2 * Post mortem Dwarf CFI based unwinding on top of regs and stack dumps.
4 * Lots of this code have been borrowed or heavily inspired from parts of
5 * the libunwind 0.99 code which are (amongst other contributors I may have
8 * Copyright (C) 2002-2007 Hewlett-Packard Co
9 * Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
11 * And the bugs have been added by:
13 * Copyright (C) 2010, Frederic Weisbecker <fweisbec@gmail.com>
14 * Copyright (C) 2012, Jiri Olsa <jolsa@redhat.com>
24 #include <linux/list.h>
25 #include <libunwind.h>
26 #include <libunwind-ptrace.h>
27 #include "callchain.h"
30 #include "perf_regs.h"
37 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
41 int need_unwind_info, void *arg);
43 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
46 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
49 const char *obj_name, unw_word_t start,
52 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
54 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
55 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
57 /* Pointer-encoding formats: */
58 #define DW_EH_PE_omit 0xff
59 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
60 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
61 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
62 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
63 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
65 /* Pointer-encoding application: */
66 #define DW_EH_PE_absptr 0x00 /* absolute value */
67 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
70 * The following are not documented by LSB v1.3, yet they are used by
71 * GCC, presumably they aren't documented by LSB since they aren't
74 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
75 #define DW_EH_PE_aligned 0x50 /* aligned pointer */
77 /* Flags intentionaly not handled, since they're not needed:
78 * #define DW_EH_PE_indirect 0x80
79 * #define DW_EH_PE_uleb128 0x01
80 * #define DW_EH_PE_udata2 0x02
81 * #define DW_EH_PE_sleb128 0x09
82 * #define DW_EH_PE_sdata2 0x0a
83 * #define DW_EH_PE_textrel 0x20
84 * #define DW_EH_PE_datarel 0x30
88 struct perf_sample *sample;
89 struct machine *machine;
90 struct thread *thread;
93 #define dw_read(ptr, type, end) ({ \
94 type *__p = (type *) ptr; \
96 if ((__p + 1) > (type *) end) \
99 ptr = (typeof(ptr)) __p; \
103 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
114 *val = dw_read(cur, unsigned long, end);
120 switch (encoding & DW_EH_PE_APPL_MASK) {
121 case DW_EH_PE_absptr:
124 *val = (unsigned long) cur;
130 if ((encoding & 0x07) == 0x00)
131 encoding |= DW_EH_PE_udata4;
133 switch (encoding & DW_EH_PE_FORMAT_MASK) {
134 case DW_EH_PE_sdata4:
135 *val += dw_read(cur, s32, end);
137 case DW_EH_PE_udata4:
138 *val += dw_read(cur, u32, end);
140 case DW_EH_PE_sdata8:
141 *val += dw_read(cur, s64, end);
143 case DW_EH_PE_udata8:
144 *val += dw_read(cur, u64, end);
155 #define dw_read_encoded_value(ptr, end, enc) ({ \
157 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
163 static u64 elf_section_offset(int fd, const char *name)
170 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
175 if (gelf_getehdr(elf, &ehdr) == NULL)
178 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
181 offset = shdr.sh_offset;
188 #ifndef NO_LIBUNWIND_DEBUG_FRAME
189 static int elf_is_exec(int fd, const char *name)
195 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
198 if (gelf_getehdr(elf, &ehdr) == NULL)
201 retval = (ehdr.e_type == ET_EXEC);
205 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
215 struct eh_frame_hdr {
216 unsigned char version;
217 unsigned char eh_frame_ptr_enc;
218 unsigned char fde_count_enc;
219 unsigned char table_enc;
222 * The rest of the header is variable-length and consists of the
225 * encoded_t eh_frame_ptr;
226 * encoded_t fde_count;
229 /* A single encoded pointer should not be more than 8 bytes. */
234 * encoded_t start_ip;
235 * encoded_t fde_addr;
236 * } binary_search_table[fde_count];
241 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
