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 #include <libunwind.h>
26 #include <libunwind-ptrace.h>
27 #include "callchain.h"
30 #include "perf_regs.h"
38 UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
42 int need_unwind_info, void *arg);
44 #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
47 UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
50 const char *obj_name, unw_word_t start,
53 #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
55 #define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */
56 #define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */
58 /* Pointer-encoding formats: */
59 #define DW_EH_PE_omit 0xff
60 #define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */
61 #define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */
62 #define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */
63 #define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */
64 #define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */
66 /* Pointer-encoding application: */
67 #define DW_EH_PE_absptr 0x00 /* absolute value */
68 #define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */
71 * The following are not documented by LSB v1.3, yet they are used by
72 * GCC, presumably they aren't documented by LSB since they aren't
75 #define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */
76 #define DW_EH_PE_aligned 0x50 /* aligned pointer */
78 /* Flags intentionaly not handled, since they're not needed:
79 * #define DW_EH_PE_indirect 0x80
80 * #define DW_EH_PE_uleb128 0x01
81 * #define DW_EH_PE_udata2 0x02
82 * #define DW_EH_PE_sleb128 0x09
83 * #define DW_EH_PE_sdata2 0x0a
84 * #define DW_EH_PE_textrel 0x20
85 * #define DW_EH_PE_datarel 0x30
89 struct perf_sample *sample;
90 struct machine *machine;
91 struct thread *thread;
94 #define dw_read(ptr, type, end) ({ \
95 type *__p = (type *) ptr; \
97 if ((__p + 1) > (type *) end) \
100 ptr = (typeof(ptr)) __p; \
104 static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
115 *val = dw_read(cur, unsigned long, end);
121 switch (encoding & DW_EH_PE_APPL_MASK) {
122 case DW_EH_PE_absptr:
125 *val = (unsigned long) cur;
131 if ((encoding & 0x07) == 0x00)
132 encoding |= DW_EH_PE_udata4;
134 switch (encoding & DW_EH_PE_FORMAT_MASK) {
135 case DW_EH_PE_sdata4:
136 *val += dw_read(cur, s32, end);
138 case DW_EH_PE_udata4:
139 *val += dw_read(cur, u32, end);
141 case DW_EH_PE_sdata8:
142 *val += dw_read(cur, s64, end);
144 case DW_EH_PE_udata8:
145 *val += dw_read(cur, u64, end);
156 #define dw_read_encoded_value(ptr, end, enc) ({ \
158 if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \
164 static u64 elf_section_offset(int fd, const char *name)
171 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
176 if (gelf_getehdr(elf, &ehdr) == NULL)
179 if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
182 offset = shdr.sh_offset;
189 #ifndef NO_LIBUNWIND_DEBUG_FRAME
190 static int elf_is_exec(int fd, const char *name)
196 elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
199 if (gelf_getehdr(elf, &ehdr) == NULL)
202 retval = (ehdr.e_type == ET_EXEC);
206 pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval);
216 struct eh_frame_hdr {
217 unsigned char version;
218 unsigned char eh_frame_ptr_enc;
219 unsigned char fde_count_enc;
220 unsigned char table_enc;
223 * The rest of the header is variable-length and consists of the
226 * encoded_t eh_frame_ptr;
227 * encoded_t fde_count;
230 /* A single encoded pointer should not be more than 8 bytes. */
235 * encoded_t start_ip;
236 * encoded_t fde_addr;
237 * } binary_search_table[fde_count];
242 static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
243 u64 offset, u64 *table_data, u64 *segbase,
246 struct eh_frame_hdr hdr;
247 u8 *enc = (u8 *) &hdr.enc;
248 u8 *end = (u8 *) &hdr.data;
251 r = dso__data_read_offset(dso, machine, offset,
252 (u8 *) &hdr, sizeof(hdr));
253 if (r != sizeof(hdr))
256 /* We dont need eh_frame_ptr, just skip it. */
257 dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
259 *fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
261 *table_data = (enc - (u8 *) &hdr) + offset;
265 static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
266 u64 *table_data, u64 *segbase,
269 int ret = -EINVAL, fd;
270 u64 offset = dso->data.eh_frame_hdr_offset;
273 fd = dso__data_get_fd(dso, machine);
277 /* Check the .eh_frame section for unwinding info */
278 offset = elf_section_offset(fd, ".eh_frame_hdr");
279 dso->data.eh_frame_hdr_offset = offset;
280 dso__data_put_fd(dso);
284 ret = unwind_spec_ehframe(dso, machine, offset,
291 #ifndef NO_LIBUNWIND_DEBUG_FRAME
292 static int read_unwind_spec_debug_frame(struct dso *dso,
293 struct machine *machine, u64 *offset)
296 u64 ofs = dso->data.debug_frame_offset;
299 fd = dso__data_get_fd(dso, machine);
303 /* Check the .debug_frame section for unwinding info */
304 ofs = elf_section_offset(fd, ".debug_frame");
305 dso->data.debug_frame_offset = ofs;
306 dso__data_put_fd(dso);
317 static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
319 struct addr_location al;
321 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
322 MAP__FUNCTION, ip, &al);
325 * We've seen cases (softice) where DWARF unwinder went
326 * through non executable mmaps, which we need to lookup
327 * in MAP__VARIABLE tree.
