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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * stacktrace.c : stacktracing APIs needed by rest of kernel
4 * (wrappers over ARC dwarf based unwinder)
5 *
6 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
7 *
8 * vineetg: aug 2009
9 * -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
10 * for displaying task's kernel mode call stack in /proc/<pid>/stack
11 * -Iterator based approach to have single copy of unwinding core and APIs
12 * needing unwinding, implement the logic in iterator regarding:
13 * = which frame onwards to start capture
14 * = which frame to stop capturing (wchan)
15 * = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
16 *
17 * vineetg: March 2009
18 * -Implemented correct versions of thread_saved_pc() and get_wchan()
19 *
20 * rajeshwarr: 2008
21 * -Initial implementation
22 */
23
24#include <linux/ptrace.h>
25#include <linux/export.h>
26#include <linux/stacktrace.h>
27#include <linux/kallsyms.h>
28#include <linux/sched/debug.h>
29
30#include <asm/arcregs.h>
31#include <asm/unwind.h>
32#include <asm/switch_to.h>
33
34/*-------------------------------------------------------------------------
35 * Unwinder Iterator
36 *-------------------------------------------------------------------------
37 */
38
39#ifdef CONFIG_ARC_DW2_UNWIND
40
41static void seed_unwind_frame_info(struct task_struct *tsk,
42 struct pt_regs *regs,
43 struct unwind_frame_info *frame_info)
44{
45 /*
46 * synchronous unwinding (e.g. dump_stack)
47 * - uses current values of SP and friends
48 */
49 if (tsk == NULL && regs == NULL) {
50 unsigned long fp, sp, blink, ret;
51 frame_info->task = current;
52
53 __asm__ __volatile__(
54 "mov %0,r27\n\t"
55 "mov %1,r28\n\t"
56 "mov %2,r31\n\t"
57 "mov %3,r63\n\t"
58 : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
59 );
60
61 frame_info->regs.r27 = fp;
62 frame_info->regs.r28 = sp;
63 frame_info->regs.r31 = blink;
64 frame_info->regs.r63 = ret;
65 frame_info->call_frame = 0;
66 } else if (regs == NULL) {
67 /*
68 * Asynchronous unwinding of sleeping task
69 * - Gets SP etc from task's pt_regs (saved bottom of kernel
70 * mode stack of task)
71 */
72
73 frame_info->task = tsk;
74
75 frame_info->regs.r27 = TSK_K_FP(tsk);
76 frame_info->regs.r28 = TSK_K_ESP(tsk);
77 frame_info->regs.r31 = TSK_K_BLINK(tsk);
78 frame_info->regs.r63 = (unsigned int)__switch_to;
79
80 /* In the prologue of __switch_to, first FP is saved on stack
81 * and then SP is copied to FP. Dwarf assumes cfa as FP based
82 * but we didn't save FP. The value retrieved above is FP's
83 * state in previous frame.
84 * As a work around for this, we unwind from __switch_to start
85 * and adjust SP accordingly. The other limitation is that
86 * __switch_to macro is dwarf rules are not generated for inline
87 * assembly code
88 */
89 frame_info->regs.r27 = 0;
90 frame_info->regs.r28 += 60;
91 frame_info->call_frame = 0;
92
93 } else {
94 /*
95 * Asynchronous unwinding of intr/exception
96 * - Just uses the pt_regs passed
97 */
98 frame_info->task = tsk;
99
100 frame_info->regs.r27 = regs->fp;
101 frame_info->regs.r28 = regs->sp;
102 frame_info->regs.r31 = regs->blink;
103 frame_info->regs.r63 = regs->ret;
104 frame_info->call_frame = 0;
105 }
106}
107
108#endif
109
110notrace noinline unsigned int
111arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
112 int (*consumer_fn) (unsigned int, void *), void *arg)
113{
114#ifdef CONFIG_ARC_DW2_UNWIND
115 int ret = 0;
116 unsigned int address;
117 struct unwind_frame_info frame_info;
118
119 seed_unwind_frame_info(tsk, regs, &frame_info);
120
121 while (1) {
122 address = UNW_PC(&frame_info);
123
124 if (!address || !__kernel_text_address(address))
125 break;
126
127 if (consumer_fn(address, arg) == -1)
128 break;
129
130 ret = arc_unwind(&frame_info);
131 if (ret)
132 break;
133
134 frame_info.regs.r63 = frame_info.regs.r31;
135 }
136
137 return address; /* return the last address it saw */
138#else
139 /* On ARC, only Dward based unwinder works. fp based backtracing is
140 * not possible (-fno-omit-frame-pointer) because of the way function
141 * prelogue is setup (callee regs saved and then fp set and not other
142 * way around
143 */
144 pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
145 return 0;
146
147#endif
148}
149
150/*-------------------------------------------------------------------------
151 * callbacks called by unwinder iterator to implement kernel APIs
152 *
153 * The callback can return -1 to force the iterator to stop, which by default
154 * keeps going till the bottom-most frame.
