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