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2f293651ec
Trying to build livepatch on powerpc/32 results in:
kernel/livepatch/core.c: In function 'klp_resolve_symbols':
kernel/livepatch/core.c:221:23: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
221 | sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
| ^
kernel/livepatch/core.c:221:21: error: assignment to 'Elf32_Sym *' {aka 'struct elf32_sym *'} from incompatible pointer type 'Elf64_Sym *' {aka 'struct elf64_sym *'} [-Werror=incompatible-pointer-types]
221 | sym = (Elf64_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
| ^
kernel/livepatch/core.c: In function 'klp_apply_section_relocs':
kernel/livepatch/core.c:312:35: error: passing argument 1 of 'klp_resolve_symbols' from incompatible pointer type [-Werror=incompatible-pointer-types]
312 | ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname);
| ^~~~~~~
| |
| Elf32_Shdr * {aka struct elf32_shdr *}
kernel/livepatch/core.c:193:44: note: expected 'Elf64_Shdr *' {aka 'struct elf64_shdr *'} but argument is of type 'Elf32_Shdr *' {aka 'struct elf32_shdr *'}
193 | static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,
| ~~~~~~~~~~~~^~~~~~~
Fix it by using the right types instead of forcing 64 bits types.
Fixes: 7c8e2bdd5f
("livepatch: Apply vmlinux-specific KLP relocations early")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Petr Mladek <pmladek@suse.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/5288e11b018a762ea3351cc8fb2d4f15093a4457.1640017960.git.christophe.leroy@csgroup.eu
1274 lines
30 KiB
C
1274 lines
30 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* core.c - Kernel Live Patching Core
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*
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* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
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* Copyright (C) 2014 SUSE
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/mutex.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#include <linux/kallsyms.h>
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#include <linux/livepatch.h>
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#include <linux/elf.h>
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#include <linux/moduleloader.h>
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#include <linux/completion.h>
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#include <linux/memory.h>
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#include <linux/rcupdate.h>
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#include <asm/cacheflush.h>
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#include "core.h"
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#include "patch.h"
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#include "state.h"
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#include "transition.h"
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/*
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* klp_mutex is a coarse lock which serializes access to klp data. All
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* accesses to klp-related variables and structures must have mutex protection,
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* except within the following functions which carefully avoid the need for it:
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*
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* - klp_ftrace_handler()
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* - klp_update_patch_state()
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*/
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DEFINE_MUTEX(klp_mutex);
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/*
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* Actively used patches: enabled or in transition. Note that replaced
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* or disabled patches are not listed even though the related kernel
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* module still can be loaded.
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*/
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LIST_HEAD(klp_patches);
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static struct kobject *klp_root_kobj;
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static bool klp_is_module(struct klp_object *obj)
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{
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return obj->name;
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}
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/* sets obj->mod if object is not vmlinux and module is found */
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static void klp_find_object_module(struct klp_object *obj)
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{
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struct module *mod;
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if (!klp_is_module(obj))
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return;
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rcu_read_lock_sched();
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/*
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* We do not want to block removal of patched modules and therefore
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* we do not take a reference here. The patches are removed by
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* klp_module_going() instead.
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*/
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mod = find_module(obj->name);
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/*
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* Do not mess work of klp_module_coming() and klp_module_going().
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* Note that the patch might still be needed before klp_module_going()
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* is called. Module functions can be called even in the GOING state
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* until mod->exit() finishes. This is especially important for
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* patches that modify semantic of the functions.
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*/
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if (mod && mod->klp_alive)
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obj->mod = mod;
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rcu_read_unlock_sched();
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}
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static bool klp_initialized(void)
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{
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return !!klp_root_kobj;
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}
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static struct klp_func *klp_find_func(struct klp_object *obj,
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struct klp_func *old_func)
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{
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struct klp_func *func;
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klp_for_each_func(obj, func) {
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if ((strcmp(old_func->old_name, func->old_name) == 0) &&
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(old_func->old_sympos == func->old_sympos)) {
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return func;
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}
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}
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return NULL;
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}
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static struct klp_object *klp_find_object(struct klp_patch *patch,
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struct klp_object *old_obj)
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{
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struct klp_object *obj;
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klp_for_each_object(patch, obj) {
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if (klp_is_module(old_obj)) {
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if (klp_is_module(obj) &&
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strcmp(old_obj->name, obj->name) == 0) {
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return obj;
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}
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} else if (!klp_is_module(obj)) {
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return obj;
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}
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}
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return NULL;
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}
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struct klp_find_arg {
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const char *objname;
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const char *name;
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unsigned long addr;
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unsigned long count;
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unsigned long pos;
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};
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static int klp_find_callback(void *data, const char *name,
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struct module *mod, unsigned long addr)
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{
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struct klp_find_arg *args = data;
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if ((mod && !args->objname) || (!mod && args->objname))
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return 0;
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if (strcmp(args->name, name))
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return 0;
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if (args->objname && strcmp(args->objname, mod->name))
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return 0;
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args->addr = addr;
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args->count++;
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/*
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* Finish the search when the symbol is found for the desired position
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* or the position is not defined for a non-unique symbol.
