perf tools: Introduce tools/lib/lk library

This introduces the tools/lib/lk library, that will gradually have the
routines that now are used in tools/perf/ and other tools and that can
be shared.

Start by carving out debugfs routines for general use.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1361374353-30385-5-git-send-email-bp@alien8.de
[ committer note: Add tools/lib/lk/ to perf's MANIFEST so that its tarballs continue to build ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/tools/lib/lk/debugfs.c b/tools/lib/lk/debugfs.c
new file mode 100644
index 00000000000..9cda7a6f591
--- /dev/null
+++ b/tools/lib/lk/debugfs.c
@@ -0,0 +1,116 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <sys/vfs.h>
+#include <sys/mount.h>
+#include <linux/magic.h>
+#include <linux/kernel.h>
+
+#include "debugfs.h"
+
+char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
+char tracing_events_path[PATH_MAX + 1] = "/sys/kernel/debug/tracing/events";
+
+static const char * const debugfs_known_mountpoints[] = {
+	"/sys/kernel/debug/",
+	"/debug/",
+	0,
+};
+
+static bool debugfs_found;
+
+/* find the path to the mounted debugfs */
+const char *debugfs_find_mountpoint(void)
+{
+	const char * const *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 = true;
+			strcpy(debugfs_mountpoint, *ptr);
+			return debugfs_mountpoint;
+		}
+		ptr++;
+	}
+
+	/* give up and parse /proc/mounts */
+	fp = fopen("/proc/mounts", "r");
+	if (fp == NULL)
+		return NULL;
+
+	while (fscanf(fp, "%*s %" STR(PATH_MAX) "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 = true;
+
+	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;
+}
+
+static void debugfs_set_tracing_events_path(const char *mountpoint)
+{
+	snprintf(tracing_events_path, sizeof(tracing_events_path), "%s/%s",
+		 mountpoint, "tracing/events");
+}
+
+/* mount the debugfs somewhere if it's not mounted */
+
+char *debugfs_mount(const char *mountpoint)
+{
+	/* see if it's already mounted */
+	if (debugfs_find_mountpoint())
+		goto out;
+
+	/* 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";
+	}
+
+	if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
+		return NULL;
+
+	/* save the mountpoint */
+	debugfs_found = true;
+	strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
+out:
+	debugfs_set_tracing_events_path(debugfs_mountpoint);
+	return debugfs_mountpoint;
+}
+
+void debugfs_set_path(const char *mountpoint)
+{
+	snprintf(debugfs_mountpoint, sizeof(debugfs_mountpoint), "%s", mountpoint);
+	debugfs_set_tracing_events_path(mountpoint);
+}