1 // SPDX-License-Identifier: GPL-2.0
3 * Post mortem Dwarf CFI based unwinding on top of regs and stack dumps.
5 * Lots of this code have been borrowed or heavily inspired from parts of
6 * the libunwind 0.99 code which are (amongst other contributors I may have
9 * Copyright (C) 2002-2007 Hewlett-Packard Co
10 * Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
12 * And the bugs have been added by:
14 * Copyright (C) 2010, Frederic Weisbecker <fweisbec@gmail.com>
15 * Copyright (C) 2012, Jiri Olsa <jolsa@redhat.com>
27 #include <linux/list.h>
28 #include <linux/zalloc.h>
29 #ifndef REMOTE_UNWIND_LIBUNWIND
30 #include <libunwind.h>
31 #include <libunwind-ptrace.h>
33 #include "callchain.h"
36 #include "perf_regs.h"
45 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
49 int need_unwind_info, void *arg);
51 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
54 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
57 const char *obj_name, unw_word_t start,
60 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
62 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
63 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
65 /* Pointer-encoding formats: */
66 #define DW_EH_PE_omit 0xff
67 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
68 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
69 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
70 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
71 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
73 /* Pointer-encoding application: */
74 #define DW_EH_PE_absptr 0x00 /* absolute value */
75 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
78 * The following are not documented by LSB v1.3, yet they are used by
79 * GCC, presumably they aren't documented by LSB since they aren't
82 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
83 #define DW_EH_PE_aligned 0x50 /* aligned pointer */
85 /* Flags intentionally not handled, since they're not needed:
86 * #define DW_EH_PE_indirect 0x80
87 * #define DW_EH_PE_uleb128 0x01
88 * #define DW_EH_PE_udata2 0x02
89 * #define DW_EH_PE_sleb128 0x09
90 * #define DW_EH_PE_sdata2 0x0a
91 * #define DW_EH_PE_textrel 0x20
92 * #define DW_EH_PE_datarel 0x30
96 struct perf_sample *sample;
97 struct machine *machine;
98 struct thread *thread;
102 #define dw_read(ptr, type, end) ({ \
103 type *__p = (type *) ptr; \
105 if ((__p + 1) > (type *) end) \
108 ptr = (typeof(ptr)) __p; \
112 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
123 *val = dw_read(cur, unsigned long, end);
129 switch (encoding & DW_EH_PE_APPL_MASK) {
130 case DW_EH_PE_absptr:
133 *val = (unsigned long) cur;
139 if ((encoding & 0x07) == 0x00)
140 encoding |= DW_EH_PE_udata4;
142 switch (encoding & DW_EH_PE_FORMAT_MASK) {
143 case DW_EH_PE_sdata4:
144 *val += dw_read(cur, s32, end);
146 case DW_EH_PE_udata4:
147 *val += dw_read(cur, u32, end);
149 case DW_EH_PE_sdata8:
150 *val += dw_read(cur, s64, end);
152 case DW_EH_PE_udata8:
153 *val += dw_read(cur, u64, end);
164 #define dw_read_encoded_value(ptr, end, enc) ({ \
166 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
172 static int elf_section_address_and_offset(int fd, const char *name, u64 *address, u64 *offset)
179 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
183 if (gelf_getehdr(elf, &ehdr) == NULL)
186 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
189 *address = shdr.sh_addr;
190 *offset = shdr.sh_offset;
197 #ifndef NO_LIBUNWIND_DEBUG_FRAME
198 static u64 elf_section_offset(int fd, const char *name)
200 u64 address, offset = 0;
202 if (elf_section_address_and_offset(fd, name, &address, &offset))
209 static u64 elf_base_address(int fd)
211 Elf *elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