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*/
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if ((args->pos && (args->count == args->pos)) ||
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(!args->pos && (args->count > 1)))
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return 1;
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return 0;
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}
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static int klp_find_object_symbol(const char *objname, const char *name,
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unsigned long sympos, unsigned long *addr)
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{
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struct klp_find_arg args = {
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.objname = objname,
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.name = name,
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.addr = 0,
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.count = 0,
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.pos = sympos,
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};
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if (objname)
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module_kallsyms_on_each_symbol(klp_find_callback, &args);
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else
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kallsyms_on_each_symbol(klp_find_callback, &args);
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/*
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* Ensure an address was found. If sympos is 0, ensure symbol is unique;
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* otherwise ensure the symbol position count matches sympos.
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*/
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if (args.addr == 0)
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pr_err("symbol '%s' not found in symbol table\n", name);
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else if (args.count > 1 && sympos == 0) {
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pr_err("unresolvable ambiguity for symbol '%s' in object '%s'\n",
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name, objname);
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} else if (sympos != args.count && sympos > 0) {
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pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
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sympos, name, objname ? objname : "vmlinux");
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} else {
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*addr = args.addr;
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return 0;
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}
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*addr = 0;
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return -EINVAL;
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}
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static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
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unsigned int symndx, Elf_Shdr *relasec,
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const char *sec_objname)
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{
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int i, cnt, ret;
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char sym_objname[MODULE_NAME_LEN];
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char sym_name[KSYM_NAME_LEN];
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Elf_Rela *relas;
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Elf_Sym *sym;
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unsigned long sympos, addr;
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bool sym_vmlinux;
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bool sec_vmlinux = !strcmp(sec_objname, "vmlinux");
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/*
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* Since the field widths for sym_objname and sym_name in the sscanf()
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* call are hard-coded and correspond to MODULE_NAME_LEN and
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* KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
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* and KSYM_NAME_LEN have the values we expect them to have.
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*
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* Because the value of MODULE_NAME_LEN can differ among architectures,
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* we use the smallest/strictest upper bound possible (56, based on
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* the current definition of MODULE_NAME_LEN) to prevent overflows.
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*/
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BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
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relas = (Elf_Rela *) relasec->sh_addr;
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/* For each rela in this klp relocation section */
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for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
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sym = (Elf_Sym *)sechdrs[symndx].sh_addr + ELF_R_SYM(relas[i].r_info);
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if (sym->st_shndx != SHN_LIVEPATCH) {
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pr_err("symbol %s is not marked as a livepatch symbol\n",
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strtab + sym->st_name);
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return -EINVAL;
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}
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/* Format: .klp.sym.sym_objname.sym_name,sympos */
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cnt = sscanf(strtab + sym->st_name,
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".klp.sym.%55[^.].%127[^,],%lu",
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sym_objname, sym_name, &sympos);
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if (cnt != 3) {
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pr_err("symbol %s has an incorrectly formatted name\n",
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strtab + sym->st_name);
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return -EINVAL;
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}
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sym_vmlinux = !strcmp(sym_objname, "vmlinux");
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/*
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* Prevent module-specific KLP rela sections from referencing
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* vmlinux symbols. This helps prevent ordering issues with
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* module special section initializations. Presumably such
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* symbols are exported and normal relas can be used instead.
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*/
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if (!sec_vmlinux && sym_vmlinux) {
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pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section",
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sym_name);
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return -EINVAL;
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}
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/* klp_find_object_symbol() treats a NULL objname as vmlinux */
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ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname,
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sym_name, sympos, &addr);
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if (ret)
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return ret;
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sym->st_value = addr;
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}
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return 0;
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}
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/*
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* At a high-level, there are two types of klp relocation sections: those which
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* reference symbols which live in vmlinux; and those which reference symbols
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* which live in other modules. This function is called for both types:
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*
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* 1) When a klp module itself loads, the module code calls this function to
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* write vmlinux-specific klp relocations (.klp.rela.vmlinux.* sections).
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* These relocations are written to the klp module text to allow the patched
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* code/data to reference unexported vmlinux symbols. They're written as
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* early as possible to ensure that other module init code (.e.g.,
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* jump_label_apply_nops) can access any unexported vmlinux symbols which
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* might be referenced by the klp module's special sections.
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*
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* 2) When a to-be-patched module loads -- or is already loaded when a
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* corresponding klp module loads -- klp code calls this function to write
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* module-specific klp relocations (.klp.rela.{module}.* sections). These
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* are written to the klp module text to allow the patched code/data to
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* reference symbols which live in the to-be-patched module or one of its
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* module dependencies. Exported symbols are supported, in addition to
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* unexported symbols, in order to enable late module patching, which allows
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* the to-be-patched module to be loaded and patched sometime *after* the
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* klp module is loaded.
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*/
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int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
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const char *shstrtab, const char *strtab,
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unsigned int symndx, unsigned int secndx,
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const char *objname)
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{
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int cnt, ret;
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char sec_objname[MODULE_NAME_LEN];
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Elf_Shdr *sec = sechdrs + secndx;
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/*
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* Format: .klp.rela.sec_objname.section_name
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* See comment in klp_resolve_symbols() for an explanation
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* of the selected field width value.