155 *-------------------------------------------------------------------------
156 */
157
158/* Call-back which plugs into unwinding core to dump the stack in
159 * case of panic/OOPs/BUG etc
160 */
161static int __print_sym(unsigned int address, void *unused)
162{
163 printk(" %pS\n", (void *)address);
164 return 0;
165}
166
167#ifdef CONFIG_STACKTRACE
168
169/* Call-back which plugs into unwinding core to capture the
170 * traces needed by kernel on /proc/<pid>/stack
171 */
172static int __collect_all(unsigned int address, void *arg)
173{
174 struct stack_trace *trace = arg;
175
176 if (trace->skip > 0)
177 trace->skip--;
178 else
179 trace->entries[trace->nr_entries++] = address;
180
181 if (trace->nr_entries >= trace->max_entries)
182 return -1;
183
184 return 0;
185}
186
187static int __collect_all_but_sched(unsigned int address, void *arg)
188{
189 struct stack_trace *trace = arg;
190
191 if (in_sched_functions(address))
192 return 0;
193
194 if (trace->skip > 0)
195 trace->skip--;
196 else
197 trace->entries[trace->nr_entries++] = address;
198
199 if (trace->nr_entries >= trace->max_entries)
200 return -1;
201
202 return 0;
203}
204
205#endif
206
207static int __get_first_nonsched(unsigned int address, void *unused)
208{
209 if (in_sched_functions(address))
210 return 0;
211
212 return -1;
213}
214
215/*-------------------------------------------------------------------------
216 * APIs expected by various kernel sub-systems
217 *-------------------------------------------------------------------------
218 */
219
220noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
221{
222 pr_info("\nStack Trace:\n");
223 arc_unwind_core(tsk, regs, __print_sym, NULL);
224}
225EXPORT_SYMBOL(show_stacktrace);
226
227/* Expected by sched Code */
228void show_stack(struct task_struct *tsk, unsigned long *sp)
229{
230 show_stacktrace(tsk, NULL);
231}
232
233/* Another API expected by schedular, shows up in "ps" as Wait Channel
234 * Of course just returning schedule( ) would be pointless so unwind until
235 * the function is not in schedular code
236 */
237unsigned int get_wchan(struct task_struct *tsk)
238{
239 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
240}
241
242#ifdef CONFIG_STACKTRACE
243
244/*
245 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
246 * A typical use is when /proc/<pid>/stack is queried by userland
247 */
248void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
249{
250 /* Assumes @tsk is sleeping so unwinds from __switch_to */
251 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
252}
253
254void save_stack_trace(struct stack_trace *trace)
255{
256 /* Pass NULL for task so it unwinds the current call frame */
