// 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 intentionally 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;
bool best_effort;
};
#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 int elf_section_address_and_offset(int fd, const char *name, u64 *address, u64 *offset)
{
Elf *elf;
GElf_Ehdr ehdr;
GElf_Shdr shdr;
int ret = -1;
elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
if (elf == NULL)
return -1;
if (gelf_getehdr(elf, &ehdr) == NULL)
goto out_err;
if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
goto out_err;
*address = shdr.sh_addr;
*offset = shdr.sh_offset;
ret = 0;
out_err:
elf_end(elf);
return ret;
}
#ifndef NO_LIBUNWIND_DEBUG_FRAME
static u64 elf_section_offset(int fd, const char *name)
{
u64 address, offset = 0;
if (elf_section_address_and_offset(fd, name, &address, &offset))
return 0;
return offset;
}
#endif
static u64 elf_base_address(int fd)
{
Elf *elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
GElf_Phdr phdr;
u64 retval = 0;
size_t i, phdrnum = 0;
if (elf == NULL)
return 0;
(void)elf_getphdrnum(elf, &phdrnum);
/* PT_LOAD segments are sorted by p_vaddr, so the first has the minimum p_vaddr. */
for (i = 0; i < phdrnum; i++) {
if (gelf_getphdr(elf, i, &phdr) && phdr.p_type == PT_LOAD) {
retval = phdr.p_vaddr & -getpagesize();
break;
}
}
elf_end(elf);
return retval;
}
#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[];
} __packed;
static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
u64 offset, u64 *table_data_offset, 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);
*table_data_offset = enc - (u8 *) &hdr;
return 0;
}
static int read_unwind_spec_eh_frame(struct dso *dso, struct unwind_info *ui,
u64 *table_data, u64 *segbase,
u64 *fde_count)
{
struct map_rb_node *map_node;
u64 base_addr = UINT64_MAX;
int ret, fd;
if (dso->data.eh_frame_hdr_offset == 0) {
fd = dso__data_get_fd(dso, ui->machine);
if (fd < 0)
return -EINVAL;
/* Check the .eh_frame section for unwinding info */
ret = elf_section_address_and_offset(fd, ".eh_frame_hdr",
&dso->data.eh_frame_hdr_addr,
&dso->data.eh_frame_hdr_offset);
dso->data.elf_base_addr = elf_base_address(fd);
dso__data_put_fd(dso);
if (ret || dso->data.eh_frame_hdr_offset == 0)
return -EINVAL;
}
maps__for_each_entry(thread__maps(ui->thread), map_node) {
struct map *map = map_node->map;
u64 start = map__start(map);
if (map__dso(map) == dso && start < base_addr)
base_addr = start;
}
base_addr -= dso->data.elf_base_addr;
/* Address of .eh_frame_hdr */
*segbase = base_addr + dso->data.eh_frame_hdr_addr;
ret = unwind_spec_ehframe(dso, ui->machine, dso->data.eh_frame_hdr_offset,
table_data, fde_count);
if (ret)
return ret;
/* binary_search_table offset plus .eh_frame_hdr address */
*table_data += *segbase;
return 0;
}
#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;
struct map *ret;
addr_location__init(&al);
thread__find_map(ui->thread, PERF_RECORD_MISC_USER, ip, &al);
ret = map__get(al.map);
addr_location__exit(&al);
return ret;
}
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;
struct dso *dso;
unw_dyn_info_t di;
u64 table_data, segbase, fde_count;
int ret = -EINVAL;
map = find_map(ip, ui);
if (!map)
return -EINVAL;
dso = map__dso(map);
if (!dso) {
map__put(map);
return -EINVAL;
}
pr_debug("unwind: find_proc_info dso %s\n", dso->name);
/* Check the .eh_frame section for unwinding info */
if (!read_unwind_spec_eh_frame(dso, ui, &table_data, &segbase, &fde_count)) {
memset(&di, 0, sizeof(di));
di.format = UNW_INFO_FORMAT_REMOTE_TABLE;
di.start_ip = map__start(map);
di.end_ip = map__end(map);
di.u.rti.segbase = segbase;
di.u.rti.table_data = table_data;
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(dso, ui->machine, &segbase)) {
int fd = dso__data_get_fd(dso, ui->machine);
int is_exec = elf_is_exec(fd, dso->name);
u64 start = map__start(map);
unw_word_t base = is_exec ? 0 : start;
const char *symfile;
if (fd >= 0)
dso__data_put_fd(dso);
symfile = dso->symsrc_filename ?: dso->name;
memset(&di, 0, sizeof(di));
if (dwarf_find_debug_frame(0, &di, ip, base, symfile, start, map__end(map)))
ret = dwarf_search_unwind_table(as, ip, &di, pi,
need_unwind_info, arg);
}
#endif
map__put(map);
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;
struct dso *dso;
ssize_t size;
map = find_map(addr, ui);
if (!map) {
pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
return -1;
}
dso = map__dso(map);
if (!dso) {
map__put(map);
return -1;
}
size = dso__data_read_addr(dso, map, ui->machine,
addr, (u8 *) data, sizeof(*data));
map__put(map);
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;
const char *arch = perf_env__arch(ui->machine->env);
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,
perf_arch_reg_sp(arch));
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) {
if (!ui->best_effort)
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;
int ret;
addr_location__init(&al);
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 ? map__map_ip(al.map, ip) : (u64) 0);
ret = cb(&e, arg);
addr_location__exit(&al);
return ret;
}
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)
{
void *addr_space = unw_create_addr_space(&accessors, 0);
RC_CHK_ACCESS(maps)->addr_space = addr_space;
if (!addr_space) {
pr_err("unwind: Can't create unwind address space.\n");
return -ENOMEM;
}
unw_set_caching_policy(addr_space, UNW_CACHE_GLOBAL);
return 0;
}
static void _unwind__flush_access(struct maps *maps)
{
unw_flush_cache(maps__addr_space(maps), 0, 0);
}
static void _unwind__finish_access(struct maps *maps)
{
unw_destroy_addr_space(maps__addr_space(maps));
}
static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
void *arg, int max_stack)
{
const char *arch = perf_env__arch(ui->machine->env);
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,
perf_arch_reg_ip(arch));
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 = maps__addr_space(thread__maps(ui->thread));
if (addr_space == NULL)
return -1;
ret = unw_init_remote(&c, addr_space, ui);
if (ret && !ui->best_effort)
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,
bool best_effort)
{
struct unwind_info ui = {
.sample = data,
.thread = thread,
.machine = maps__machine(thread__maps(thread)),
.best_effort = best_effort
};
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