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*/
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cnt = sscanf(shstrtab + sec->sh_name, ".klp.rela.%55[^.]",
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sec_objname);
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if (cnt != 1) {
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pr_err("section %s has an incorrectly formatted name\n",
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shstrtab + sec->sh_name);
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return -EINVAL;
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}
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if (strcmp(objname ? objname : "vmlinux", sec_objname))
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return 0;
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ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname);
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if (ret)
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return ret;
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return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
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}
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/*
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* Sysfs Interface
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*
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* /sys/kernel/livepatch
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* /sys/kernel/livepatch/<patch>
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* /sys/kernel/livepatch/<patch>/enabled
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* /sys/kernel/livepatch/<patch>/transition
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* /sys/kernel/livepatch/<patch>/force
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* /sys/kernel/livepatch/<patch>/<object>
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* /sys/kernel/livepatch/<patch>/<object>/<function,sympos>
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*/
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static int __klp_disable_patch(struct klp_patch *patch);
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static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr,
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const char *buf, size_t count)
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{
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struct klp_patch *patch;
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int ret;
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bool enabled;
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ret = kstrtobool(buf, &enabled);
|
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if (ret)
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return ret;
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patch = container_of(kobj, struct klp_patch, kobj);
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mutex_lock(&klp_mutex);
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if (patch->enabled == enabled) {
|
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/* already in requested state */
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ret = -EINVAL;
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goto out;
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}
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/*
|
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* Allow to reverse a pending transition in both ways. It might be
|
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* necessary to complete the transition without forcing and breaking
|
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* the system integrity.
|
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*
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* Do not allow to re-enable a disabled patch.
|
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*/
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if (patch == klp_transition_patch)
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klp_reverse_transition();
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else if (!enabled)
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ret = __klp_disable_patch(patch);
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else
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ret = -EINVAL;
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out:
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mutex_unlock(&klp_mutex);
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|
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if (ret)
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return ret;
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return count;
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}
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static ssize_t enabled_show(struct kobject *kobj,
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struct kobj_attribute *attr, char *buf)
|
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{
|
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struct klp_patch *patch;
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patch = container_of(kobj, struct klp_patch, kobj);
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return snprintf(buf, PAGE_SIZE-1, "%d\n", patch->enabled);
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}
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static ssize_t transition_show(struct kobject *kobj,
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struct kobj_attribute *attr, char *buf)
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{
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struct klp_patch *patch;
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patch = container_of(kobj, struct klp_patch, kobj);
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return snprintf(buf, PAGE_SIZE-1, "%d\n",
|
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patch == klp_transition_patch);
|
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}
|
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|
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static ssize_t force_store(struct kobject *kobj, struct kobj_attribute *attr,
|
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const char *buf, size_t count)
|
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{
|
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struct klp_patch *patch;
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int ret;
|
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bool val;
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ret = kstrtobool(buf, &val);
|
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if (ret)
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return ret;
|
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|
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if (!val)
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return count;
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|
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mutex_lock(&klp_mutex);
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patch = container_of(kobj, struct klp_patch, kobj);
|
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if (patch != klp_transition_patch) {
|
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mutex_unlock(&klp_mutex);
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return -EINVAL;
|
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}
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|
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klp_force_transition();
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|
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mutex_unlock(&klp_mutex);
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return count;
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}
|
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|
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static struct kobj_attribute enabled_kobj_attr = __ATTR_RW(enabled);
|
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static struct kobj_attribute transition_kobj_attr = __ATTR_RO(transition);
|
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static struct kobj_attribute force_kobj_attr = __ATTR_WO(force);
|
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static struct attribute *klp_patch_attrs[] = {
|
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&enabled_kobj_attr.attr,
|
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&transition_kobj_attr.attr,
|
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&force_kobj_attr.attr,
|
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NULL
|
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};
|
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ATTRIBUTE_GROUPS(klp_patch);
|
|
|
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static void klp_free_object_dynamic(struct klp_object *obj)
|
|
{
|
|
kfree(obj->name);
|
|
kfree(obj);
|
|
}
|
|
|
|
static void klp_init_func_early(struct klp_object *obj,
|
|
struct klp_func *func);
|
|
static void klp_init_object_early(struct klp_patch *patch,
|
|
struct klp_object *obj);
|
|
|
|
static struct klp_object *klp_alloc_object_dynamic(const char *name,
|
|
struct klp_patch *patch)
|
|
{
|
|
struct klp_object *obj;
|
|
|
|
obj = kzalloc(sizeof(*obj), GFP_KERNEL);
|
|
if (!obj)
|
|
return NULL;
|
|
|
|
if (name) {
|
|
obj->name = kstrdup(name, GFP_KERNEL);
|
|
if (!obj->name) {
|
|
kfree(obj);
|
|
return NULL;
|
|
}
|
|
}
|
|
|
|
klp_init_object_early(patch, obj);
|
|
obj->dynamic = true;
|
|
|
|
return obj;
|
|
}
|
|
|
|
static void klp_free_func_nop(struct klp_func *func)
|
|
{
|
|
kfree(func->old_name);
|
|
kfree(func);
|
|
}
|
|
|
|
static struct klp_func *klp_alloc_func_nop(struct klp_func *old_func,
|
|
struct klp_object *obj)
|
|
{
|
|
struct klp_func *func;
|
|
|
|
func = kzalloc(sizeof(*func), GFP_KERNEL);
|
|
if (!func)
|
|
return NULL;
|
|
|
|
if (old_func->old_name) {
|
|
func->old_name = kstrdup(old_func->old_name, GFP_KERNEL);
|
|
if (!func->old_name) {
|
|
kfree(func);
|
|
return NULL;
|
|
}
|
|
}
|
|
|
|
klp_init_func_early(obj, func);
|
|
/*
|
|
* func->new_func is same as func->old_func. These addresses are
|
|
* set when the object is loaded, see klp_init_object_loaded().
