perf tools: Add sysfs mountpoint interface

Adding sysfs object to provide sysfs mount information in the same way
as debugfs object does.

The object provides following function:
  sysfs_find_mountpoint

which returns the sysfs mount mount.

Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1327674868-10486-4-git-send-email-jolsa@redhat.com
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 60 insertions, 0 deletions

diff --git a/tools/perf/util/sysfs.c b/tools/perf/util/sysfs.c
new file mode 100644
index 000000000000..48c6902e749f
--- /dev/null
+++ b/tools/perf/util/sysfs.c
@@ -0,0 +1,60 @@
+
+#include "util.h"
+#include "sysfs.h"
+
+static const char * const sysfs_known_mountpoints[] = {
+        "/sys",
+        0,
+};
+
+static int sysfs_found;
+char sysfs_mountpoint[PATH_MAX];
+
+static int sysfs_valid_mountpoint(const char *sysfs)
+{
+        struct statfs st_fs;
+
+        if (statfs(sysfs, &st_fs) < 0)
+                return -ENOENT;
+        else if (st_fs.f_type != (long) SYSFS_MAGIC)
+                return -ENOENT;
+
+        return 0;
+}
+
+const char *sysfs_find_mountpoint(void)
+{
+        const char * const *ptr;
+        char type[100];
+        FILE *fp;
+
+        if (sysfs_found)
+                return (const char *) sysfs_mountpoint;
+
+        ptr = sysfs_known_mountpoints;
+        while (*ptr) {
+                if (sysfs_valid_mountpoint(*ptr) == 0) {
+                        sysfs_found = 1;
+                        strcpy(sysfs_mountpoint, *ptr);
+                        return sysfs_mountpoint;
+                }
+                ptr++;
+        }
+
+        /* give up and parse /proc/mounts */
+        fp = fopen("/proc/mounts", "r");
+        if (fp == NULL)
+                return NULL;
+
+        while (!sysfs_found &&
+               fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
+                      sysfs_mountpoint, type) == 2) {
+
+                if (strcmp(type, "sysfs") == 0)
+                        sysfs_found = 1;
+        }
+
+        fclose(fp);
+
+        return sysfs_found ? sysfs_mountpoint : NULL;
+}