/* * 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 <gelf.h> #include <fcntl.h> #include <string.h> #include <unistd.h> #include <sys/mman.h> #include <linux/list.h> #include <libunwind.h> #include <libunwind-ptrace.h> #include "thread.h" #include "session.h" #include "perf_regs.h" #include "unwind.h" #include "util.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) #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; u64 sample_uregs; }; #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 Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep, GElf_Shdr *shp, const char *name) { Elf_Scn *sec = NULL; while ((sec = elf_nextscn(elf, sec)) != NULL) { char *str; gelf_getshdr(sec, shp); str = elf_strptr(elf, ep->e_shstrndx, shp->sh_name); if (!strcmp(name, str)) break; } return sec; } 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)) break; offset = shdr.sh_offset; } while (0); elf_end(elf); return offset; } 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(struct dso *dso, struct machine *machine, u64 *table_data, u64 *segbase, u64 *fde_count) { int ret = -EINVAL, fd; u64 offset; fd = dso__data_fd(dso, machine); if (fd < 0) return -EINVAL; offset = elf_section_offset(fd, ".eh_frame_hdr"); close(fd); if (offset) ret = unwind_spec_ehframe(dso, machine, offset, table_data, segbase, fde_count); /* TODO .debug_frame check if eh_frame_hdr fails */ return ret; } static struct map *find_map(unw_word_t ip, struct unwind_info *ui) { struct addr_location al; thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER, MAP__FUNCTION, ip, &al); return al.map; } 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; map = find_map(ip, ui); if (!map || !map->dso) return -EINVAL; pr_debug("unwind: find_proc_info dso %s\n", map->dso->name); if (read_unwind_spec(map->dso, ui->machine, &table_data, &segbase, &fde_count)) return -EINVAL; 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; di.u.rti.table_data = map->start + table_data; di.u.rti.table_len = fde_count * sizeof(struct table_entry) / sizeof(unw_word_t); return dwarf_search_unwind_table(as, ip, &di, pi, need_unwind_info, arg); } 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 addr_location al; ssize_t size; thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER, MAP__FUNCTION, addr, &al); if (!al.map) { pr_debug("unwind: no map for %lx\n", (unsigned long)addr); return -1; } if (!al.map->dso) return -1; size = dso__data_read_addr(al.map->dso, al.map, ui->machine, addr, (u8 *) data, sizeof(*data)); return !(size == sizeof(*data)); } static int reg_value(unw_word_t *valp, struct regs_dump *regs, int id, u64 sample_regs) { int i, idx = 0; if (!(sample_regs & (1 << id))) return -EINVAL; for (i = 0; i < id; i++) { if (sample_regs & (1 << i)) idx++; } *valp = regs->regs[idx]; return 0; } 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; unw_word_t 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 = reg_value(&start, &ui->sample->user_regs, PERF_REG_SP, ui->sample_uregs); 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 %p-%p\n", (void *)addr, (void *)start, (void *)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 *)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; /* 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 = unwind__arch_reg_id(regnum); if (id < 0) return -EINVAL; ret = reg_value(valp, &ui->sample->user_regs, id, ui->sample_uregs); if (ret) { pr_err("unwind: can't read reg %d\n", regnum); return ret; } 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, struct machine *machine, unwind_entry_cb_t cb, void *arg) { struct unwind_entry e; struct addr_location al; thread__find_addr_location(thread, machine, PERF_RECORD_MISC_USER, MAP__FUNCTION, ip, &al, NULL); e.ip = ip; e.map = al.map; e.sym = al.sym; 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 get_entries(struct unwind_info *ui, unwind_entry_cb_t cb, void *arg) { unw_addr_space_t addr_space; unw_cursor_t c; int ret; addr_space = unw_create_addr_space(&accessors, 0); if (!addr_space) { pr_err("unwind: Can't create unwind address space.\n"); return -ENOMEM; } ret = unw_init_remote(&c, addr_space, ui); if (ret) display_error(ret); while (!ret && (unw_step(&c) > 0)) { unw_word_t ip; unw_get_reg(&c, UNW_REG_IP, &ip); ret = entry(ip, ui->thread, ui->machine, cb, arg); } unw_destroy_addr_space(addr_space); return ret; } int unwind__get_entries(unwind_entry_cb_t cb, void *arg, struct machine *machine, struct thread *thread, u64 sample_uregs, struct perf_sample *data) { unw_word_t ip; struct unwind_info ui = { .sample = data, .sample_uregs = sample_uregs, .thread = thread, .machine = machine, }; int ret; if (!data->user_regs.regs) return -EINVAL; ret = reg_value(&ip, &data->user_regs, PERF_REG_IP, sample_uregs); if (ret) return ret; ret = entry(ip, thread, machine, cb, arg); if (ret) return -ENOMEM; return get_entries(&ui, cb, arg); }