|
|
*/
|
|
func->old_sympos = old_func->old_sympos;
|
|
func->nop = true;
|
|
|
|
return func;
|
|
}
|
|
|
|
static int klp_add_object_nops(struct klp_patch *patch,
|
|
struct klp_object *old_obj)
|
|
{
|
|
struct klp_object *obj;
|
|
struct klp_func *func, *old_func;
|
|
|
|
obj = klp_find_object(patch, old_obj);
|
|
|
|
if (!obj) {
|
|
obj = klp_alloc_object_dynamic(old_obj->name, patch);
|
|
if (!obj)
|
|
return -ENOMEM;
|
|
}
|
|
|
|
klp_for_each_func(old_obj, old_func) {
|
|
func = klp_find_func(obj, old_func);
|
|
if (func)
|
|
continue;
|
|
|
|
func = klp_alloc_func_nop(old_func, obj);
|
|
if (!func)
|
|
return -ENOMEM;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Add 'nop' functions which simply return to the caller to run
|
|
* the original function. The 'nop' functions are added to a
|
|
* patch to facilitate a 'replace' mode.
|
|
*/
|
|
static int klp_add_nops(struct klp_patch *patch)
|
|
{
|
|
struct klp_patch *old_patch;
|
|
struct klp_object *old_obj;
|
|
|
|
klp_for_each_patch(old_patch) {
|
|
klp_for_each_object(old_patch, old_obj) {
|
|
int err;
|
|
|
|
err = klp_add_object_nops(patch, old_obj);
|
|
if (err)
|
|
return err;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void klp_kobj_release_patch(struct kobject *kobj)
|
|
{
|
|
struct klp_patch *patch;
|
|
|
|
patch = container_of(kobj, struct klp_patch, kobj);
|
|
complete(&patch->finish);
|
|
}
|
|
|
|
static struct kobj_type klp_ktype_patch = {
|
|
.release = klp_kobj_release_patch,
|
|
.sysfs_ops = &kobj_sysfs_ops,
|
|
.default_groups = klp_patch_groups,
|
|
};
|
|
|
|
static void klp_kobj_release_object(struct kobject *kobj)
|
|
{
|
|
struct klp_object *obj;
|
|
|
|
obj = container_of(kobj, struct klp_object, kobj);
|
|
|
|
if (obj->dynamic)
|
|
klp_free_object_dynamic(obj);
|
|
}
|
|
|
|
static struct kobj_type klp_ktype_object = {
|
|
.release = klp_kobj_release_object,
|
|
.sysfs_ops = &kobj_sysfs_ops,
|
|
};
|
|
|
|
static void klp_kobj_release_func(struct kobject *kobj)
|
|
{
|
|
struct klp_func *func;
|
|
|
|
func = container_of(kobj, struct klp_func, kobj);
|
|
|
|
if (func->nop)
|
|
klp_free_func_nop(func);
|
|
}
|
|
|
|
static struct kobj_type klp_ktype_func = {
|
|
.release = klp_kobj_release_func,
|
|
.sysfs_ops = &kobj_sysfs_ops,
|
|
};
|
|
|
|
static void __klp_free_funcs(struct klp_object *obj, bool nops_only)
|
|
{
|
|
struct klp_func *func, *tmp_func;
|
|
|
|
klp_for_each_func_safe(obj, func, tmp_func) {
|
|
if (nops_only && !func->nop)
|
|
continue;
|
|
|
|
list_del(&func->node);
|
|
kobject_put(&func->kobj);
|
|
}
|
|
}
|
|
|
|
/* Clean up when a patched object is unloaded */
|
|
static void klp_free_object_loaded(struct klp_object *obj)
|
|
{
|
|
struct klp_func *func;
|
|
|
|
obj->mod = NULL;
|
|
|
|
klp_for_each_func(obj, func) {
|
|
func->old_func = NULL;
|
|
|
|
if (func->nop)
|
|
func->new_func = NULL;
|
|
}
|
|
}
|
|
|
|
static void __klp_free_objects(struct klp_patch *patch, bool nops_only)
|
|
{
|
|
struct klp_object *obj, *tmp_obj;
|
|
|
|
klp_for_each_object_safe(patch, obj, tmp_obj) {
|
|
__klp_free_funcs(obj, nops_only);
|
|
|
|
if (nops_only && !obj->dynamic)
|
|
continue;
|
|
|
|
list_del(&obj->node);
|
|
kobject_put(&obj->kobj);
|
|
}
|
|
}
|
|
|
|
static void klp_free_objects(struct klp_patch *patch)
|
|
{
|
|
__klp_free_objects(patch, false);
|
|
}
|
|
|
|
static void klp_free_objects_dynamic(struct klp_patch *patch)
|
|
{
|
|
__klp_free_objects(patch, true);
|
|
}
|
|
|
|
/*
|
|
* This function implements the free operations that can be called safely
|
|
* under klp_mutex.
