A throw once master enable switch to protect against any
further overlay applications if the administrator desires so.
Signed-off-by: Pantelis Antoniou <pantelis.anton...@konsulko.com>
---
drivers/of/overlay.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 42 insertions(+), 1 deletion(-)
diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
index f17f5ef..37ec858 100644
--- a/drivers/of/overlay.c
+++ b/drivers/of/overlay.c
@@ -21,6 +21,7 @@
#include <linux/err.h>
#include <linux/idr.h>
#include <linux/sysfs.h>
+#include <linux/atomic.h>
#include "of_private.h"
@@ -55,8 +56,12 @@ struct of_overlay {
struct kobject kobj;
};
+/* master enable switch; once set to 0 can't be re-enabled */
+static atomic_t ov_enable = ATOMIC_INIT(1);
+
static int of_overlay_apply_one(struct of_overlay *ov,
struct device_node *target, const struct device_node *overlay);
+static int overlay_removal_is_ok(struct of_overlay *ov);
static int of_overlay_apply_single_property(struct of_overlay *ov,
struct device_node *target, struct property *prop)
@@ -339,6 +344,35 @@ void of_overlay_release(struct kobject *kobj)
kfree(ov);
}
+static ssize_t enable_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return snprintf(buf, PAGE_SIZE, "%d\n", atomic_read(&ov_enable));
+}
+
+static ssize_t enable_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf, size_t count)
+{
+ int ret;
+ bool new_enable;
+
+ ret = strtobool(buf, &new_enable);
+ if (ret != 0)
+ return ret;
+ /* if we've disabled it, no going back */
+ if (atomic_read(&ov_enable) == 0)
+ return -EPERM;
+ atomic_set(&ov_enable, (int)new_enable);
+ return count;
+}
+
+static struct kobj_attribute enable_attr = __ATTR_RW(enable);
+
+static const struct attribute *overlay_global_attrs[] = {
+ &enable_attr.attr,
+ NULL
+};
+
static struct kobj_type of_overlay_ktype = {
.release = of_overlay_release,
};
@@ -360,6 +394,10 @@ int of_overlay_create(struct device_node *tree)
struct of_overlay *ov;
int err, id;
+ /* administratively disabled */
+ if (!atomic_read(&ov_enable))
+ return -EPERM;
+
/* allocate the overlay structure */
ov = kzalloc(sizeof(*ov), GFP_KERNEL);
if (ov == NULL)
@@ -596,5 +634,8 @@ int of_overlay_init(void)
if (!ov_kset)
return -ENOMEM;
- return 0;
+ rc = sysfs_create_files(&ov_kset->kobj, overlay_global_attrs);
+ WARN(rc, "%s: error adding global attributes\n", __func__);
+
+ return rc;
}
--
1.7.12
--
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