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->map = al.map;
  85        e->sym = al.sym;
  86
  87        pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
  88                 al.sym ? al.sym->name : "''",
  89                 ip,
  90                 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
  91        return 0;
  92}
  93
  94static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
  95{
  96        /* We want only single thread to be processed. */
  97        if (*thread_argp != NULL)
  98                return 0;
  99
 100        *thread_argp = arg;
 101        return dwfl_pid(dwfl);
 102}
 103
 104static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
 105                          Dwarf_Word *data)
 106{
 107        struct addr_location al;
 108        ssize_t size;
 109
 110        if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
 111                pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 112                return -1;
 113        }
 114
 115        if (!al.map->dso)
 116                return -1;
 117
 118        size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
 119                                   addr, (u8 *) data, sizeof(*data));
 120
 121        return !(size == sizeof(*data));
 122}
 123
 124static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
 125                        void *arg)
 126{
 127        struct unwind_info *ui = arg;
 128        struct stack_dump *stack = &ui->sample->user_stack;
 129        u64 start, end;
 130        int offset;
 131        int ret;
 132
 133        ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
 134        if (ret)
 135                return false;
 136
 137        end = start + stack->size;
 138
 139        /* Check overflow. */
 140        if (addr + sizeof(Dwarf_Word) < addr)
 141                return false;
 142
 143        if (addr < start || addr + sizeof(Dwarf_Word) > end) {
 144                ret = access_dso_mem(ui, addr, result);
 145                if (ret) {
 146                        pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
 147                                 " 0x%" PRIx64 "-0x%" PRIx64 "\n",
 148                                addr, start, end);
 149                        return false;
 150                }
 151                return true;
 152        }
 153
 154        offset  = addr - start;
 155        *result = *(Dwarf_Word *)&stack->data[offset];
 156        pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
 157                 addr, (unsigned long)*result, offset);
 158        return true;
 159}
 160
 161static const Dwfl_Thread_Callbacks callbacks = {
 162        .next_thread            = next_thread,
 163        .memory_read            = memory_read,
 164        .set_initial_registers  = libdw__arch_set_initial_registers,
 165};
 166
 167static int
 168frame_callback(Dwfl_Frame *state, void *arg)
 169{
 170        struct unwind_info *ui = arg;
 171        Dwarf_Addr pc;
 172        bool isactivation;
 173
 174        if (!dwfl_frame_pc(state, &pc, NULL)) {
 175                pr_err("%s", dwfl_errmsg(-1));
 176                return DWARF_CB_ABORT;
 177        }
 178
 179        // report the module before we query for isactivation
 180        report_module(pc, ui);
 181
 182        if (!dwfl_frame_pc(state, &pc, &isactivation)) {
 183                pr_err("%s", dwfl_errmsg(-1));
 184                return DWARF_CB_ABORT;
 185        }
 186
 187        if (!isactivation)
 188                --pc;
 189
 190        return entry(pc, ui) || !(--ui->max_stack) ?
 191               DWARF_CB_ABORT : DWARF_CB_OK;
 192}
 193
 194int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 195                        struct thread *thread,
 196                        struct perf_sample *data,
 197                        int max_stack)
 198{
 199        struct unwind_info *ui, ui_buf = {
 200                .sample         = data,
 201                .thread         = thread,
 202                .machine        = thread->mg->machine,
 203                .cb             = cb,
 204                .arg            = arg,
 205                .max_stack      = max_stack,
 206        };
 207        Dwarf_Word ip;
 208        int err = -EINVAL, i;
 209
 210        if (!data->user_regs.regs)
 211                return -EINVAL;
 212
 213        ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
 214        if (!ui)
 215                return -ENOMEM;
 216
 217        *ui = ui_buf;
 218
 219        ui->dwfl = dwfl_begin(&offline_callbacks);
 220        if (!ui->dwfl)
 221                goto out;
 222
 223        err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
 224        if (err)
 225                goto out;
 226
 227        err = report_module(ip, ui);
 228        if (err)
 229                goto out;
 230
 231        err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread->tid, &callbacks, ui);
 232        if (err)
 233                goto out;
 234
 235        err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
 236
 237        if (err && ui->max_stack != max_stack)
 238                err = 0;
 239
 240        /*
 241         * Display what we got based on the order setup.
 242         */
 243        for (i = 0; i < ui->idx && !err; i++) {
 244                int j = i;
 245
 246                if (callchain_param.order == ORDER_CALLER)
 247                        j = ui->idx - i - 1;
 248
 249                err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
 250        }
 251
 252 out:
 253        if (err)
 254                pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
 255
 256        dwfl_end(ui->dwfl);
 257        free(ui);
 258        return 0;
 259}
 260