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Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching

Browse Source 
Pull livepatching updates from Jiri Kosina:

 - remove of our own implementation of architecture-specific relocation
   code and leveraging existing code in the module loader to perform
   arch-dependent work, from Jessica Yu.

   The relevant patches have been acked by Rusty (for module.c) and
   Heiko (for s390).

 - live patching support for ppc64le, which is a joint work of Michael
   Ellerman and Torsten Duwe.  This is coming from topic branch that is
   share between livepatching.git and ppc tree.

 - addition of livepatching documentation from Petr Mladek

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching:
  livepatch: make object/func-walking helpers more robust
  livepatch: Add some basic livepatch documentation
  powerpc/livepatch: Add live patching support on ppc64le
  powerpc/livepatch: Add livepatch stack to struct thread_info
  powerpc/livepatch: Add livepatch header
  livepatch: Allow architectures to specify an alternate ftrace location
  ftrace: Make ftrace_location_range() global
  livepatch: robustify klp_register_patch() API error checking
  Documentation: livepatch: outline Elf format and requirements for patch modules
  livepatch: reuse module loader code to write relocations
  module: s390: keep mod_arch_specific for livepatch modules
  module: preserve Elf information for livepatch modules
  Elf: add livepatch-specific Elf constants
This commit is contained in:
Linus Torvalds
2016-05-17 17:11:27 -07:00
parent 16bf834805 be69f70e63
commit 0b86c75db6
24 changed files with 1201 additions and 182 deletions
Download Patch File Download Diff File Expand all files Collapse all files