|
|
*
|
|
* The operation must be completed by calling klp_free_patch_finish()
|
|
* outside klp_mutex.
|
|
*/
|
|
static void klp_free_patch_start(struct klp_patch *patch)
|
|
{
|
|
if (!list_empty(&patch->list))
|
|
list_del(&patch->list);
|
|
|
|
klp_free_objects(patch);
|
|
}
|
|
|
|
/*
|
|
* This function implements the free part that must be called outside
|
|
* klp_mutex.
|
|
*
|
|
* It must be called after klp_free_patch_start(). And it has to be
|
|
* the last function accessing the livepatch structures when the patch
|
|
* gets disabled.
|
|
*/
|
|
static void klp_free_patch_finish(struct klp_patch *patch)
|
|
{
|
|
/*
|
|
* Avoid deadlock with enabled_store() sysfs callback by
|
|
* calling this outside klp_mutex. It is safe because
|
|
* this is called when the patch gets disabled and it
|
|
* cannot get enabled again.
|
|
*/
|
|
kobject_put(&patch->kobj);
|
|
wait_for_completion(&patch->finish);
|
|
|
|
/* Put the module after the last access to struct klp_patch. */
|
|
if (!patch->forced)
|
|
module_put(patch->mod);
|
|
}
|
|
|
|
/*
|
|
* The livepatch might be freed from sysfs interface created by the patch.
|
|
* This work allows to wait until the interface is destroyed in a separate
|
|
* context.
|
|
*/
|
|
static void klp_free_patch_work_fn(struct work_struct *work)
|
|
{
|
|
struct klp_patch *patch =
|
|
container_of(work, struct klp_patch, free_work);
|
|
|
|
klp_free_patch_finish(patch);
|
|
}
|
|
|
|
void klp_free_patch_async(struct klp_patch *patch)
|
|
{
|
|
klp_free_patch_start(patch);
|
|
schedule_work(&patch->free_work);
|
|
}
|
|
|
|
void klp_free_replaced_patches_async(struct klp_patch *new_patch)
|
|
{
|
|
struct klp_patch *old_patch, *tmp_patch;
|
|
|
|
klp_for_each_patch_safe(old_patch, tmp_patch) {
|
|
if (old_patch == new_patch)
|
|
return;
|
|
klp_free_patch_async(old_patch);
|
|
}
|
|
}
|
|
|
|
static int klp_init_func(struct klp_object *obj, struct klp_func *func)
|
|
{
|
|
if (!func->old_name)
|
|
return -EINVAL;
|
|
|
|
/*
|
|
* NOPs get the address later. The patched module must be loaded,
|
|
* see klp_init_object_loaded().
|
|
*/
|
|
if (!func->new_func && !func->nop)
|
|
return -EINVAL;
|
|
|
|
if (strlen(func->old_name) >= KSYM_NAME_LEN)
|
|
return -EINVAL;
|
|
|
|
INIT_LIST_HEAD(&func->stack_node);
|
|
func->patched = false;
|
|
func->transition = false;
|
|
|
|
/* The format for the sysfs directory is <function,sympos> where sympos
|
|
* is the nth occurrence of this symbol in kallsyms for the patched
|
|
* object. If the user selects 0 for old_sympos, then 1 will be used
|
|
* since a unique symbol will be the first occurrence.
|
|
*/
|
|
return kobject_add(&func->kobj, &obj->kobj, "%s,%lu",
|
|
func->old_name,
|
|
func->old_sympos ? func->old_sympos : 1);
|
|
}
|
|
|
|
static int klp_apply_object_relocs(struct klp_patch *patch,
|
|
struct klp_object *obj)
|
|
{
|
|
int i, ret;
|
|
struct klp_modinfo *info = patch->mod->klp_info;
|
|
|
|
for (i = 1; i < info->hdr.e_shnum; i++) {
|
|
Elf_Shdr *sec = info->sechdrs + i;
|
|
|
|
if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
|
|
continue;
|
|
|
|
ret = klp_apply_section_relocs(patch->mod, info->sechdrs,
|
|
info->secstrings,
|
|
patch->mod->core_kallsyms.strtab,
|
|
info->symndx, i, obj->name);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* parts of the initialization that is done only when the object is loaded */
|
|
static int klp_init_object_loaded(struct klp_patch *patch,
|
|
struct klp_object *obj)
|
|
{
|
|
struct klp_func *func;
|
|
int ret;
|
|
|
|
if (klp_is_module(obj)) {
|
|
/*
|
|
* Only write module-specific relocations here
|
|
* (.klp.rela.{module}.*). vmlinux-specific relocations were
|
|
* written earlier during the initialization of the klp module
|
|
* itself.
