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>
26 #include <linux/list.h>
27 #ifndef REMOTE_UNWIND_LIBUNWIND
28 #include <libunwind.h>
29 #include <libunwind-ptrace.h>
31 #include "callchain.h"
34 #include "perf_regs.h"
43 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
47 int need_unwind_info, void *arg);
49 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
52 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
55 const char *obj_name, unw_word_t start,
58 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
60 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
61 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
63 /* Pointer-encoding formats: */
64 #define DW_EH_PE_omit 0xff
65 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
66 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
67 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
68 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
69 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
71 /* Pointer-encoding application: */
72 #define DW_EH_PE_absptr 0x00 /* absolute value */
73 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
76 * The following are not documented by LSB v1.3, yet they are used by
77 * GCC, presumably they aren't documented by LSB since they aren't
80 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
81 #define DW_EH_PE_aligned 0x50 /* aligned pointer */
83 /* Flags intentionaly not handled, since they're not needed:
84 * #define DW_EH_PE_indirect 0x80
85 * #define DW_EH_PE_uleb128 0x01
86 * #define DW_EH_PE_udata2 0x02
87 * #define DW_EH_PE_sleb128 0x09
88 * #define DW_EH_PE_sdata2 0x0a
89 * #define DW_EH_PE_textrel 0x20
90 * #define DW_EH_PE_datarel 0x30
94 struct perf_sample *sample;
95 struct machine *machine;
96 struct thread *thread;
99 #define dw_read(ptr, type, end) ({ \
100 type *__p = (type *) ptr; \
102 if ((__p + 1) > (type *) end) \
105 ptr = (typeof(ptr)) __p; \
109 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
120 *val = dw_read(cur, unsigned long, end);
126 switch (encoding & DW_EH_PE_APPL_MASK) {
127 case DW_EH_PE_absptr:
130 *val = (unsigned long) cur;
136 if ((encoding & 0x07) == 0x00)
137 encoding |= DW_EH_PE_udata4;
139 switch (encoding & DW_EH_PE_FORMAT_MASK) {
140 case DW_EH_PE_sdata4:
141 *val += dw_read(cur, s32, end);
143 case DW_EH_PE_udata4:
144 *val += dw_read(cur, u32, end);
146 case DW_EH_PE_sdata8:
147 *val += dw_read(cur, s64, end);
149 case DW_EH_PE_udata8:
150 *val += dw_read(cur, u64, end);
161 #define dw_read_encoded_value(ptr, end, enc) ({ \
163 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
169 static u64 elf_section_offset(int fd, const char *name)
176 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
181 if (gelf_getehdr(elf, &ehdr) == NULL)
184 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
187 offset = shdr.sh_offset;
194 #ifndef NO_LIBUNWIND_DEBUG_FRAME
195 static int elf_is_exec(int fd, const char *name)
201 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
204 if (gelf_getehdr(elf, &ehdr) == NULL)
207 retval = (ehdr.e_type == ET_EXEC);
211 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
221 struct eh_frame_hdr {
222 unsigned char version;
223 unsigned char eh_frame_ptr_enc;
224 unsigned char fde_count_enc;
225 unsigned char table_enc;
228 * The rest of the header is variable-length and consists of the
231 * encoded_t eh_frame_ptr;
232 * encoded_t fde_count;
235 /* A single encoded pointer should not be more than 8 bytes. */
240 * encoded_t start_ip;
241 * encoded_t fde_addr;
242 * } binary_search_table[fde_count];
247 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
248 u64 offset, u64 *table_data, u64 *segbase,
251 struct eh_frame_hdr hdr;
252 u8 *enc = (u8 *) &hdr.enc;
253 u8 *end = (u8 *) &hdr.data;
256 r = dso__data_read_offset(dso, machine, offset,
257 (u8 *) &hdr, sizeof(hdr));
258 if (r != sizeof(hdr))
261 /* We dont need eh_frame_ptr, just skip it. */
262 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
264 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
266 *table_data = (enc - (u8 *) &hdr) + offset;
270 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
271 u64 *table_data, u64 *segbase,
274 int ret = -EINVAL, fd;
275 u64 offset = dso->data.eh_frame_hdr_offset;
278 fd = dso__data_get_fd(dso, machine);
282 /* Check the .eh_frame section for unwinding info */
283 offset = elf_section_offset(fd, ".eh_frame_hdr");
