[POC 21/23] livepatch: Remove obsolete arch_klp_init_object_loaded()

Petr Mladek
2020-01-17T15:04:21Z

The livepatch specific-relocation is finally done together with the normal
module relocations. As a result, alternatives, paraintructions, and other
architecture-specific modifications are done correctly by the module
loader out of box. There is no longer need to do them explicitely by
arch_klp_init_object_loaded().

Signed-off-by: Petr Mladek <pmladek@suse.com>
---
Documentation/livepatch/module-elf-format.rst | 29 ---------------
arch/x86/kernel/Makefile | 1 -
arch/x86/kernel/livepatch.c | 52 ---------------------------
include/linux/livepatch.h | 2 --
kernel/livepatch/core.c | 11 ------
5 files changed, 95 deletions(-)
delete mode 100644 arch/x86/kernel/livepatch.c

diff --git a/Documentation/livepatch/module-elf-format.rst b/Documentation/livepatch/module-elf-format.rst
index 2a591e6f8e6c..9f0c997d4940 100644
--- a/Documentation/livepatch/module-elf-format.rst
+++ b/Documentation/livepatch/module-elf-format.rst
@@ -14,8 +14,6 @@ This document outlines the Elf format requirements that livepatch modules must f
4. Livepatch symbols
4.1 A livepatch module's symbol table
4.2 Livepatch symbol format
- 5. Architecture-specific sections
- 6. Symbol table and Elf section access

1. Background and motivation
============================
@@ -297,30 +295,3 @@ See include/uapi/linux/elf.h for the actual definitions.
[*]
Note that the 'Ndx' (Section index) for these symbols is SHN_LIVEPATCH (0xff20).
"OS" means OS-specific.
-
-5. Architecture-specific sections
-=================================
-Architectures may override arch_klp_init_object_loaded() to perform
-additional arch-specific tasks when a target module loads, such as applying
-arch-specific sections. On x86 for example, we must apply per-object
-.altinstructions and .parainstructions sections when a target module loads.
-These sections must be prefixed with ".klp.arch.$objname." so that they can
-be easily identified when iterating through a patch module's Elf sections
-(See arch/x86/kernel/livepatch.c for a complete example).
-
-6. Symbol table and Elf section access
-======================================
-A livepatch module's symbol table is accessible through module->symtab.
-
-Since apply_relocate_add() requires access to a module's section headers,
-symbol table, and relocation section indices, Elf information is preserved for
-livepatch modules and is made accessible by the module loader through
-module->klp_info, which is a klp_modinfo struct. When a livepatch module loads,
-this struct is filled in by the module loader. Its fields are documented below::
-
- struct klp_modinfo {
- Elf_Ehdr hdr; /* Elf header */
- Elf_Shdr *sechdrs; /* Section header table */
- char *secstrings; /* String table for the section headers */
- unsigned int symndx; /* The symbol table section index */
- };
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 6175e370ee4a..21540cac67b9 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -89,7 +89,6 @@ obj-$(CONFIG_X86_MPPARSE) += mpparse.o
obj-y += apic/
obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o
obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
-obj-$(CONFIG_LIVEPATCH) += livepatch.o
obj-$(CONFIG_FUNCTION_TRACER) += ftrace_$(BITS).o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o
diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c
deleted file mode 100644
index 728b44eaa168..000000000000
--- a/arch/x86/kernel/livepatch.c
+++ /dev/null
@@ -1,52 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * livepatch.c - x86-specific Kernel Live Patching Core
- */
-
-#include <linux/module.h>
-#include <linux/kallsyms.h>
-#include <linux/livepatch.h>
-#include <asm/text-patching.h>
-
-/* Apply per-object alternatives. Based on x86 module_finalize() */
-void arch_klp_init_object_loaded(struct klp_object *obj)
-{
- int cnt;
- struct klp_modinfo *info;
- Elf_Shdr *s, *alt = NULL, *para = NULL;
- void *aseg, *pseg;
- const char *objname;
- char sec_objname[MODULE_NAME_LEN];
- char secname[KSYM_NAME_LEN];
-
- info = obj->mod->klp_info;
- objname = obj->name ? obj->name : "vmlinux";
-
- /* See livepatch core code for BUILD_BUG_ON() explanation */
- BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
-
- for (s = info->sechdrs; s < info->sechdrs + info->hdr.e_shnum; s++) {
- /* Apply per-object .klp.arch sections */
- cnt = sscanf(info->secstrings + s->sh_name,
- ".klp.arch.%55[^.].%127s",
- sec_objname, secname);
- if (cnt != 2)
- continue;
- if (strcmp(sec_objname, objname))
- continue;
- if (!strcmp(".altinstructions", secname))
- alt = s;
- if (!strcmp(".parainstructions", secname))
- para = s;
- }
-
- if (alt) {
- aseg = (void *) alt->sh_addr;
- apply_alternatives(aseg, aseg + alt->sh_size);
- }
-
- if (para) {
- pseg = (void *) para->sh_addr;
- apply_paravirt(pseg, pseg + para->sh_size);
- }
-}
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index d721e79ac691..3b27ef1a7291 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -204,8 +204,6 @@ struct klp_patch {
int klp_enable_patch(struct klp_patch *);
int klp_add_object(struct klp_object *);

-void arch_klp_init_object_loaded(struct klp_object *obj);
-
/* Called from the module loader during module coming/going states */
bool klp_break_recursion(struct module *mod);
int klp_module_coming(struct module *mod);
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 4da6bbd687d0..cc0ac93fe8cd 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -701,23 +701,12 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
func->old_sympos ? func->old_sympos : 1);
}

-/* Arches may override this to finish any remaining arch-specific tasks */
-void __weak arch_klp_init_object_loaded(struct klp_object *obj)
-{
-}
-
/* parts of the initialization that is done only when the object is loaded */
static int klp_init_object_loaded(struct klp_object *obj)
{
struct klp_func *func;
int ret;

- mutex_lock(&text_mutex);
- module_disable_ro(obj->mod);
- arch_klp_init_object_loaded(obj);
- module_enable_ro(obj->mod, true);
- mutex_unlock(&text_mutex);
-
klp_for_each_func(obj, func) {
ret = klp_find_object_symbol(obj->name, func->old_name,
func->old_sympos,
--
2.16.4