|
|
*/
|
|
ret = klp_apply_object_relocs(patch, obj);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
|
|
klp_for_each_func(obj, func) {
|
|
ret = klp_find_object_symbol(obj->name, func->old_name,
|
|
func->old_sympos,
|
|
(unsigned long *)&func->old_func);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = kallsyms_lookup_size_offset((unsigned long)func->old_func,
|
|
&func->old_size, NULL);
|
|
if (!ret) {
|
|
pr_err("kallsyms size lookup failed for '%s'\n",
|
|
func->old_name);
|
|
return -ENOENT;
|
|
}
|
|
|
|
if (func->nop)
|
|
func->new_func = func->old_func;
|
|
|
|
ret = kallsyms_lookup_size_offset((unsigned long)func->new_func,
|
|
&func->new_size, NULL);
|
|
if (!ret) {
|
|
pr_err("kallsyms size lookup failed for '%s' replacement\n",
|
|
func->old_name);
|
|
return -ENOENT;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int klp_init_object(struct klp_patch *patch, struct klp_object *obj)
|
|
{
|
|
struct klp_func *func;
|
|
int ret;
|
|
const char *name;
|
|
|
|
if (klp_is_module(obj) && strlen(obj->name) >= MODULE_NAME_LEN)
|
|
return -EINVAL;
|
|
|
|
obj->patched = false;
|
|
obj->mod = NULL;
|
|
|
|
klp_find_object_module(obj);
|
|
|
|
name = klp_is_module(obj) ? obj->name : "vmlinux";
|
|
ret = kobject_add(&obj->kobj, &patch->kobj, "%s", name);
|
|
if (ret)
|
|
return ret;
|
|
|
|
klp_for_each_func(obj, func) {
|
|
ret = klp_init_func(obj, func);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
|
|
if (klp_is_object_loaded(obj))
|
|
ret = klp_init_object_loaded(patch, obj);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static void klp_init_func_early(struct klp_object *obj,
|
|
struct klp_func *func)
|
|
{
|
|
kobject_init(&func->kobj, &klp_ktype_func);
|
|
list_add_tail(&func->node, &obj->func_list);
|
|
}
|
|
|
|
static void klp_init_object_early(struct klp_patch *patch,
|
|
struct klp_object *obj)
|
|
{
|
|
INIT_LIST_HEAD(&obj->func_list);
|
|
kobject_init(&obj->kobj, &klp_ktype_object);
|
|
list_add_tail(&obj->node, &patch->obj_list);
|
|
}
|
|
|
|
static void klp_init_patch_early(struct klp_patch *patch)
|
|
{
|
|
struct klp_object *obj;
|
|
struct klp_func *func;
|
|
|
|
INIT_LIST_HEAD(&patch->list);
|
|
INIT_LIST_HEAD(&patch->obj_list);
|
|
kobject_init(&patch->kobj, &klp_ktype_patch);
|
|
patch->enabled = false;
|
|
patch->forced = false;
|
|
INIT_WORK(&patch->free_work, klp_free_patch_work_fn);
|
|
init_completion(&patch->finish);
|
|
|
|
klp_for_each_object_static(patch, obj) {
|
|
klp_init_object_early(patch, obj);
|
|
|
|
klp_for_each_func_static(obj, func) {
|
|
klp_init_func_early(obj, func);
|
|
}
|
|
}
|
|
}
|
|
|
|
static int klp_init_patch(struct klp_patch *patch)
|
|
{
|
|
struct klp_object *obj;
|
|
int ret;
|
|
|
|
ret = kobject_add(&patch->kobj, klp_root_kobj, "%s", patch->mod->name);
|
|
if (ret)
|
|
return ret;
|
|
|
|
if (patch->replace) {
|
|
ret = klp_add_nops(patch);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
|
|
klp_for_each_object(patch, obj) {
|
|
ret = klp_init_object(patch, obj);
|
|
if (ret)
|
|
return ret;
|
|
}
|
|
|
|
list_add_tail(&patch->list, &klp_patches);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int __klp_disable_patch(struct klp_patch *patch)
|
|
{
|
|
struct klp_object *obj;
|
|
|
|
if (WARN_ON(!patch->enabled))
|
|
return -EINVAL;
|
|
|
|
if (klp_transition_patch)
|
|
return -EBUSY;
|
|
|
|
klp_init_transition(patch, KLP_UNPATCHED);
|
|
|
|
klp_for_each_object(patch, obj)
|
|
if (obj->patched)
|
|
klp_pre_unpatch_callback(obj);
|
|
|
|
/*
|
|
* Enforce the order of the func->transition writes in
|
|
* klp_init_transition() and the TIF_PATCH_PENDING writes in
|
|
* klp_start_transition(). In the rare case where klp_ftrace_handler()
|
|
* is called shortly after klp_update_patch_state() switches the task,
|
|
* this ensures the handler sees that func->transition is set.
|
|
*/
|
|
smp_wmb();
|
|
|
|
klp_start_transition();
|
|
patch->enabled = false;
|
|
klp_try_complete_transition();
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int __klp_enable_patch(struct klp_patch *patch)
|
|
{
|
|
struct klp_object *obj;
|
|
int ret;
|
|
|
|
if (klp_transition_patch)
|
|
return -EBUSY;
|
|
|
|
if (WARN_ON(patch->enabled))
|
|
return -EINVAL;
|
|
|
|
pr_notice("enabling patch '%s'\n", patch->mod->name);
|
|
|
|
klp_init_transition(patch, KLP_PATCHED);
|
|
|
|
/*
|
|
* Enforce the order of the func->transition writes in
|
|
* klp_init_transition() and the ops->func_stack writes in
|
|
* klp_patch_object(), so that klp_ftrace_handler() will see the
|
|
* func->transition updates before the handler is registered and the
|
|
* new funcs become visible to the handler.
|
|
*/
|
|
smp_wmb();
|
|
|
|
klp_for_each_object(patch, obj) {
|
|
if (!klp_is_object_loaded(obj))
|
|
continue;
|
|
|
|
ret = klp_pre_patch_callback(obj);
|
|
if (ret) {
|
|
pr_warn("pre-patch callback failed for object '%s'\n",
|
|
klp_is_module(obj) ? obj->name : "vmlinux");
|
|
goto err;
|
|
}
|
|
|
|
ret = klp_patch_object(obj);
|
|
if (ret) {
|
|
pr_warn("failed to patch object '%s'\n",
|
|
klp_is_module(obj) ? obj->name : "vmlinux");
|
|
goto err;
|
|
}
|
|
}
|
|
|
|
klp_start_transition();
|
|
patch->enabled = true;
|
|
klp_try_complete_transition();
|
|
|
|
return 0;
|
|
err:
|
|
pr_warn("failed to enable patch '%s'\n", patch->mod->name);
|
|
|
|
klp_cancel_transition();
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* klp_enable_patch() - enable the livepatch
|
|
* @patch: patch to be enabled
|
|
*
|
|
* Initializes the data structure associated with the patch, creates the sysfs
|
|
* interface, performs the needed symbol lookups and code relocations,
|
|
* registers the patched functions with ftrace.
|
|
*
|
|
* This function is supposed to be called from the livepatch module_init()
|
|
* callback.
|
|
*
|
|
* Return: 0 on success, otherwise error
|
|
*/
|
|
int klp_enable_patch(struct klp_patch *patch)
|
|
{
|
|
int ret;
|
|
struct klp_object *obj;
|
|
|
|
if (!patch || !patch->mod || !patch->objs)
|
|
return -EINVAL;
|
|
|
|
klp_for_each_object_static(patch, obj) {
|
|
if (!obj->funcs)
|
|
return -EINVAL;
|
|
}
|
|
|
|
|
|
if (!is_livepatch_module(patch->mod)) {
|
|
pr_err("module %s is not marked as a livepatch module\n",
|
|
patch->mod->name);
|
|
return -EINVAL;
|
|
}
|
|
|
|
if (!klp_initialized())
|
|
return -ENODEV;
|
|
|
|
if (!klp_have_reliable_stack()) {
|
|
pr_warn("This architecture doesn't have support for the livepatch consistency model.\n");
|
|
pr_warn("The livepatch transition may never complete.\n");
|
|
}
|
|
|
|
mutex_lock(&klp_mutex);
|
|
|
|
if (!klp_is_patch_compatible(patch)) {
|
|
pr_err("Livepatch patch (%s) is not compatible with the already installed livepatches.\n",
|
|
patch->mod->name);
|
|
mutex_unlock(&klp_mutex);
|
|
return -EINVAL;
|
|
}
|
|
|
|
if (!try_module_get(patch->mod)) {
|
|
mutex_unlock(&klp_mutex);
|
|
return -ENODEV;
|
|
}
|
|
|
|
klp_init_patch_early(patch);
|
|
|
|
ret = klp_init_patch(patch);
|
|
if (ret)
|
|
goto err;
|
|
|
|
ret = __klp_enable_patch(patch);
|
|
if (ret)
|
|
goto err;
|
|
|
|
mutex_unlock(&klp_mutex);
|
|
|
|
return 0;
|
|
|
|
err:
|
|
klp_free_patch_start(patch);
|
|
|
|
mutex_unlock(&klp_mutex);
|
|
|
|
klp_free_patch_finish(patch);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(klp_enable_patch);
|
|
|
|
/*
|
|
* This function unpatches objects from the replaced livepatches.
|
|
*
|
|
* We could be pretty aggressive here. It is called in the situation where
|
|
* these structures are no longer accessed from the ftrace handler.
|
|
* All functions are redirected by the klp_transition_patch. They
|
|
* use either a new code or they are in the original code because
|
|
* of the special nop function patches.
|
|
*
|
|
* The only exception is when the transition was forced. In this case,
|
|
* klp_ftrace_handler() might still see the replaced patch on the stack.
|
|
* Fortunately, it is carefully designed to work with removed functions
|
|
* thanks to RCU. We only have to keep the patches on the system. Also
|
|
* this is handled transparently by patch->module_put.
|
|
*/
|
|
void klp_unpatch_replaced_patches(struct klp_patch *new_patch)
|
|
{
|
|
struct klp_patch *old_patch;
|
|
|
|
klp_for_each_patch(old_patch) {
|
|
if (old_patch == new_patch)
|
|
return;
|
|
|
|
old_patch->enabled = false;
|
|
klp_unpatch_objects(old_patch);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* This function removes the dynamically allocated 'nop' functions.
|
|
*
|
|
* We could be pretty aggressive. NOPs do not change the existing
|
|
* behavior except for adding unnecessary delay by the ftrace handler.
|
|
*
|
|
* It is safe even when the transition was forced. The ftrace handler
|
|
* will see a valid ops->func_stack entry thanks to RCU.
|
|
*
|
|
* We could even free the NOPs structures. They must be the last entry
|
|
* in ops->func_stack. Therefore unregister_ftrace_function() is called.
