- 根目录:
- tools
- perf
- util
- unwind.c
/*
* 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);
}