1/*
2 * Kernel and userspace stack tracing.
3 *
4 * This file is subject to the terms and conditions of the GNU General Public
5 * License. See the file "COPYING" in the main directory of this archive
6 * for more details.
7 *
8 * Copyright (C) 2001 - 2013 Tensilica Inc.
9 * Copyright (C) 2015 Cadence Design Systems Inc.
10 */
11#include <linux/export.h>
12#include <linux/sched.h>
13#include <linux/stacktrace.h>
14
15#include <asm/ftrace.h>
16#include <asm/sections.h>
17#include <asm/stacktrace.h>
18#include <asm/traps.h>
19#include <linux/uaccess.h>
20
21#if IS_ENABLED(CONFIG_PERF_EVENTS)
22
23/* Address of common_exception_return, used to check the
24 * transition from kernel to user space.
25 */
26extern int common_exception_return;
27
28void xtensa_backtrace_user(struct pt_regs *regs, unsigned int depth,
29 int (*ufn)(struct stackframe *frame, void *data),
30 void *data)
31{
32 unsigned long windowstart = regs->windowstart;
33 unsigned long windowbase = regs->windowbase;
34 unsigned long a0 = regs->areg[0];
35 unsigned long a1 = regs->areg[1];
36 unsigned long pc = regs->pc;
37 struct stackframe frame;
38 int index;
39
40 if (!depth--)
41 return;
42
43 frame.pc = pc;
44 frame.sp = a1;
45
46 if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
47 return;
48
49 if (IS_ENABLED(CONFIG_USER_ABI_CALL0_ONLY) ||
50 (IS_ENABLED(CONFIG_USER_ABI_CALL0_PROBE) &&
51 !(regs->ps & PS_WOE_MASK)))
52 return;
53
54 /* Two steps:
55 *
56 * 1. Look through the register window for the
57 * previous PCs in the call trace.
58 *
59 * 2. Look on the stack.
60 */
61
62 /* Step 1. */
63 /* Rotate WINDOWSTART to move the bit corresponding to
64 * the current window to the bit #0.
65 */
66 windowstart = (windowstart << WSBITS | windowstart) >> windowbase;
67
68 /* Look for bits that are set, they correspond to
69 * valid windows.
70 */
71 for (index = WSBITS - 1; (index > 0) && depth; depth--, index--)
72 if (windowstart & (1 << index)) {
73 /* Get the PC from a0 and a1. */
74 pc = MAKE_PC_FROM_RA(a0, pc);
75 /* Read a0 and a1 from the
76 * corresponding position in AREGs.
77 */
78 a0 = regs->areg[index * 4];
79 a1 = regs->areg[index * 4 + 1];
80
81 frame.pc = pc;
82 frame.sp = a1;
83
84 if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
85 return;
86 }
87
88 /* Step 2. */
89 /* We are done with the register window, we need to
90 * look through the stack.
91 */
92 if (!depth)
93 return;
94
95 /* Start from the a1 register. */
96 /* a1 = regs->areg[1]; */
97 while (a0 != 0 && depth--) {
98 pc = MAKE_PC_FROM_RA(a0, pc);
99
100 /* Check if the region is OK to access. */
101 if (!access_ok(&SPILL_SLOT(a1, 0), 8))
102 return;
103 /* Copy a1, a0 from user space stack frame. */
104 if (__get_user(a0, &SPILL_SLOT(a1, 0)) ||
105 __get_user(a1, &SPILL_SLOT(a1, 1)))
106 return;
107
108 frame.pc = pc;
109 frame.sp = a1;
110
111 if (pc == 0 || pc >= TASK_SIZE || ufn(&frame, data))
112 return;
113 }
114}
115EXPORT_SYMBOL(xtensa_backtrace_user);
116
117void xtensa_backtrace_kernel(struct pt_regs *regs, unsigned int depth,
118 int (*kfn)(struct stackframe *frame, void *data),
119 int (*ufn)(struct stackframe *frame, void *data),
120 void *data)
121{
122 unsigned long pc = regs->depc > VALID_DOUBLE_EXCEPTION_ADDRESS ?
