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> --- kernel/livepatch/core.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 6fa022cce4bf..00ead77e58ba 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -30,6 +30,7 @@ #include <linux/elf.h> #include <linux/moduleloader.h> #include <linux/completion.h> +#include <linux/debugfs.h> #include <asm/cacheflush.h> #include "core.h" #include "patch.h" @@ -82,6 +83,13 @@ static void klp_init_patch_list(struct klp_patch *patch) klp_init_object_list(patch, obj); } +/* + * 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; @@ -467,6 +475,9 @@ 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; @@ -1375,6 +1386,7 @@ void klp_module_going(struct module *mod) static int __init klp_init(void) { int ret; + struct dentry *d; ret = klp_check_compiler_support(); if (ret) { @@ -1386,6 +1398,10 @@ static int __init klp_init(void) 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; } -- 2.25.1 _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel
