1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/compiler.h>
3 #include <elfutils/libdw.h>
4 #include <elfutils/libdwfl.h>
5 #include <inttypes.h>
6 #include <errno.h>
7 #include "debug.h"
8 #include "dso.h"
9 #include "unwind.h"
10 #include "unwind-libdw.h"
11 #include "machine.h"
12 #include "map.h"
13 #include "symbol.h"
14 #include "thread.h"
15 #include <linux/types.h>
16 #include <linux/zalloc.h>
17 #include "event.h"
18 #include "perf_regs.h"
19 #include "callchain.h"
20
21 static char *debuginfo_path;
22
__find_debuginfo(Dwfl_Module * mod __maybe_unused,void ** userdata,const char * modname __maybe_unused,Dwarf_Addr base __maybe_unused,const char * file_name,const char * debuglink_file __maybe_unused,GElf_Word debuglink_crc __maybe_unused,char ** debuginfo_file_name)23 static int __find_debuginfo(Dwfl_Module *mod __maybe_unused, void **userdata,
24 const char *modname __maybe_unused, Dwarf_Addr base __maybe_unused,
25 const char *file_name, const char *debuglink_file __maybe_unused,
26 GElf_Word debuglink_crc __maybe_unused, char **debuginfo_file_name)
27 {
28 const struct dso *dso = *userdata;
29
30 assert(dso);
31 if (dso->symsrc_filename && strcmp (file_name, dso->symsrc_filename))
32 *debuginfo_file_name = strdup(dso->symsrc_filename);
33 return -1;
34 }
35
36 static const Dwfl_Callbacks offline_callbacks = {
37 .find_debuginfo = __find_debuginfo,
38 .debuginfo_path = &debuginfo_path,
39 .section_address = dwfl_offline_section_address,
40 // .find_elf is not set as we use dwfl_report_elf() instead.
41 };
42
__report_module(struct addr_location * al,u64 ip,struct unwind_info * ui)43 static int __report_module(struct addr_location *al, u64 ip,
44 struct unwind_info *ui)
45 {
46 Dwfl_Module *mod;
47 struct dso *dso = NULL;
48 /*
49 * Some callers will use al->sym, so we can't just use the
50 * cheaper thread__find_map() here.
51 */
52 thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al);
53
54 if (al->map)
55 dso = al->map->dso;
56
57 if (!dso)
58 return 0;
59
60 mod = dwfl_addrmodule(ui->dwfl, ip);
61 if (mod) {
62 Dwarf_Addr s;
63
64 dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
65 if (s != al->map->start - al->map->pgoff)
66 mod = 0;
67 }
68
69 if (!mod)
70 mod = dwfl_report_elf(ui->dwfl, dso->short_name, dso->long_name, -1,
71 al->map->start - al->map->pgoff, false);
72 if (!mod) {
73 char filename[PATH_MAX];
74
75 if (dso__build_id_filename(dso, filename, sizeof(filename), false))
76 mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
77 al->map->start - al->map->pgoff, false);
78 }
79
80 if (mod) {
81 void **userdatap;
82
83 dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL);
84 *userdatap = dso;
85 }
86
87 return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
88 }
89
report_module(u64 ip,struct unwind_info * ui)90 static int report_module(u64 ip, struct unwind_info *ui)
91 {
92 struct addr_location al;
93
94 return __report_module(&al, ip, ui);
95 }
96
97 /*
98 * Store all entries within entries array,
99 * we will process it after we finish unwind.
