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 #ifndef REMOTE_UNWIND_LIBUNWIND
26 #include <libunwind.h>
27 #include <libunwind-ptrace.h>
29 #include "callchain.h"
32 #include "perf_regs.h"
41 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
45 int need_unwind_info, void *arg);
47 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
50 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
53 const char *obj_name, unw_word_t start,
56 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
58 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
59 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
61 /* Pointer-encoding formats: */
62 #define DW_EH_PE_omit 0xff
63 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
64 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
65 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
66 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
67 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
69 /* Pointer-encoding application: */
70 #define DW_EH_PE_absptr 0x00 /* absolute value */
71 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
74 * The following are not documented by LSB v1.3, yet they are used by
75 * GCC, presumably they aren't documented by LSB since they aren't
78 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
79 #define DW_EH_PE_aligned 0x50 /* aligned pointer */
81 /* Flags intentionaly not handled, since they're not needed:
82 * #define DW_EH_PE_indirect 0x80
83 * #define DW_EH_PE_uleb128 0x01
84 * #define DW_EH_PE_udata2 0x02
85 * #define DW_EH_PE_sleb128 0x09
86 * #define DW_EH_PE_sdata2 0x0a
87 * #define DW_EH_PE_textrel 0x20
88 * #define DW_EH_PE_datarel 0x30
92 struct perf_sample *sample;
93 struct machine *machine;
94 struct thread *thread;
97 #define dw_read(ptr, type, end) ({ \
98 type *__p = (type *) ptr; \
100 if ((__p + 1) > (type *) end) \
103 ptr = (typeof(ptr)) __p; \
107 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
118 *val = dw_read(cur, unsigned long, end);
124 switch (encoding & DW_EH_PE_APPL_MASK) {
125 case DW_EH_PE_absptr:
128 *val = (unsigned long) cur;
134 if ((encoding & 0x07) == 0x00)
135 encoding |= DW_EH_PE_udata4;
137 switch (encoding & DW_EH_PE_FORMAT_MASK) {
138 case DW_EH_PE_sdata4:
139 *val += dw_read(cur, s32, end);
141 case DW_EH_PE_udata4:
142 *val += dw_read(cur, u32, end);
144 case DW_EH_PE_sdata8:
145 *val += dw_read(cur, s64, end);
147 case DW_EH_PE_udata8:
148 *val += dw_read(cur, u64, end);
159 #define dw_read_encoded_value(ptr, end, enc) ({ \
161 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
167 static u64 elf_section_offset(int fd, const char *name)
174 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
179 if (gelf_getehdr(elf, &ehdr) == NULL)
182 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
185 offset = shdr.sh_offset;
192 #ifndef NO_LIBUNWIND_DEBUG_FRAME
193 static int elf_is_exec(int fd, const char *name)
199 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
202 if (gelf_getehdr(elf, &ehdr) == NULL)
205 retval = (ehdr.e_type == ET_EXEC);
209 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
219 struct eh_frame_hdr {
220 unsigned char version;
221 unsigned char eh_frame_ptr_enc;
222 unsigned char fde_count_enc;
223 unsigned char table_enc;
226 * The rest of the header is variable-length and consists of the
229 * encoded_t eh_frame_ptr;
230 * encoded_t fde_count;
233 /* A single encoded pointer should not be more than 8 bytes. */
238 * encoded_t start_ip;
239 * encoded_t fde_addr;
240 * } binary_search_table[fde_count];
245 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
246 u64 offset, u64 *table_data, u64 *segbase,
249 struct eh_frame_hdr hdr;
250 u8 *enc = (u8 *) &hdr.enc;
251 u8 *end = (u8 *) &hdr.data;
254 r = dso__data_read_offset(dso, machine, offset,
255 (u8 *) &hdr, sizeof(hdr));
256 if (r != sizeof(hdr))
259 /* We dont need eh_frame_ptr, just skip it. */
260 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
262 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
264 *table_data = (enc - (u8 *) &hdr) + offset;
268 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
269 u64 *table_data, u64 *segbase,
272 int ret = -EINVAL, fd;
273 u64 offset = dso->data.eh_frame_hdr_offset;
276 fd = dso__data_get_fd(dso, machine);
280 /* Check the .eh_frame section for unwinding info */
281 offset = elf_section_offset(fd, ".eh_frame_hdr");
