sf_vdso->return_address))
128 break;
129 sp = (unsigned long)sf + STACK_FRAME_VDSO_OVERHEAD;
130 sf = (void __user *)sp;
131 if (__get_user(sp, &sf->back_chain))
132 break;
133 } else {
134 sf = (void __user *)sp;
135 if (__get_user(ip, &sf->gprs[8]))
136 break;
137 }
138 /* Sanity check: ABI requires SP to be 8 byte aligned. */
139 if (sp & 0x7)
140 break;
141 if (ip_invalid(ip)) {
142 /*
143 * If the instruction address is invalid, and this
144 * is the first stack frame, assume r14 has not
145 * been written to the stack yet. Otherwise exit.
146 */
147 if (!first)
148 break;
149 ip = regs->gprs[14];
150 if (ip_invalid(ip))
151 break;
152 }
153 if (!store_ip(consume_entry, cookie, entry, perf, ip))
154 return;
155 first = false;
156 }
157 pagefault_enable();
158 }
159
160 void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
161 const struct pt_regs *regs)
162 {
163 arch_stack_walk_user_common(consume_entry, cookie, NULL, regs, false);
164 }
165
166 unsigned long return_address(unsigned int n)
167 {
168 struct unwind_state state;
169 unsigned long addr;
170
171 /* Increment to skip current stack entry */
172 n++;
173
174 unwind_for_each_frame(&state, NULL, NULL, 0) {
175 addr = unwind_get_return_address(&state);
176 if (!addr)
177 break;
178 if (!n--)
179 return addr;
180 }
181 return 0;
182 }
183 EXPORT_SYMBOL_GPL(return_address);
184
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