329 thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
330 MAP__VARIABLE, ip, &al);
336 find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
337 int need_unwind_info, void *arg)
339 struct unwind_info *ui = arg;
342 u64 table_data, segbase, fde_count;
345 map = find_map(ip, ui);
346 if (!map || !map->dso)
349 pr_debug("unwind: find_proc_info dso %s\n", map->dso->name);
351 /* Check the .eh_frame section for unwinding info */
352 if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
353 &table_data, &segbase, &fde_count)) {
354 memset(&di, 0, sizeof(di));
355 di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
356 di.start_ip = map->start;
357 di.end_ip = map->end;
358 di.u.rti.segbase = map->start + segbase;
359 di.u.rti.table_data = map->start + table_data;
360 di.u.rti.table_len = fde_count * sizeof(struct table_entry)
361 / sizeof(unw_word_t);
362 ret = dwarf_search_unwind_table(as, ip, &di, pi,
363 need_unwind_info, arg);
366 #ifndef NO_LIBUNWIND_DEBUG_FRAME
367 /* Check the .debug_frame section for unwinding info */
369 !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
370 int fd = dso__data_get_fd(map->dso, ui->machine);
371 int is_exec = elf_is_exec(fd, map->dso->name);
372 unw_word_t base = is_exec ? 0 : map->start;
376 dso__data_put_fd(map->dso);
378 symfile = map->dso->symsrc_filename ?: map->dso->name;
380 memset(&di, 0, sizeof(di));
381 if (dwarf_find_debug_frame(0, &di, ip, base, symfile,
382 map->start, map->end))
383 return dwarf_search_unwind_table(as, ip, &di, pi,
384 need_unwind_info, arg);
391 static int access_fpreg(unw_addr_space_t __maybe_unused as,
392 unw_regnum_t __maybe_unused num,
393 unw_fpreg_t __maybe_unused *val,
394 int __maybe_unused __write,
395 void __maybe_unused *arg)
397 pr_err("unwind: access_fpreg unsupported\n");
401 static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
402 unw_word_t __maybe_unused *dil_addr,
403 void __maybe_unused *arg)
408 static int resume(unw_addr_space_t __maybe_unused as,
409 unw_cursor_t __maybe_unused *cu,
410 void __maybe_unused *arg)
412 pr_err("unwind: resume unsupported\n");
417 get_proc_name(unw_addr_space_t __maybe_unused as,
418 unw_word_t __maybe_unused addr,
419 char __maybe_unused *bufp, size_t __maybe_unused buf_len,
420 unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
422 pr_err("unwind: get_proc_name unsupported\n");
426 static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
432 map = find_map(addr, ui);
434 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
441 size = dso__data_read_addr(map->dso, map, ui->machine,
442 addr, (u8 *) data, sizeof(*data));
444 return !(size == sizeof(*data));
447 static int access_mem(unw_addr_space_t __maybe_unused as,
448 unw_word_t addr, unw_word_t *valp,
449 int __write, void *arg)
451 struct unwind_info *ui = arg;
452 struct stack_dump *stack = &ui->sample->user_stack;
457 /* Don't support write, probably not needed. */
458 if (__write || !stack || !ui->sample->user_regs.regs) {
463 ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
467 end = start + stack->size;
469 /* Check overflow. */
470 if (addr + sizeof(unw_word_t) < addr)
473 if (addr < start || addr + sizeof(unw_word_t) >= end) {
474 ret = access_dso_mem(ui, addr, valp);
476 pr_debug("unwind: access_mem %p not inside range"
477 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
478 (void *) (uintptr_t) addr, start, end);
485 offset = addr - start;
486 *valp = *(unw_word_t *)&stack->data[offset];
