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Subject[PATCH 1/3] debugfs utility routines for perf

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

Signed-off-by: Clark Williams <williams@redhat.com>
---
tools/perf/util/debugfs.c | 241 +++++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/debugfs.h | 22 ++++
2 files changed, 263 insertions(+), 0 deletions(-)
create mode 100644 tools/perf/util/debugfs.c
create mode 100644 tools/perf/util/debugfs.h
diff --git a/tools/perf/util/debugfs.c b/tools/perf/util/debugfs.c
new file mode 100644
index 0000000..34f7983
--- /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 = 0;
+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;
+}
+
+/* find the path to the mounted debugfs */
+const char *
+debugfs_find_mountpoint(void)
+{
+ static int debugfs_found = 0;
+ char type[100];
+ FILE *fp;
+ const char **ptr;
+
+ 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 */
+ if ((fp = fopen("/proc/mounts","r")) == 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)
+{
+ int ret;
+ char umountcmd[128];
+
+ /* if it was already mounted, leave it */
+ if (debugfs_premounted)
+ return 0;
+
+ /* make sure it's a valid mount point */
+ if ((ret = debugfs_valid_mountpoint(debugfs_mountpoint)))
+ return ret;
+
+ snprintf(umountcmd, sizeof(umountcmd),
+ "/bin/umount %s", debugfs_mountpoint);
+ return system(umountcmd);
+}
+
+
+int
+debugfs_write(const char *entry, const char *value)
+{
+ int ret, count;
+ int fd;
+ char path[MAX_PATH+1];
+
+ /* construct the path */
+ snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
+
+ /* verify that it exists */
+ if ((ret = debugfs_valid_entry(path)))
+ return ret;
+
+ /* get how many chars we're going to write */
+ count = strlen(value);
+
+ /* open the debugfs entry */
+ if ((fd = open(path, O_RDWR)) < 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)
+{
+ int ret;
+ int fd;
+ char path[MAX_PATH+1];
+
+ /* construct the path */
+ snprintf(path, sizeof(path), "%s/%s", debugfs_mountpoint, entry);
+
+ /* verify that it exists */
+ if ((ret = debugfs_valid_entry(path)))
+ return ret;
+
+ /* open the debugfs entry */
+ if ((fd = open(path, O_RDONLY)) < 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 0000000..df14c2a
--- /dev/null
+++ b/tools/perf/util/debugfs.h
@@ -0,0 +1,22 @@
+#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
--
1.6.2.5

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