242 u64 offset, u64 *table_data, u64 *segbase,
245 struct eh_frame_hdr hdr;
246 u8 *enc = (u8 *) &hdr.enc;
247 u8 *end = (u8 *) &hdr.data;
250 r = dso__data_read_offset(dso, machine, offset,
251 (u8 *) &hdr, sizeof(hdr));
252 if (r != sizeof(hdr))
255 /* We dont need eh_frame_ptr, just skip it. */
256 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
258 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
260 *table_data = (enc - (u8 *) &hdr) + offset;
264 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
265 u64 *table_data, u64 *segbase,
268 int ret = -EINVAL, fd;
269 u64 offset = dso->data.eh_frame_hdr_offset;
272 fd = dso__data_fd(dso, machine);
276 /* Check the .eh_frame section for unwinding info */
277 offset = elf_section_offset(fd, ".eh_frame_hdr");
278 dso->data.eh_frame_hdr_offset = offset;
282 ret = unwind_spec_ehframe(dso, machine, offset,
289 #ifndef NO_LIBUNWIND_DEBUG_FRAME
290 static int read_unwind_spec_debug_frame(struct dso *dso,
291 struct machine *machine, u64 *offset)
294 u64 ofs = dso->data.debug_frame_offset;
297 fd = dso__data_fd(dso, machine);
301 /* Check the .debug_frame section for unwinding info */
302 ofs = elf_section_offset(fd, ".debug_frame");
303 dso->data.debug_frame_offset = ofs;
314 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
316 struct addr_location al;
318 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
319 MAP__FUNCTION, ip, &al);
324 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
325 int need_unwind_info, void *arg)
327 struct unwind_info *ui = arg;
330 u64 table_data, segbase, fde_count;
332 map = find_map(ip, ui);
333 if (!map || !map->dso)
336 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
338 /* Check the .eh_frame section for unwinding info */
339 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
340 &table_data, &segbase, &fde_count)) {
341 memset(&di, 0, sizeof(di));
342 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
343 di.start_ip = map->start;
344 di.end_ip = map->end;
345 di.u.rti.segbase = map->start + segbase;
346 di.u.rti.table_data = map->start + table_data;
347 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
348 / sizeof(unw_word_t);
349 return dwarf_search_unwind_table(as, ip, &di, pi,
350 need_unwind_info, arg);
353 #ifndef NO_LIBUNWIND_DEBUG_FRAME
354 /* Check the .debug_frame section for unwinding info */
355 if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
356 int fd = dso__data_fd(map->dso, ui->machine);
357 int is_exec = elf_is_exec(fd, map->dso->name);
358 unw_word_t base = is_exec ? 0 : map->start;
360 memset(&di, 0, sizeof(di));
361 if (dwarf_find_debug_frame(0, &di, ip, base, map->dso->name,
362 map->start, map->end))
363 return dwarf_search_unwind_table(as, ip, &di, pi,
364 need_unwind_info, arg);
371 static int access_fpreg(unw_addr_space_t __maybe_unused as,
372 unw_regnum_t __maybe_unused num,
373 unw_fpreg_t __maybe_unused *val,
374 int __maybe_unused __write,
375 void __maybe_unused *arg)
377 pr_err("unwind: access_fpreg unsupported\n");
381 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
382 unw_word_t __maybe_unused *dil_addr,
383 void __maybe_unused *arg)
388 static int resume(unw_addr_space_t __maybe_unused as,
389 unw_cursor_t __maybe_unused *cu,
390 void __maybe_unused *arg)
392 pr_err("unwind: resume unsupported\n");
397 get_proc_name(unw_addr_space_t __maybe_unused as,
398 unw_word_t __maybe_unused addr,
399 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
400 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
402 pr_err("unwind: get_proc_name unsupported\n");
406 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
409 struct addr_location al;
412 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
413 MAP__FUNCTION, addr, &al);
415 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
422 size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
423 addr, (u8 *) data, sizeof(*data));
425 return !(size == sizeof(*data));
428 static int access_mem(unw_addr_space_t __maybe_unused as,
