perf tools: Add debugfs utility routines for perf

Add routines to locate the debugfs mount point and to manage the
mounting and unmounting of the debugfs.

Signed-off-by: Clark Williams <williams@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20091101155621.2b3503ee@torg>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 266 insertions, 0 deletions

diff --git a/tools/perf/util/debugfs.c b/tools/perf/util/debugfs.c
new file mode 100644
index 000000000000..06b73ee02c49
--- /dev/null
+++ b/tools/perf/util/debugfs.c
@@ -0,0 +1,241 @@
+#include "util.h"
+#include "debugfs.h"
+#include "cache.h"
+
+static int debugfs_premounted;
+static char debugfs_mountpoint[MAX_PATH+1];
+
+static const char *debugfs_known_mountpoints[] = {
+        "/sys/kernel/debug/",
+        "/debug/",
+        0,
+};
+
+/* use this to force a umount */
+void debugfs_force_cleanup(void)
+{
+        debugfs_find_mountpoint();
+        debugfs_premounted = 0;
+        debugfs_umount();
+}
+
+/* construct a full path to a debugfs element */
+int debugfs_make_path(const char *element, char *buffer, int size)
+{
+        int len;
+
+        if (strlen(debugfs_mountpoint) == 0) {
+                buffer[0] = '\0';
+                return -1;
+        }
+
+        len = strlen(debugfs_mountpoint) + strlen(element) + 1;
+        if (len >= size)
+                return len+1;
+
+        snprintf(buffer, size-1, "%s/%s", debugfs_mountpoint, element);
+        return 0;
+}
+
+static int debugfs_found;
+
+/* find the path to the mounted debugfs */
+const char *debugfs_find_mountpoint(void)
+{
+        const char **ptr;
+        char type[100];
+        FILE *fp;
+
+        if (debugfs_found)
+                return (const char *) debugfs_mountpoint;
+
+        ptr = debugfs_known_mountpoints;
+        while (*ptr) {
+                if (debugfs_valid_mountpoint(*ptr) == 0) {
+                        debugfs_found = 1;
+                        strcpy(debugfs_mountpoint, *ptr);
+                        return debugfs_mountpoint;
+                }
+                ptr++;
+        }
+
+        /* give up and parse /proc/mounts */
+        fp = fopen("/proc/mounts", "r");
+        if (fp == NULL)
+                die("Can't open /proc/mounts for read");
+
+        while (fscanf(fp, "%*s %"
+                      STR(MAX_PATH)
+                      "s %99s %*s %*d %*d\n",
+                      debugfs_mountpoint, type) == 2) {
+                if (strcmp(type, "debugfs") == 0)
+                        break;
+        }
+        fclose(fp);
+
+        if (strcmp(type, "debugfs") != 0)
+                return NULL;
+
+        debugfs_found = 1;
+
+        return debugfs_mountpoint;
+}
+
+/* verify that a mountpoint is actually a debugfs instance */
+
+int debugfs_valid_mountpoint(const char *debugfs)
+{
+        struct statfs st_fs;
+
+        if (statfs(debugfs, &st_fs) < 0)
+                return -ENOENT;
+        else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
+                return -ENOENT;
+
+        return 0;
+}
+
+
+int debugfs_valid_entry(const char *path)
+{
+        struct stat st;
+
+        if (stat(path, &st))
+                return -errno;
+
+        return 0;
+}
+
+/* mount the debugfs somewhere */
+
+int debugfs_mount(const char *mountpoint)
+{
+        char mountcmd[128];
+
+        /* see if it's already mounted */
+        if (debugfs_find_mountpoint()) {
+                debugfs_premounted = 1;
+                return 0;
+        }
+
+        /* if not mounted and no argument */
+        if (mountpoint == NULL) {
+                /* see if environment variable set */
+                mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
+                /* if no environment variable, use default */
+                if (mountpoint == NULL)
+                        mountpoint = "/sys/kernel/debug";
