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735 lines
17 KiB
735 lines
17 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* Post mortem Dwarf CFI based unwinding on top of regs and stack dumps. |
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* |
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* Lots of this code have been borrowed or heavily inspired from parts of |
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* the libunwind 0.99 code which are (amongst other contributors I may have |
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* forgotten): |
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* |
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* Copyright (C) 2002-2007 Hewlett-Packard Co |
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* Contributed by David Mosberger-Tang <[email protected]> |
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* |
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* And the bugs have been added by: |
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* |
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* Copyright (C) 2010, Frederic Weisbecker <[email protected]> |
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* Copyright (C) 2012, Jiri Olsa <[email protected]> |
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* |
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*/ |
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|
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#include <elf.h> |
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#include <errno.h> |
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#include <gelf.h> |
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#include <fcntl.h> |
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#include <inttypes.h> |
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#include <string.h> |
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#include <unistd.h> |
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#include <sys/mman.h> |
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#include <linux/list.h> |
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#include <linux/zalloc.h> |
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#ifndef REMOTE_UNWIND_LIBUNWIND |
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#include <libunwind.h> |
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#include <libunwind-ptrace.h> |
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#endif |
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#include "callchain.h" |
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#include "thread.h" |
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#include "session.h" |
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#include "perf_regs.h" |
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#include "unwind.h" |
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#include "map.h" |
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#include "symbol.h" |
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#include "debug.h" |
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#include "asm/bug.h" |
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#include "dso.h" |
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|
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extern int |
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UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as, |
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unw_word_t ip, |
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unw_dyn_info_t *di, |
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unw_proc_info_t *pi, |
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int need_unwind_info, void *arg); |
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|
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#define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table) |
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|
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extern int |
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UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug, |
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unw_word_t ip, |
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unw_word_t segbase, |
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const char *obj_name, unw_word_t start, |
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unw_word_t end); |
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|
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#define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame) |
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|
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#define DW_EH_PE_FORMAT_MASK 0x0f /* format of the encoded value */ |
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#define DW_EH_PE_APPL_MASK 0x70 /* how the value is to be applied */ |
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|
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/* Pointer-encoding formats: */ |
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#define DW_EH_PE_omit 0xff |
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#define DW_EH_PE_ptr 0x00 /* pointer-sized unsigned value */ |
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#define DW_EH_PE_udata4 0x03 /* unsigned 32-bit value */ |
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#define DW_EH_PE_udata8 0x04 /* unsigned 64-bit value */ |
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#define DW_EH_PE_sdata4 0x0b /* signed 32-bit value */ |
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#define DW_EH_PE_sdata8 0x0c /* signed 64-bit value */ |
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|
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/* Pointer-encoding application: */ |
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#define DW_EH_PE_absptr 0x00 /* absolute value */ |
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#define DW_EH_PE_pcrel 0x10 /* rel. to addr. of encoded value */ |
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|
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/* |
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* The following are not documented by LSB v1.3, yet they are used by |
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* GCC, presumably they aren't documented by LSB since they aren't |
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* used on Linux: |
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*/ |
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#define DW_EH_PE_funcrel 0x40 /* start-of-procedure-relative */ |
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#define DW_EH_PE_aligned 0x50 /* aligned pointer */ |
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|
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/* Flags intentionally not handled, since they're not needed: |
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* #define DW_EH_PE_indirect 0x80 |
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* #define DW_EH_PE_uleb128 0x01 |
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* #define DW_EH_PE_udata2 0x02 |
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* #define DW_EH_PE_sleb128 0x09 |
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* #define DW_EH_PE_sdata2 0x0a |
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* #define DW_EH_PE_textrel 0x20 |
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* #define DW_EH_PE_datarel 0x30 |
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*/ |
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|