214 size_t i, phdrnum = 0;
218 (void)elf_getphdrnum(elf, &phdrnum);
219 /* PT_LOAD segments are sorted by p_vaddr, so the first has the minimum p_vaddr. */
220 for (i = 0; i < phdrnum; i++) {
221 if (gelf_getphdr(elf, i, &phdr) && phdr.p_type == PT_LOAD) {
222 retval = phdr.p_vaddr & -getpagesize();
231 #ifndef NO_LIBUNWIND_DEBUG_FRAME
232 static int elf_is_exec(int fd, const char *name)
238 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
241 if (gelf_getehdr(elf, &ehdr) == NULL)
244 retval = (ehdr.e_type == ET_EXEC);
248 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
258 struct eh_frame_hdr {
259 unsigned char version;
260 unsigned char eh_frame_ptr_enc;
261 unsigned char fde_count_enc;
262 unsigned char table_enc;
265 * The rest of the header is variable-length and consists of the
268 * encoded_t eh_frame_ptr;
269 * encoded_t fde_count;
272 /* A single encoded pointer should not be more than 8 bytes. */
277 * encoded_t start_ip;
278 * encoded_t fde_addr;
279 * } binary_search_table[fde_count];
284 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
285 u64 offset, u64 *table_data_offset, u64 *fde_count)
287 struct eh_frame_hdr hdr;
288 u8 *enc = (u8 *) &hdr.enc;
289 u8 *end = (u8 *) &hdr.data;
292 r = dso__data_read_offset(dso, machine, offset,
293 (u8 *) &hdr, sizeof(hdr));
294 if (r != sizeof(hdr))
297 /* We dont need eh_frame_ptr, just skip it. */
298 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
300 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
301 *table_data_offset = enc - (u8 *) &hdr;
305 static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
306 u64 *table_data, u64 *segbase,
310 u64 base_addr = UINT64_MAX;
313 if (dso->data.eh_frame_hdr_offset == 0) {
314 fd = dso__data_get_fd(dso, ui->machine);
318 /* Check the .eh_frame section for unwinding info */
319 ret = elf_section_address_and_offset(fd, ".eh_frame_hdr",
320 &dso->data.eh_frame_hdr_addr,
321 &dso->data.eh_frame_hdr_offset);
322 dso->data.elf_base_addr = elf_base_address(fd);
323 dso__data_put_fd(dso);
324 if (ret || dso->data.eh_frame_hdr_offset == 0)
328 maps__for_each_entry(ui->thread->maps, map) {
329 if (map->dso == dso && map->start < base_addr)
330 base_addr = map->start;
332 base_addr -= dso->data.elf_base_addr;
333 /* Address of .eh_frame_hdr */
334 *segbase = base_addr + dso->data.eh_frame_hdr_addr;
335 ret = unwind_spec_ehframe(dso, ui->machine, dso->data.eh_frame_hdr_offset,
336 table_data, fde_count);
339 /* binary_search_table offset plus .eh_frame_hdr address */
340 *table_data += *segbase;
344 #ifndef NO_LIBUNWIND_DEBUG_FRAME
345 static int read_unwind_spec_debug_frame(struct dso *dso,
346 struct machine *machine, u64 *offset)
349 u64 ofs = dso->data.debug_frame_offset;
351 /* debug_frame can reside in:
353 * - debug pointed by symsrc_filename
354 * - gnu_debuglink, which doesn't necessary
355 * has to be pointed by symsrc_filename
358 fd = dso__data_get_fd(dso, machine);
360 ofs = elf_section_offset(fd, ".debug_frame");
361 dso__data_put_fd(dso);
365 fd = open(dso->symsrc_filename, O_RDONLY);
367 ofs = elf_section_offset(fd, ".debug_frame");
373 char *debuglink = malloc(PATH_MAX);
376 ret = dso__read_binary_type_filename(
377 dso, DSO_BINARY_TYPE__DEBUGLINK,
378 machine->root_dir, debuglink, PATH_MAX);
380 fd = open(debuglink, O_RDONLY);
382 ofs = elf_section_offset(fd,
388 if (dso->symsrc_filename != NULL) {
390 "%s: overwrite symsrc(%s,%s)\n",
392 dso->symsrc_filename,
394 zfree(&dso->symsrc_filename);
396 dso->symsrc_filename = debuglink;
402 dso->data.debug_frame_offset = ofs;
413 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
415 struct addr_location al;