282 dso->data.eh_frame_hdr_offset = offset;
283 dso__data_put_fd(dso);
287 ret = unwind_spec_ehframe(dso, machine, offset,
294 #ifndef NO_LIBUNWIND_DEBUG_FRAME
295 static int read_unwind_spec_debug_frame(struct dso *dso,
296 struct machine *machine, u64 *offset)
299 u64 ofs = dso->data.debug_frame_offset;
301 /* debug_frame can reside in:
303 * - debug pointed by symsrc_filename
304 * - gnu_debuglink, which doesn't necessary
305 * has to be pointed by symsrc_filename
308 fd = dso__data_get_fd(dso, machine);
310 ofs = elf_section_offset(fd, ".debug_frame");
311 dso__data_put_fd(dso);
315 fd = open(dso->symsrc_filename, O_RDONLY);
317 ofs = elf_section_offset(fd, ".debug_frame");
323 char *debuglink = malloc(PATH_MAX);
326 ret = dso__read_binary_type_filename(
327 dso, DSO_BINARY_TYPE__DEBUGLINK,
328 machine->root_dir, debuglink, PATH_MAX);
330 fd = open(debuglink, O_RDONLY);
332 ofs = elf_section_offset(fd,
338 if (dso->symsrc_filename != NULL) {
340 "%s: overwrite symsrc(%s,%s)\n",
342 dso->symsrc_filename,
344 free(dso->symsrc_filename);
346 dso->symsrc_filename = debuglink;
352 dso->data.debug_frame_offset = ofs;
363 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
365 struct addr_location al;
367 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
368 MAP__FUNCTION, ip, &al);
371 * We've seen cases (softice) where DWARF unwinder went
372 * through non executable mmaps, which we need to lookup
373 * in MAP__VARIABLE tree.
375 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
376 MAP__VARIABLE, ip, &al);
382 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
383 int need_unwind_info, void *arg)
385 struct unwind_info *ui = arg;
388 u64 table_data, segbase, fde_count;
391 map = find_map(ip, ui);
392 if (!map || !map->dso)
395 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
397 /* Check the .eh_frame section for unwinding info */
398 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
399 &table_data, &segbase, &fde_count)) {
400 memset(&di, 0, sizeof(di));
401 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
402 di.start_ip = map->start;
403 di.end_ip = map->end;
404 di.u.rti.segbase = map->start + segbase - map->pgoff;
405 di.u.rti.table_data = map->start + table_data - map->pgoff;
406 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
407 / sizeof(unw_word_t);
408 ret = dwarf_search_unwind_table(as, ip, &di, pi,
409 need_unwind_info, arg);
412 #ifndef NO_LIBUNWIND_DEBUG_FRAME
413 /* Check the .debug_frame section for unwinding info */
415 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
416 int fd = dso__data_get_fd(map->dso, ui->machine);
417 int is_exec = elf_is_exec(fd, map->dso->name);
418 unw_word_t base = is_exec ? 0 : map->start;
422 dso__data_put_fd(map->dso);
424 symfile = map->dso->symsrc_filename ?: map->dso->name;
426 memset(&di, 0, sizeof(di));
427 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
428 map->start, map->end))
429 return dwarf_search_unwind_table(as, ip, &di, pi,
430 need_unwind_info, arg);
437 static int access_fpreg(unw_addr_space_t __maybe_unused as,
438 unw_regnum_t __maybe_unused num,
439 unw_fpreg_t __maybe_unused *val,
440 int __maybe_unused __write,
441 void __maybe_unused *arg)
443 pr_err("unwind: access_fpreg unsupported\n");
447 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
448 unw_word_t __maybe_unused *dil_addr,
449 void __maybe_unused *arg)
454 static int resume(unw_addr_space_t __maybe_unused as,
455 unw_cursor_t __maybe_unused *cu,
456 void __maybe_unused *arg)
458 pr_err("unwind: resume unsupported\n");
463 get_proc_name(unw_addr_space_t __maybe_unused as,
464 unw_word_t __maybe_unused addr,
465 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
466 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
468 pr_err("unwind: get_proc_name unsupported\n");
472 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
478 map = find_map(addr, ui);
480 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
487 size = dso__data_read_addr(map->dso, map, ui->machine,
488 addr, (u8 *) data, sizeof(*data));
490 return !(size == sizeof(*data));
493 static int access_mem(unw_addr_space_t __maybe_unused as,
494 unw_word_t addr, unw_word_t *valp,
495 int __write, void *arg)
497 struct unwind_info *ui = arg;
498 struct stack_dump *stack = &ui->sample->user_stack;
503 /* Don't support write, probably not needed. */
504 if (__write || !stack || !ui->sample->user_regs.regs) {