257 arc_unwind_core(NULL, NULL, __collect_all, trace);
258}
259EXPORT_SYMBOL_GPL(save_stack_trace);
260#endif
1/*
2 * stacktrace.c : stacktracing APIs needed by rest of kernel
3 * (wrappers over ARC dwarf based unwinder)
4 *
5 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * vineetg: aug 2009
12 * -Implemented CONFIG_STACKTRACE APIs, primarily save_stack_trace_tsk( )
13 * for displaying task's kernel mode call stack in /proc/<pid>/stack
14 * -Iterator based approach to have single copy of unwinding core and APIs
15 * needing unwinding, implement the logic in iterator regarding:
16 * = which frame onwards to start capture
17 * = which frame to stop capturing (wchan)
18 * = specifics of data structs where trace is saved(CONFIG_STACKTRACE etc)
19 *
20 * vineetg: March 2009
21 * -Implemented correct versions of thread_saved_pc() and get_wchan()
22 *
23 * rajeshwarr: 2008
24 * -Initial implementation
25 */
26
27#include <linux/ptrace.h>
28#include <linux/export.h>
29#include <linux/stacktrace.h>
30#include <linux/kallsyms.h>
31#include <linux/sched/debug.h>
32
33#include <asm/arcregs.h>
34#include <asm/unwind.h>
35#include <asm/switch_to.h>
36
37/*-------------------------------------------------------------------------
38 * Unwinder Iterator
39 *-------------------------------------------------------------------------
40 */
41
42#ifdef CONFIG_ARC_DW2_UNWIND
43
44static void seed_unwind_frame_info(struct task_struct *tsk,
45 struct pt_regs *regs,
46 struct unwind_frame_info *frame_info)
47{
48 /*
49 * synchronous unwinding (e.g. dump_stack)
50 * - uses current values of SP and friends
51 */
52 if (tsk == NULL && regs == NULL) {
53 unsigned long fp, sp, blink, ret;
54 frame_info->task = current;
55
56 __asm__ __volatile__(
57 "mov %0,r27\n\t"
58 "mov %1,r28\n\t"
59 "mov %2,r31\n\t"
60 "mov %3,r63\n\t"
61 : "=r"(fp), "=r"(sp), "=r"(blink), "=r"(ret)
62 );
63
64 frame_info->regs.r27 = fp;
65 frame_info->regs.r28 = sp;
66 frame_info->regs.r31 = blink;
67 frame_info->regs.r63 = ret;
68 frame_info->call_frame = 0;
69 } else if (regs == NULL) {
70 /*
71 * Asynchronous unwinding of sleeping task
72 * - Gets SP etc from task's pt_regs (saved bottom of kernel
73 * mode stack of task)
74 */
75
76 frame_info->task = tsk;
77
78 frame_info->regs.r27 = TSK_K_FP(tsk);
79 frame_info->regs.r28 = TSK_K_ESP(tsk);
80 frame_info->regs.r31 = TSK_K_BLINK(tsk);
81 frame_info->regs.r63 = (unsigned int)__switch_to;
82
83 /* In the prologue of __switch_to, first FP is saved on stack
84 * and then SP is copied to FP. Dwarf assumes cfa as FP based
85 * but we didn't save FP. The value retrieved above is FP's
86 * state in previous frame.