123 regs->depc : regs->pc;
124 unsigned long sp_start, sp_end;
125 unsigned long a0 = regs->areg[0];
126 unsigned long a1 = regs->areg[1];
127
128 sp_start = a1 & ~(THREAD_SIZE - 1);
129 sp_end = sp_start + THREAD_SIZE;
130
131 /* Spill the register window to the stack first. */
132 spill_registers();
133
134 /* Read the stack frames one by one and create the PC
135 * from the a0 and a1 registers saved there.
136 */
137 while (a1 > sp_start && a1 < sp_end && depth--) {
138 struct stackframe frame;
139
140 frame.pc = pc;
141 frame.sp = a1;
142
143 if (kernel_text_address(addr: pc) && kfn(&frame, data))
144 return;
145
146 if (pc == (unsigned long)&common_exception_return) {
147 regs = (struct pt_regs *)a1;
148 if (user_mode(regs)) {
149 if (ufn == NULL)
150 return;
151 xtensa_backtrace_user(regs, depth, ufn, data);
152 return;
153 }
154 a0 = regs->areg[0];
155 a1 = regs->areg[1];
156 continue;
157 }
158
159 sp_start = a1;
160
161 pc = MAKE_PC_FROM_RA(a0, pc);
162 a0 = SPILL_SLOT(a1, 0);
163 a1 = SPILL_SLOT(a1, 1);
164 }
165}
166EXPORT_SYMBOL(xtensa_backtrace_kernel);
167
168#endif
169
170void walk_stackframe(unsigned long *sp,
171 int (*fn)(struct stackframe *frame, void *data),
172 void *data)
173{
174 unsigned long a0, a1;
175 unsigned long sp_end;
176
177 a1 = (unsigned long)sp;
178 sp_end = ALIGN(a1, THREAD_SIZE);
179
180 spill_registers();
181
182 while (a1 < sp_end) {
183 struct stackframe frame;
184
185 sp = (unsigned long *)a1;
186
187 a0 = SPILL_SLOT(a1, 0);
188 a1 = SPILL_SLOT(a1, 1);
189
190 if (a1 <= (unsigned long)sp)
191 break;
192
193 frame.pc = MAKE_PC_FROM_RA(a0, _text);
194 frame.sp = a1;
195
196 if (fn(&frame, data))
197 return;
198 }
199}
200
201#ifdef CONFIG_STACKTRACE
202
203struct stack_trace_data {
204 struct stack_trace *trace;
205 unsigned skip;
206};
207
208static int stack_trace_cb(struct stackframe *frame, void *data)
209{
210 struct stack_trace_data *trace_data = data;
211 struct stack_trace *trace = trace_data->trace;
212
213 if (trace_data->skip) {
214 --trace_data->skip;
215 return 0;
216 }
217 if (!kernel_text_address(addr: frame->pc))
218 return 0;
219
220 trace->entries[trace->nr_entries++] = frame->pc;
221 return trace->nr_entries >= trace->max_entries;
222}
223
224void save_stack_trace_tsk(struct task_struct *task, struct stack_trace *trace)
225{
226 struct stack_trace_data trace_data = {
227 .trace = trace,
228 .skip = trace->skip,
229 };
230 walk_stackframe(sp: stack_pointer(task), fn: stack_trace_cb, data: &trace_data);
231}
232EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
233
234void save_stack_trace(struct stack_trace *trace)
235{
236 save_stack_trace_tsk(current, trace);
237}
238EXPORT_SYMBOL_GPL(save_stack_trace);
239
240#endif
241
242struct return_addr_data {
243 unsigned long addr;
244 unsigned skip;
245};
246
247static int return_address_cb(struct stackframe *frame, void *data)
248{
249 struct return_addr_data *r = data;
250
251 if (r->skip) {
252 --r->skip;
253 return 0;
254 }
255 if (!kernel_text_address(addr: frame->pc))
256 return 0;
257 r->addr = frame->pc;
258 return 1;
259}
260
261/*
262 * level == 0 is for the return address from the caller of this function,
263 * not from this function itself.
264 */
265unsigned long return_address(unsigned level)
266{
267 struct return_addr_data r = {
268 .skip = level,
269 };
270 walk_stackframe(sp: stack_pointer(NULL), fn: return_address_cb, data: &r);
271 return r.addr;
272}
273EXPORT_SYMBOL(return_address);
274

source code of linux/arch/xtensa/kernel/stacktrace.c