509 ret = perf_reg_value(&start, &ui->sample->user_regs,
510 LIBUNWIND__ARCH_REG_SP);
514 end = start + stack->size;
516 /* Check overflow. */
517 if (addr + sizeof(unw_word_t) < addr)
520 if (addr < start || addr + sizeof(unw_word_t) >= end) {
521 ret = access_dso_mem(ui, addr, valp);
523 pr_debug("unwind: access_mem %p not inside range"
524 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
525 (void *) (uintptr_t) addr, start, end);
532 offset = addr - start;
533 *valp = *(unw_word_t *)&stack->data[offset];
534 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
535 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
539 static int access_reg(unw_addr_space_t __maybe_unused as,
540 unw_regnum_t regnum, unw_word_t *valp,
541 int __write, void *arg)
543 struct unwind_info *ui = arg;
547 /* Don't support write, I suspect we don't need it. */
549 pr_err("unwind: access_reg w %d\n", regnum);
553 if (!ui->sample->user_regs.regs) {
558 id = LIBUNWIND__ARCH_REG_ID(regnum);
562 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
564 pr_err("unwind: can't read reg %d\n", regnum);
568 *valp = (unw_word_t) val;
569 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
573 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
574 unw_proc_info_t *pi __maybe_unused,
575 void *arg __maybe_unused)
577 pr_debug("unwind: put_unwind_info called\n");
580 static int entry(u64 ip, struct thread *thread,
581 unwind_entry_cb_t cb, void *arg)
583 struct unwind_entry e;
584 struct addr_location al;
586 thread__find_addr_location(thread, PERF_RECORD_MISC_USER,
587 MAP__FUNCTION, ip, &al);
593 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
594 al.sym ? al.sym->name : "''",
596 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
601 static void display_error(int err)
605 pr_err("unwind: Only supports local.\n");
608 pr_err("unwind: Unspecified error.\n");
611 pr_err("unwind: Register unavailable.\n");
618 static unw_accessors_t accessors = {
619 .find_proc_info = find_proc_info,
620 .put_unwind_info = put_unwind_info,
621 .get_dyn_info_list_addr = get_dyn_info_list_addr,
622 .access_mem = access_mem,
623 .access_reg = access_reg,
624 .access_fpreg = access_fpreg,
626 .get_proc_name = get_proc_name,
629 static int _unwind__prepare_access(struct thread *thread)
631 if (callchain_param.record_mode != CALLCHAIN_DWARF)
634 thread->addr_space = unw_create_addr_space(&accessors, 0);
635 if (!thread->addr_space) {
636 pr_err("unwind: Can't create unwind address space.\n");
640 unw_set_caching_policy(thread->addr_space, UNW_CACHE_GLOBAL);
644 static void _unwind__flush_access(struct thread *thread)
646 if (callchain_param.record_mode != CALLCHAIN_DWARF)
649 unw_flush_cache(thread->addr_space, 0, 0);
652 static void _unwind__finish_access(struct thread *thread)
654 if (callchain_param.record_mode != CALLCHAIN_DWARF)
657 unw_destroy_addr_space(thread->addr_space);
660 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
661 void *arg, int max_stack)
664 unw_word_t ips[max_stack];
665 unw_addr_space_t addr_space;
669 ret = perf_reg_value(&val, &ui->sample->user_regs,
670 LIBUNWIND__ARCH_REG_IP);
674 ips[i++] = (unw_word_t) val;
677 * If we need more than one entry, do the DWARF
680 if (max_stack - 1 > 0) {
681 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
682 addr_space = ui->thread->addr_space;
684 if (addr_space == NULL)
687 ret = unw_init_remote(&c, addr_space, ui);
691 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
692 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
700 * Display what we got based on the order setup.
702 for (i = 0; i < max_stack && !ret; i++) {
705 if (callchain_param.order == ORDER_CALLER)
706 j = max_stack - i - 1;
707 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
713 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
714 struct thread *thread,
715 struct perf_sample *data, int max_stack)
717 struct unwind_info ui = {
720 .machine = thread->mg->machine,
723 if (!data->user_regs.regs)
729 return get_entries(&ui, cb, arg, max_stack);
732 static struct unwind_libunwind_ops
733 _unwind_libunwind_ops = {
734 .prepare_access = _unwind__prepare_access,
735 .flush_access = _unwind__flush_access,
736 .finish_access = _unwind__finish_access,
737 .get_entries = _unwind__get_entries,
740 #ifndef REMOTE_UNWIND_LIBUNWIND
741 struct unwind_libunwind_ops *
742 local_unwind_libunwind_ops = &_unwind_libunwind_ops;