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 #ifndef REMOTE_UNWIND_LIBUNWIND
29 #include <libunwind.h>
30 #include <libunwind-ptrace.h>
32 #include "callchain.h"
35 #include "perf_regs.h"
44 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
48 int need_unwind_info, void *arg);
50 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
53 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
56 const char *obj_name, unw_word_t start,
59 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
61 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
62 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
64 /* Pointer-encoding formats: */
65 #define DW_EH_PE_omit 0xff
66 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
67 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
68 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
69 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
70 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
72 /* Pointer-encoding application: */
73 #define DW_EH_PE_absptr 0x00 /* absolute value */
74 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
77 * The following are not documented by LSB v1.3, yet they are used by
78 * GCC, presumably they aren't documented by LSB since they aren't
81 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
82 #define DW_EH_PE_aligned 0x50 /* aligned pointer */
84 /* Flags intentionaly not handled, since they're not needed:
85 * #define DW_EH_PE_indirect 0x80
86 * #define DW_EH_PE_uleb128 0x01
87 * #define DW_EH_PE_udata2 0x02
88 * #define DW_EH_PE_sleb128 0x09
89 * #define DW_EH_PE_sdata2 0x0a
90 * #define DW_EH_PE_textrel 0x20
91 * #define DW_EH_PE_datarel 0x30
95 struct perf_sample *sample;
96 struct machine *machine;
97 struct thread *thread;
100 #define dw_read(ptr, type, end) ({ \
101 type *__p = (type *) ptr; \
103 if ((__p + 1) > (type *) end) \
106 ptr = (typeof(ptr)) __p; \
110 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
121 *val = dw_read(cur, unsigned long, end);
127 switch (encoding & DW_EH_PE_APPL_MASK) {
128 case DW_EH_PE_absptr:
131 *val = (unsigned long) cur;
137 if ((encoding & 0x07) == 0x00)
138 encoding |= DW_EH_PE_udata4;
140 switch (encoding & DW_EH_PE_FORMAT_MASK) {
141 case DW_EH_PE_sdata4:
142 *val += dw_read(cur, s32, end);
144 case DW_EH_PE_udata4:
145 *val += dw_read(cur, u32, end);
147 case DW_EH_PE_sdata8:
148 *val += dw_read(cur, s64, end);
150 case DW_EH_PE_udata8:
151 *val += dw_read(cur, u64, end);
162 #define dw_read_encoded_value(ptr, end, enc) ({ \
164 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
170 static u64 elf_section_offset(int fd, const char *name)
177 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
182 if (gelf_getehdr(elf, &ehdr) == NULL)
185 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
188 offset = shdr.sh_offset;
195 #ifndef NO_LIBUNWIND_DEBUG_FRAME
196 static int elf_is_exec(int fd, const char *name)
202 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
205 if (gelf_getehdr(elf, &ehdr) == NULL)
208 retval = (ehdr.e_type == ET_EXEC);
212 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
222 struct eh_frame_hdr {
223 unsigned char version;
224 unsigned char eh_frame_ptr_enc;
225 unsigned char fde_count_enc;
226 unsigned char table_enc;
229 * The rest of the header is variable-length and consists of the
232 * encoded_t eh_frame_ptr;
233 * encoded_t fde_count;
236 /* A single encoded pointer should not be more than 8 bytes. */
241 * encoded_t start_ip;
242 * encoded_t fde_addr;
243 * } binary_search_table[fde_count];
248 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
249 u64 offset, u64 *table_data, u64 *segbase,
252 struct eh_frame_hdr hdr;
253 u8 *enc = (u8 *) &hdr.enc;
254 u8 *end = (u8 *) &hdr.data;
257 r = dso__data_read_offset(dso, machine, offset,
258 (u8 *) &hdr, sizeof(hdr));
259 if (r != sizeof(hdr))
262 /* We dont need eh_frame_ptr, just skip it. */
263 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
265 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
267 *table_data = (enc - (u8 *) &hdr) + offset;
271 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
272 u64 *table_data, u64 *segbase,
275 int ret = -EINVAL, fd;
276 u64 offset = dso->data.eh_frame_hdr_offset;
279 fd = dso__data_get_fd(dso, machine);
283 /* Check the .eh_frame section for unwinding info */
284 offset = elf_section_offset(fd, ".eh_frame_hdr");
