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
41 static int
seed_unwind_frame_info(struct task_struct * tsk,struct pt_regs * regs,struct unwind_frame_info * frame_info)42 seed_unwind_frame_info(struct task_struct *tsk, 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 (regs == NULL && (tsk == NULL || tsk == current)) {
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 a likely sleeping task
69 * - first ensure it is actually sleeping
70 * - if so, it will be in __switch_to, kernel mode SP of task
71 * is safe-kept and BLINK at a well known location in there
72 */
73
74 if (tsk->state == TASK_RUNNING)
75 return -1;
76
77 frame_info->task = tsk;
78
79 frame_info->regs.r27 = TSK_K_FP(tsk);
80 frame_info->regs.r28 = TSK_K_ESP(tsk);
81 frame_info->regs.r31 = TSK_K_BLINK(tsk);
82 frame_info->regs.r63 = (unsigned int)__switch_to;
83
84 /* In the prologue of __switch_to, first FP is saved on stack
85 * and then SP is copied to FP. Dwarf assumes cfa as FP based
86 * but we didn't save FP. The value retrieved above is FP's
87 * state in previous frame.
88 * As a work around for this, we unwind from __switch_to start
89 * and adjust SP accordingly. The other limitation is that
90 * __switch_to macro is dwarf rules are not generated for inline
91 * assembly code
92 */
93 frame_info->regs.r27 = 0;
94 frame_info->regs.r28 += 60;
95 frame_info->call_frame = 0;
96
97 } else {
98 /*
99 * Asynchronous unwinding of intr/exception
100 * - Just uses the pt_regs passed
101 */
102 frame_info->task = tsk;
103
104 frame_info->regs.r27 = regs->fp;
105 frame_info->regs.r28 = regs->sp;
106 frame_info->regs.r31 = regs->blink;
107 frame_info->regs.r63 = regs->ret;
108 frame_info->call_frame = 0;
109 }
110
111 return 0;
112 }
113
114 #endif
115
116 notrace noinline unsigned int
arc_unwind_core(struct task_struct * tsk,struct pt_regs * regs,int (* consumer_fn)(unsigned int,void *),void * arg)117 arc_unwind_core(struct task_struct *tsk, struct pt_regs *regs,
118 int (*consumer_fn) (unsigned int, void *), void *arg)
119 {
120 #ifdef CONFIG_ARC_DW2_UNWIND
121 int ret = 0, cnt = 0;
122 unsigned int address;
123 struct unwind_frame_info frame_info;
124
125 if (seed_unwind_frame_info(tsk, regs, &frame_info))
126 return 0;
127
128 while (1) {
129 address = UNW_PC(&frame_info);
130
131 if (!address || !__kernel_text_address(address))
132 break;
133
134 if (consumer_fn(address, arg) == -1)
135 break;
136
137 ret = arc_unwind(&frame_info);
138 if (ret)
139 break;
140
141 frame_info.regs.r63 = frame_info.regs.r31;
142
143 if (cnt++ > 128) {
144 printk("unwinder looping too long, aborting !\n");
145 return 0;
146 }
147 }
148
149 return address; /* return the last address it saw */
150 #else
151 /* On ARC, only Dward based unwinder works. fp based backtracing is
152 * not possible (-fno-omit-frame-pointer) because of the way function
153 * prelogue is setup (callee regs saved and then fp set and not other
154 * way around
155 */
156 pr_warn_once("CONFIG_ARC_DW2_UNWIND needs to be enabled\n");
157 return 0;
158
159 #endif
160 }
161
162 /*-------------------------------------------------------------------------
163 * callbacks called by unwinder iterator to implement kernel APIs
164 *
165 * The callback can return -1 to force the iterator to stop, which by default
166 * keeps going till the bottom-most frame.
167 *-------------------------------------------------------------------------
168 */
169
170 /* Call-back which plugs into unwinding core to dump the stack in
171 * case of panic/OOPs/BUG etc
172 */
__print_sym(unsigned int address,void * unused)173 static int __print_sym(unsigned int address, void *unused)
174 {
175 printk(" %pS\n", (void *)address);
176 return 0;
177 }
178
179 #ifdef CONFIG_STACKTRACE
180
181 /* Call-back which plugs into unwinding core to capture the
182 * traces needed by kernel on /proc/<pid>/stack
183 */
__collect_all(unsigned int address,void * arg)184 static int __collect_all(unsigned int address, void *arg)
185 {
186 struct stack_trace *trace = arg;
187
188 if (trace->skip > 0)
189 trace->skip--;
190 else
191 trace->entries[trace->nr_entries++] = address;
192
193 if (trace->nr_entries >= trace->max_entries)
194 return -1;
195
196 return 0;
197 }
198
__collect_all_but_sched(unsigned int address,void * arg)199 static int __collect_all_but_sched(unsigned int address, void *arg)
200 {
201 struct stack_trace *trace = arg;
202
203 if (in_sched_functions(address))
204 return 0;
205
206 if (trace->skip > 0)
207 trace->skip--;
208 else
209 trace->entries[trace->nr_entries++] = address;
210
211 if (trace->nr_entries >= trace->max_entries)
212 return -1;
213
214 return 0;
215 }
216
217 #endif
218
__get_first_nonsched(unsigned int address,void * unused)219 static int __get_first_nonsched(unsigned int address, void *unused)
220 {
221 if (in_sched_functions(address))
222 return 0;
223
224 return -1;
225 }
226
227 /*-------------------------------------------------------------------------
228 * APIs expected by various kernel sub-systems
229 *-------------------------------------------------------------------------
230 */
231
show_stacktrace(struct task_struct * tsk,struct pt_regs * regs)232 noinline void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs)
233 {
234 pr_info("\nStack Trace:\n");
235 arc_unwind_core(tsk, regs, __print_sym, NULL);
236 }
237 EXPORT_SYMBOL(show_stacktrace);
238
239 /* Expected by sched Code */
show_stack(struct task_struct * tsk,unsigned long * sp)240 void show_stack(struct task_struct *tsk, unsigned long *sp)
241 {
242 show_stacktrace(tsk, NULL);
243 }
244
245 /* Another API expected by schedular, shows up in "ps" as Wait Channel
246 * Of course just returning schedule( ) would be pointless so unwind until
247 * the function is not in schedular code
248 */
get_wchan(struct task_struct * tsk)249 unsigned int get_wchan(struct task_struct *tsk)
250 {
251 return arc_unwind_core(tsk, NULL, __get_first_nonsched, NULL);
252 }
253
254 #ifdef CONFIG_STACKTRACE
255
256 /*
257 * API required by CONFIG_STACKTRACE, CONFIG_LATENCYTOP.
258 * A typical use is when /proc/<pid>/stack is queried by userland
259 */
save_stack_trace_tsk(struct task_struct * tsk,struct stack_trace * trace)260 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
261 {
262 /* Assumes @tsk is sleeping so unwinds from __switch_to */
263 arc_unwind_core(tsk, NULL, __collect_all_but_sched, trace);
264 }
265
save_stack_trace(struct stack_trace * trace)266 void save_stack_trace(struct stack_trace *trace)
267 {
268 /* Pass NULL for task so it unwinds the current call frame */
269 arc_unwind_core(NULL, NULL, __collect_all, trace);
270 }
271 EXPORT_SYMBOL_GPL(save_stack_trace);
272 #endif
273