+        }
+
+        /* save the mountpoint */
+        strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
+
+        /* mount it */
+        snprintf(mountcmd, sizeof(mountcmd),
+                 "/bin/mount -t debugfs debugfs %s", mountpoint);
+        return system(mountcmd);
+}
+
+/* umount the debugfs */
+
+int debugfs_umount(void)
+{
+        char umountcmd[128];
+        int ret;
+
+        /* if it was already mounted, leave it */
+        if (debugfs_premounted)
+                return 0;
+
+        /* make sure it's a valid mount point */
+        ret = debugfs_valid_mountpoint(debugfs_mountpoint);
+        if (ret)
+                return ret;
+
+        snprintf(umountcmd, sizeof(umountcmd),
+                 "/bin/umount %s", debugfs_mountpoint);
+        return system(umountcmd);
+}
+
+int debugfs_write(const char *entry, const char *value)
+{
+        char path[MAX_PATH+1];
+        int ret, count;
+        int fd;
+
+        /* construct the path */
+        snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
+
+        /* verify that it exists */
+        ret = debugfs_valid_entry(path);
+        if (ret)
+                return ret;
+
+        /* get how many chars we're going to write */
+        count = strlen(value);
+
+        /* open the debugfs entry */
+        fd = open(path, O_RDWR);
+        if (fd < 0)
+                return -errno;
+
+        while (count > 0) {
+                /* write it */
+                ret = write(fd, value, count);
+                if (ret <= 0) {
+                        if (ret == EAGAIN)
+                                continue;
+                        close(fd);
+                        return -errno;
+                }
+                count -= ret;
+        }
+
+        /* close it */
+        close(fd);
+
+        /* return success */
+        return 0;
+}
+
+/*
+ * read a debugfs entry
+ * returns the number of chars read or a negative errno
+ */
+int debugfs_read(const char *entry, char *buffer, size_t size)
+{
+        char path[MAX_PATH+1];
+        int ret;
+        int fd;
+
+        /* construct the path */
+        snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
+
+        /* verify that it exists */
+        ret = debugfs_valid_entry(path);
+        if (ret)
+                return ret;
+
+        /* open the debugfs entry */
+        fd = open(path, O_RDONLY);
+        if (fd < 0)
+                return -errno;
+
+        do {
+                /* read it */
+                ret = read(fd, buffer, size);
+                if (ret == 0) {
+                        close(fd);
+                        return EOF;
+                }
+        } while (ret < 0 && errno == EAGAIN);
+
+        /* close it */
+        close(fd);
+
+        /* make *sure* there's a null character at the end */
+        buffer[ret] = '\0';
+
+        /* return the number of chars read */
+        return ret;
+}
diff --git a/tools/perf/util/debugfs.h b/tools/perf/util/debugfs.h
new file mode 100644
index 000000000000..3cd14f9ae784
--- /dev/null
+++ b/tools/perf/util/debugfs.h
@@ -0,0 +1,25 @@
+#ifndef __DEBUGFS_H__
+#define __DEBUGFS_H__
+
+#include <sys/mount.h>
+
+#ifndef MAX_PATH
+# define MAX_PATH 256
+#endif
+
+#ifndef STR
+# define _STR(x) #x
+# define STR(x) _STR(x)
+#endif
+
+extern const char *debugfs_find_mountpoint(void);
+extern int debugfs_valid_mountpoint(const char *debugfs);
+extern int debugfs_valid_entry(const char *path);
+extern int debugfs_mount(const char *mountpoint);
+extern int debugfs_umount(void);
+extern int debugfs_write(const char *entry, const char *value);
+extern int debugfs_read(const char *entry, char *buffer, size_t size);
+extern void debugfs_force_cleanup(void);
+extern int debugfs_make_path(const char *element, char *buffer, int size);
+
+#endif /* __DEBUGFS_H__ */