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
15static char *debuginfo_path;
16
17static const Dwfl_Callbacks offline_callbacks = {
18	.find_debuginfo		= dwfl_standard_find_debuginfo,
19	.debuginfo_path		= &debuginfo_path,
20	.section_address	= dwfl_offline_section_address,
21};
22
23static int __report_module(struct addr_location *al, u64 ip,
24			    struct unwind_info *ui)
25{
26	Dwfl_Module *mod;
27	struct dso *dso = NULL;
28
29	thread__find_addr_location(ui->thread,
30				   PERF_RECORD_MISC_USER,
31				   MAP__FUNCTION, ip, al);
32
33	if (al->map)
34		dso = al->map->dso;
35
36	if (!dso)
37		return 0;
38
39	mod = dwfl_addrmodule(ui->dwfl, ip);
40	if (!mod)
41		mod = dwfl_report_elf(ui->dwfl, dso->short_name,
42				      dso->long_name, -1, al->map->start,
43				      false);
44
45	return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
46}
47
48static int report_module(u64 ip, struct unwind_info *ui)
49{
50	struct addr_location al;
51
52	return __report_module(&al, ip, ui);
53}
54
55static int entry(u64 ip, struct unwind_info *ui)
56
57{
58	struct unwind_entry e;
59	struct addr_location al;
60
61	if (__report_module(&al, ip, ui))
62		return -1;
63
64	e.ip  = ip;
65	e.map = al.map;
66	e.sym = al.sym;
67
68	pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
69		 al.sym ? al.sym->name : "''",
70		 ip,
71		 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
72
73	return ui->cb(&e, ui->arg);
74}
75
76static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
77{
78	/* We want only single thread to be processed. */
79	if (*thread_argp != NULL)
80		return 0;
81
82	*thread_argp = arg;
83	return dwfl_pid(dwfl);
84}
85
86static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
87			  Dwarf_Word *data)
88{
89	struct addr_location al;
90	ssize_t size;
91
92	thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
93			      MAP__FUNCTION, addr, &al);
94	if (!al.map) {
95		pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
96		return -1;
97	}
98
99	if (!al.map->dso)
100		return -1;
101
102	size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
103				   addr, (u8 *) data, sizeof(*data));
104
105	return !(size == sizeof(*data));
106}
107
108static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
109			void *arg)
110{
111	struct unwind_info *ui = arg;
112	struct stack_dump *stack = &ui->sample->user_stack;
113	u64 start, end;
114	int offset;
115	int ret;
116
117	ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
118	if (ret)
119		return false;
120
121	end = start + stack->size;
122
123	/* Check overflow. */
124	if (addr + sizeof(Dwarf_Word) < addr)
125		return false;
126
127	if (addr < start || addr + sizeof(Dwarf_Word) > end) {
128		ret = access_dso_mem(ui, addr, result);
129		if (ret) {
130			pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
131				 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
132				addr, start, end);
133			return false;
134		}
135		return true;
136	}
137
138	offset  = addr - start;
139	*result = *(Dwarf_Word *)&stack->data[offset];
140	pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
141		 addr, (unsigned long)*result, offset);
142	return true;
143}
144
145static const Dwfl_Thread_Callbacks callbacks = {
146	.next_thread		= next_thread,
147	.memory_read		= memory_read,
148	.set_initial_registers	= libdw__arch_set_initial_registers,
149};
150
151static int
152frame_callback(Dwfl_Frame *state, void *arg)
153{
154	struct unwind_info *ui = arg;
155	Dwarf_Addr pc;
156
157	if (!dwfl_frame_pc(state, &pc, NULL)) {
158		pr_err("%s", dwfl_errmsg(-1));
159		return DWARF_CB_ABORT;
160	}
161
162	return entry(pc, ui) || !(--ui->max_stack) ?
163	       DWARF_CB_ABORT : DWARF_CB_OK;
164}
165
166int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
167			struct thread *thread,
168			struct perf_sample *data,
169			int max_stack)
170{
171	struct unwind_info ui = {
172		.sample		= data,
173		.thread		= thread,
174		.machine	= thread->mg->machine,
175		.cb		= cb,
176		.arg		= arg,
177		.max_stack	= max_stack,
178	};
179	Dwarf_Word ip;
180	int err = -EINVAL;
181
182	if (!data->user_regs.regs)
183		return -EINVAL;
184
185	ui.dwfl = dwfl_begin(&offline_callbacks);
186	if (!ui.dwfl)
187		goto out;
188
189	err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
190	if (err)
191		goto out;
192
193	err = report_module(ip, &ui);
194	if (err)
195		goto out;
196
197	if (!dwfl_attach_state(ui.dwfl, EM_NONE, thread->tid, &callbacks, &ui))
198		goto out;
199
200	err = dwfl_getthread_frames(ui.dwfl, thread->tid, frame_callback, &ui);
201
202	if (err && !ui.max_stack)
203		err = 0;
204
205 out:
206	if (err)
207		pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
208
209	dwfl_end(ui.dwfl);
210	return 0;
211}
212