tools/perf/util/vdso.c

   1
   2 #include <unistd.h>
   3 #include <stdio.h>
   4 #include <string.h>
   5 #include <sys/types.h>
   6 #include <sys/stat.h>
   7 #include <fcntl.h>
   8 #include <stdlib.h>
   9 #include <linux/kernel.h>
  10
  11 #include "vdso.h"
  12 #include "util.h"
  13 #include "symbol.h"
  14 #include "machine.h"
  15 #include "linux/string.h"
  16 #include "debug.h"
  17
  18 #define VDSO__TEMP_FILE_NAME "/tmp/perf-vdso.so-XXXXXX"
  19
  20 struct vdso_file {
  21         bool found;
  22         bool error;
  23         char temp_file_name[sizeof(VDSO__TEMP_FILE_NAME)];
  24         const char *dso_name;
  25 };
  26
  27 struct vdso_info {
  28         struct vdso_file vdso;
  29 };
  30
  31 static struct vdso_info *vdso_info__new(void)
  32 {
  33         static const struct vdso_info vdso_info_init = {
  34                 .vdso    = {
  35                         .temp_file_name = VDSO__TEMP_FILE_NAME,
  36                         .dso_name = DSO__NAME_VDSO,
  37                 },
  38         };
  39
  40         return memdup(&vdso_info_init, sizeof(vdso_info_init));
  41 }
  42
  43 static int find_vdso_map(void **start, void **end)
  44 {
  45         FILE *maps;
  46         char line[128];
  47         int found = 0;
  48
  49         maps = fopen("/proc/self/maps", "r");
  50         if (!maps) {
  51                 pr_err("vdso: cannot open maps\n");
  52                 return -1;
  53         }
  54
  55         while (!found && fgets(line, sizeof(line), maps)) {
  56                 int m = -1;
  57
  58                 /* We care only about private r-x mappings. */
  59                 if (2 != sscanf(line, "%p-%p r-xp %*x %*x:%*x %*u %n",
  60                                 start, end, &m))
  61                         continue;
  62                 if (m < 0)
  63                         continue;
  64
  65                 if (!strncmp(&line[m], VDSO__MAP_NAME,
  66                              sizeof(VDSO__MAP_NAME) - 1))
  67                         found = 1;
  68         }
  69
  70         fclose(maps);
  71         return !found;
  72 }
  73
  74 static char *get_file(struct vdso_file *vdso_file)
  75 {
  76         char *vdso = NULL;
  77         char *buf = NULL;
  78         void *start, *end;
  79         size_t size;
  80         int fd;
  81
  82         if (vdso_file->found)
  83                 return vdso_file->temp_file_name;
  84
  85         if (vdso_file->error || find_vdso_map(&start, &end))
  86                 return NULL;
  87
  88         size = end - start;
  89
  90         buf = memdup(start, size);
  91         if (!buf)
  92                 return NULL;
  93
  94         fd = mkstemp(vdso_file->temp_file_name);
  95         if (fd < 0)
  96                 goto out;
  97
  98         if (size == (size_t) write(fd, buf, size))
  99                 vdso = vdso_file->temp_file_name;
 100
 101         close(fd);
 102
 103  out:
 104         free(buf);
 105
 106         vdso_file->found = (vdso != NULL);
 107         vdso_file->error = !vdso_file->found;
 108         return vdso;
 109 }
 110
 111 void vdso__exit(struct machine *machine)
 112 {
 113         struct vdso_info *vdso_info = machine->vdso_info;
 114
 115         if (!vdso_info)
 116                 return;
 117
 118         if (vdso_info->vdso.found)
 119                 unlink(vdso_info->vdso.temp_file_name);
 120
 121         zfree(&machine->vdso_info);
 122 }
 123
 124 static struct dso *vdso__new(struct machine *machine, const char *short_name,
 125                              const char *long_name)
 126 {
 127         struct dso *dso;
 128
 129         dso = dso__new(short_name);
 130         if (dso != NULL) {
 131                 dsos__add(&machine->user_dsos, dso);
 132                 dso__set_long_name(dso, long_name, false);
 133         }
 134
 135         return dso;
 136 }
 137
 138 struct dso *vdso__dso_findnew(struct machine *machine,
 139                               struct thread *thread __maybe_unused)
 140 {
 141         struct vdso_info *vdso_info;
 142         struct dso *dso;
 143
 144         if (!machine->vdso_info)
 145                 machine->vdso_info = vdso_info__new();
 146
 147         vdso_info = machine->vdso_info;
 148         if (!vdso_info)
 149                 return NULL;
 150
 151         dso = dsos__find(&machine->user_dsos, DSO__NAME_VDSO, true);
 152         if (!dso) {
 153                 char *file;
 154
 155                 file = get_file(&vdso_info->vdso);
 156                 if (!file)
 157                         return NULL;
 158
 159                 dso = vdso__new(machine, DSO__NAME_VDSO, file);
 160         }
 161
 162         return dso;
 163 }
 164
 165 bool dso__is_vdso(struct dso *dso)
 166 {
 167         return !strcmp(dso->short_name, DSO__NAME_VDSO);
 168 }