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struct unwind_info { |
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struct perf_sample *sample; |
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struct machine *machine; |
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struct thread *thread; |
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}; |
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|
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#define dw_read(ptr, type, end) ({ \ |
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type *__p = (type *) ptr; \ |
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type __v; \ |
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if ((__p + 1) > (type *) end) \ |
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return -EINVAL; \ |
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__v = *__p++; \ |
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ptr = (typeof(ptr)) __p; \ |
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__v; \ |
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}) |
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|
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static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val, |
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u8 encoding) |
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{ |
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u8 *cur = *p; |
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*val = 0; |
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|
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switch (encoding) { |
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case DW_EH_PE_omit: |
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*val = 0; |
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goto out; |
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case DW_EH_PE_ptr: |
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*val = dw_read(cur, unsigned long, end); |
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goto out; |
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default: |
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break; |
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} |
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|
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switch (encoding & DW_EH_PE_APPL_MASK) { |
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case DW_EH_PE_absptr: |
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break; |
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case DW_EH_PE_pcrel: |
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*val = (unsigned long) cur; |
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break; |
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default: |
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return -EINVAL; |
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} |
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|
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if ((encoding & 0x07) == 0x00) |
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encoding |= DW_EH_PE_udata4; |
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|
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switch (encoding & DW_EH_PE_FORMAT_MASK) { |
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case DW_EH_PE_sdata4: |
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*val += dw_read(cur, s32, end); |
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break; |
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case DW_EH_PE_udata4: |
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*val += dw_read(cur, u32, end); |
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break; |
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case DW_EH_PE_sdata8: |
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*val += dw_read(cur, s64, end); |
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break; |
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case DW_EH_PE_udata8: |
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*val += dw_read(cur, u64, end); |
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break; |
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default: |
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return -EINVAL; |
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} |
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out: |
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*p = cur; |
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return 0; |
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} |
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#define dw_read_encoded_value(ptr, end, enc) ({ \ |
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u64 __v; \ |
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if (__dw_read_encoded_value(&ptr, end, &__v, enc)) { \ |
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return -EINVAL; \ |
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} \ |
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__v; \ |
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}) |
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static u64 elf_section_offset(int fd, const char *name) |
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{ |
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Elf *elf; |
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GElf_Ehdr ehdr; |
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GElf_Shdr shdr; |
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u64 offset = 0; |
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|
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elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); |
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if (elf == NULL) |
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return 0; |
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|
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do { |
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if (gelf_getehdr(elf, &ehdr) == NULL) |
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break; |
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|
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if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL)) |
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break; |
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offset = shdr.sh_offset; |
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} while (0); |
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elf_end(elf); |
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return offset; |
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} |
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#ifndef NO_LIBUNWIND_DEBUG_FRAME |
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static int elf_is_exec(int fd, const char *name) |
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{ |
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Elf *elf; |
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GElf_Ehdr ehdr; |
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int retval = 0; |
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|
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elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); |
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if (elf == NULL) |
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return 0; |
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if (gelf_getehdr(elf, &ehdr) == NULL) |
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goto out; |
