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 intentionaly 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;
101 #define dw_read(ptr, type, end) ({ \
102 type *__p = (type *) ptr; \
104 if ((__p + 1) > (type *) end) \
107 ptr = (typeof(ptr)) __p; \
111 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
122 *val = dw_read(cur, unsigned long, end);
128 switch (encoding & DW_EH_PE_APPL_MASK) {
129 case DW_EH_PE_absptr:
132 *val = (unsigned long) cur;
138 if ((encoding & 0x07) == 0x00)
139 encoding |= DW_EH_PE_udata4;
141 switch (encoding & DW_EH_PE_FORMAT_MASK) {
142 case DW_EH_PE_sdata4:
143 *val += dw_read(cur, s32, end);
145 case DW_EH_PE_udata4:
146 *val += dw_read(cur, u32, end);
148 case DW_EH_PE_sdata8:
149 *val += dw_read(cur, s64, end);
151 case DW_EH_PE_udata8:
152 *val += dw_read(cur, u64, end);
163 #define dw_read_encoded_value(ptr, end, enc) ({ \
165 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
171 static u64 elf_section_offset(int fd, const char *name)
178 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 offset = shdr.sh_offset;
196 #ifndef NO_LIBUNWIND_DEBUG_FRAME
197 static int elf_is_exec(int fd, const char *name)
203 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
206 if (gelf_getehdr(elf, &ehdr) == NULL)
209 retval = (ehdr.e_type == ET_EXEC);
213 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
223 struct eh_frame_hdr {
224 unsigned char version;
225 unsigned char eh_frame_ptr_enc;
226 unsigned char fde_count_enc;
227 unsigned char table_enc;
230 * The rest of the header is variable-length and consists of the
233 * encoded_t eh_frame_ptr;
234 * encoded_t fde_count;
237 /* A single encoded pointer should not be more than 8 bytes. */
242 * encoded_t start_ip;
243 * encoded_t fde_addr;
244 * } binary_search_table[fde_count];
249 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
250 u64 offset, u64 *table_data, u64 *segbase,
253 struct eh_frame_hdr hdr;
254 u8 *enc = (u8 *) &hdr.enc;
255 u8 *end = (u8 *) &hdr.data;
258 r = dso__data_read_offset(dso, machine, offset,
259 (u8 *) &hdr, sizeof(hdr));
260 if (r != sizeof(hdr))
263 /* We dont need eh_frame_ptr, just skip it. */
264 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
266 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
268 *table_data = (enc - (u8 *) &hdr) + offset;
272 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
273 u64 *table_data, u64 *segbase,
276 int ret = -EINVAL, fd;
277 u64 offset = dso->data.eh_frame_hdr_offset;
280 fd = dso__data_get_fd(dso, machine);
284 /* Check the .eh_frame section for unwinding info */
285 offset = elf_section_offset(fd, ".eh_frame_hdr");
286 dso->data.eh_frame_hdr_offset = offset;
287 dso__data_put_fd(dso);
291 ret = unwind_spec_ehframe(dso, machine, offset,
298 #ifndef NO_LIBUNWIND_DEBUG_FRAME
299 static int read_unwind_spec_debug_frame(struct dso *dso,
300 struct machine *machine, u64 *offset)
303 u64 ofs = dso->data.debug_frame_offset;
305 /* debug_frame can reside in:
307 * - debug pointed by symsrc_filename
308 * - gnu_debuglink, which doesn't necessary
309 * has to be pointed by symsrc_filename
312 fd = dso__data_get_fd(dso, machine);
314 ofs = elf_section_offset(fd, ".debug_frame");
315 dso__data_put_fd(dso);
319 fd = open(dso->symsrc_filename, O_RDONLY);
321 ofs = elf_section_offset(fd, ".debug_frame");
327 char *debuglink = malloc(PATH_MAX);
330 ret = dso__read_binary_type_filename(
331 dso, DSO_BINARY_TYPE__DEBUGLINK,
332 machine->root_dir, debuglink, PATH_MAX);
334 fd = open(debuglink, O_RDONLY);
336 ofs = elf_section_offset(fd,
342 if (dso->symsrc_filename != NULL) {
344 "%s: overwrite symsrc(%s,%s)\n",
346 dso->symsrc_filename,
348 zfree(&dso->symsrc_filename);
350 dso->symsrc_filename = debuglink;
