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 static bool vdso_found;
  19 static char vdso_file[] = "/tmp/perf-vdso.so-XXXXXX";
  20
  21 static int find_vdso_map(void **start, void **end)
  22 {
  23         FILE *maps;
  24         char line[128];
  25         int found = 0;
  26
  27         maps = fopen("/proc/self/maps", "r");
  28         if (!maps) {
  29                 pr_err("vdso: cannot open maps\n");
  30                 return -1;
  31         }
  32
  33         while (!found && fgets(line, sizeof(line), maps)) {
  34                 int m = -1;
  35
  36                 /* We care only about private r-x mappings. */
  37                 if (2 != sscanf(line, "%p-%p r-xp %*x %*x:%*x %*u %n",
  38                                 start, end, &m))
  39                         continue;
  40                 if (m < 0)
  41                         continue;
  42
  43                 if (!strncmp(&line[m], VDSO__MAP_NAME,
  44                              sizeof(VDSO__MAP_NAME) - 1))
  45                         found = 1;
  46         }
  47
  48         fclose(maps);
  49         return !found;
  50 }
  51
  52 static char *get_file(void)
  53 {
  54         char *vdso = NULL;
  55         char *buf = NULL;
  56         void *start, *end;
  57         size_t size;
  58         int fd;
  59
  60         if (vdso_found)
  61                 return vdso_file;
  62
  63         if (find_vdso_map(&start, &end))
  64                 return NULL;
  65
  66         size = end - start;
  67
  68         buf = memdup(start, size);
  69         if (!buf)
  70                 return NULL;
  71
  72         fd = mkstemp(vdso_file);
  73         if (fd < 0)
  74                 goto out;
  75
  76         if (size == (size_t) write(fd, buf, size))
  77                 vdso = vdso_file;
  78
  79         close(fd);
  80
  81  out:
  82         free(buf);
  83
  84         vdso_found = (vdso != NULL);
  85         return vdso;
  86 }
  87
  88 void vdso__exit(void)
  89 {
  90         if (vdso_found)
  91                 unlink(vdso_file);
  92 }
  93
  94 struct dso *vdso__dso_findnew(struct machine *machine)
  95 {
  96         struct dso *dso = dsos__find(&machine->user_dsos, VDSO__MAP_NAME, true);
  97
  98         if (!dso) {
  99                 char *file;
 100
 101                 file = get_file();
 102                 if (!file)
 103                         return NULL;
 104
 105                 dso = dso__new(VDSO__MAP_NAME);
 106                 if (dso != NULL) {
 107                         dsos__add(&machine->user_dsos, dso);
 108                         dso__set_long_name(dso, file, false);
 109                 }
 110         }
 111
 112         return dso;
 113 }