linux/tools/perf/util/unwind-libdw.c
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   1// SPDX-License-Identifier: GPL-2.0
   2#include <linux/compiler.h>
   3#include <elfutils/libdw.h>
   4#include <elfutils/libdwfl.h>
   5#include <inttypes.h>
   6#include <errno.h>
   7#include "debug.h"
   8#include "dso.h"
   9#include "unwind.h"
  10#include "unwind-libdw.h"
  11#include "machine.h"
  12#include "map.h"
  13#include "symbol.h"
  14#include "thread.h"
  15#include <linux/types.h>
  16#include <linux/zalloc.h>
  17#include "event.h"
  18#include "perf_regs.h"
  19#include "callchain.h"
  20
  21static char *debuginfo_path;
  22
  23static const Dwfl_Callbacks offline_callbacks = {
  24        .find_debuginfo         = dwfl_standard_find_debuginfo,
  25        .debuginfo_path         = &debuginfo_path,
  26        .section_address        = dwfl_offline_section_address,
  27};
  28
  29static int __report_module(struct addr_location *al, u64 ip,
  30                            struct unwind_info *ui)
  31{
  32        Dwfl_Module *mod;
  33        struct dso *dso = NULL;
  34        /*
  35         * Some callers will use al->sym, so we can't just use the
  36         * cheaper thread__find_map() here.
  37         */
  38        thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al);
  39
  40        if (al->map)
  41                dso = al->map->dso;
  42
  43        if (!dso)
  44                return 0;
  45
  46        mod = dwfl_addrmodule(ui->dwfl, ip);
  47        if (mod) {
  48                Dwarf_Addr s;
  49
  50                dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
  51                if (s != al->map->start - al->map->pgoff)
  52                        mod = 0;
  53        }
  54
  55        if (!mod)
  56                mod = dwfl_report_elf(ui->dwfl, dso->short_name,
  57                                      (dso->symsrc_filename ? dso->symsrc_filename : dso->long_name), -1, al->map->start - al->map->pgoff,
  58                                      false);
  59
  60        return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
  61}
  62
  63static int report_module(u64 ip, struct unwind_info *ui)
  64{
  65        struct addr_location al;
  66
  67        return __report_module(&al, ip, ui);
  68}
  69
  70/*
  71 * Store all entries within entries array,
  72 * we will process it after we finish unwind.
  73 */
  74static int entry(u64 ip, struct unwind_info *ui)
  75
  76{
  77        struct unwind_entry *e = &ui->entries[ui->idx++];
  78        struct addr_location al;
  79
  80        if (__report_module(&al, ip, ui))
  81                return -1;
  82
  83        e->ip     = ip;
  84        e->ms.maps = al.maps;
  85        e->ms.map = al.map;
  86        e->ms.sym = al.sym;
  87
  88        pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
  89                 al.sym ? al.sym->name : "''",
  90                 ip,
  91                 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
  92        return 0;
  93}
  94
  95static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
  96{
  97        /* We want only single thread to be processed. */
  98        if (*thread_argp != NULL)
  99                return 0;
 100
 101        *thread_argp = arg;
 102        return dwfl_pid(dwfl);
 103}
 104
 105static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
 106                          Dwarf_Word *data)
 107{
 108        struct addr_location al;
 109        ssize_t size;
 110
 111        if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
 112                pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 113                return -1;
 114        }
 115
 116        if (!al.map->dso)
 117                return -1;
 118
 119        size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
 120                                   addr, (u8 *) data, sizeof(*data));
 121
 122        return !(size == sizeof(*data));
 123}
 124
 125static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
 126                        void *arg)
 127{
 128        struct unwind_info *ui = arg;
 129        struct stack_dump *stack = &ui->sample->user_stack;
 130        u64 start, end;
 131        int offset;
 132        int ret;
 133
 134        ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
 135        if (ret)
 136                return false;
 137
 138        end = start + stack->size;
 139
 140        /* Check overflow. */
 141        if (addr + sizeof(Dwarf_Word) < addr)
 142                return false;
 143
 144        if (addr < start || addr + sizeof(Dwarf_Word) > end) {
 145                ret = access_dso_mem(ui, addr, result);
 146                if (ret) {
 147                        pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
 148                                 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
 149                                addr, start, end);
 150                        return false;
 151                }
 152                return true;
 153        }
 154
 155        offset  = addr - start;
 156        *result = *(Dwarf_Word *)&stack->data[offset];
 157        pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
 158                 addr, (unsigned long)*result, offset);
 159        return true;
 160}
 161
 162static const Dwfl_Thread_Callbacks callbacks = {
 163        .next_thread            = next_thread,
 164        .memory_read            = memory_read,
 165        .set_initial_registers  = libdw__arch_set_initial_registers,
 166};
 167
 168static int
 169frame_callback(Dwfl_Frame *state, void *arg)
 170{
 171        struct unwind_info *ui = arg;
 172        Dwarf_Addr pc;
 173        bool isactivation;
 174
 175        if (!dwfl_frame_pc(state, &pc, NULL)) {
 176                pr_err("%s", dwfl_errmsg(-1));
 177                return DWARF_CB_ABORT;
 178        }
 179
 180        // report the module before we query for isactivation
 181        report_module(pc, ui);
 182
 183        if (!dwfl_frame_pc(state, &pc, &isactivation)) {
 184                pr_err("%s", dwfl_errmsg(-1));
 185                return DWARF_CB_ABORT;
 186        }
 187
 188        if (!isactivation)
 189                --pc;
 190
 191        return entry(pc, ui) || !(--ui->max_stack) ?
 192               DWARF_CB_ABORT : DWARF_CB_OK;
 193}
 194
 195int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 196                        struct thread *thread,
 197                        struct perf_sample *data,
 198                        int max_stack)
 199{
 200        struct unwind_info *ui, ui_buf = {
 201                .sample         = data,
 202                .thread         = thread,
 203                .machine        = thread->maps->machine,
 204                .cb             = cb,
 205                .arg            = arg,
 206                .max_stack      = max_stack,
 207        };
 208        Dwarf_Word ip;
 209        int err = -EINVAL, i;
 210
 211        if (!data->user_regs.regs)
 212                return -EINVAL;
 213
 214        ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
 215        if (!ui)
 216                return -ENOMEM;
 217
 218        *ui = ui_buf;
 219
 220        ui->dwfl = dwfl_begin(&offline_callbacks);
 221        if (!ui->dwfl)
 222                goto out;
 223
 224        err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
 225        if (err)
 226                goto out;
 227
 228        err = report_module(ip, ui);
 229        if (err)
 230                goto out;
 231
 232        err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread->tid, &callbacks, ui);
 233        if (err)
 234                goto out;
 235
 236        err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
 237
 238        if (err && ui->max_stack != max_stack)
 239                err = 0;
 240
 241        /*
 242         * Display what we got based on the order setup.
 243         */
 244        for (i = 0; i < ui->idx && !err; i++) {
 245                int j = i;
 246
 247                if (callchain_param.order == ORDER_CALLER)
 248                        j = ui->idx - i - 1;
 249
 250                err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
 251        }
 252
 253 out:
 254        if (err)
 255                pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
 256
 257        dwfl_end(ui->dwfl);
 258        free(ui);
 259        return 0;
 260}
 261