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Date: Mon, 9 Nov 2015 23:45:53 -0500
From: Jessica Yu <jeyu@...hat.com>
To: Rusty Russell <rusty@...tcorp.com.au>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Seth Jennings <sjenning@...hat.com>,
Jiri Kosina <jikos@...nel.org>,
Vojtech Pavlik <vojtech@...e.com>,
Miroslav Benes <mbenes@...e.cz>
Cc: linux-api@...r.kernel.org, live-patching@...r.kernel.org,
x86@...nel.org, linux-kernel@...r.kernel.org,
Jessica Yu <jeyu@...hat.com>
Subject: [RFC PATCH 3/5] livepatch: reuse module loader code to write relocations
Reuse module loader code to write relocations, thereby eliminating the
need for architecture specific code in livepatch. Namely, we reuse
apply_relocate_add() in the module loader to write relocs instead of
duplicating functionality in livepatch's klp_write_module_reloc(). To
apply relocation sections, remaining SHN_LIVEPATCH symbols referenced by
relocs are resolved and then apply_relocate_add() is called to apply
those relocations.
Signed-off-by: Jessica Yu <jeyu@...hat.com>
---
include/linux/livepatch.h | 11 ++++--
include/linux/module.h | 6 ++++
kernel/livepatch/core.c | 89 +++++++++++++++++++++++++++++------------------
3 files changed, 70 insertions(+), 36 deletions(-)
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 31db7a0..601e892 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -85,7 +85,7 @@ struct klp_reloc {
/**
* struct klp_object - kernel object structure for live patching
* @name: module name (or NULL for vmlinux)
- * @relocs: relocation entries to be applied at load time
+ * @reloc_secs: relocation sections to be applied at load time
* @funcs: function entries for functions to be patched in the object
* @kobj: kobject for sysfs resources
* @mod: kernel module associated with the patched object
@@ -95,7 +95,7 @@ struct klp_reloc {
struct klp_object {
/* external */
const char *name;
- struct klp_reloc *relocs;
+ struct list_head reloc_secs;
struct klp_func *funcs;
/* internal */
@@ -129,6 +129,13 @@ struct klp_patch {
#define klp_for_each_func(obj, func) \
for (func = obj->funcs; func->old_name; func++)
+struct klp_reloc_sec {
+ unsigned int index;
+ char *name;
+ char *objname;
+ struct list_head list;
+};
+
int klp_register_patch(struct klp_patch *);
int klp_unregister_patch(struct klp_patch *);
int klp_enable_patch(struct klp_patch *);
diff --git a/include/linux/module.h b/include/linux/module.h
index c8680b1..3c34eb8 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -793,9 +793,15 @@ extern int module_sysfs_initialized;
#ifdef CONFIG_DEBUG_SET_MODULE_RONX
extern void set_all_modules_text_rw(void);
extern void set_all_modules_text_ro(void);
+extern void
+set_page_attributes(void *start, void *end,
+ int (*set)(unsigned long start, int num_pages));
#else
static inline void set_all_modules_text_rw(void) { }
static inline void set_all_modules_text_ro(void) { }
+static inline void
+set_page_attributes(void *start, void *end,
+ int (*set)(unsigned long start, int num_pages)) { }
#endif
#ifdef CONFIG_GENERIC_BUG
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 087a8c7..26c419f 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -28,6 +28,8 @@
#include <linux/list.h>
#include <linux/kallsyms.h>
#include <linux/livepatch.h>
+#include <linux/elf.h>
+#include <asm/cacheflush.h>
/**
* struct klp_ops - structure for tracking registered ftrace ops structs
@@ -281,46 +283,54 @@ static int klp_find_external_symbol(struct module *pmod, const char *name,
}
static int klp_write_object_relocations(struct module *pmod,
- struct klp_object *obj)
+ struct klp_object *obj,
+ struct klp_patch *patch)
{
- int ret;
- struct klp_reloc *reloc;
+ int relindex, num_relas;
+ int i, ret = 0;
+ unsigned long addr;
+ unsigned int bind;
+ char *symname;
+ struct klp_reloc_sec *reloc_sec;
+ struct load_info *info;
+ Elf_Rela *rela;
+ Elf_Sym *sym, *symtab;
+ Elf_Shdr *symsect;
if (WARN_ON(!klp_is_object_loaded(obj)))
return -EINVAL;
- if (WARN_ON(!obj->relocs))
- return -EINVAL;
-
- for (reloc = obj->relocs; reloc->name; reloc++) {
- if (!klp_is_module(obj)) {
- ret = klp_verify_vmlinux_symbol(reloc->name,
- reloc->val);
- if (ret)
- return ret;
- } else {
- /* module, reloc->val needs to be discovered */
- if (reloc->external)
- ret = klp_find_external_symbol(pmod,
- reloc->name,
- &reloc->val);
- else
- ret = klp_find_object_symbol(obj->mod->name,
- reloc->name,
- &reloc->val);
- if (ret)
- return ret;
- }
- ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
- reloc->val + reloc->addend);
- if (ret) {
- pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
- reloc->name, reloc->val, ret);
- return ret;
+ info = pmod->info;
+ symsect = info->sechdrs + info->index.sym;
+ symtab = (void *)info->hdr + symsect->sh_offset;
+
+ /* For each __klp_rela section for this object */
+ list_for_each_entry(reloc_sec, &obj->reloc_secs, list) {
+ relindex = reloc_sec->index;
+ num_relas = info->sechdrs[relindex].sh_size / sizeof(Elf_Rela);
+ rela = (Elf_Rela *) info->sechdrs[relindex].sh_addr;
+
+ /* For each rela in this __klp_rela section */
+ for (i = 0; i < num_relas; i++, rela++) {
+ sym = symtab + ELF_R_SYM(rela->r_info);
+ symname = info->strtab + sym->st_name;
+ bind = ELF_ST_BIND(sym->st_info);
+
+ if (sym->st_shndx == SHN_LIVEPATCH) {
+ if (bind == STB_LIVEPATCH_EXT)
+ ret = klp_find_external_symbol(pmod, symname, &addr);
+ else
+ ret = klp_find_object_symbol(obj->name, symname, &addr);
+ if (ret)
+ return ret;
+ sym->st_value = addr;
+ }
}
+ ret = apply_relocate_add(info->sechdrs, info->strtab,
+ info->index.sym, relindex, pmod);
}
- return 0;
+ return ret;
}
static void notrace klp_ftrace_handler(unsigned long ip,
@@ -741,12 +751,23 @@ static int klp_init_object_loaded(struct klp_patch *patch,
struct klp_object *obj)
{
struct klp_func *func;
+ struct module *pmod;
int ret;
- if (obj->relocs) {
- ret = klp_write_object_relocations(patch->mod, obj);
+ pmod = patch->mod;
+
+ if (!list_empty(&obj->reloc_secs)) {
+ set_page_attributes(pmod->module_core,
+ pmod->module_core + pmod->core_text_size,
+ set_memory_rw);
+
+ ret = klp_write_object_relocations(pmod, obj, patch);
if (ret)
return ret;
+
+ set_page_attributes(pmod->module_core,
+ pmod->module_core + pmod->core_text_size,
+ set_memory_ro);
}
klp_for_each_func(obj, func) {
--
2.4.3
--
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