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-rw-r--r--samples/livepatch/livepatch-shadow-fix2.c132
1 files changed, 132 insertions, 0 deletions
diff --git a/samples/livepatch/livepatch-shadow-fix2.c b/samples/livepatch/livepatch-shadow-fix2.c
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+++ b/samples/livepatch/livepatch-shadow-fix2.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
+ */
+
+/*
+ * livepatch-shadow-fix2.c - Shadow variables, livepatch demo
+ *
+ * Purpose
+ * -------
+ *
+ * Adds functionality to livepatch-shadow-mod's in-flight data
+ * structures through a shadow variable. The livepatch patches a
+ * routine that periodically inspects data structures, incrementing a
+ * per-data-structure counter, creating the counter if needed.
+ *
+ *
+ * Usage
+ * -----
+ *
+ * This module is not intended to be standalone. See the "Usage"
+ * section of livepatch-shadow-mod.c.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/livepatch.h>
+#include <linux/slab.h>
+
+/* Shadow variable enums */
+#define SV_LEAK 1
+#define SV_COUNTER 2
+
+struct dummy {
+ struct list_head list;
+ unsigned long jiffies_expire;
+};
+
+static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
+{
+ int *shadow_count;
+
+ /*
+ * Patch: handle in-flight dummy structures, if they do not
+ * already have a SV_COUNTER shadow variable, then attach a
+ * new one.
+ */
+ shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
+ sizeof(*shadow_count), GFP_NOWAIT,
+ NULL, NULL);
+ if (shadow_count)
+ *shadow_count += 1;
+
+ return time_after(jiffies, d->jiffies_expire);
+}
+
+static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
+{
+ void *d = obj;
+ int **shadow_leak = shadow_data;
+
+ pr_info("%s: dummy @ %p, prevented leak @ %p\n",
+ __func__, d, *shadow_leak);
+ kfree(*shadow_leak);
+}
+
+static void livepatch_fix2_dummy_free(struct dummy *d)
+{
+ int **shadow_leak;
+ int *shadow_count;
+
+ /* Patch: copy the memory leak patch from the fix1 module. */
+ shadow_leak = klp_shadow_get(d, SV_LEAK);
+ if (shadow_leak)
+ klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
+ else
+ pr_info("%s: dummy @ %p leaked!\n", __func__, d);
+
+ /*
+ * Patch: fetch the SV_COUNTER shadow variable and display
+ * the final count. Detach the shadow variable.
+ */
+ shadow_count = klp_shadow_get(d, SV_COUNTER);
+ if (shadow_count) {
+ pr_info("%s: dummy @ %p, check counter = %d\n",
+ __func__, d, *shadow_count);
+ klp_shadow_free(d, SV_COUNTER, NULL);
+ }
+
+ kfree(d);
+}
+
+static struct klp_func funcs[] = {
+ {
+ .old_name = "dummy_check",
+ .new_func = livepatch_fix2_dummy_check,
+ },
+ {
+ .old_name = "dummy_free",
+ .new_func = livepatch_fix2_dummy_free,
+ }, { }
+};
+
+static struct klp_object objs[] = {
+ {
+ .name = "livepatch_shadow_mod",
+ .funcs = funcs,
+ }, { }
+};
+
+static struct klp_patch patch = {
+ .mod = THIS_MODULE,
+ .objs = objs,
+};
+
+static int livepatch_shadow_fix2_init(void)
+{
+ return klp_enable_patch(&patch);
+}
+
+static void livepatch_shadow_fix2_exit(void)
+{
+ /* Cleanup any existing SV_COUNTER shadow variables */
+ klp_shadow_free_all(SV_COUNTER, NULL);
+}
+
+module_init(livepatch_shadow_fix2_init);
+module_exit(livepatch_shadow_fix2_exit);
+MODULE_LICENSE("GPL");
+MODULE_INFO(livepatch, "Y");