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retval = (ehdr.e_type == ET_EXEC); |
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out: |
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elf_end(elf); |
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pr_debug("unwind: elf_is_exec(%s): %d\n", name, retval); |
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return retval; |
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} |
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#endif |
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|
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struct table_entry { |
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u32 start_ip_offset; |
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u32 fde_offset; |
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}; |
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|
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struct eh_frame_hdr { |
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unsigned char version; |
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unsigned char eh_frame_ptr_enc; |
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unsigned char fde_count_enc; |
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unsigned char table_enc; |
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|
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/* |
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* The rest of the header is variable-length and consists of the |
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* following members: |
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* |
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* encoded_t eh_frame_ptr; |
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* encoded_t fde_count; |
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*/ |
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|
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/* A single encoded pointer should not be more than 8 bytes. */ |
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u64 enc[2]; |
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|
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/* |
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* struct { |
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* encoded_t start_ip; |
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* encoded_t fde_addr; |
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* } binary_search_table[fde_count]; |
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*/ |
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char data[]; |
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} __packed; |
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|
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static int unwind_spec_ehframe(struct dso *dso, struct machine *machine, |
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u64 offset, u64 *table_data, u64 *segbase, |
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u64 *fde_count) |
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{ |
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struct eh_frame_hdr hdr; |
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u8 *enc = (u8 *) &hdr.enc; |
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u8 *end = (u8 *) &hdr.data; |
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ssize_t r; |
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r = dso__data_read_offset(dso, machine, offset, |
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(u8 *) &hdr, sizeof(hdr)); |
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if (r != sizeof(hdr)) |
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return -EINVAL; |
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/* We dont need eh_frame_ptr, just skip it. */ |
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dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc); |
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*fde_count = dw_read_encoded_value(enc, end, hdr.fde_count_enc); |
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*segbase = offset; |
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*table_data = (enc - (u8 *) &hdr) + offset; |
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return 0; |
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} |
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static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine, |
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u64 *table_data, u64 *segbase, |
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u64 *fde_count) |
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{ |
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int ret = -EINVAL, fd; |
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u64 offset = dso->data.eh_frame_hdr_offset; |
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|
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if (offset == 0) { |
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fd = dso__data_get_fd(dso, machine); |
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if (fd < 0) |
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return -EINVAL; |
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|
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/* Check the .eh_frame section for unwinding info */ |
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offset = elf_section_offset(fd, ".eh_frame_hdr"); |
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dso->data.eh_frame_hdr_offset = offset; |
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dso__data_put_fd(dso); |
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} |
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if (offset) |
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ret = unwind_spec_ehframe(dso, machine, offset, |
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table_data, segbase, |
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fde_count); |
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return ret; |
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} |
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#ifndef NO_LIBUNWIND_DEBUG_FRAME |
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static int read_unwind_spec_debug_frame(struct dso *dso, |
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struct machine *machine, u64 *offset) |
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{ |
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int fd; |
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u64 ofs = dso->data.debug_frame_offset; |
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|
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/* debug_frame can reside in: |
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* - dso |
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* - debug pointed by symsrc_filename |
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* - gnu_debuglink, which doesn't necessary |
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* has to be pointed by symsrc_filename |
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*/ |
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if (ofs == 0) { |
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fd = dso__data_get_fd(dso, machine); |
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if (fd >= 0) { |
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ofs = elf_section_offset(fd, ".debug_frame"); |
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dso__data_put_fd(dso); |
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} |
