557 lines
13 KiB
C
557 lines
13 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/init.h>
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#include <linux/static_call.h>
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#include <linux/bug.h>
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#include <linux/smp.h>
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#include <linux/sort.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/cpu.h>
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#include <linux/processor.h>
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#include <asm/sections.h>
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extern struct static_call_site __start_static_call_sites[],
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__stop_static_call_sites[];
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extern struct static_call_tramp_key __start_static_call_tramp_key[],
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__stop_static_call_tramp_key[];
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static int static_call_initialized;
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/*
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* Must be called before early_initcall() to be effective.
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*/
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void static_call_force_reinit(void)
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{
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if (WARN_ON_ONCE(!static_call_initialized))
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return;
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static_call_initialized++;
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}
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/* mutex to protect key modules/sites */
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static DEFINE_MUTEX(static_call_mutex);
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static void static_call_lock(void)
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{
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mutex_lock(&static_call_mutex);
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}
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static void static_call_unlock(void)
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{
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mutex_unlock(&static_call_mutex);
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}
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static inline void *static_call_addr(struct static_call_site *site)
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{
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return (void *)((long)site->addr + (long)&site->addr);
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}
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static inline unsigned long __static_call_key(const struct static_call_site *site)
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{
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return (long)site->key + (long)&site->key;
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}
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static inline struct static_call_key *static_call_key(const struct static_call_site *site)
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{
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return (void *)(__static_call_key(site) & ~STATIC_CALL_SITE_FLAGS);
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}
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/* These assume the key is word-aligned. */
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static inline bool static_call_is_init(struct static_call_site *site)
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{
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return __static_call_key(site) & STATIC_CALL_SITE_INIT;
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}
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static inline bool static_call_is_tail(struct static_call_site *site)
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{
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return __static_call_key(site) & STATIC_CALL_SITE_TAIL;
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}
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static inline void static_call_set_init(struct static_call_site *site)
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{
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site->key = (__static_call_key(site) | STATIC_CALL_SITE_INIT) -
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(long)&site->key;
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}
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static int static_call_site_cmp(const void *_a, const void *_b)
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{
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const struct static_call_site *a = _a;
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const struct static_call_site *b = _b;
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const struct static_call_key *key_a = static_call_key(a);
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const struct static_call_key *key_b = static_call_key(b);
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if (key_a < key_b)
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return -1;
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if (key_a > key_b)
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return 1;
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return 0;
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}
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static void static_call_site_swap(void *_a, void *_b, int size)
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{
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long delta = (unsigned long)_a - (unsigned long)_b;
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struct static_call_site *a = _a;
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struct static_call_site *b = _b;
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struct static_call_site tmp = *a;
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a->addr = b->addr - delta;
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a->key = b->key - delta;
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b->addr = tmp.addr + delta;
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b->key = tmp.key + delta;
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}
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static inline void static_call_sort_entries(struct static_call_site *start,
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struct static_call_site *stop)
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{
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sort(start, stop - start, sizeof(struct static_call_site),
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static_call_site_cmp, static_call_site_swap);
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}
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static inline bool static_call_key_has_mods(struct static_call_key *key)
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{
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return !(key->type & 1);
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}
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static inline struct static_call_mod *static_call_key_next(struct static_call_key *key)
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{
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if (!static_call_key_has_mods(key))
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return NULL;
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return key->mods;
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}
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static inline struct static_call_site *static_call_key_sites(struct static_call_key *key)
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{
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if (static_call_key_has_mods(key))
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return NULL;
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return (struct static_call_site *)(key->type & ~1);
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}
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void __static_call_update(struct static_call_key *key, void *tramp, void *func)
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{
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struct static_call_site *site, *stop;
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struct static_call_mod *site_mod, first;
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cpus_read_lock();
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static_call_lock();
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if (key->func == func)
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goto done;
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key->func = func;
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arch_static_call_transform(NULL, tramp, func, false);
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/*
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* If uninitialized, we'll not update the callsites, but they still
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* point to the trampoline and we just patched that.
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*/
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if (WARN_ON_ONCE(!static_call_initialized))
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goto done;
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first = (struct static_call_mod){
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.next = static_call_key_next(key),
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.mod = NULL,
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.sites = static_call_key_sites(key),
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};
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for (site_mod = &first; site_mod; site_mod = site_mod->next) {
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bool init = system_state < SYSTEM_RUNNING;
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struct module *mod = site_mod->mod;
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if (!site_mod->sites) {
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/*
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* This can happen if the static call key is defined in
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* a module which doesn't use it.
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*
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* It also happens in the has_mods case, where the
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* 'first' entry has no sites associated with it.