487 pr_debug("unwind: access_mem addr %p val %lx, offset %d\n",
488 (void *) (uintptr_t) addr, (unsigned long)*valp, offset);
492 static int access_reg(unw_addr_space_t __maybe_unused as,
493 unw_regnum_t regnum, unw_word_t *valp,
494 int __write, void *arg)
496 struct unwind_info *ui = arg;
500 /* Don't support write, I suspect we don't need it. */
502 pr_err("unwind: access_reg w %d\n", regnum);
506 if (!ui->sample->user_regs.regs) {
511 id = libunwind__arch_reg_id(regnum);
515 ret = perf_reg_value(&val, &ui->sample->user_regs, id);
517 pr_err("unwind: can't read reg %d\n", regnum);
521 *valp = (unw_word_t) val;
522 pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp);
526 static void put_unwind_info(unw_addr_space_t __maybe_unused as,
527 unw_proc_info_t *pi __maybe_unused,
528 void *arg __maybe_unused)
530 pr_debug("unwind: put_unwind_info called\n");
533 static int entry(u64 ip, struct thread *thread,
534 unwind_entry_cb_t cb, void *arg)
536 struct unwind_entry e;
537 struct addr_location al;
539 thread__find_addr_location(thread, PERF_RECORD_MISC_USER,
540 MAP__FUNCTION, ip, &al);
546 pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
547 al.sym ? al.sym->name : "''",
549 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
554 static void display_error(int err)
558 pr_err("unwind: Only supports local.\n");
561 pr_err("unwind: Unspecified error.\n");
564 pr_err("unwind: Register unavailable.\n");
571 static unw_accessors_t accessors = {
572 .find_proc_info = find_proc_info,
573 .put_unwind_info = put_unwind_info,
574 .get_dyn_info_list_addr = get_dyn_info_list_addr,
575 .access_mem = access_mem,
576 .access_reg = access_reg,
577 .access_fpreg = access_fpreg,
579 .get_proc_name = get_proc_name,
582 int unwind__prepare_access(struct thread *thread)
584 if (callchain_param.record_mode != CALLCHAIN_DWARF)
587 thread->addr_space = unw_create_addr_space(&accessors, 0);
588 if (!thread->addr_space) {
589 pr_err("unwind: Can't create unwind address space.\n");
593 unw_set_caching_policy(thread->addr_space, UNW_CACHE_GLOBAL);
597 void unwind__flush_access(struct thread *thread)
599 if (callchain_param.record_mode != CALLCHAIN_DWARF)
602 unw_flush_cache(thread->addr_space, 0, 0);
605 void unwind__finish_access(struct thread *thread)
607 if (callchain_param.record_mode != CALLCHAIN_DWARF)
610 unw_destroy_addr_space(thread->addr_space);
613 static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
614 void *arg, int max_stack)
617 unw_word_t ips[max_stack];
618 unw_addr_space_t addr_space;
622 ret = perf_reg_value(&val, &ui->sample->user_regs, PERF_REG_IP);
626 ips[i++] = (unw_word_t) val;
629 * If we need more than one entry, do the DWARF
632 if (max_stack - 1 > 0) {
633 WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL");
634 addr_space = ui->thread->addr_space;
636 if (addr_space == NULL)
639 ret = unw_init_remote(&c, addr_space, ui);
643 while (!ret && (unw_step(&c) > 0) && i < max_stack) {
644 unw_get_reg(&c, UNW_REG_IP, &ips[i]);
652 * Display what we got based on the order setup.
654 for (i = 0; i < max_stack && !ret; i++) {
657 if (callchain_param.order == ORDER_CALLER)
658 j = max_stack - i - 1;
659 ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
665 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
666 struct thread *thread,
667 struct perf_sample *data, int max_stack)
669 struct unwind_info ui = {
672 .machine = thread->mg->machine,
675 if (!data->user_regs.regs)
681 return get_entries(&ui, cb, arg, max_stack);