193
kernel/livepatch/core.c
View File

@@ -28,6 +28,8 @@
#include <linux/list.h>
#include <linux/kallsyms.h>
#include <linux/livepatch.h>
#include <linux/elf.h>
#include <linux/moduleloader.h>
#include <asm/cacheflush.h>
/**
@@ -204,75 +206,109 @@ static int klp_find_object_symbol(const char *objname, const char *name,
return -EINVAL;
}
/*
* external symbols are located outside the parent object (where the parent
* object is either vmlinux or the kmod being patched).
*/
static int klp_find_external_symbol(struct module *pmod, const char *name,
unsigned long *addr)
static int klp_resolve_symbols(Elf_Shdr *relasec, struct module *pmod)
{
const struct kernel_symbol *sym;
/* first, check if it's an exported symbol */
preempt_disable();
sym = find_symbol(name, NULL, NULL, true, true);
if (sym) {
*addr = sym->value;
preempt_enable();
return 0;
}
preempt_enable();
int i, cnt, vmlinux, ret;
char objname[MODULE_NAME_LEN];
char symname[KSYM_NAME_LEN];
char *strtab = pmod->core_kallsyms.strtab;
Elf_Rela *relas;
Elf_Sym *sym;
unsigned long sympos, addr;
/*
* Check if it's in another .o within the patch module. This also
* checks that the external symbol is unique.
* Since the field widths for objname and symname in the sscanf()
* call are hard-coded and correspond to MODULE_NAME_LEN and
* KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
* and KSYM_NAME_LEN have the values we expect them to have.
*
* Because the value of MODULE_NAME_LEN can differ among architectures,
* we use the smallest/strictest upper bound possible (56, based on
* the current definition of MODULE_NAME_LEN) to prevent overflows.
*/
return klp_find_object_symbol(pmod->name, name, 0, addr);
BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
relas = (Elf_Rela *) relasec->sh_addr;
/* For each rela in this klp relocation section */
for (i = 0; i < relasec->sh_size / sizeof(Elf_Rela); i++) {
sym = pmod->core_kallsyms.symtab + ELF_R_SYM(relas[i].r_info);
if (sym->st_shndx != SHN_LIVEPATCH) {
pr_err("symbol %s is not marked as a livepatch symbol",
strtab + sym->st_name);
return -EINVAL;
}
/* Format: .klp.sym.objname.symname,sympos */
cnt = sscanf(strtab + sym->st_name,
".klp.sym.%55[^.].%127[^,],%lu",
objname, symname, &sympos);
if (cnt != 3) {
pr_err("symbol %s has an incorrectly formatted name",
strtab + sym->st_name);
return -EINVAL;
}
/* klp_find_object_symbol() treats a NULL objname as vmlinux */
vmlinux = !strcmp(objname, "vmlinux");
ret = klp_find_object_symbol(vmlinux ? NULL : objname,
symname, sympos, &addr);
if (ret)
return ret;
sym->st_value = addr;
}
return 0;
}
static int klp_write_object_relocations(struct module *pmod,
struct klp_object *obj)
{
int ret = 0;
unsigned long val;
struct klp_reloc *reloc;
int i, cnt, ret = 0;
const char *objname, *secname;
char sec_objname[MODULE_NAME_LEN];
Elf_Shdr *sec;
if (WARN_ON(!klp_is_object_loaded(obj)))
return -EINVAL;
if (WARN_ON(!obj->relocs))
return -EINVAL;
objname = klp_is_module(obj) ? obj->name : "vmlinux";
module_disable_ro(pmod);
/* For each klp relocation section */
for (i = 1; i < pmod->klp_info->hdr.e_shnum; i++) {
sec = pmod->klp_info->sechdrs + i;
secname = pmod->klp_info->secstrings + sec->sh_name;
if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
continue;
for (reloc = obj->relocs; reloc->name; reloc++) {
/* discover the address of the referenced symbol */
if (reloc->external) {
if (reloc->sympos > 0) {
pr_err("non-zero sympos for external reloc symbol '%s' is not supported\n",
reloc->name);
ret = -EINVAL;
goto out;
}
ret = klp_find_external_symbol(pmod, reloc->name, &val);
} else
ret = klp_find_object_symbol(obj->name,
reloc->name,
reloc->sympos,
&val);
if (ret)
goto out;
ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
val + reloc->addend);
if (ret) {
pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
reloc->name, val, ret);
goto out;
/*
* Format: .klp.rela.sec_objname.section_name
* See comment in klp_resolve_symbols() for an explanation
* of the selected field width value.
*/
cnt = sscanf(secname, ".klp.rela.%55[^.]", sec_objname);
if (cnt != 1) {
pr_err("section %s has an incorrectly formatted name",
secname);
ret = -EINVAL;
break;
}
if (strcmp(objname, sec_objname))
continue;
ret = klp_resolve_symbols(sec, pmod);
if (ret)
break;
ret = apply_relocate_add(pmod->klp_info->sechdrs,
pmod->core_kallsyms.strtab,
pmod->klp_info->symndx, i, pmod);
if (ret)
break;
}
out:
module_enable_ro(pmod);
return ret;
}
@@ -298,6 +334,19 @@ unlock:
rcu_read_unlock();
}
/*
* Convert a function address into the appropriate ftrace location.
*
* Usually this is just the address of the function, but on some architectures
* it's more complicated so allow them to provide a custom behaviour.
*/
#ifndef klp_get_ftrace_location
static unsigned long klp_get_ftrace_location(unsigned long faddr)
{
return faddr;
}
#endif
static void klp_disable_func(struct klp_func *func)
{
struct klp_ops *ops;
@@ -312,8 +361,14 @@ static void klp_disable_func(struct klp_func *func)
return;
if (list_is_singular(&ops->func_stack)) {
unsigned long ftrace_loc;
ftrace_loc = klp_get_ftrace_location(func->old_addr);
if (WARN_ON(!ftrace_loc))
return;
WARN_ON(unregister_ftrace_function(&ops->fops));
WARN_ON(ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0));
WARN_ON(ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0));
list_del_rcu(&func->stack_node);
list_del(&ops->node);
@@ -338,6 +393,15 @@ static int klp_enable_func(struct klp_func *func)
ops = klp_find_ops(func->old_addr);
if (!ops) {
unsigned long ftrace_loc;
ftrace_loc = klp_get_ftrace_location(func->old_addr);
if (!ftrace_loc) {
pr_err("failed to find location for function '%s'\n",
func->old_name);
return -EINVAL;
}
ops = kzalloc(sizeof(*ops), GFP_KERNEL);
if (!ops)
return -ENOMEM;
@@ -352,7 +416,7 @@ static int klp_enable_func(struct klp_func *func)
INIT_LIST_HEAD(&ops->func_stack);
list_add_rcu(&func->stack_node, &ops->func_stack);
ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0);
ret = ftrace_set_filter_ip(&ops->fops, ftrace_loc, 0, 0);
if (ret) {
pr_err("failed to set ftrace filter for function '%s' (%d)\n",
func->old_name, ret);
@@ -363,7 +427,7 @@ static int klp_enable_func(struct klp_func *func)
if (ret) {
pr_err("failed to register ftrace handler for function '%s' (%d)\n",
func->old_name, ret);
ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0);
ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0);
goto err;
}
@@ -683,6 +747,9 @@ static void klp_free_patch(struct klp_patch *patch)
static int klp_init_func(struct klp_object *obj, struct klp_func *func)
{
if (!func->old_name || !func->new_func)
return -EINVAL;
INIT_LIST_HEAD(&func->stack_node);
func->state = KLP_DISABLED;
@@ -703,11 +770,9 @@ static int klp_init_object_loaded(struct klp_patch *patch,
struct klp_func *func;
int ret;
if (obj->relocs) {
ret = klp_write_object_relocations(patch->mod, obj);
if (ret)
return ret;
}
ret = klp_write_object_relocations(patch->mod, obj);
if (ret)
return ret;
klp_for_each_func(obj, func) {
ret = klp_find_object_symbol(obj->name, func->old_name,
@@ -842,12 +907,18 @@ int klp_register_patch(struct klp_patch *patch)
{
int ret;
if (!klp_initialized())
return -ENODEV;
if (!patch || !patch->mod)
return -EINVAL;
if (!is_livepatch_module(patch->mod)) {
pr_err("module %s is not marked as a livepatch module",
patch->mod->name);
return -EINVAL;
}
if (!klp_initialized())
return -ENODEV;
/*
* A reference is taken on the patch module to prevent it from being
* unloaded. Right now, we don't allow patch modules to unload since

