The main thing that I want from the kobj mapper is to add 
the mode_t on the struct kobj_map that reflects with 
permissions are associated with this particular map. This 
mode is to be returned via the kobj_lookup.

I use the FMODE_XXX flags to handle the permissions bits, 
as I will compare these ones to the file->f_mode later.
By default all bits are set (for the initial container).

The additional things I need are kobj_remap() to change 
that permission and kobj_iterate() to walk the map.

The kobj_map_fini() is the roll-back for the kobj_map_init().

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

---

diff --git a/drivers/base/map.c b/drivers/base/map.c
index e87017f..1aa2b58 100644
--- a/drivers/base/map.c
+++ b/drivers/base/map.c
@@ -15,11 +15,13 @@
 #include <linux/kdev_t.h>
 #include <linux/kobject.h>
 #include <linux/kobj_map.h>
+#include <linux/fs.h>
 
 struct kobj_map {
 	struct probe {
 		struct probe *next;
 		dev_t dev;
+		mode_t mode;
 		unsigned long range;
 		struct module *owner;
 		kobj_probe_t *get;
@@ -29,9 +31,9 @@ struct kobj_map {
 	struct mutex *lock;
 };
 
-int kobj_map(struct kobj_map *domain, dev_t dev, unsigned long range,
-	     struct module *module, kobj_probe_t *probe,
-	     int (*lock)(dev_t, void *), void *data)
+static int __kobj_map(struct kobj_map *domain, dev_t dev, mode_t mode,
+		unsigned long range, struct module *module,
+		kobj_probe_t *probe, int (*lock)(dev_t, void *), void *data)
 {
 	unsigned n = MAJOR(dev + range - 1) - MAJOR(dev) + 1;
 	unsigned index = MAJOR(dev);
@@ -53,8 +55,10 @@ int kobj_map(struct kobj_map *domain, dev_t dev, unsigned long range,
 		p->dev = dev;
 		p->range = range;
 		p->data = data;
+		/* we allow these ones always by default */
+		p->mode = mode | FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
 	}
-	mutex_lock(domain->lock);
+
 	for (i = 0, p -= n; i < n; i++, p++, index++) {
 		struct probe **s = &domain->probes[index % 255];
 		while (*s && (*s)->range < range)
@@ -62,10 +66,57 @@ int kobj_map(struct kobj_map *domain, dev_t dev, unsigned long range,
 		p->next = *s;
 		*s = p;
 	}
-	mutex_unlock(domain->lock);
 	return 0;
 }
 
+int kobj_map(struct kobj_map *domain, dev_t dev, unsigned long range,
+	     struct module *module, kobj_probe_t *probe,
+	     int (*lock)(dev_t, void *), void *data)
+{
+	int err;
+
+	mutex_lock(domain->lock);
+	err = __kobj_map(domain, dev, FMODE_READ | FMODE_WRITE, range,
+			module, probe, lock, data);
+	mutex_unlock(domain->lock);
+	return err;
+}
+
+#ifdef CONFIG_CGROUP_DEVS
+int kobj_remap(struct kobj_map *domain, dev_t dev, mode_t mode,
+		unsigned long range, struct module *module,
+		kobj_probe_t *probe, int (*lock)(dev_t, void *), void *data)
+{
+	unsigned n = MAJOR(dev + range - 1) - MAJOR(dev) + 1;
+	unsigned index = MAJOR(dev);
+	unsigned i;
+	int err = -ESRCH;
+
+	if (n > 255)
+		n = 255;
+
+	mutex_lock(domain->lock);
+	for (i = 0; i < n; i++, index++) {
+		struct probe **s;
+		for (s = &domain->probes[index % 255]; *s; s = &(*s)->next) {
+			struct probe *p = *s;
+			if (p->dev == dev) {
+				p->mode = mode | FMODE_LSEEK |
+					FMODE_PREAD | FMODE_PWRITE;
+				err = 0;
+				break;
+			}
+		}
+	}
+
+	if (err)
+		err = __kobj_map(domain, dev, mode, range, module,
+				probe, lock, data);
+	mutex_unlock(domain->lock);
+	return err;
+}
+#endif
+
 void kobj_unmap(struct kobj_map *domain, dev_t dev, unsigned long range)
 {
 	unsigned n = MAJOR(dev + range - 1) - MAJOR(dev) + 1;
@@ -93,7 +144,8 @@ void kobj_unmap(struct kobj_map *domain, dev_t dev, unsigned long range)
 	kfree(found);
 }
 