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if (ofs <= 0) { |
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fd = open(dso->symsrc_filename, O_RDONLY); |
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if (fd >= 0) { |
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ofs = elf_section_offset(fd, ".debug_frame"); |
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close(fd); |
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} |
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} |
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if (ofs <= 0) { |
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char *debuglink = malloc(PATH_MAX); |
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int ret = 0; |
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ret = dso__read_binary_type_filename( |
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dso, DSO_BINARY_TYPE__DEBUGLINK, |
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machine->root_dir, debuglink, PATH_MAX); |
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if (!ret) { |
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fd = open(debuglink, O_RDONLY); |
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if (fd >= 0) { |
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ofs = elf_section_offset(fd, |
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".debug_frame"); |
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close(fd); |
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} |
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} |
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if (ofs > 0) { |
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if (dso->symsrc_filename != NULL) { |
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pr_warning( |
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"%s: overwrite symsrc(%s,%s)\n", |
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__func__, |
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dso->symsrc_filename, |
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debuglink); |
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zfree(&dso->symsrc_filename); |
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} |
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dso->symsrc_filename = debuglink; |
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} else { |
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free(debuglink); |
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} |
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} |
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dso->data.debug_frame_offset = ofs; |
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} |
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*offset = ofs; |
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if (*offset) |
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return 0; |
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|
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return -EINVAL; |
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} |
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#endif |
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static struct map *find_map(unw_word_t ip, struct unwind_info *ui) |
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{ |
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struct addr_location al; |
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return thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al); |
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} |
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|
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static int |
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find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi, |
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int need_unwind_info, void *arg) |
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{ |
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struct unwind_info *ui = arg; |
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struct map *map; |
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unw_dyn_info_t di; |
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u64 table_data, segbase, fde_count; |
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int ret = -EINVAL; |
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map = find_map(ip, ui); |
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if (!map || !map->dso) |
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return -EINVAL; |
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pr_debug("unwind: find_proc_info dso %s\n", map->dso->name); |
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|
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/* Check the .eh_frame section for unwinding info */ |
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if (!read_unwind_spec_eh_frame(map->dso, ui->machine, |
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&table_data, &segbase, &fde_count)) { |
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memset(&di, 0, sizeof(di)); |
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di.format = UNW_INFO_FORMAT_REMOTE_TABLE; |
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di.start_ip = map->start; |
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di.end_ip = map->end; |
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di.u.rti.segbase = map->start + segbase - map->pgoff; |
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di.u.rti.table_data = map->start + table_data - map->pgoff; |
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di.u.rti.table_len = fde_count * sizeof(struct table_entry) |
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/ sizeof(unw_word_t); |
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ret = dwarf_search_unwind_table(as, ip, &di, pi, |
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need_unwind_info, arg); |
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} |
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|
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#ifndef NO_LIBUNWIND_DEBUG_FRAME |
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/* Check the .debug_frame section for unwinding info */ |
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if (ret < 0 && |
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!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) { |
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int fd = dso__data_get_fd(map->dso, ui->machine); |
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int is_exec = elf_is_exec(fd, map->dso->name); |
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unw_word_t base = is_exec ? 0 : map->start; |
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const char *symfile; |
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|
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if (fd >= 0) |
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dso__data_put_fd(map->dso); |
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symfile = map->dso->symsrc_filename ?: map->dso->name; |
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|
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memset(&di, 0, sizeof(di)); |
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if (dwarf_find_debug_frame(0, &di, ip, base, symfile, |
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map->start, map->end)) |
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return dwarf_search_unwind_table(as, ip, &di, pi, |
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need_unwind_info, arg); |
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} |
