linux/tools/perf/util/unwind-libunwind-local.c
James Clark fa7095c5c3 perf unwind: Don't show unwind error messages when augmenting frame pointer stack
Commit Fixes: b9f6fbb3b2 ("perf arm64: Inject missing frames when
using 'perf record --call-graph=fp'") intended to add a 'best effort'
DWARF unwind that improved the frame pointer stack in most scenarios.

It's expected that the unwind will fail sometimes, but this shouldn't be
reported as an error. It only works when the return address can be
determined from the contents of the link register alone.

Fix the error shown when the unwinder requires extra registers by adding
a new flag that suppresses error messages. This flag is not set in the
normal --call-graph=dwarf unwind mode so that behavior is not changed.

Fixes: b9f6fbb3b2 ("perf arm64: Inject missing frames when using 'perf record --call-graph=fp'")
Reported-by: John Garry <john.garry@huawei.com>
Signed-off-by: James Clark <james.clark@arm.com>
Tested-by: John Garry <john.garry@huawei.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Truong <alexandre.truong@arm.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20220406145651.1392529-1-james.clark@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2022-04-09 12:34:29 -03:00

740 lines
17 KiB
C

// 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 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[];
} __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) {
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;
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 && !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 = thread->maps->machine,
.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