Add three exported API for livepatch modules:
void *klp_shadow_attach(void *obj, char *var, gfp_t gfp, void *data);
void klp_shadow_detach(void *obj, char *var);
void *klp_shadow_get(void *obj, char *var);
that implement "shadow" variables, which allow callers to associate new
shadow fields to existing data structures.
Signed-off-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
---
include/linux/livepatch.h | 4 ++
kernel/livepatch/Makefile | 2 +-
kernel/livepatch/shadow.c | 115 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 120 insertions(+), 1 deletion(-)
create mode 100644 kernel/livepatch/shadow.c
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 194991ef9347..a0d068ecf7f8 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -164,6 +164,10 @@ static inline bool klp_have_reliable_stack(void)
IS_ENABLED(CONFIG_HAVE_RELIABLE_STACKTRACE);
}
+void *klp_shadow_attach(void *obj, char *var, gfp_t gfp, void *data);
+void klp_shadow_detach(void *obj, char *var);
+void *klp_shadow_get(void *obj, char *var);
+
#else /* !CONFIG_LIVEPATCH */
static inline int klp_module_coming(struct module *mod) { return 0; }
diff --git a/kernel/livepatch/Makefile b/kernel/livepatch/Makefile
index 2b8bdb1925da..b36ceda6488e 100644
--- a/kernel/livepatch/Makefile
+++ b/kernel/livepatch/Makefile
@@ -1,3 +1,3 @@
obj-$(CONFIG_LIVEPATCH) += livepatch.o
-livepatch-objs := core.o patch.o transition.o
+livepatch-objs := core.o patch.o shadow.o transition.o
diff --git a/kernel/livepatch/shadow.c b/kernel/livepatch/shadow.c
new file mode 100644
index 000000000000..72d5e567dff9
--- /dev/null
+++ b/kernel/livepatch/shadow.c
@@ -0,0 +1,115 @@
+/*
+ * shadow.c - Shadow Variables
+ *
+ * Copyright (C) 2014 Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
+ * Copyright (C) 2014 Seth Jennings <sjenning@xxxxxxxxxx>
+ * Copyright (C) 2017 Joe Lawrence <joe.lawrence@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/hashtable.h>
+#include <linux/slab.h>
+#include <linux/livepatch.h>
+
+static DEFINE_HASHTABLE(klp_shadow_hash, 12);
+static DEFINE_SPINLOCK(klp_shadow_lock);
+
+struct klp_shadow {
+ struct hlist_node node;
+ struct rcu_head rcu_head;
+ void *obj;
+ char *var;
+ void *data;
+};
+
+void *klp_shadow_attach(void *obj, char *var, gfp_t gfp, void *data)
+{
+ unsigned long flags;
+ struct klp_shadow *shadow;
+
+ shadow = kmalloc(sizeof(*shadow), gfp);
+ if (!shadow)
+ return NULL;
+
+ shadow->obj = obj;
+
+ shadow->var = kstrdup(var, gfp);
+ if (!shadow->var) {
+ kfree(shadow);
+ return NULL;
+ }
+
+ shadow->data = data;
+
+ spin_lock_irqsave(&klp_shadow_lock, flags);
+ hash_add_rcu(klp_shadow_hash, &shadow->node, (unsigned long)obj);
+ spin_unlock_irqrestore(&klp_shadow_lock, flags);
+
+ return shadow->data;
+}
+EXPORT_SYMBOL_GPL(klp_shadow_attach);
+
+static void klp_shadow_rcu_free(struct rcu_head *head)
+{
+ struct klp_shadow *shadow;
+
+ shadow = container_of(head, struct klp_shadow, rcu_head);
+
+ kfree(shadow->var);
+ kfree(shadow);
+}
+
+void klp_shadow_detach(void *obj, char *var)
+{
+ unsigned long flags;
+ struct klp_shadow *shadow;
+
+ spin_lock_irqsave(&klp_shadow_lock, flags);
+
+ hash_for_each_possible(klp_shadow_hash, shadow, node,
+ (unsigned long)obj) {
+ if (shadow->obj == obj && !strcmp(shadow->var, var)) {
+ hash_del_rcu(&shadow->node);
+ spin_unlock_irqrestore(&klp_shadow_lock, flags);
+ call_rcu(&shadow->rcu_head, klp_shadow_rcu_free);
+ return;
+ }
+ }
+
+ spin_unlock_irqrestore(&klp_shadow_lock, flags);
+}
+EXPORT_SYMBOL_GPL(klp_shadow_detach);
+
+void *klp_shadow_get(void *obj, char *var)
+{
+ struct klp_shadow *shadow;
+
+ rcu_read_lock();
+
+ hash_for_each_possible_rcu(klp_shadow_hash, shadow, node,
+ (unsigned long)obj) {
+ if (shadow->obj == obj && !strcmp(shadow->var, var)) {
+ rcu_read_unlock();
+ return shadow->data;
+ }
+ }
+
+ rcu_read_unlock();
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(klp_shadow_get);
--
1.8.3.1
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