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
]);
697 * Decrement the IP for any non-activation frames.
698 * this is required to properly find the srcline
700 * See also the documentation for dwfl_frame_pc(),
701 * which this code tries to replicate.
703 if (unw_is_signal_frame(&c
) <= 0)
713 * Display what we got based on the order setup.
715 for (i
= 0; i
< max_stack
&& !ret
; i
++) {
718 if (callchain_param
.order
== ORDER_CALLER
)
719 j
= max_stack
- i
- 1;
720 ret
= ips
[j
] ? entry(ips
[j
], ui
->thread
, cb
, arg
) : 0;
726 static int _unwind__get_entries(unwind_entry_cb_t cb
, void *arg
,
727 struct thread
*thread
,
728 struct perf_sample
*data
, int max_stack
)
730 struct unwind_info ui
= {
733 .machine
= thread
->mg
->machine
,
736 if (!data
->user_regs
.regs
)
742 return get_entries(&ui
, cb
, arg
, max_stack
);
745 static struct unwind_libunwind_ops
746 _unwind_libunwind_ops
= {
747 .prepare_access
= _unwind__prepare_access
,
748 .flush_access
= _unwind__flush_access
,
749 .finish_access
= _unwind__finish_access
,
750 .get_entries
= _unwind__get_entries
,
753 #ifndef REMOTE_UNWIND_LIBUNWIND
754 struct unwind_libunwind_ops
*
755 local_unwind_libunwind_ops
= &_unwind_libunwind_ops
;