416 return thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
420 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
421 int need_unwind_info, void *arg)
423 struct unwind_info *ui = arg;
426 u64 table_data, segbase, fde_count;
429 map = find_map(ip, ui);
430 if (!map || !map->dso)
433 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
435 /* Check the .eh_frame section for unwinding info */
436 if (!read_unwind_spec_eh_frame(map->dso, ui,
437 &table_data, &segbase, &fde_count)) {
438 memset(&di, 0, sizeof(di));
439 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
440 di.start_ip = map->start;
441 di.end_ip = map->end;
442 di.u.rti.segbase = segbase;
443 di.u.rti.table_data = table_data;
444 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
445 / sizeof(unw_word_t);
446 ret = dwarf_search_unwind_table(as, ip, &di, pi,
447 need_unwind_info, arg);
450 #ifndef NO_LIBUNWIND_DEBUG_FRAME
451 /* Check the .debug_frame section for unwinding info */
453 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
454 int fd = dso__data_get_fd(map->dso, ui->machine);
455 int is_exec = elf_is_exec(fd, map->dso->name);
456 unw_word_t base = is_exec ? 0 : map->start;
460 dso__data_put_fd(map->dso);
462 symfile = map->dso->symsrc_filename ?: map->dso->name;
464 memset(&di, 0, sizeof(di));
465 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
466 map->start, map->end))
467 return dwarf_search_unwind_table(as, ip, &di, pi,
468 need_unwind_info, arg);
475 static int access_fpreg(unw_addr_space_t __maybe_unused as,
476 unw_regnum_t __maybe_unused num,
477 unw_fpreg_t __maybe_unused *val,
478 int __maybe_unused __write,
479 void __maybe_unused *arg)
481 pr_err("unwind: access_fpreg unsupported\n");
485 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
486 unw_word_t __maybe_unused *dil_addr,
487 void __maybe_unused *arg)
492 static int resume(unw_addr_space_t __maybe_unused as,
493 unw_cursor_t __maybe_unused *cu,
494 void __maybe_unused *arg)
496 pr_err("unwind: resume unsupported\n");
501 get_proc_name(unw_addr_space_t __maybe_unused as,
502 unw_word_t __maybe_unused addr,
503 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
504 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
506 pr_err("unwind: get_proc_name unsupported\n");
510 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
516 map = find_map(addr, ui);
518 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
525 size = dso__data_read_addr(map->dso, map, ui->machine,
526 addr, (u8 *) data, sizeof(*data));
528 return !(size == sizeof(*data));
531 static int access_mem(unw_addr_space_t __maybe_unused as,
532 unw_word_t addr, unw_word_t *valp,
533 int __write, void *arg)
535 struct unwind_info *ui = arg;
536 struct stack_dump *stack = &ui->sample->user_stack;
541 /* Don't support write, probably not needed. */
542 if (__write || !stack || !ui->sample->user_regs.regs) {
547 ret = perf_reg_value(&start, &ui->sample->user_regs,
548 LIBUNWIND__ARCH_REG_SP);
552 end = start + stack->size;
554 /* Check overflow. */
555 if (addr + sizeof(unw_word_t) < addr)
558 if (addr < start || addr + sizeof(unw_word_t) >= end) {
559 ret = access_dso_mem(ui, addr, valp);
561 pr_debug("unwind: access_mem %p not inside range"
562 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
563 (void *) (uintptr_t) addr, start, end);
570 offset = addr - start;
571 *valp = *(unw_word_t *)&stack->data[offset];
572 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
573 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
577 static int access_reg(unw_addr_space_t __maybe_unused as,
578 unw_regnum_t regnum, unw_word_t *valp,
579 int __write, void *arg)
581 struct unwind_info *ui = arg;