356 dso->data.debug_frame_offset = ofs;
367 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
369 struct addr_location al;
370 return thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
374 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
375 int need_unwind_info, void *arg)
377 struct unwind_info *ui = arg;
380 u64 table_data, segbase, fde_count;
383 map = find_map(ip, ui);
384 if (!map || !map->dso)
387 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
389 /* Check the .eh_frame section for unwinding info */
390 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
391 &table_data, &segbase, &fde_count)) {
392 memset(&di, 0, sizeof(di));
393 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
394 di.start_ip = map->start;
395 di.end_ip = map->end;
396 di.u.rti.segbase = map->start + segbase - map->pgoff;
397 di.u.rti.table_data = map->start + table_data - map->pgoff;
398 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
399 / sizeof(unw_word_t);
400 ret = dwarf_search_unwind_table(as, ip, &di, pi,
401 need_unwind_info, arg);
404 #ifndef NO_LIBUNWIND_DEBUG_FRAME
405 /* Check the .debug_frame section for unwinding info */
407 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
408 int fd = dso__data_get_fd(map->dso, ui->machine);
409 int is_exec = elf_is_exec(fd, map->dso->name);
410 unw_word_t base = is_exec ? 0 : map->start;
414 dso__data_put_fd(map->dso);
416 symfile = map->dso->symsrc_filename ?: map->dso->name;
418 memset(&di, 0, sizeof(di));
419 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
420 map->start, map->end))
421 return dwarf_search_unwind_table(as, ip, &di, pi,
422 need_unwind_info, arg);
429 static int access_fpreg(unw_addr_space_t __maybe_unused as,
430 unw_regnum_t __maybe_unused num,
431 unw_fpreg_t __maybe_unused *val,
432 int __maybe_unused __write,
433 void __maybe_unused *arg)
435 pr_err("unwind: access_fpreg unsupported\n");
439 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
440 unw_word_t __maybe_unused *dil_addr,
441 void __maybe_unused *arg)
446 static int resume(unw_addr_space_t __maybe_unused as,
447 unw_cursor_t __maybe_unused *cu,
448 void __maybe_unused *arg)
450 pr_err("unwind: resume unsupported\n");
455 get_proc_name(unw_addr_space_t __maybe_unused as,
456 unw_word_t __maybe_unused addr,
457 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
458 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
460 pr_err("unwind: get_proc_name unsupported\n");
464 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
470 map = find_map(addr, ui);
472 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
479 size = dso__data_read_addr(map->dso, map, ui->machine,
480 addr, (u8 *) data, sizeof(*data));
482 return !(size == sizeof(*data));
485 static int access_mem(unw_addr_space_t __maybe_unused as,
486 unw_word_t addr, unw_word_t *valp,
487 int __write, void *arg)
489 struct unwind_info *ui = arg;
490 struct stack_dump *stack = &ui->sample->user_stack;
495 /* Don't support write, probably not needed. */
496 if (__write || !stack || !ui->sample->user_regs.regs) {
501 ret = perf_reg_value(&start, &ui->sample->user_regs,
502 LIBUNWIND__ARCH_REG_SP);
506 end = start + stack->size;
508 /* Check overflow. */
509 if (addr + sizeof(unw_word_t) < addr)
512 if (addr < start || addr + sizeof(unw_word_t) >= end) {
513 ret = access_dso_mem(ui, addr, valp);
515 pr_debug("unwind: access_mem %p not inside range"
516 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
517 (void *) (uintptr_t) addr, start, end);
524 offset = addr - start;
525 *valp = *(unw_word_t *)&stack->data[offset];
526 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
527 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
531 static int access_reg(unw_addr_space_t __maybe_unused as,
