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 #include "util/env.h"
21
22 static char *debuginfo_path;
23
__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)24 static int __find_debuginfo(Dwfl_Module *mod __maybe_unused, void **userdata,
25 const char *modname __maybe_unused, Dwarf_Addr base __maybe_unused,
26 const char *file_name, const char *debuglink_file __maybe_unused,
27 GElf_Word debuglink_crc __maybe_unused, char **debuginfo_file_name)
28 {
29 const struct dso *dso = *userdata;
30
31 assert(dso);
32 if (dso->symsrc_filename && strcmp (file_name, dso->symsrc_filename))
33 *debuginfo_file_name = strdup(dso->symsrc_filename);
34 return -1;
35 }
36
37 static const Dwfl_Callbacks offline_callbacks = {
38 .find_debuginfo = __find_debuginfo,
39 .debuginfo_path = &debuginfo_path,
40 .section_address = dwfl_offline_section_address,
41 // .find_elf is not set as we use dwfl_report_elf() instead.
42 };
43
__report_module(struct addr_location * al,u64 ip,struct unwind_info * ui)44 static int __report_module(struct addr_location *al, u64 ip,
45 struct unwind_info *ui)
46 {
47 Dwfl_Module *mod;
48 struct dso *dso = NULL;
49 Dwarf_Addr base;
50 /*
51 * Some callers will use al->sym, so we can't just use the
52 * cheaper thread__find_map() here.
53 */
54 thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al);
55
56 if (al->map)
57 dso = map__dso(al->map);
58
59 if (!dso)
60 return 0;
61
62 /*
63 * The generated JIT DSO files only map the code segment without
64 * ELF headers. Since JIT codes used to be packed in a memory
65 * segment, calculating the base address using pgoff falls into
66 * a different code in another DSO. So just use the map->start
67 * directly to pick the correct one.
68 */
69 if (!strncmp(dso->long_name, "/tmp/jitted-", 12))
70 base = map__start(al->map);
71 else
72 base = map__start(al->map) - map__pgoff(al->map);
73
74 mod = dwfl_addrmodule(ui->dwfl, ip);
75 if (mod) {
76 Dwarf_Addr s;
77
78 dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
79 if (s != base)
80 mod = NULL;
81 }
82
83 if (!mod) {
84 char filename[PATH_MAX];
85
86 __symbol__join_symfs(filename, sizeof(filename), dso->long_name);
87 mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
88 base, false);
89 }
90 if (!mod) {
91 char filename[PATH_MAX];
92
93 if (dso__build_id_filename(dso, filename, sizeof(filename), false))
94 mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
95 base, false);
96 }
97
98 if (mod) {
99 void **userdatap;
100
101 dwfl_module_info(mod, &userdatap, NULL, NULL, NULL, NULL, NULL, NULL);
102 *userdatap = dso;
103 }
104
105 return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
106 }
107
report_module(u64 ip,struct unwind_info * ui)108 static int report_module(u64 ip, struct unwind_info *ui)
109 {
110 struct addr_location al;
111 int res;
112
113 addr_location__init(&al);
114 res = __report_module(&al, ip, ui);
115 addr_location__exit(&al);
116 return res;
117 }
118
119 /*
120 * Store all entries within entries array,
121 * we will process it after we finish unwind.
122 */
entry(u64 ip,struct unwind_info * ui)123 static int entry(u64 ip, struct unwind_info *ui)
124
125 {
126 struct unwind_entry *e = &ui->entries[ui->idx++];
127 struct addr_location al;
128
129 addr_location__init(&al);
130 if (__report_module(&al, ip, ui)) {
131 addr_location__exit(&al);
132 return -1;
133 }
134
135 e->ip = ip;
136 e->ms.maps = al.maps;
137 e->ms.map = al.map;
138 e->ms.sym = al.sym;
139
140 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
141 al.sym ? al.sym->name : "''",
142 ip,
143 al.map ? map__map_ip(al.map, ip) : (u64) 0);
144 addr_location__exit(&al);
145 return 0;
146 }
147
next_thread(Dwfl * dwfl,void * arg,void ** thread_argp)148 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
149 {
150 /* We want only single thread to be processed. */
151 if (*thread_argp != NULL)
152 return 0;
153
154 *thread_argp = arg;
155 return dwfl_pid(dwfl);
156 }
157
access_dso_mem(struct unwind_info * ui,Dwarf_Addr addr,Dwarf_Word * data)158 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
159 Dwarf_Word *data)
160 {
161 struct addr_location al;
162 ssize_t size;
163 struct dso *dso;
164
165 addr_location__init(&al);
