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-rw-r--r--samples/livepatch/livepatch-shadow-fix2.c168
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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
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+/*
+ * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
+ *
+ * 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/>.
+ */
+
+/*
+ * 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;
+};
+
+bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
+{
+ int *shadow_count;
+ int count;
+
+ /*
+ * Patch: handle in-flight dummy structures, if they do not
+ * already have a SV_COUNTER shadow variable, then attach a
+ * new one.
+ */
+ count = 0;
+ shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
+ &count, sizeof(count),
+ GFP_NOWAIT);
+ if (shadow_count)
+ *shadow_count += 1;
+
+ return time_after(jiffies, d->jiffies_expire);
+}
+
+void livepatch_fix2_dummy_free(struct dummy *d)
+{
+ void **shadow_leak, *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) {
+ leak = *shadow_leak;
+ klp_shadow_free(d, SV_LEAK);
+ kfree(leak);
+ pr_info("%s: dummy @ %p, prevented leak @ %p\n",
+ __func__, d, leak);
+ } 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);
+ }
+
+ 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)
+{
+ int ret;
+
+ if (!klp_have_reliable_stack() && !patch.immediate) {
+ /*
+ * WARNING: Be very careful when using 'patch.immediate' in
+ * your patches. It's ok to use it for simple patches like
+ * this, but for more complex patches which change function
+ * semantics, locking semantics, or data structures, it may not
+ * be safe. Use of this option will also prevent removal of
+ * the patch.
+ *
+ * See Documentation/livepatch/livepatch.txt for more details.
+ */
+ patch.immediate = true;
+ pr_notice("The consistency model isn't supported for your architecture. Bypassing safety mechanisms and applying the patch immediately.\n");
+ }
+
+ ret = klp_register_patch(&patch);
+ if (ret)
+ return ret;
+ ret = klp_enable_patch(&patch);
+ if (ret) {
+ WARN_ON(klp_unregister_patch(&patch));
+ return ret;
+ }
+ return 0;
+}
+
+static void livepatch_shadow_fix2_exit(void)
+{
+ /* Cleanup any existing SV_COUNTER shadow variables */
+ klp_shadow_free_all(SV_COUNTER);
+
+ WARN_ON(klp_unregister_patch(&patch));
+}
+
+module_init(livepatch_shadow_fix2_init);
+module_exit(livepatch_shadow_fix2_exit);
+MODULE_LICENSE("GPL");
+MODULE_INFO(livepatch, "Y");