backport upstream patch to enhance livepatch-patch-hook.c readability
Signed-off-by: hubin <hubin57@huawei.com>
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Bin Hu
hubin
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232
0035-livepatch-patch-hook-add-comments.patch
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232
0035-livepatch-patch-hook-add-comments.patch
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From 005bd5ac6878b48ade7402156b2224c1b8c8ff5e Mon Sep 17 00:00:00 2001
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From: Joe Lawrence <joe.lawrence@redhat.com>
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Date: Fri, 24 Jul 2020 15:33:28 -0400
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Subject: [PATCH] livepatch-patch-hook: add comments
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Add some commentary to the livepatch-patch-hook file to explain what
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it's doing.
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Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
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---
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kmod/patch/livepatch-patch-hook.c | 106 ++++++++++++++++++++++++++++++
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1 file changed, 106 insertions(+)
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diff --git a/kmod/patch/livepatch-patch-hook.c b/kmod/patch/livepatch-patch-hook.c
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index d3fb1db..17b40b9 100644
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--- a/kmod/patch/livepatch-patch-hook.c
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+++ b/kmod/patch/livepatch-patch-hook.c
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@@ -92,10 +92,28 @@
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* done, the scaffold structs are no longer needed.
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*/
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+/*
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+ * lpatch is the kernel data structure that will be created on patch
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+ * init, registered with the livepatch API on init, and finally
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+ * unregistered when the patch exits. Its struct klp_object *objs
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+ * member must be dynamically allocated according to the number of
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+ * target objects it will be patching.
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+ */
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static struct klp_patch *lpatch;
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static LIST_HEAD(patch_objects);
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static int patch_objects_nr;
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+
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+/**
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+ * struct patch_object - scaffolding structure tracking patch target objects
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+ * @list: list of patch_object (threaded onto patch_objects)
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+ * @funcs: list of patch_func associated with this object
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+ * @relocs: list of patch_reloc associated with this object
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+ * @callbacks: kernel struct of object callbacks
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+ * @name: patch target object name (NULL for vmlinux)
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+ * @funcs_nr: count of kpatch_patch_func added to @funcs
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+ * @relocs_nr: count of patch_reloc added to @relocs
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+ */
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struct patch_object {
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struct list_head list;
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struct list_head funcs;
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@@ -107,16 +125,36 @@ struct patch_object {
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int funcs_nr, relocs_nr;
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};
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+/**
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+ * struct patch_func - scaffolding structure for kpatch_patch_func
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+ * @list: list of patch_func (threaded onto patch_object.funcs)
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+ * @kfunc: array of kpatch_patch_func
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+ */
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struct patch_func {
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struct list_head list;
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struct kpatch_patch_func *kfunc;
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};
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+/**
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+ * struct patch_reloc - scaffolding structure for kpatch_patch_dynrela
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+ * @list: list of patch_reloc (threaded onto patch_object.relocs)
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+ * @kdynrela: array of kpatch_patch_dynrela
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+ */
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struct patch_reloc {
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struct list_head list;
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struct kpatch_patch_dynrela *kdynrela;
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};
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+/**
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+ * patch_alloc_new_object() - creates and initializes a new patch_object
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+ * @name: target object name
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+ *
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+ * Return: pointer to new patch_object, NULL on failure.
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+ *
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+ * Does not check for previously created patch_objects with the same
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+ * name. Updates patch_objects_nr and threads new data structure onto
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+ * the patch_objects list.
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+ */
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static struct patch_object *patch_alloc_new_object(const char *name)
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{
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struct patch_object *object;
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@@ -135,6 +173,16 @@ static struct patch_object *patch_alloc_new_object(const char *name)
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return object;
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}
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+/**
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+ * patch_find_object_by_name() - find or create a patch_object with a
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+ * given name
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+ * @name: target object name
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+ *
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+ * Return: pointer to patch_object, NULL on failure.
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+ *
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+ * Searches the patch_objects list for an already created instance with
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+ * @name, otherwise tries to create it via patch_alloc_new_object()
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+ */
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static struct patch_object *patch_find_object_by_name(const char *name)
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{
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struct patch_object *object;
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@@ -146,6 +194,17 @@ static struct patch_object *patch_find_object_by_name(const char *name)
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return patch_alloc_new_object(name);
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}
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+/**
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+ * patch_add_func_to_object() - create scaffolding from kpatch_patch_func data
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+ *
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+ * @kfunc: Individual kpatch_patch_func pointer
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+ *
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+ * Return: 0 on success, -ENOMEM on failure.
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+ *
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+ * Builds scaffolding data structures from .kpatch.funcs section's array
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+ * of kpatch_patch_func structures. Updates the associated
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+ * patch_object's funcs_nr count.
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+ */
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static int patch_add_func_to_object(struct kpatch_patch_func *kfunc)
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{
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struct patch_func *func;
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@@ -168,6 +227,17 @@ static int patch_add_func_to_object(struct kpatch_patch_func *kfunc)
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}
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#ifndef HAVE_ELF_RELOCS
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+/**
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+ * patch_add_reloc_to_object() - create scaffolding from kpatch_patch_dynrela data
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+ *
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+ * @kdynrela: Individual kpatch_patch_dynrela pointer
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+ *
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+ * Return: 0 on success, -ENOMEM on failure.
