The commit is pushed to "branch-rh9-5.14.vz9.1.x-ovz" and will appear at
https://src.openvz.org/scm/ovz/vzkernel.git
after ark-5.14
------>
commit 840361524f43e6ce38de736377d878bdd4e93a8d
Author: Evgenii Shatokhin <eshatok...@virtuozzo.com>
Date: Thu Sep 30 16:01:00 2021 +0300
livepatch: added minimal support for failure injection
It can be useful when testing loading and replacement of live kernel
patches. It may be needed to check that, if loading of a patch fails,
the system remains in a consistent state.
Livepatch subsystem will now create file 'livepatch/fail_apply' in
debugfs. If one writes 1 (or whatever else kstrtobool() takes as "yes")
to it, the attempts to apply live patches will fail with -EBUSY. The
currently loaded patches remain loaded.
Writing 0 to livepatch/fail_apply disables injection of such failures.
Livepatch is more likely to apply a patch successfully than the old
KPatch core used in VZ7. However, it can still refuse to load a valid
patch with -EBUSY if another patch is currently being processed.
Failure injection added here mimics that behaviour.
Done in the scope of https://jira.sw.ru/browse/PSBM-102582.
Signed-off-by: Evgenii Shatokhin <eshatok...@virtuozzo.com>
(cherry picked from vz8 commit 19d7df1e5402e06ff3ccc06566331bd023c7f8c3)
Signed-off-by: Andrey Zhadchenko <andrey.zhadche...@virtuozzo.com>
---
kernel/livepatch/core.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 335d988bd811..52911a1d6a8e 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -20,6 +20,7 @@
#include <linux/completion.h>
#include <linux/memory.h>
#include <linux/rcupdate.h>
+#include <linux/debugfs.h>
#include <asm/cacheflush.h>
#include "core.h"
#include "patch.h"
@@ -45,6 +46,13 @@ LIST_HEAD(klp_patches);
static struct kobject *klp_root_kobj;
+/*
+ * Can be set via livepatch/fail_apply file in debugfs.
+ * If set, livepatch will fail with -EBUSY when requested to apply a patch.
+ * Might be useful for testing and debugging livepatch.
+ */
+static bool fail_apply;
+
static bool klp_is_module(struct klp_object *obj)
{
return obj->name;
@@ -961,6 +969,9 @@ static int __klp_enable_patch(struct klp_patch *patch)
if (klp_transition_patch)
return -EBUSY;
+ if (fail_apply)
+ return -EBUSY;
+
if (WARN_ON(patch->enabled))
return -EINVAL;
@@ -1266,10 +1277,16 @@ void klp_module_going(struct module *mod)
static int __init klp_init(void)
{
+ struct dentry *d;
+
klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
if (!klp_root_kobj)
return -ENOMEM;
+ d = debugfs_create_dir("livepatch", NULL);
+ if (d)
+ debugfs_create_bool("fail_apply", 0644, d, &fail_apply);
+
return 0;
}
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