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*/
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continue;
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}
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stop = __stop_static_call_sites;
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if (mod) {
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#ifdef CONFIG_MODULES
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stop = mod->static_call_sites +
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mod->num_static_call_sites;
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init = mod->state == MODULE_STATE_COMING;
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#endif
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}
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for (site = site_mod->sites;
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site < stop && static_call_key(site) == key; site++) {
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void *site_addr = static_call_addr(site);
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if (!init && static_call_is_init(site))
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continue;
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if (!kernel_text_address((unsigned long)site_addr)) {
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/*
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* This skips patching built-in __exit, which
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* is part of init_section_contains() but is
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* not part of kernel_text_address().
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*
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* Skipping built-in __exit is fine since it
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* will never be executed.
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*/
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WARN_ONCE(!static_call_is_init(site),
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"can't patch static call site at %pS",
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site_addr);
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continue;
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}
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arch_static_call_transform(site_addr, NULL, func,
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static_call_is_tail(site));
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}
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}
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done:
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static_call_unlock();
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cpus_read_unlock();
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}
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EXPORT_SYMBOL_GPL(__static_call_update);
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static int __static_call_init(struct module *mod,
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struct static_call_site *start,
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struct static_call_site *stop)
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{
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struct static_call_site *site;
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struct static_call_key *key, *prev_key = NULL;
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struct static_call_mod *site_mod;
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if (start == stop)
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return 0;
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static_call_sort_entries(start, stop);
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for (site = start; site < stop; site++) {
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void *site_addr = static_call_addr(site);
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if ((mod && within_module_init((unsigned long)site_addr, mod)) ||
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(!mod && init_section_contains(site_addr, 1)))
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static_call_set_init(site);
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key = static_call_key(site);
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if (key != prev_key) {
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prev_key = key;
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/*
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* For vmlinux (!mod) avoid the allocation by storing
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* the sites pointer in the key itself. Also see
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* __static_call_update()'s @first.
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*
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* This allows architectures (eg. x86) to call
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* static_call_init() before memory allocation works.
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*/
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if (!mod) {
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key->sites = site;
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key->type |= 1;
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goto do_transform;
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}
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site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
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if (!site_mod)
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return -ENOMEM;
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/*
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* When the key has a direct sites pointer, extract
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* that into an explicit struct static_call_mod, so we
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* can have a list of modules.
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*/
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if (static_call_key_sites(key)) {
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site_mod->mod = NULL;
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site_mod->next = NULL;
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site_mod->sites = static_call_key_sites(key);
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key->mods = site_mod;
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site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
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if (!site_mod)
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return -ENOMEM;
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}
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site_mod->mod = mod;
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site_mod->sites = site;
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site_mod->next = static_call_key_next(key);
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key->mods = site_mod;
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}
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do_transform:
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arch_static_call_transform(site_addr, NULL, key->func,
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static_call_is_tail(site));
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}
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return 0;
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}
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static int addr_conflict(struct static_call_site *site, void *start, void *end)
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{
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unsigned long addr = (unsigned long)static_call_addr(site);
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if (addr <= (unsigned long)end &&
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addr + CALL_INSN_SIZE > (unsigned long)start)
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return 1;
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return 0;
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}
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static int __static_call_text_reserved(struct static_call_site *iter_start,
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struct static_call_site *iter_stop,
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void *start, void *end, bool init)
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{
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struct static_call_site *iter = iter_start;
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while (iter < iter_stop) {
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if (init || !static_call_is_init(iter)) {
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if (addr_conflict(iter, start, end))
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return 1;
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}
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iter++;
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}
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return 0;
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}
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#ifdef CONFIG_MODULES
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static int __static_call_mod_text_reserved(void *start, void *end)
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{
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struct module *mod;
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int ret;
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preempt_disable();
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mod = __module_text_address((unsigned long)start);
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WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
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if (!try_module_get(mod))
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mod = NULL;
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preempt_enable();
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if (!mod)
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return 0;
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ret = __static_call_text_reserved(mod->static_call_sites,
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mod->static_call_sites + mod->num_static_call_sites,
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start, end, mod->state == MODULE_STATE_COMING);
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module_put(mod);
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return ret;
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}
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static unsigned long tramp_key_lookup(unsigned long addr)
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{
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struct static_call_tramp_key *start = __start_static_call_tramp_key;
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struct static_call_tramp_key *stop = __stop_static_call_tramp_key;
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struct static_call_tramp_key *tramp_key;
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for (tramp_key = start; tramp_key != stop; tramp_key++) {
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unsigned long tramp;
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tramp = (long)tramp_key->tramp + (long)&tramp_key->tramp;
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if (tramp == addr)
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return (long)tramp_key->key + (long)&tramp_key->key;
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}
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return 0;
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}
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static int static_call_add_module(struct module *mod)
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{
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struct static_call_site *start = mod->static_call_sites;
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struct static_call_site *stop = start + mod->num_static_call_sites;
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struct static_call_site *site;
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for (site = start; site != stop; site++) {
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unsigned long s_key = __static_call_key(site);
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unsigned long addr = s_key & ~STATIC_CALL_SITE_FLAGS;
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unsigned long key;
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/*
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* Is the key is exported, 'addr' points to the key, which
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* means modules are allowed to call static_call_update() on
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* it.
