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 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
110 notrace noinline unsigned int
111 arc_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 */
161 static 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 */
172 static 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
187 static 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
207 static 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
220 noinline 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 }
225 EXPORT_SYMBOL(show_stacktrace);
226
227 /* Expected by sched Code */
228 void 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 */
237 unsigned 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 */
248 void 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
254 void 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 }
259 EXPORT_SYMBOL_GPL(save_stack_trace);
260 #endif