87 * As a work around for this, we unwind from __switch_to start
88 * and adjust SP accordingly. The other limitation is that
89 * __switch_to macro is dwarf rules are not generated for inline
90 * assembly code
91 */
92 frame_info->regs.r27 = 0;
93 frame_info->regs.r28 += 60;
94 frame_info->call_frame = 0;
95
96 } else {
97 /*
98 * Asynchronous unwinding of intr/exception
99 * - Just uses the pt_regs passed
100 */
101 frame_info->task = tsk;
102
103 frame_info->regs.r27 = regs->fp;
104 frame_info->regs.r28 = regs->sp;
105 frame_info->regs.r31 = regs->blink;
106 frame_info->regs.r63 = regs->ret;
107 frame_info->call_frame = 0;
108 }
109}
110
111#endif
112
113notrace noinline unsigned int
114arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
115 int (*consumer_fn) (unsigned int, void *), void *arg)
116{
117#ifdef CONFIG_ARC_DW2_UNWIND
118 int ret = 0;
119 unsigned int address;
120 struct unwind_frame_info frame_info;
121
122 seed_unwind_frame_info(tsk, regs, &frame_info);
123
124 while (1) {
125 address = UNW_PC(&frame_info);
126
127 if (!address || !__kernel_text_address(address))
128 break;
129
130 if (consumer_fn(address, arg) == -1)
131 break;
132
133 ret = arc_unwind(&frame_info);
134 if (ret)
135 break;
136
137 frame_info.regs.r63 = frame_info.regs.r31;
138 }
139
140 return address; /* return the last address it saw */
141#else
142 /* On ARC, only Dward based unwinder works. fp based backtracing is
143 * not possible (-fno-omit-frame-pointer) because of the way function
144 * prelogue is setup (callee regs saved and then fp set and not other
145 * way around
146 */
147 pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
148 return 0;
149
150#endif
151}
152
153/*-------------------------------------------------------------------------
154 * callbacks called by unwinder iterator to implement kernel APIs
155 *
156 * The callback can return -1 to force the iterator to stop, which by default
157 * keeps going till the bottom-most frame.
158 *-------------------------------------------------------------------------
159 */
160
161/* Call-back which plugs into unwinding core to dump the stack in
162 * case of panic/OOPs/BUG etc
163 */
164static int __print_sym(unsigned int address, void *unused)
165{
166 printk(" %pS\n", (void *)address);
167 return 0;
168}
169
170#ifdef CONFIG_STACKTRACE
171
172/* Call-back which plugs into unwinding core to capture the
173 * traces needed by kernel on /proc/<pid>/stack
174 */
175static int __collect_all(unsigned int address, void *arg)
176{
177 struct stack_trace *trace = arg;
178
179 if (trace->skip > 0)
180 trace->skip--;
181 else
182 trace->entries[trace->nr_entries++] = address;
183
184 if (trace->nr_entries >= trace->max_entries)
185 return -1;
186
187 return 0;
188}
189
190static int __collect_all_but_sched(unsigned int address, void *arg)
191{
192 struct stack_trace *trace = arg;
193
194 if (in_sched_functions(address))
195 return 0;
196
197 if (trace->skip > 0)
198 trace->skip--;
199 else
200 trace->entries[trace->nr_entries++] = address;
201
202 if (trace->nr_entries >= trace->max_entries)
203 return -1;
204
205 return 0;
206}
207
208#endif
209
210static int __get_first_nonsched(unsigned int address, void *unused)
211{
212 if (in_sched_functions(address))
213 return 0;
214
215 return -1;
216}
217
218/*-------------------------------------------------------------------------
219 * APIs expected by various kernel sub-systems
220 *-------------------------------------------------------------------------
221 */
222
223noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
224{
225 pr_info("\nStack Trace:\n");
226 arc_unwind_core(tsk, regs, __print_sym, NULL);
227}
228EXPORT_SYMBOL(show_stacktrace);
229
230/* Expected by sched Code */
231void show_stack(struct task_struct *tsk, unsigned long *sp)
232{
233 show_stacktrace(tsk, NULL);
234}
235
236/* Another API expected by schedular, shows up in "ps" as Wait Channel
237 * Of course just returning schedule( ) would be pointless so unwind until
238 * the function is not in schedular code
239 */
240unsigned int get_wchan(struct task_struct *tsk)
241{
242 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
243}
244
245#ifdef CONFIG_STACKTRACE
246
247/*
248 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
249 * A typical use is when /proc/<pid>/stack is queried by userland
250 */
251void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
252{
253 /* Assumes @tsk is sleeping so unwinds from __switch_to */
254 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
255}
256
257void save_stack_trace(struct stack_trace *trace)
258{
259 /* Pass NULL for task so it unwinds the current call frame */
260 arc_unwind_core(NULL, NULL, __collect_all, trace);
261}
262EXPORT_SYMBOL_GPL(save_stack_trace);
263#endif