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#endif |
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return ret; |
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} |
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|
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static int access_fpreg(unw_addr_space_t __maybe_unused as, |
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unw_regnum_t __maybe_unused num, |
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unw_fpreg_t __maybe_unused *val, |
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int __maybe_unused __write, |
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void __maybe_unused *arg) |
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{ |
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pr_err("unwind: access_fpreg unsupported\n"); |
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return -UNW_EINVAL; |
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} |
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|
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static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as, |
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unw_word_t __maybe_unused *dil_addr, |
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void __maybe_unused *arg) |
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{ |
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return -UNW_ENOINFO; |
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} |
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|
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static int resume(unw_addr_space_t __maybe_unused as, |
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unw_cursor_t __maybe_unused *cu, |
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void __maybe_unused *arg) |
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{ |
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pr_err("unwind: resume unsupported\n"); |
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return -UNW_EINVAL; |
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} |
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|
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static int |
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get_proc_name(unw_addr_space_t __maybe_unused as, |
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unw_word_t __maybe_unused addr, |
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char __maybe_unused *bufp, size_t __maybe_unused buf_len, |
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unw_word_t __maybe_unused *offp, void __maybe_unused *arg) |
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{ |
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pr_err("unwind: get_proc_name unsupported\n"); |
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return -UNW_EINVAL; |
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} |
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|
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static int access_dso_mem(struct unwind_info *ui, unw_word_t addr, |
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unw_word_t *data) |
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{ |
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struct map *map; |
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ssize_t size; |
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|
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map = find_map(addr, ui); |
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if (!map) { |
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pr_debug("unwind: no map for %lx\n", (unsigned long)addr); |
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return -1; |
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} |
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|
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if (!map->dso) |
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return -1; |
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|
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size = dso__data_read_addr(map->dso, map, ui->machine, |
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addr, (u8 *) data, sizeof(*data)); |
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|
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return !(size == sizeof(*data)); |
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} |
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|
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static int access_mem(unw_addr_space_t __maybe_unused as, |
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unw_word_t addr, unw_word_t *valp, |
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int __write, void *arg) |
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{ |
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struct unwind_info *ui = arg; |
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struct stack_dump *stack = &ui->sample->user_stack; |
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u64 start, end; |
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int offset; |
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int ret; |
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|
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/* Don't support write, probably not needed. */ |
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if (__write || !stack || !ui->sample->user_regs.regs) { |
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*valp = 0; |
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return 0; |
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} |
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|
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ret = perf_reg_value(&start, &ui->sample->user_regs, |
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LIBUNWIND__ARCH_REG_SP); |
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if (ret) |
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return ret; |
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|
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end = start + stack->size; |
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|
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/* Check overflow. */ |
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if (addr + sizeof(unw_word_t) < addr) |
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return -EINVAL; |
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|
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if (addr < start || addr + sizeof(unw_word_t) >= end) { |
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ret = access_dso_mem(ui, addr, valp); |
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if (ret) { |
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pr_debug("unwind: access_mem %p not inside range" |
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" 0x%" PRIx64 "-0x%" PRIx64 "\n", |
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(void *) (uintptr_t) addr, start, end); |
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*valp = 0; |
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return ret; |
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} |
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return 0; |
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} |
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|
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offset = addr - start; |
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*valp = *(unw_word_t *)&stack->data[offset]; |
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pr_debug("unwind: access_mem addr %p val %lx, offset %d\n", |