285 dso->data.eh_frame_hdr_offset = offset;
286 dso__data_put_fd(dso);
290 ret = unwind_spec_ehframe(dso, machine, offset,
297 #ifndef NO_LIBUNWIND_DEBUG_FRAME
298 static int read_unwind_spec_debug_frame(struct dso *dso,
299 struct machine *machine, u64 *offset)
302 u64 ofs = dso->data.debug_frame_offset;
304 /* debug_frame can reside in:
306 * - debug pointed by symsrc_filename
307 * - gnu_debuglink, which doesn't necessary
308 * has to be pointed by symsrc_filename
311 fd = dso__data_get_fd(dso, machine);
313 ofs = elf_section_offset(fd, ".debug_frame");
314 dso__data_put_fd(dso);
318 fd = open(dso->symsrc_filename, O_RDONLY);
320 ofs = elf_section_offset(fd, ".debug_frame");
326 char *debuglink = malloc(PATH_MAX);
329 ret = dso__read_binary_type_filename(
330 dso, DSO_BINARY_TYPE__DEBUGLINK,
331 machine->root_dir, debuglink, PATH_MAX);
333 fd = open(debuglink, O_RDONLY);
335 ofs = elf_section_offset(fd,
341 if (dso->symsrc_filename != NULL) {
343 "%s: overwrite symsrc(%s,%s)\n",
345 dso->symsrc_filename,
347 free(dso->symsrc_filename);
349 dso->symsrc_filename = debuglink;
355 dso->data.debug_frame_offset = ofs;
366 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
368 struct addr_location al;
369 return thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
373 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
374 int need_unwind_info, void *arg)
376 struct unwind_info *ui = arg;
379 u64 table_data, segbase, fde_count;
382 map = find_map(ip, ui);
383 if (!map || !map->dso)
386 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
388 /* Check the .eh_frame section for unwinding info */
389 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
390 &table_data, &segbase, &fde_count)) {
391 memset(&di, 0, sizeof(di));
392 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
393 di.start_ip = map->start;
394 di.end_ip = map->end;
395 di.u.rti.segbase = map->start + segbase - map->pgoff;
396 di.u.rti.table_data = map->start + table_data - map->pgoff;
397 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
398 / sizeof(unw_word_t);
399 ret = dwarf_search_unwind_table(as, ip, &di, pi,
400 need_unwind_info, arg);
403 #ifndef NO_LIBUNWIND_DEBUG_FRAME
404 /* Check the .debug_frame section for unwinding info */
406 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
407 int fd = dso__data_get_fd(map->dso, ui->machine);
408 int is_exec = elf_is_exec(fd, map->dso->name);
409 unw_word_t base = is_exec ? 0 : map->start;
413 dso__data_put_fd(map->dso);
415 symfile = map->dso->symsrc_filename ?: map->dso->name;
417 memset(&di, 0, sizeof(di));
418 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
419 map->start, map->end))
420 return dwarf_search_unwind_table(as, ip, &di, pi,
421 need_unwind_info, arg);
428 static int access_fpreg(unw_addr_space_t __maybe_unused as,
429 unw_regnum_t __maybe_unused num,
430 unw_fpreg_t __maybe_unused *val,
431 int __maybe_unused __write,
432 void __maybe_unused *arg)
434 pr_err("unwind: access_fpreg unsupported\n");
438 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
439 unw_word_t __maybe_unused *dil_addr,
440 void __maybe_unused *arg)
445 static int resume(unw_addr_space_t __maybe_unused as,
446 unw_cursor_t __maybe_unused *cu,
447 void __maybe_unused *arg)
449 pr_err("unwind: resume unsupported\n");
454 get_proc_name(unw_addr_space_t __maybe_unused as,
455 unw_word_t __maybe_unused addr,
456 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
457 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
459 pr_err("unwind: get_proc_name unsupported\n");
463 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
469 map = find_map(addr, ui);
471 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
478 size = dso__data_read_addr(map->dso, map, ui->machine,
479 addr, (u8 *) data, sizeof(*data));
481 return !(size == sizeof(*data));
484 static int access_mem(unw_addr_space_t __maybe_unused as,
485 unw_word_t addr, unw_word_t *valp,
486 int __write, void *arg)
488 struct unwind_info *ui = arg;
489 struct stack_dump *stack = &ui->sample->user_stack;
494 /* Don't support write, probably not needed. */
495 if (__write || !stack || !ui->sample->user_regs.regs) {
500 ret = perf_reg_value(&start, &ui->sample->user_regs,
501 LIBUNWIND__ARCH_REG_SP);
505 end = start + stack->size;
507 /* Check overflow. */
508 if (addr + sizeof(unw_word_t) < addr)
