[PATCH] patch for libsysfs sysfs directory handling

Here's a quick patch to:

1) Add an environment variable "SYSFS_PATH" that libsysfs will check
for when getting mount point before searching system's sysfs mount
point.

2) A quick fix to sysfs_get_link where the bug was.

I have tested this out with libsysfs and with udev. I couldn't test
with klibc because I haven't got the tree to build with klibc without
my changes either. I made the link but get an error finding
linux/linits.h. I will figure that out.

Please have a look at the patch. If it's agreeable, please test it. I
really want to add some generic path manipulation functions for the
sysfs_get_link error, rather than my patch's hack. But, I haven't had
time yet to do that. You really sounded like you needed this for
testing, so I'm sending it out to you. I should probably add a
function to set the env variable(?).

2 files changed, 30 insertions, 13 deletions

diff --git a/libsysfs/libsysfs.h b/libsysfs/libsysfs.h
index ccb9898cb5..b3ffc467d0 100644
--- a/libsysfs/libsysfs.h
+++ b/libsysfs/libsysfs.h
@@ -40,6 +40,7 @@
 #define SYSFS_DRIVERS_NAME	"drivers"
 #define SYSFS_NAME_ATTRIBUTE	"name"
 #define SYSFS_UNKNOWN		"unknown"
+#define SYSFS_PATH_ENV		"SYSFS_PATH"
 
 /* Some "block" subsystem specific #defines */
 #define SYSFS_QUEUE_NAME	"queue"
diff --git a/libsysfs/sysfs_utils.c b/libsysfs/sysfs_utils.c
index f1303cacb3..3e50bc6120 100644
--- a/libsysfs/sysfs_utils.c
+++ b/libsysfs/sysfs_utils.c
@@ -84,12 +84,18 @@ static int sysfs_get_fs_mnt_path(const unsigned char *fs_type,
  */
 int sysfs_get_mnt_path(unsigned char *mnt_path, size_t len)
 {
-	int ret = -1;
+	char *sysfs_path = NULL;
+	int ret = 0;
 
-	if (mnt_path != NULL)
-		ret = sysfs_get_fs_mnt_path(SYSFS_FSTYPE_NAME, mnt_path, len);
-	else
+	if (mnt_path == NULL) {
 		errno = EINVAL;
+		return -1;
+	}
+	sysfs_path = getenv(SYSFS_PATH_ENV);
+	if (sysfs_path != NULL)
+		strncpy(mnt_path, sysfs_path, len);
+	else
+		ret = sysfs_get_fs_mnt_path(SYSFS_FSTYPE_NAME, mnt_path, len);
 
 	return ret;
 }
@@ -130,7 +136,8 @@ int sysfs_get_link(const unsigned char *path, unsigned char *target, size_t len)
 {
 	unsigned char devdir[SYSFS_PATH_MAX];
 	unsigned char linkpath[SYSFS_PATH_MAX];
-	unsigned char *d = NULL;
+	unsigned char *d = NULL, *s = NULL;
+	int slashes = 0, count = 0;
 
 	if (path == NULL || target == NULL) {
 		errno = EINVAL;
@@ -139,12 +146,8 @@ int sysfs_get_link(const unsigned char *path, unsigned char *target, size_t len)
 
 	memset(devdir, 0, SYSFS_PATH_MAX);
 	memset(linkpath, 0, SYSFS_PATH_MAX);
+	strncpy(devdir, path, SYSFS_PATH_MAX);
 
-	if ((sysfs_get_mnt_path(devdir, SYSFS_PATH_MAX)) != 0) {
-		dprintf("Sysfs not supported on this system\n");
-		return -1;
-	}
-								        
 	if ((readlink(path, linkpath, SYSFS_PATH_MAX)) < 0) {
 		return -1;
 	}
@@ -152,12 +155,25 @@ int sysfs_get_link(const unsigned char *path, unsigned char *target, size_t len)
 	d = linkpath;
 
 	/* getting rid of leading "../.." */	
-	while (*d == '/' || *d == '.')
+	while (*d == '/' || *d == '.') {
+		if (*d == '/')
+			slashes++;
 		d++;
+	}
 
 	d--;
-	
-	strcat(devdir, d);
+
+	s = &devdir[strlen(devdir)-1];
+	while (s != NULL && count != (slashes+1)) {
+		s--;
+		if (*s == '/')
+			count++;
+	}
+
+	if (s == NULL)
+		return -1;
+
+	strncpy(s, d, (SYSFS_PATH_MAX-strlen(devdir)));
 	strncpy(target, devdir, len);
 
 	return 0;