166 if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
167 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
168 goto out_fail;
169 }
170 dso = map__dso(al.map);
171 if (!dso)
172 goto out_fail;
173
174 size = dso__data_read_addr(dso, al.map, ui->machine, addr, (u8 *) data, sizeof(*data));
175
176 addr_location__exit(&al);
177 return !(size == sizeof(*data));
178 out_fail:
179 addr_location__exit(&al);
180 return -1;
181 }
182
memory_read(Dwfl * dwfl __maybe_unused,Dwarf_Addr addr,Dwarf_Word * result,void * arg)183 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
184 void *arg)
185 {
186 struct unwind_info *ui = arg;
187 const char *arch = perf_env__arch(ui->machine->env);
188 struct stack_dump *stack = &ui->sample->user_stack;
189 u64 start, end;
190 int offset;
191 int ret;
192
193 ret = perf_reg_value(&start, &ui->sample->user_regs,
194 perf_arch_reg_sp(arch));
195 if (ret)
196 return false;
197
198 end = start + stack->size;
199
200 /* Check overflow. */
201 if (addr + sizeof(Dwarf_Word) < addr)
202 return false;
203
204 if (addr < start || addr + sizeof(Dwarf_Word) > end) {
205 ret = access_dso_mem(ui, addr, result);
206 if (ret) {
207 pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
208 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
209 addr, start, end);
210 return false;
211 }
212 return true;
213 }
214
215 offset = addr - start;
216 *result = *(Dwarf_Word *)&stack->data[offset];
217 pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
218 addr, (unsigned long)*result, offset);
219 return true;
220 }
221
222 static const Dwfl_Thread_Callbacks callbacks = {
223 .next_thread = next_thread,
224 .memory_read = memory_read,
225 .set_initial_registers = libdw__arch_set_initial_registers,
226 };
227
228 static int
frame_callback(Dwfl_Frame * state,void * arg)229 frame_callback(Dwfl_Frame *state, void *arg)
230 {
231 struct unwind_info *ui = arg;
232 Dwarf_Addr pc;
233 bool isactivation;
234
235 if (!dwfl_frame_pc(state, &pc, NULL)) {
236 if (!ui->best_effort)
237 pr_err("%s", dwfl_errmsg(-1));
238 return DWARF_CB_ABORT;
239 }
240
241 // report the module before we query for isactivation
242 report_module(pc, ui);
243
244 if (!dwfl_frame_pc(state, &pc, &isactivation)) {
245 if (!ui->best_effort)
246 pr_err("%s", dwfl_errmsg(-1));
247 return DWARF_CB_ABORT;
248 }
249
250 if (!isactivation)
251 --pc;
252
253 return entry(pc, ui) || !(--ui->max_stack) ?
254 DWARF_CB_ABORT : DWARF_CB_OK;
255 }
256
unwind__get_entries(unwind_entry_cb_t cb,void * arg,struct thread * thread,struct perf_sample * data,int max_stack,bool best_effort)257 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
258 struct thread *thread,
259 struct perf_sample *data,
260 int max_stack,
261 bool best_effort)
262 {
263 struct unwind_info *ui, ui_buf = {
264 .sample = data,
265 .thread = thread,
266 .machine = RC_CHK_ACCESS(thread__maps(thread))->machine,
267 .cb = cb,
268 .arg = arg,
269 .max_stack = max_stack,
270 .best_effort = best_effort
271 };
272 const char *arch = perf_env__arch(ui_buf.machine->env);
273 Dwarf_Word ip;
274 int err = -EINVAL, i;
275
276 if (!data->user_regs.regs)
277 return -EINVAL;
278
279 ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
280 if (!ui)
281 return -ENOMEM;
282
283 *ui = ui_buf;
284
285 ui->dwfl = dwfl_begin(&offline_callbacks);
286 if (!ui->dwfl)
287 goto out;
288
289 err = perf_reg_value(&ip, &data->user_regs, perf_arch_reg_ip(arch));
290 if (err)
291 goto out;
292
293 err = report_module(ip, ui);
294 if (err)
295 goto out;
296
297 err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread__tid(thread), &callbacks, ui);
298 if (err)
299 goto out;
300
301 err = dwfl_getthread_frames(ui->dwfl, thread__tid(thread), frame_callback, ui);
302
303 if (err && ui->max_stack != max_stack)
304 err = 0;
305
306 /*
307 * Display what we got based on the order setup.
308 */
309 for (i = 0; i < ui->idx && !err; i++) {
310 int j = i;
311
312 if (callchain_param.order == ORDER_CALLER)
313 j = ui->idx - i - 1;
314
315 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
316 }
317
318 out:
319 if (err)
320 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
321
322 dwfl_end(ui->dwfl);
323 free(ui);
324 return 0;
325 }
326