585 /* Don't support write, I suspect we don't need it. */
587 pr_err("unwind: access_reg w %d\n", regnum);
591 if (!ui->sample->user_regs.regs) {
596 id = LIBUNWIND__ARCH_REG_ID(regnum);
600 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
602 if (!ui->best_effort)
603 pr_err("unwind: can't read reg %d\n", regnum);
607 *valp = (unw_word_t) val;
608 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
612 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
613 unw_proc_info_t *pi __maybe_unused,
614 void *arg __maybe_unused)
616 pr_debug("unwind: put_unwind_info called\n");
619 static int entry(u64 ip, struct thread *thread,
620 unwind_entry_cb_t cb, void *arg)
622 struct unwind_entry e;
623 struct addr_location al;
625 e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
630 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
631 al.sym ? al.sym->name : "''",
633 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
638 static void display_error(int err)
642 pr_err("unwind: Only supports local.\n");
645 pr_err("unwind: Unspecified error.\n");
648 pr_err("unwind: Register unavailable.\n");
655 static unw_accessors_t accessors = {
656 .find_proc_info = find_proc_info,
657 .put_unwind_info = put_unwind_info,
658 .get_dyn_info_list_addr = get_dyn_info_list_addr,
659 .access_mem = access_mem,
660 .access_reg = access_reg,
661 .access_fpreg = access_fpreg,
663 .get_proc_name = get_proc_name,
666 static int _unwind__prepare_access(struct maps *maps)
668 maps->addr_space = unw_create_addr_space(&accessors, 0);
669 if (!maps->addr_space) {
670 pr_err("unwind: Can't create unwind address space.\n");
674 unw_set_caching_policy(maps->addr_space, UNW_CACHE_GLOBAL);
678 static void _unwind__flush_access(struct maps *maps)
680 unw_flush_cache(maps->addr_space, 0, 0);
683 static void _unwind__finish_access(struct maps *maps)
685 unw_destroy_addr_space(maps->addr_space);
688 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
689 void *arg, int max_stack)
692 unw_word_t ips[max_stack];
693 unw_addr_space_t addr_space;
697 ret = perf_reg_value(&val, &ui->sample->user_regs,
698 LIBUNWIND__ARCH_REG_IP);
702 ips[i++] = (unw_word_t) val;
705 * If we need more than one entry, do the DWARF
708 if (max_stack - 1 > 0) {
709 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
710 addr_space = ui->thread->maps->addr_space;
712 if (addr_space == NULL)
715 ret = unw_init_remote(&c, addr_space, ui);
716 if (ret && !ui->best_effort)
719 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
720 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
723 * Decrement the IP for any non-activation frames.
724 * this is required to properly find the srcline
726 * See also the documentation for dwfl_frame_pc(),
727 * which this code tries to replicate.
729 if (unw_is_signal_frame(&c) <= 0)
739 * Display what we got based on the order setup.
741 for (i = 0; i < max_stack && !ret; i++) {
744 if (callchain_param.order == ORDER_CALLER)
745 j = max_stack - i - 1;
746 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
752 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
753 struct thread *thread,
754 struct perf_sample *data, int max_stack,
757 struct unwind_info ui = {
760 .machine = thread->maps->machine,
761 .best_effort = best_effort
764 if (!data->user_regs.regs)
770 return get_entries(&ui, cb, arg, max_stack);
773 static struct unwind_libunwind_ops
774 _unwind_libunwind_ops = {
775 .prepare_access = _unwind__prepare_access,
776 .flush_access = _unwind__flush_access,
777 .finish_access = _unwind__finish_access,
778 .get_entries = _unwind__get_entries,
781 #ifndef REMOTE_UNWIND_LIBUNWIND
782 struct unwind_libunwind_ops *
783 local_unwind_libunwind_ops = &_unwind_libunwind_ops;