511 if (addr < start || addr + sizeof(unw_word_t) >= end) {
512 ret = access_dso_mem(ui, addr, valp);
514 pr_debug("unwind: access_mem %p not inside range"
515 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
516 (void *) (uintptr_t) addr, start, end);
523 offset = addr - start;
524 *valp = *(unw_word_t *)&stack->data[offset];
525 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
526 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
530 static int access_reg(unw_addr_space_t __maybe_unused as,
531 unw_regnum_t regnum, unw_word_t *valp,
532 int __write, void *arg)
534 struct unwind_info *ui = arg;
538 /* Don't support write, I suspect we don't need it. */
540 pr_err("unwind: access_reg w %d\n", regnum);
544 if (!ui->sample->user_regs.regs) {
549 id = LIBUNWIND__ARCH_REG_ID(regnum);
553 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
555 pr_err("unwind: can't read reg %d\n", regnum);
559 *valp = (unw_word_t) val;
560 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
564 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
565 unw_proc_info_t *pi __maybe_unused,
566 void *arg __maybe_unused)
568 pr_debug("unwind: put_unwind_info called\n");
571 static int entry(u64 ip, struct thread *thread,
572 unwind_entry_cb_t cb, void *arg)
574 struct unwind_entry e;
575 struct addr_location al;
577 e.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
581 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
582 al.sym ? al.sym->name : "''",
584 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
589 static void display_error(int err)
593 pr_err("unwind: Only supports local.\n");
596 pr_err("unwind: Unspecified error.\n");
599 pr_err("unwind: Register unavailable.\n");
606 static unw_accessors_t accessors = {
607 .find_proc_info = find_proc_info,
608 .put_unwind_info = put_unwind_info,
609 .get_dyn_info_list_addr = get_dyn_info_list_addr,
610 .access_mem = access_mem,
611 .access_reg = access_reg,
612 .access_fpreg = access_fpreg,
614 .get_proc_name = get_proc_name,
617 static int _unwind__prepare_access(struct thread *thread)
619 if (!dwarf_callchain_users)
621 thread->addr_space = unw_create_addr_space(&accessors, 0);
622 if (!thread->addr_space) {
623 pr_err("unwind: Can't create unwind address space.\n");
627 unw_set_caching_policy(thread->addr_space, UNW_CACHE_GLOBAL);
631 static void _unwind__flush_access(struct thread *thread)
633 if (!dwarf_callchain_users)
635 unw_flush_cache(thread->addr_space, 0, 0);
638 static void _unwind__finish_access(struct thread *thread)
640 if (!dwarf_callchain_users)
642 unw_destroy_addr_space(thread->addr_space);
645 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
646 void *arg, int max_stack)
649 unw_word_t ips[max_stack];
650 unw_addr_space_t addr_space;
654 ret = perf_reg_value(&val, &ui->sample->user_regs,
655 LIBUNWIND__ARCH_REG_IP);
659 ips[i++] = (unw_word_t) val;
662 * If we need more than one entry, do the DWARF
665 if (max_stack - 1 > 0) {
666 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
667 addr_space = ui->thread->addr_space;
669 if (addr_space == NULL)
672 ret = unw_init_remote(&c, addr_space, ui);
676 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
677 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
680 * Decrement the IP for any non-activation frames.
681 * this is required to properly find the srcline
683 * See also the documentation for dwfl_frame_pc(),
684 * which this code tries to replicate.
686 if (unw_is_signal_frame(&c) <= 0)
696 * Display what we got based on the order setup.
698 for (i = 0; i < max_stack && !ret; i++) {
701 if (callchain_param.order == ORDER_CALLER)
702 j = max_stack - i - 1;
703 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
709 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
710 struct thread *thread,
711 struct perf_sample *data, int max_stack)
713 struct unwind_info ui = {
716 .machine = thread->mg->machine,
719 if (!data->user_regs.regs)
725 return get_entries(&ui, cb, arg, max_stack);
728 static struct unwind_libunwind_ops
729 _unwind_libunwind_ops = {
730 .prepare_access = _unwind__prepare_access,
731 .flush_access = _unwind__flush_access,
732 .finish_access = _unwind__finish_access,
733 .get_entries = _unwind__get_entries,
736 #ifndef REMOTE_UNWIND_LIBUNWIND
737 struct unwind_libunwind_ops *
738 local_unwind_libunwind_ops = &_unwind_libunwind_ops;