532 unw_regnum_t regnum, unw_word_t *valp,
533 int __write, void *arg)
535 struct unwind_info *ui = arg;
539 /* Don't support write, I suspect we don't need it. */
541 pr_err("unwind: access_reg w %d\n", regnum);
545 if (!ui->sample->user_regs.regs) {
550 id = LIBUNWIND__ARCH_REG_ID(regnum);
554 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
556 pr_err("unwind: can't read reg %d\n", regnum);
560 *valp = (unw_word_t) val;
561 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
565 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
566 unw_proc_info_t *pi __maybe_unused,
567 void *arg __maybe_unused)
569 pr_debug("unwind: put_unwind_info called\n");
572 static int entry(u64 ip, struct thread *thread,
573 unwind_entry_cb_t cb, void *arg)
575 struct unwind_entry e;
576 struct addr_location al;
578 e.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al);
582 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
583 al.sym ? al.sym->name : "''",
585 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
590 static void display_error(int err)
594 pr_err("unwind: Only supports local.\n");
597 pr_err("unwind: Unspecified error.\n");
600 pr_err("unwind: Register unavailable.\n");
607 static unw_accessors_t accessors = {
608 .find_proc_info = find_proc_info,
609 .put_unwind_info = put_unwind_info,
610 .get_dyn_info_list_addr = get_dyn_info_list_addr,
611 .access_mem = access_mem,
612 .access_reg = access_reg,
613 .access_fpreg = access_fpreg,
615 .get_proc_name = get_proc_name,
618 static int _unwind__prepare_access(struct map_groups *mg)
620 mg->addr_space = unw_create_addr_space(&accessors, 0);
621 if (!mg->addr_space) {
622 pr_err("unwind: Can't create unwind address space.\n");
626 unw_set_caching_policy(mg->addr_space, UNW_CACHE_GLOBAL);
630 static void _unwind__flush_access(struct map_groups *mg)
632 unw_flush_cache(mg->addr_space, 0, 0);
635 static void _unwind__finish_access(struct map_groups *mg)
637 unw_destroy_addr_space(mg->addr_space);
640 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
641 void *arg, int max_stack)
644 unw_word_t ips[max_stack];
645 unw_addr_space_t addr_space;
649 ret = perf_reg_value(&val, &ui->sample->user_regs,
650 LIBUNWIND__ARCH_REG_IP);
654 ips[i++] = (unw_word_t) val;
657 * If we need more than one entry, do the DWARF
660 if (max_stack - 1 > 0) {
661 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
662 addr_space = ui->thread->mg->addr_space;
664 if (addr_space == NULL)
667 ret = unw_init_remote(&c, addr_space, ui);
671 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
672 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
675 * Decrement the IP for any non-activation frames.
676 * this is required to properly find the srcline
678 * See also the documentation for dwfl_frame_pc(),
679 * which this code tries to replicate.
681 if (unw_is_signal_frame(&c) <= 0)
691 * Display what we got based on the order setup.
693 for (i = 0; i < max_stack && !ret; i++) {
696 if (callchain_param.order == ORDER_CALLER)
697 j = max_stack - i - 1;
698 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
704 static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg,
705 struct thread *thread,
706 struct perf_sample *data, int max_stack)
708 struct unwind_info ui = {
711 .machine = thread->mg->machine,
714 if (!data->user_regs.regs)
720 return get_entries(&ui, cb, arg, max_stack);
723 static struct unwind_libunwind_ops
724 _unwind_libunwind_ops = {
725 .prepare_access = _unwind__prepare_access,
726 .flush_access = _unwind__flush_access,
727 .finish_access = _unwind__finish_access,
728 .get_entries = _unwind__get_entries,
731 #ifndef REMOTE_UNWIND_LIBUNWIND
732 struct unwind_libunwind_ops *
733 local_unwind_libunwind_ops = &_unwind_libunwind_ops;