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