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+ *
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+ * Builds scaffolding data structures from .kpatch.dynrelas section's array
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+ * of kpatch_patch_dynrela structures. Updates the associated
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+ * patch_object's relocs_nr count.
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+ */
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static int patch_add_reloc_to_object(struct kpatch_patch_dynrela *kdynrela)
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{
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struct patch_reloc *reloc;
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@@ -190,6 +260,9 @@ static int patch_add_reloc_to_object(struct kpatch_patch_dynrela *kdynrela)
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}
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#endif
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+/**
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+ * patch_free_scaffold() - tear down the temporary kpatch scaffolding
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+ */
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static void patch_free_scaffold(void) {
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struct patch_func *func, *safefunc;
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struct patch_object *object, *safeobject;
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@@ -215,6 +288,9 @@ static void patch_free_scaffold(void) {
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}
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}
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+/**
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+ * patch_free_livepatch() - release the klp_patch and friends
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+ */
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static void patch_free_livepatch(struct klp_patch *patch)
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{
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struct klp_object *object;
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@@ -234,6 +310,7 @@ static void patch_free_livepatch(struct klp_patch *patch)
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}
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}
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+/* Defined by kpatch.lds.S */
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extern struct kpatch_pre_patch_callback __kpatch_callbacks_pre_patch[], __kpatch_callbacks_pre_patch_end[];
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extern struct kpatch_post_patch_callback __kpatch_callbacks_post_patch[], __kpatch_callbacks_post_patch_end[];
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extern struct kpatch_pre_unpatch_callback __kpatch_callbacks_pre_unpatch[], __kpatch_callbacks_pre_unpatch_end[];
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@@ -267,6 +344,14 @@ static int add_kpatch_objects(void)
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#ifdef HAVE_CALLBACKS
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+/**
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+ * add_callbacks_to_patch_objects() - create patch_objects that have callbacks
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+ *
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+ * Return: 0 on success, -ENOMEM or -EINVAL on failure
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+ *
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+ * Iterates through all kpatch pre/post-(un)patch callback data
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+ * structures and creates scaffolding patch_objects for them.
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+ */
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static int add_callbacks_to_patch_objects(void)
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{
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struct kpatch_pre_patch_callback *p_pre_patch_callback;
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@@ -356,6 +441,7 @@ static inline int add_callbacks_to_patch_objects(void)
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}
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#endif /* HAVE_CALLBACKS */
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+/* Defined by kpatch.lds.S */
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extern struct kpatch_patch_func __kpatch_funcs[], __kpatch_funcs_end[];
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#ifndef HAVE_ELF_RELOCS
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extern struct kpatch_patch_dynrela __kpatch_dynrelas[], __kpatch_dynrelas_end[];
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@@ -375,6 +461,12 @@ static int __init patch_init(void)
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struct klp_reloc *lrelocs, *lreloc;
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#endif
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+
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+ /*
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+ * Step 1 - read from output.o, create temporary scaffolding
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+ * data-structures
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+ */
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+
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/* organize functions and relocs by object in scaffold */
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for (kfunc = __kpatch_funcs;
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kfunc != __kpatch_funcs_end;
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@@ -404,6 +496,16 @@ static int __init patch_init(void)
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/* past this point, only possible return code is -ENOMEM */
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ret = -ENOMEM;
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+ /*
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+ * Step 2 - create livepatch klp_patch and friends
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+ *
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+ * There are two dynamically allocated parts:
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+ *
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+ * klp_patch
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+ * klp_object objs [patch_objects_nr] <= i
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+ * klp_func funcs [object->funcs_nr] <= j
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+ */
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+
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/* allocate and fill livepatch structures */
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lpatch = kzalloc(sizeof(*lpatch), GFP_KERNEL);
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if (!lpatch)
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@@ -478,6 +580,10 @@ static int __init patch_init(void)
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i++;
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}
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+ /*
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+ * Step 3 - throw away scaffolding
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+ */
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+
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/*
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* Once the patch structure that the live patching API expects
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* has been built, we can release the scaffold structure.
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--
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2.27.0
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@ -1,7 +1,7 @@
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Name: kpatch
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Epoch: 1
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Version: 0.9.1
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Release: 20
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Release: 21
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Summary: A Linux dynamic kernel patching infrastructure
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License: GPLv2
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@ -46,6 +46,7 @@ Patch0031:0031-create-diff-object-fix-segment-fault-when-sec2-rela-.patch
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Patch0032:0032-create-diff-object-Fix-out-of-range-relocation-error.patch
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Patch0033:0033-create-diff-object-Fix-out-of-range-relocation-check.patch
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Patch0034:0034-add-openEuler-build-support.patch
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Patch0035:0035-livepatch-patch-hook-add-comments.patch
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BuildRequires: gcc elfutils-libelf-devel kernel-devel git
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Requires: bc make gcc patch bison flex openssl-devel
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@ -106,6 +107,12 @@ popd
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%{_mandir}/man1/*.1.gz
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%changelog
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* Sat Oct 30 2021 Bin Hu<hubin57@huawei.com> -1:0.9.1-21
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- Type:enhancement
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- ID:NA
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- SUG:NA
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- DESC:backport upstream patch
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* Tue Oct 26 2021 Zhipeng Xie<xiezhipeng1@huawei.com> -1:0.9.1-20
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- Type:enhancement
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- ID:NA
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