100 */
entry(u64 ip,struct unwind_info * ui)101 static int entry(u64 ip, struct unwind_info *ui)
102
103 {
104 struct unwind_entry *e = &ui->entries[ui->idx++];
105 struct addr_location al;
106
107 if (__report_module(&al, ip, ui))
108 return -1;
109
110 e->ip = ip;
111 e->ms.maps = al.maps;
112 e->ms.map = al.map;
113 e->ms.sym = al.sym;
114
115 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
116 al.sym ? al.sym->name : "''",
117 ip,
118 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
119 return 0;
120 }
121
next_thread(Dwfl * dwfl,void * arg,void ** thread_argp)122 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
123 {
124 /* We want only single thread to be processed. */
125 if (*thread_argp != NULL)
126 return 0;
127
128 *thread_argp = arg;
129 return dwfl_pid(dwfl);
130 }
131
access_dso_mem(struct unwind_info * ui,Dwarf_Addr addr,Dwarf_Word * data)132 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
133 Dwarf_Word *data)
134 {
135 struct addr_location al;
136 ssize_t size;
137
138 if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
139 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
140 return -1;
141 }
142
143 if (!al.map->dso)
144 return -1;
145
146 size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
147 addr, (u8 *) data, sizeof(*data));
148
149 return !(size == sizeof(*data));
150 }
151
memory_read(Dwfl * dwfl __maybe_unused,Dwarf_Addr addr,Dwarf_Word * result,void * arg)152 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
153 void *arg)
154 {
155 struct unwind_info *ui = arg;
156 struct stack_dump *stack = &ui->sample->user_stack;
157 u64 start, end;
158 int offset;
159 int ret;
160
161 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
162 if (ret)
163 return false;
164
165 end = start + stack->size;
166
167 /* Check overflow. */
168 if (addr + sizeof(Dwarf_Word) < addr)
169 return false;
170
171 if (addr < start || addr + sizeof(Dwarf_Word) > end) {
172 ret = access_dso_mem(ui, addr, result);
173 if (ret) {
174 pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
175 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
176 addr, start, end);
177 return false;
178 }
179 return true;
180 }
181
182 offset = addr - start;
183 *result = *(Dwarf_Word *)&stack->data[offset];
184 pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
185 addr, (unsigned long)*result, offset);
186 return true;
187 }
188
189 static const Dwfl_Thread_Callbacks callbacks = {
190 .next_thread = next_thread,
191 .memory_read = memory_read,
192 .set_initial_registers = libdw__arch_set_initial_registers,
193 };
194
195 static int
frame_callback(Dwfl_Frame * state,void * arg)196 frame_callback(Dwfl_Frame *state, void *arg)
197 {
198 struct unwind_info *ui = arg;
199 Dwarf_Addr pc;
200 bool isactivation;
201
202 if (!dwfl_frame_pc(state, &pc, NULL)) {
203 if (!ui->best_effort)
204 pr_err("%s", dwfl_errmsg(-1));
205 return DWARF_CB_ABORT;
206 }
207
208 // report the module before we query for isactivation
209 report_module(pc, ui);
210
211 if (!dwfl_frame_pc(state, &pc, &isactivation)) {
212 if (!ui->best_effort)
213 pr_err("%s", dwfl_errmsg(-1));
214 return DWARF_CB_ABORT;
215 }
216
217 if (!isactivation)
218 --pc;
219
220 return entry(pc, ui) || !(--ui->max_stack) ?
221 DWARF_CB_ABORT : DWARF_CB_OK;
222 }
223
unwind__get_entries(unwind_entry_cb_t cb,void * arg,struct thread * thread,struct perf_sample * data,int max_stack,bool best_effort)224 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
225 struct thread *thread,
226 struct perf_sample *data,
227 int max_stack,
228 bool best_effort)
229 {
230 struct unwind_info *ui, ui_buf = {
231 .sample = data,
232 .thread = thread,
233 .machine = thread->maps->machine,
234 .cb = cb,
235 .arg = arg,
236 .max_stack = max_stack,
237 .best_effort = best_effort
238 };
239 Dwarf_Word ip;
240 int err = -EINVAL, i;
241
242 if (!data->user_regs.regs)
243 return -EINVAL;
244
245 ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
246 if (!ui)
247 return -ENOMEM;
248
249 *ui = ui_buf;
250
251 ui->dwfl = dwfl_begin(&offline_callbacks);
252 if (!ui->dwfl)
253 goto out;
254
255 err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
256 if (err)
257 goto out;
258
259 err = report_module(ip, ui);
260 if (err)
261 goto out;
262
263 err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread->tid, &callbacks, ui);
264 if (err)
265 goto out;
266
267 err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
268
269 if (err && ui->max_stack != max_stack)
270 err = 0;
271
272 /*
273 * Display what we got based on the order setup.
274 */
275 for (i = 0; i < ui->idx && !err; i++) {
276 int j = i;
277
278 if (callchain_param.order == ORDER_CALLER)
279 j = ui->idx - i - 1;
280
281 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
282 }
283
284 out:
285 if (err)
286 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
287
288 dwfl_end(ui->dwfl);
289 free(ui);
290 return 0;
291 }
292