429 unw_word_t addr, unw_word_t *valp,
430 int __write, void *arg)
432 struct unwind_info *ui = arg;
433 struct stack_dump *stack = &ui->sample->user_stack;
438 /* Don't support write, probably not needed. */
439 if (__write || !stack || !ui->sample->user_regs.regs) {
444 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
448 end = start + stack->size;
450 /* Check overflow. */
451 if (addr + sizeof(unw_word_t) < addr)
454 if (addr < start || addr + sizeof(unw_word_t) >= end) {
455 ret = access_dso_mem(ui, addr, valp);
457 pr_debug("unwind: access_mem %p not inside range"
458 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
459 (void *) addr, start, end);
466 offset = addr - start;
467 *valp = *(unw_word_t *)&stack->data[offset];
468 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
469 (void *) addr, (unsigned long)*valp, offset);
473 static int access_reg(unw_addr_space_t __maybe_unused as,
474 unw_regnum_t regnum, unw_word_t *valp,
475 int __write, void *arg)
477 struct unwind_info *ui = arg;
481 /* Don't support write, I suspect we don't need it. */
483 pr_err("unwind: access_reg w %d\n", regnum);
487 if (!ui->sample->user_regs.regs) {
492 id = libunwind__arch_reg_id(regnum);
496 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
498 pr_err("unwind: can't read reg %d\n", regnum);
502 *valp = (unw_word_t) val;
503 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
507 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
508 unw_proc_info_t *pi __maybe_unused,
509 void *arg __maybe_unused)
511 pr_debug("unwind: put_unwind_info called\n");
514 static int entry(u64 ip, struct thread *thread,
515 unwind_entry_cb_t cb, void *arg)
517 struct unwind_entry e;
518 struct addr_location al;
520 thread__find_addr_location(thread, PERF_RECORD_MISC_USER,
521 MAP__FUNCTION, ip, &al);
527 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
528 al.sym ? al.sym->name : "''",
530 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
535 static void display_error(int err)
539 pr_err("unwind: Only supports local.\n");
542 pr_err("unwind: Unspecified error.\n");
545 pr_err("unwind: Register unavailable.\n");
552 static unw_accessors_t accessors = {
553 .find_proc_info = find_proc_info,
554 .put_unwind_info = put_unwind_info,
555 .get_dyn_info_list_addr = get_dyn_info_list_addr,
556 .access_mem = access_mem,
557 .access_reg = access_reg,
558 .access_fpreg = access_fpreg,
560 .get_proc_name = get_proc_name,
563 int unwind__prepare_access(struct thread *thread)
565 unw_addr_space_t addr_space;
567 if (callchain_param.record_mode != CALLCHAIN_DWARF)
570 addr_space = unw_create_addr_space(&accessors, 0);
572 pr_err("unwind: Can't create unwind address space.\n");
576 unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL);
577 thread__set_priv(thread, addr_space);
582 void unwind__flush_access(struct thread *thread)
584 unw_addr_space_t addr_space;
586 if (callchain_param.record_mode != CALLCHAIN_DWARF)
589 addr_space = thread__priv(thread);
590 unw_flush_cache(addr_space, 0, 0);
593 void unwind__finish_access(struct thread *thread)
595 unw_addr_space_t addr_space;
597 if (callchain_param.record_mode != CALLCHAIN_DWARF)
600 addr_space = thread__priv(thread);
601 unw_destroy_addr_space(addr_space);
604 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
605 void *arg, int max_stack)
607 unw_addr_space_t addr_space;
611 addr_space = thread__priv(ui->thread);
612 if (addr_space == NULL)
615 ret = unw_init_remote(&c, addr_space, ui);
619 while (!ret && (unw_step(&c) > 0) && max_stack--) {
622 unw_get_reg(&c, UNW_REG_IP, &ip);
623 ret = ip ? entry(ip, ui->thread, cb, arg) : 0;
629 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
630 struct thread *thread,
631 struct perf_sample *data, int max_stack)
634 struct unwind_info ui = {
637 .machine = thread->mg->machine,
641 if (!data->user_regs.regs)
644 ret = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
648 ret = entry(ip, thread, cb, arg);
652 return --max_stack > 0 ? get_entries(&ui, cb, arg, max_stack) : 0;