284 dso->data.eh_frame_hdr_offset = offset;
285 dso__data_put_fd(dso);
289 ret = unwind_spec_ehframe(dso, machine, offset,
296 #ifndef NO_LIBUNWIND_DEBUG_FRAME
297 static int read_unwind_spec_debug_frame(struct dso *dso,
298 struct machine *machine, u64 *offset)
301 u64 ofs = dso->data.debug_frame_offset;
303 /* debug_frame can reside in:
305 * - debug pointed by symsrc_filename
306 * - gnu_debuglink, which doesn't necessary
307 * has to be pointed by symsrc_filename
310 fd = dso__data_get_fd(dso, machine);
312 ofs = elf_section_offset(fd, ".debug_frame");
313 dso__data_put_fd(dso);
317 fd = open(dso->symsrc_filename, O_RDONLY);
319 ofs = elf_section_offset(fd, ".debug_frame");
325 char *debuglink = malloc(PATH_MAX);
328 ret = dso__read_binary_type_filename(
329 dso, DSO_BINARY_TYPE__DEBUGLINK,
330 machine->root_dir, debuglink, PATH_MAX);
332 fd = open(debuglink, O_RDONLY);
334 ofs = elf_section_offset(fd,
340 if (dso->symsrc_filename != NULL) {
342 "%s: overwrite symsrc(%s,%s)\n",
344 dso->symsrc_filename,
346 free(dso->symsrc_filename);
348 dso->symsrc_filename = debuglink;
354 dso->data.debug_frame_offset = ofs;
365 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
367 struct addr_location al;
369 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
370 MAP__FUNCTION, ip, &al);
373 * We've seen cases (softice) where DWARF unwinder went
374 * through non executable mmaps, which we need to lookup
375 * in MAP__VARIABLE tree.
377 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
378 MAP__VARIABLE, ip, &al);
384 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
385 int need_unwind_info, void *arg)
387 struct unwind_info *ui = arg;
390 u64 table_data, segbase, fde_count;
393 map = find_map(ip, ui);
394 if (!map || !map->dso)
397 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
399 /* Check the .eh_frame section for unwinding info */
400 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
401 &table_data, &segbase, &fde_count)) {
402 memset(&di, 0, sizeof(di));
403 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
404 di.start_ip = map->start;
405 di.end_ip = map->end;
406 di.u.rti.segbase = map->start + segbase - map->pgoff;
407 di.u.rti.table_data = map->start + table_data - map->pgoff;
408 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
409 / sizeof(unw_word_t);
410 ret = dwarf_search_unwind_table(as, ip, &di, pi,
411 need_unwind_info, arg);
414 #ifndef NO_LIBUNWIND_DEBUG_FRAME
415 /* Check the .debug_frame section for unwinding info */
417 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
418 int fd = dso__data_get_fd(map->dso, ui->machine);
419 int is_exec = elf_is_exec(fd, map->dso->name);
420 unw_word_t base = is_exec ? 0 : map->start;
424 dso__data_put_fd(map->dso);
426 symfile = map->dso->symsrc_filename ?: map->dso->name;
428 memset(&di, 0, sizeof(di));
429 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
430 map->start, map->end))
431 return dwarf_search_unwind_table(as, ip, &di, pi,
432 need_unwind_info, arg);
439 static int access_fpreg(unw_addr_space_t __maybe_unused as,
440 unw_regnum_t __maybe_unused num,
441 unw_fpreg_t __maybe_unused *val,
442 int __maybe_unused __write,
443 void __maybe_unused *arg)
445 pr_err("unwind: access_fpreg unsupported\n");
449 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
450 unw_word_t __maybe_unused *dil_addr,
451 void __maybe_unused *arg)
456 static int resume(unw_addr_space_t __maybe_unused as,
457 unw_cursor_t __maybe_unused *cu,
458 void __maybe_unused *arg)
460 pr_err("unwind: resume unsupported\n");
465 get_proc_name(unw_addr_space_t __maybe_unused as,
466 unw_word_t __maybe_unused addr,
467 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
468 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
470 pr_err("unwind: get_proc_name unsupported\n");
474 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
480 map = find_map(addr, ui);
482 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
489 size = dso__data_read_addr(map->dso, map, ui->machine,
490 addr, (u8 *) data, sizeof(*data));
492 return !(size == sizeof(*data));
495 static int access_mem(unw_addr_space_t __maybe_unused as,
496 unw_word_t addr, unw_word_t *valp,
497 int __write, void *arg)
499 struct unwind_info *ui = arg;
500 struct stack_dump *stack = &ui->sample->user_stack;
505 /* Don't support write, probably not needed. */
506 if (__write || !stack || !ui->sample->user_regs.regs) {