|
|
* It does the same as klp_synchronize_transition() to make sure that
|
|
* nobody is inside the ftrace handler once the operation finishes.
|
|
*
|
|
* IMPORTANT: It must be called right after removing the replaced patches!
|
|
*/
|
|
void klp_discard_nops(struct klp_patch *new_patch)
|
|
{
|
|
klp_unpatch_objects_dynamic(klp_transition_patch);
|
|
klp_free_objects_dynamic(klp_transition_patch);
|
|
}
|
|
|
|
/*
|
|
* Remove parts of patches that touch a given kernel module. The list of
|
|
* patches processed might be limited. When limit is NULL, all patches
|
|
* will be handled.
|
|
*/
|
|
static void klp_cleanup_module_patches_limited(struct module *mod,
|
|
struct klp_patch *limit)
|
|
{
|
|
struct klp_patch *patch;
|
|
struct klp_object *obj;
|
|
|
|
klp_for_each_patch(patch) {
|
|
if (patch == limit)
|
|
break;
|
|
|
|
klp_for_each_object(patch, obj) {
|
|
if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
|
|
continue;
|
|
|
|
if (patch != klp_transition_patch)
|
|
klp_pre_unpatch_callback(obj);
|
|
|
|
pr_notice("reverting patch '%s' on unloading module '%s'\n",
|
|
patch->mod->name, obj->mod->name);
|
|
klp_unpatch_object(obj);
|
|
|
|
klp_post_unpatch_callback(obj);
|
|
|
|
klp_free_object_loaded(obj);
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
int klp_module_coming(struct module *mod)
|
|
{
|
|
int ret;
|
|
struct klp_patch *patch;
|
|
struct klp_object *obj;
|
|
|
|
if (WARN_ON(mod->state != MODULE_STATE_COMING))
|
|
return -EINVAL;
|
|
|
|
if (!strcmp(mod->name, "vmlinux")) {
|
|
pr_err("vmlinux.ko: invalid module name");
|
|
return -EINVAL;
|
|
}
|
|
|
|
mutex_lock(&klp_mutex);
|
|
/*
|
|
* Each module has to know that klp_module_coming()
|
|
* has been called. We never know what module will
|
|
* get patched by a new patch.
|
|
*/
|
|
mod->klp_alive = true;
|
|
|
|
klp_for_each_patch(patch) {
|
|
klp_for_each_object(patch, obj) {
|
|
if (!klp_is_module(obj) || strcmp(obj->name, mod->name))
|
|
continue;
|
|
|
|
obj->mod = mod;
|
|
|
|
ret = klp_init_object_loaded(patch, obj);
|
|
if (ret) {
|
|
pr_warn("failed to initialize patch '%s' for module '%s' (%d)\n",
|
|
patch->mod->name, obj->mod->name, ret);
|
|
goto err;
|
|
}
|
|
|
|
pr_notice("applying patch '%s' to loading module '%s'\n",
|
|
patch->mod->name, obj->mod->name);
|
|
|
|
ret = klp_pre_patch_callback(obj);
|
|
if (ret) {
|
|
pr_warn("pre-patch callback failed for object '%s'\n",
|
|
obj->name);
|
|
goto err;
|
|
}
|
|
|
|
ret = klp_patch_object(obj);
|
|
if (ret) {
|
|
pr_warn("failed to apply patch '%s' to module '%s' (%d)\n",
|
|
patch->mod->name, obj->mod->name, ret);
|
|
|
|
klp_post_unpatch_callback(obj);
|
|
goto err;
|
|
}
|
|
|
|
if (patch != klp_transition_patch)
|
|
klp_post_patch_callback(obj);
|
|
|
|
break;
|
|
}
|
|
}
|
|
|
|
mutex_unlock(&klp_mutex);
|
|
|
|
return 0;
|
|
|
|
err:
|
|
/*
|
|
* If a patch is unsuccessfully applied, return
|
|
* error to the module loader.
|
|
*/
|
|
pr_warn("patch '%s' failed for module '%s', refusing to load module '%s'\n",
|
|
patch->mod->name, obj->mod->name, obj->mod->name);
|
|
mod->klp_alive = false;
|
|
obj->mod = NULL;
|
|
klp_cleanup_module_patches_limited(mod, patch);
|
|
mutex_unlock(&klp_mutex);
|
|
|
|
return ret;
|
|
}
|
|
|
|
void klp_module_going(struct module *mod)
|
|
{
|
|
if (WARN_ON(mod->state != MODULE_STATE_GOING &&
|
|
mod->state != MODULE_STATE_COMING))
|
|
return;
|
|
|
|
mutex_lock(&klp_mutex);
|
|
/*
|
|
* Each module has to know that klp_module_going()
|
|
* has been called. We never know what module will
|
|
* get patched by a new patch.
|
|
*/
|
|
mod->klp_alive = false;
|
|
|
|
klp_cleanup_module_patches_limited(mod, NULL);
|
|
|
|
mutex_unlock(&klp_mutex);
|
|
}
|
|
|
|
static int __init klp_init(void)
|
|
{
|
|
klp_root_kobj = kobject_create_and_add("livepatch", kernel_kobj);
|
|
if (!klp_root_kobj)
|
|
return -ENOMEM;
|
|
|
|
return 0;
|
|
}
|
|
|
|
module_init(klp_init);
|