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(void *) (uintptr_t) addr, (unsigned long)*valp, offset); |
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return 0; |
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} |
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|
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static int access_reg(unw_addr_space_t __maybe_unused as, |
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unw_regnum_t regnum, unw_word_t *valp, |
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int __write, void *arg) |
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{ |
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struct unwind_info *ui = arg; |
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int id, ret; |
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u64 val; |
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|
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/* Don't support write, I suspect we don't need it. */ |
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if (__write) { |
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pr_err("unwind: access_reg w %d\n", regnum); |
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return 0; |
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} |
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|
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if (!ui->sample->user_regs.regs) { |
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*valp = 0; |
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return 0; |
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} |
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|
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id = LIBUNWIND__ARCH_REG_ID(regnum); |
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if (id < 0) |
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return -EINVAL; |
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|
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ret = perf_reg_value(&val, &ui->sample->user_regs, id); |
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if (ret) { |
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pr_err("unwind: can't read reg %d\n", regnum); |
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return ret; |
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} |
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*valp = (unw_word_t) val; |
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pr_debug("unwind: reg %d, val %lx\n", regnum, (unsigned long)*valp); |
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return 0; |
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} |
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|
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static void put_unwind_info(unw_addr_space_t __maybe_unused as, |
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unw_proc_info_t *pi __maybe_unused, |
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void *arg __maybe_unused) |
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{ |
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pr_debug("unwind: put_unwind_info called\n"); |
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} |
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|
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static int entry(u64 ip, struct thread *thread, |
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unwind_entry_cb_t cb, void *arg) |
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{ |
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struct unwind_entry e; |
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struct addr_location al; |
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|
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e.ms.sym = thread__find_symbol(thread, PERF_RECORD_MISC_USER, ip, &al); |
|
e.ip = ip; |
|
e.ms.map = al.map; |
|
e.ms.maps = al.maps; |
|
|
|
pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n", |
|
al.sym ? al.sym->name : "''", |
|
ip, |
|
al.map ? al.map->map_ip(al.map, ip) : (u64) 0); |
|
|
|
return cb(&e, arg); |
|
} |
|
|
|
static void display_error(int err) |
|
{ |
|
switch (err) { |
|
case UNW_EINVAL: |
|
pr_err("unwind: Only supports local.\n"); |
|
break; |
|
case UNW_EUNSPEC: |
|
pr_err("unwind: Unspecified error.\n"); |
|
break; |
|
case UNW_EBADREG: |
|
pr_err("unwind: Register unavailable.\n"); |
|
break; |
|
default: |
|
break; |
|
} |
|
} |
|
|
|
static unw_accessors_t accessors = { |
|
.find_proc_info = find_proc_info, |
|
.put_unwind_info = put_unwind_info, |
|
.get_dyn_info_list_addr = get_dyn_info_list_addr, |
|
.access_mem = access_mem, |
|
.access_reg = access_reg, |
|
.access_fpreg = access_fpreg, |
|
.resume = resume, |
|
.get_proc_name = get_proc_name, |
|
}; |
|
|
|
static int _unwind__prepare_access(struct maps *maps) |
|
{ |
|
maps->addr_space = unw_create_addr_space(&accessors, 0); |
|
if (!maps->addr_space) { |
|
pr_err("unwind: Can't create unwind address space.\n"); |
|
return -ENOMEM; |
|
} |
|
|
|
unw_set_caching_policy(maps->addr_space, UNW_CACHE_GLOBAL); |
|
return 0; |
|
} |
|
|
|
static void _unwind__flush_access(struct maps *maps) |
|
{ |
|
unw_flush_cache(maps->addr_space, 0, 0); |
|
} |
|
|
|
static void _unwind__finish_access(struct maps *maps) |
|
{ |
|
unw_destroy_addr_space(maps->addr_space); |
|
} |
|
|
|
static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, |
|
void *arg, int max_stack) |
|
{ |
|
u64 val; |
|
unw_word_t ips[max_stack]; |
|
unw_addr_space_t addr_space; |
|
unw_cursor_t c; |
|
int ret, i = 0; |
|
|
|
ret = perf_reg_value(&val, &ui->sample->user_regs, |
|
LIBUNWIND__ARCH_REG_IP); |
|
if (ret) |
|
return ret; |
|
|
|
ips[i++] = (unw_word_t) val; |
|
|
|
/* |
|
* If we need more than one entry, do the DWARF |
|
* unwind itself. |
|
*/ |
|
if (max_stack - 1 > 0) { |
|
WARN_ONCE(!ui->thread, "WARNING: ui->thread is NULL"); |
|
addr_space = ui->thread->maps->addr_space; |
|
|
|
if (addr_space == NULL) |
|
return -1; |
|
|
|
ret = unw_init_remote(&c, addr_space, ui); |
|
if (ret) |
|
display_error(ret); |
|
|
|
while (!ret && (unw_step(&c) > 0) && i < max_stack) { |
|
unw_get_reg(&c, UNW_REG_IP, &ips[i]); |
|
|
|
/* |
|
* Decrement the IP for any non-activation frames. |
|
* this is required to properly find the srcline |
|
* for caller frames. |
|
* See also the documentation for dwfl_frame_pc(), |
|
* which this code tries to replicate. |
|
*/ |
|
if (unw_is_signal_frame(&c) <= 0) |
|
--ips[i]; |
|
|
|
++i; |
|
} |
|
|
|
max_stack = i; |
|
} |
|
|
|
/* |
|
* Display what we got based on the order setup. |
|
*/ |
|
for (i = 0; i < max_stack && !ret; i++) { |
|
int j = i; |
|
|
|
if (callchain_param.order == ORDER_CALLER) |
|
j = max_stack - i - 1; |
|
ret = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0; |
|
} |
|
|
|
return ret; |
|
} |
|
|
|
static int _unwind__get_entries(unwind_entry_cb_t cb, void *arg, |
|
struct thread *thread, |
|
struct perf_sample *data, int max_stack) |
|
{ |
|
struct unwind_info ui = { |
|
.sample = data, |
|
.thread = thread, |
|
.machine = thread->maps->machine, |
|
}; |
|
|
|
if (!data->user_regs.regs) |
|
return -EINVAL; |
|
|
|
if (max_stack <= 0) |
|
return -EINVAL; |
|
|
|
return get_entries(&ui, cb, arg, max_stack); |
|
} |
|
|
|
static struct unwind_libunwind_ops |
|
_unwind_libunwind_ops = { |
|
.prepare_access = _unwind__prepare_access, |
|
.flush_access = _unwind__flush_access, |
|
.finish_access = _unwind__finish_access, |
|
.get_entries = _unwind__get_entries, |
|
}; |
|
|
|
#ifndef REMOTE_UNWIND_LIBUNWIND |
|
struct unwind_libunwind_ops * |
|
local_unwind_libunwind_ops = &_unwind_libunwind_ops; |
|
#endif
|
|
|