511 ret = perf_reg_value(&start, &ui->sample->user_regs,
512 LIBUNWIND__ARCH_REG_SP);
516 end = start + stack->size;
518 /* Check overflow. */
519 if (addr + sizeof(unw_word_t) < addr)
522 if (addr < start || addr + sizeof(unw_word_t) >= end) {
523 ret = access_dso_mem(ui, addr, valp);
525 pr_debug("unwind: access_mem %p not inside range"
526 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
527 (void *) (uintptr_t) addr, start, end);
534 offset = addr - start;
535 *valp = *(unw_word_t *)&stack->data[offset];
536 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
537 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
541 static int access_reg(unw_addr_space_t __maybe_unused as,
542 unw_regnum_t regnum, unw_word_t *valp,
543 int __write, void *arg)
545 struct unwind_info *ui = arg;
549 /* Don't support write, I suspect we don't need it. */
551 pr_err("unwind: access_reg w %d\n", regnum);
555 if (!ui->sample->user_regs.regs) {
560 id = LIBUNWIND__ARCH_REG_ID(regnum);
564 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
566 pr_err("unwind: can't read reg %d\n", regnum);
570 *valp = (unw_word_t) val;
571 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
575 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
576 unw_proc_info_t *pi __maybe_unused,
577 void *arg __maybe_unused)
579 pr_debug("unwind: put_unwind_info called\n");
582 static int entry(u64 ip, struct thread *thread,
583 unwind_entry_cb_t cb, void *arg)
585 struct unwind_entry e;
586 struct addr_location al;
588 thread__find_addr_location(thread, PERF_RECORD_MISC_USER,
589 MAP__FUNCTION, ip, &al);
595 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
596 al.sym ? al.sym->name : "''",
598 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
603 static void display_error(int err)
607 pr_err("unwind: Only supports local.\n");
610 pr_err("unwind: Unspecified error.\n");
613 pr_err("unwind: Register unavailable.\n");
620 static unw_accessors_t accessors = {
621 .find_proc_info = find_proc_info,
622 .put_unwind_info = put_unwind_info,
623 .get_dyn_info_list_addr = get_dyn_info_list_addr,
624 .access_mem = access_mem,
625 .access_reg = access_reg,
626 .access_fpreg = access_fpreg,
628 .get_proc_name = get_proc_name,
631 static int _unwind__prepare_access(struct thread *thread)
633 if (callchain_param.record_mode != CALLCHAIN_DWARF)
636 thread->addr_space = unw_create_addr_space(&accessors, 0);
637 if (!thread->addr_space) {
638 pr_err("unwind: Can't create unwind address space.\n");
642 unw_set_caching_policy(thread->addr_space, UNW_CACHE_GLOBAL);
646 static void _unwind__flush_access(struct thread *thread)
648 if (callchain_param.record_mode != CALLCHAIN_DWARF)
651 unw_flush_cache(thread->addr_space, 0, 0);
654 static void _unwind__finish_access(struct thread *thread)
656 if (callchain_param.record_mode != CALLCHAIN_DWARF)
659 unw_destroy_addr_space(thread->addr_space);
662 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
663 void *arg, int max_stack)
666 unw_word_t ips[max_stack];
667 unw_addr_space_t addr_space;
671 ret = perf_reg_value(&val, &ui->sample->user_regs,
672 LIBUNWIND__ARCH_REG_IP);
676 ips[i++] = (unw_word_t) val;
679 * If we need more than one entry, do the DWARF
682 if (max_stack - 1 > 0) {
683 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
684 addr_space = ui->thread->addr_space;
686 if (addr_space == NULL)
689 ret = unw_init_remote(&c, addr_space, ui);
693 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
694 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
702 * Display what we got based on the order setup.
704 for (i = 0; i < max_stack && !ret; i++) {
707 if (callchain_param.order == ORDER_CALLER)
708 j = max_stack - i - 1;
709 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
715 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
716 struct thread *thread,
717 struct perf_sample *data, int max_stack)
719 struct unwind_info ui = {
722 .machine = thread->mg->machine,
725 if (!data->user_regs.regs)
731 return get_entries(&ui, cb, arg, max_stack);
734 static struct unwind_libunwind_ops
735 _unwind_libunwind_ops = {
736 .prepare_access = _unwind__prepare_access,
737 .flush_access = _unwind__flush_access,
738 .finish_access = _unwind__finish_access,
739 .get_entries = _unwind__get_entries,
742 #ifndef REMOTE_UNWIND_LIBUNWIND
743 struct unwind_libunwind_ops *
744 local_unwind_libunwind_ops = &_unwind_libunwind_ops;