-struct kobject *kobj_lookup(struct kobj_map *domain, dev_t dev, int *index)
+struct kobject *kobj_lookup(struct kobj_map *domain, dev_t dev, mode_t *mode,
+		int *index)
 {
 	struct kobject *kobj;
 	struct probe *p;
@@ -125,14 +177,46 @@ retry:
 		kobj = probe(dev, index, data);
 		/* Currently ->owner protects _only_ ->probe() itself. */
 		module_put(owner);
-		if (kobj)
+		if (kobj) {
+			if (mode)
+				*mode = p->mode;
 			return kobj;
+		}
 		goto retry;
 	}
 	mutex_unlock(domain->lock);
 	return NULL;
 }
 
+#ifdef CONFIG_CGROUP_DEVS
+void kobj_map_iterate(struct kobj_map *domain,
+		int (*fn)(dev_t, int, mode_t, void *), void *arg)
+{
+	int i;
+	struct probe *p;
+	dev_t skip = MKDEV(0, 0);
+
+	mutex_lock(domain->lock);
+	for (i = 0; i < 255; i++) {
+		p = domain->probes[i];
+		while (p != NULL) {
+			if (p->dev == skip)
+				goto next;
+			if (p->dev == MKDEV(0, 1))
+				goto next;
+
+			skip = p->dev;
+			if (fn(p->dev, p->range, p->mode, arg))
+				goto done;
+next:
+			p = p->next;
+		}
+	}
+done:
+	mutex_unlock(domain->lock);
+}
+#endif
+
 struct kobj_map *kobj_map_init(kobj_probe_t *base_probe, struct mutex *lock)
 {
 	struct kobj_map *p = kmalloc(sizeof(struct kobj_map), GFP_KERNEL);
@@ -153,3 +237,21 @@ struct kobj_map *kobj_map_init(kobj_probe_t *base_probe, struct mutex *lock)
 	p->lock = lock;
 	return p;
 }
+
+void kobj_map_fini(struct kobj_map *map)
+{
+	int i;
+	struct probe *p, *next;
+
+	for (i = 0; i < 256; i++) {
+		p = map->probes[i];
+		while (p->next != NULL) {
+			next = p->next;
+			kfree(p);
+			p = next;
+		}
+	}
+
+	kfree(p);
+	kfree(map);
+}
diff --git a/include/linux/kobj_map.h b/include/linux/kobj_map.h
index bafe178..ecfe772 100644
--- a/include/linux/kobj_map.h
+++ b/include/linux/kobj_map.h
@@ -7,8 +7,13 @@ struct kobj_map;
 
 int kobj_map(struct kobj_map *, dev_t, unsigned long, struct module *,
 	     kobj_probe_t *, int (*)(dev_t, void *), void *);
+int kobj_remap(struct kobj_map *, dev_t, mode_t, unsigned long, struct module *,
+	     kobj_probe_t *, int (*)(dev_t, void *), void *);
 void kobj_unmap(struct kobj_map *, dev_t, unsigned long);
-struct kobject *kobj_lookup(struct kobj_map *, dev_t, int *);
+struct kobject *kobj_lookup(struct kobj_map *, dev_t, mode_t *, int *);
+void kobj_map_iterate(struct kobj_map *, int (*fn)(dev_t, int, mode_t, void *),
+		void *);
 struct kobj_map *kobj_map_init(kobj_probe_t *, struct mutex *);
+void kobj_map_fini(struct kobj_map *);
 
 #endif

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