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*
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* Otherwise, the key isn't exported, and 'addr' points to the
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* trampoline so we need to lookup the key.
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*
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* We go through this dance to prevent crazy modules from
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* abusing sensitive static calls.
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*/
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if (!kernel_text_address(addr))
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continue;
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key = tramp_key_lookup(addr);
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if (!key) {
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pr_warn("Failed to fixup __raw_static_call() usage at: %ps\n",
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static_call_addr(site));
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return -EINVAL;
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}
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key |= s_key & STATIC_CALL_SITE_FLAGS;
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site->key = key - (long)&site->key;
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}
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return __static_call_init(mod, start, stop);
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}
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static void static_call_del_module(struct module *mod)
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{
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struct static_call_site *start = mod->static_call_sites;
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struct static_call_site *stop = mod->static_call_sites +
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mod->num_static_call_sites;
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struct static_call_key *key, *prev_key = NULL;
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struct static_call_mod *site_mod, **prev;
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struct static_call_site *site;
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for (site = start; site < stop; site++) {
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key = static_call_key(site);
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if (key == prev_key)
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continue;
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prev_key = key;
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for (prev = &key->mods, site_mod = key->mods;
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site_mod && site_mod->mod != mod;
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prev = &site_mod->next, site_mod = site_mod->next)
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;
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if (!site_mod)
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continue;
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*prev = site_mod->next;
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kfree(site_mod);
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}
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}
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static int static_call_module_notify(struct notifier_block *nb,
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unsigned long val, void *data)
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{
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struct module *mod = data;
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int ret = 0;
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cpus_read_lock();
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static_call_lock();
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switch (val) {
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case MODULE_STATE_COMING:
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ret = static_call_add_module(mod);
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if (ret) {
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WARN(1, "Failed to allocate memory for static calls");
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static_call_del_module(mod);
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}
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break;
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case MODULE_STATE_GOING:
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static_call_del_module(mod);
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break;
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}
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static_call_unlock();
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cpus_read_unlock();
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return notifier_from_errno(ret);
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}
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static struct notifier_block static_call_module_nb = {
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.notifier_call = static_call_module_notify,
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};
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#else
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static inline int __static_call_mod_text_reserved(void *start, void *end)
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{
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return 0;
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}
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#endif /* CONFIG_MODULES */
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int static_call_text_reserved(void *start, void *end)
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{
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bool init = system_state < SYSTEM_RUNNING;
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int ret = __static_call_text_reserved(__start_static_call_sites,
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__stop_static_call_sites, start, end, init);
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if (ret)
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return ret;
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return __static_call_mod_text_reserved(start, end);
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}
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int __init static_call_init(void)
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{
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int ret;
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/* See static_call_force_reinit(). */
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if (static_call_initialized == 1)
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return 0;
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cpus_read_lock();
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static_call_lock();
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ret = __static_call_init(NULL, __start_static_call_sites,
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__stop_static_call_sites);
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static_call_unlock();
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cpus_read_unlock();
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if (ret) {
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pr_err("Failed to allocate memory for static_call!\n");
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BUG();
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}
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#ifdef CONFIG_MODULES
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if (!static_call_initialized)
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register_module_notifier(&static_call_module_nb);
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#endif
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static_call_initialized = 1;
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return 0;
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}
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early_initcall(static_call_init);
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#ifdef CONFIG_STATIC_CALL_SELFTEST
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static int func_a(int x)
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{
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return x+1;
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}
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static int func_b(int x)
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{
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return x+2;
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}
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DEFINE_STATIC_CALL(sc_selftest, func_a);
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static struct static_call_data {
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int (*func)(int);
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int val;
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int expect;
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} static_call_data [] __initdata = {
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{ NULL, 2, 3 },
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{ func_b, 2, 4 },
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{ func_a, 2, 3 }
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};
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static int __init test_static_call_init(void)
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{
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int i;
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for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) {
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struct static_call_data *scd = &static_call_data[i];
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if (scd->func)
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static_call_update(sc_selftest, scd->func);
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WARN_ON(static_call(sc_selftest)(scd->val) != scd->expect);
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}
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return 0;
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}
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early_initcall(test_static_call_init);
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#endif /* CONFIG_STATIC_CALL_SELFTEST */
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