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 "linux/string.h"
  15
  16 static bool vdso_found;
  17 static char vdso_file[] = "/tmp/perf-vdso.so-XXXXXX";
  18
  19 static int find_vdso_map(void **start, void **end)
  20 {
  21         FILE *maps;
  22         char line[128];
  23         int found = 0;
  24
  25         maps = fopen("/proc/self/maps", "r");
  26         if (!maps) {
  27                 pr_err("vdso: cannot open maps\n");
  28                 return -1;
  29         }
  30
  31         while (!found && fgets(line, sizeof(line), maps)) {
  32                 int m = -1;
  33
  34                 /* We care only about private r-x mappings. */
  35                 if (2 != sscanf(line, "%p-%p r-xp %*x %*x:%*x %*u %n",
  36                                 start, end, &m))
  37                         continue;
  38                 if (m < 0)
  39                         continue;
  40
  41                 if (!strncmp(&line[m], VDSO__MAP_NAME,
  42                              sizeof(VDSO__MAP_NAME) - 1))
  43                         found = 1;
  44         }
  45
  46         fclose(maps);
  47         return !found;
  48 }
  49
  50 static char *get_file(void)
  51 {
  52         char *vdso = NULL;
  53         char *buf = NULL;
  54         void *start, *end;
  55         size_t size;
  56         int fd;
  57
  58         if (vdso_found)
  59                 return vdso_file;
  60
  61         if (find_vdso_map(&start, &end))
  62                 return NULL;
  63
  64         size = end - start;
  65
  66         buf = memdup(start, size);
  67         if (!buf)
  68                 return NULL;
  69
  70         fd = mkstemp(vdso_file);
  71         if (fd < 0)
  72                 goto out;
  73
  74         if (size == (size_t) write(fd, buf, size))
  75                 vdso = vdso_file;
  76
  77         close(fd);
  78
  79  out:
  80         free(buf);
  81
  82         vdso_found = (vdso != NULL);
  83         return vdso;
  84 }
  85
  86 void vdso__exit(void)
  87 {
  88         if (vdso_found)
  89                 unlink(vdso_file);
  90 }
  91
  92 struct dso *vdso__dso_findnew(struct list_head *head)
  93 {
  94         struct dso *dso = dsos__find(head, VDSO__MAP_NAME, true);
  95
  96         if (!dso) {
  97                 char *file;
  98
  99                 file = get_file();
 100                 if (!file)
 101                         return NULL;
 102
 103                 dso = dso__new(VDSO__MAP_NAME);
 104                 if (dso != NULL) {
 105                         dsos__add(head, dso);
 106                         dso__set_long_name(dso, file, false);
 107                 }
 108         }
 109
 110         return dso;
 111 }