125
kernel/module.c
View File

@@ -1973,6 +1973,83 @@ static void module_enable_nx(const struct module *mod) { }
static void module_disable_nx(const struct module *mod) { }
#endif
#ifdef CONFIG_LIVEPATCH
/*
* Persist Elf information about a module. Copy the Elf header,
* section header table, section string table, and symtab section
* index from info to mod->klp_info.
*/
static int copy_module_elf(struct module *mod, struct load_info *info)
{
unsigned int size, symndx;
int ret;
size = sizeof(*mod->klp_info);
mod->klp_info = kmalloc(size, GFP_KERNEL);
if (mod->klp_info == NULL)
return -ENOMEM;
/* Elf header */
size = sizeof(mod->klp_info->hdr);
memcpy(&mod->klp_info->hdr, info->hdr, size);
/* Elf section header table */
size = sizeof(*info->sechdrs) * info->hdr->e_shnum;
mod->klp_info->sechdrs = kmalloc(size, GFP_KERNEL);
if (mod->klp_info->sechdrs == NULL) {
ret = -ENOMEM;
goto free_info;
}
memcpy(mod->klp_info->sechdrs, info->sechdrs, size);
/* Elf section name string table */
size = info->sechdrs[info->hdr->e_shstrndx].sh_size;
mod->klp_info->secstrings = kmalloc(size, GFP_KERNEL);
if (mod->klp_info->secstrings == NULL) {
ret = -ENOMEM;
goto free_sechdrs;
}
memcpy(mod->klp_info->secstrings, info->secstrings, size);
/* Elf symbol section index */
symndx = info->index.sym;
mod->klp_info->symndx = symndx;
/*
* For livepatch modules, core_kallsyms.symtab is a complete
* copy of the original symbol table. Adjust sh_addr to point
* to core_kallsyms.symtab since the copy of the symtab in module
* init memory is freed at the end of do_init_module().
*/
mod->klp_info->sechdrs[symndx].sh_addr = \
(unsigned long) mod->core_kallsyms.symtab;
return 0;
free_sechdrs:
kfree(mod->klp_info->sechdrs);
free_info:
kfree(mod->klp_info);
return ret;
}
static void free_module_elf(struct module *mod)
{
kfree(mod->klp_info->sechdrs);
kfree(mod->klp_info->secstrings);
kfree(mod->klp_info);
}
#else /* !CONFIG_LIVEPATCH */
static int copy_module_elf(struct module *mod, struct load_info *info)
{
return 0;
}
static void free_module_elf(struct module *mod)
{
}
#endif /* CONFIG_LIVEPATCH */
void __weak module_memfree(void *module_region)
{
vfree(module_region);
@@ -2011,6 +2088,9 @@ static void free_module(struct module *mod)
/* Free any allocated parameters. */
destroy_params(mod->kp, mod->num_kp);
if (is_livepatch_module(mod))
free_module_elf(mod);
/* Now we can delete it from the lists */
mutex_lock(&module_mutex);
/* Unlink carefully: kallsyms could be walking list. */
@@ -2126,6 +2206,10 @@ static int simplify_symbols(struct module *mod, const struct load_info *info)
(long)sym[i].st_value);
break;
case SHN_LIVEPATCH:
/* Livepatch symbols are resolved by livepatch */
break;
case SHN_UNDEF:
ksym = resolve_symbol_wait(mod, info, name);
/* Ok if resolved. */
@@ -2174,6 +2258,10 @@ static int apply_relocations(struct module *mod, const struct load_info *info)
if (!(info->sechdrs[infosec].sh_flags & SHF_ALLOC))
continue;
/* Livepatch relocation sections are applied by livepatch */
if (info->sechdrs[i].sh_flags & SHF_RELA_LIVEPATCH)
continue;
if (info->sechdrs[i].sh_type == SHT_REL)
err = apply_relocate(info->sechdrs, info->strtab,
info->index.sym, i, mod);
@@ -2469,7 +2557,7 @@ static void layout_symtab(struct module *mod, struct load_info *info)
/* Compute total space required for the core symbols' strtab. */
for (ndst = i = 0; i < nsrc; i++) {
if (i == 0 ||
if (i == 0 || is_livepatch_module(mod) ||
is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum,
info->index.pcpu)) {
strtab_size += strlen(&info->strtab[src[i].st_name])+1;
@@ -2528,7 +2616,7 @@ static void add_kallsyms(struct module *mod, const struct load_info *info)
mod->core_kallsyms.strtab = s = mod->core_layout.base + info->stroffs;
src = mod->kallsyms->symtab;
for (ndst = i = 0; i < mod->kallsyms->num_symtab; i++) {
if (i == 0 ||
if (i == 0 || is_livepatch_module(mod) ||
is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum,
info->index.pcpu)) {
dst[ndst] = src[i];
@@ -2667,6 +2755,26 @@ static int copy_chunked_from_user(void *dst, const void __user *usrc, unsigned l
return 0;
}
#ifdef CONFIG_LIVEPATCH
static int find_livepatch_modinfo(struct module *mod, struct load_info *info)
{
mod->klp = get_modinfo(info, "livepatch") ? true : false;
return 0;
}
#else /* !CONFIG_LIVEPATCH */
static int find_livepatch_modinfo(struct module *mod, struct load_info *info)
{
if (get_modinfo(info, "livepatch")) {
pr_err("%s: module is marked as livepatch module, but livepatch support is disabled",
mod->name);
return -ENOEXEC;
}
return 0;
}
#endif /* CONFIG_LIVEPATCH */
/* Sets info->hdr and info->len. */
static int copy_module_from_user(const void __user *umod, unsigned long len,
struct load_info *info)
@@ -2821,6 +2929,10 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
"is unknown, you have been warned.\n", mod->name);
}
err = find_livepatch_modinfo(mod, info);
if (err)
return err;
/* Set up license info based on the info section */
set_license(mod, get_modinfo(info, "license"));
@@ -3494,6 +3606,12 @@ static int load_module(struct load_info *info, const char __user *uargs,
if (err < 0)
goto coming_cleanup;
if (is_livepatch_module(mod)) {
err = copy_module_elf(mod, info);
if (err < 0)
goto sysfs_cleanup;
}
/* Get rid of temporary copy. */
free_copy(info);
@@ -3502,11 +3620,12 @@ static int load_module(struct load_info *info, const char __user *uargs,
return do_init_module(mod);
sysfs_cleanup:
mod_sysfs_teardown(mod);
coming_cleanup:
blocking_notifier_call_chain(&module_notify_list,
MODULE_STATE_GOING, mod);
klp_module_going(mod);
bug_cleanup:
/* module_bug_cleanup needs module_mutex protection */
mutex_lock(&module_mutex);

14
kernel/trace/ftrace.c
View File

@@ -1530,7 +1530,19 @@ static int ftrace_cmp_recs(const void *a, const void *b)
return 0;
}
static unsigned long ftrace_location_range(unsigned long start, unsigned long end)
/**
* ftrace_location_range - return the first address of a traced location
* if it touches the given ip range
* @start: start of range to search.
* @end: end of range to search (inclusive). @end points to the last byte
* to check.
*
* Returns rec->ip if the related ftrace location is a least partly within
* the given address range. That is, the first address of the instruction
* that is either a NOP or call to the function tracer. It checks the ftrace
* internal tables to determine if the address belongs or not.
*/
unsigned long ftrace_location_range(unsigned long start, unsigned long end)
{
struct ftrace_page *pg;
struct dyn_ftrace *rec;