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-rw-r--r--kernel/livepatch/Makefile2
-rw-r--r--kernel/livepatch/state.c83
2 files changed, 84 insertions, 1 deletions
diff --git a/kernel/livepatch/Makefile b/kernel/livepatch/Makefile
index cf9b5bcdb952..cf03d4bdfc66 100644
--- a/kernel/livepatch/Makefile
+++ b/kernel/livepatch/Makefile
@@ -1,4 +1,4 @@
# SPDX-License-Identifier: GPL-2.0-only
obj-$(CONFIG_LIVEPATCH) += livepatch.o
-livepatch-objs := core.o patch.o shadow.o transition.o
+livepatch-objs := core.o patch.o shadow.o state.o transition.o
diff --git a/kernel/livepatch/state.c b/kernel/livepatch/state.c
new file mode 100644
index 000000000000..6ab15b642c0a
--- /dev/null
+++ b/kernel/livepatch/state.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * system_state.c - State of the system modified by livepatches
+ *
+ * Copyright (C) 2019 SUSE
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/livepatch.h>
+#include "core.h"
+#include "transition.h"
+
+#define klp_for_each_state(patch, state) \
+ for (state = patch->states; state && state->id; state++)
+
+/**
+ * klp_get_state() - get information about system state modified by
+ * the given patch
+ * @patch: livepatch that modifies the given system state
+ * @id: custom identifier of the modified system state
+ *
+ * Checks whether the given patch modifies the given system state.
+ *
+ * The function can be called either from pre/post (un)patch
+ * callbacks or from the kernel code added by the livepatch.
+ *
+ * Return: pointer to struct klp_state when found, otherwise NULL.
+ */
+struct klp_state *klp_get_state(struct klp_patch *patch, unsigned long id)
+{
+ struct klp_state *state;
+
+ klp_for_each_state(patch, state) {
+ if (state->id == id)
+ return state;
+ }
+
+ return NULL;
+}
+EXPORT_SYMBOL_GPL(klp_get_state);
+
+/**
+ * klp_get_prev_state() - get information about system state modified by
+ * the already installed livepatches
+ * @id: custom identifier of the modified system state
+ *
+ * Checks whether already installed livepatches modify the given
+ * system state.
+ *
+ * The same system state can be modified by more non-cumulative
+ * livepatches. It is expected that the latest livepatch has
+ * the most up-to-date information.
+ *
+ * The function can be called only during transition when a new
+ * livepatch is being enabled or when such a transition is reverted.
+ * It is typically called only from from pre/post (un)patch
+ * callbacks.
+ *
+ * Return: pointer to the latest struct klp_state from already
+ * installed livepatches, NULL when not found.
+ */
+struct klp_state *klp_get_prev_state(unsigned long id)
+{
+ struct klp_patch *patch;
+ struct klp_state *state, *last_state = NULL;
+
+ if (WARN_ON_ONCE(!klp_transition_patch))
+ return NULL;
+
+ klp_for_each_patch(patch) {
+ if (patch == klp_transition_patch)
+ goto out;
+
+ state = klp_get_state(patch, id);
+ if (state)
+ last_state = state;
+ }
+
+out:
+ return last_state;
+}
+EXPORT_SYMBOL_GPL(klp_get_prev_state);