[PATCH 5.16 285/285] static_call: Dont make __static_call_return0 static

Greg Kroah-Hartman
2022-04-12T08:25:56Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>

commit 8fd4ddda2f49a66bf5dd3d0c01966c4b1971308b upstream.

System.map shows that vmlinux contains several instances of
__static_call_return0():

c0004fc0 t __static_call_return0
c0011518 t __static_call_return0
c00d8160 t __static_call_return0

arch_static_call_transform() uses the middle one to check whether we are
setting a call to __static_call_return0 or not:

c0011520 <arch_static_call_transform>:
c0011520: 3d 20 c0 01 lis r9,-16383 <== r9 = 0xc001 << 16
c0011524: 39 29 15 18 addi r9,r9,5400 <== r9 += 0x1518
c0011528: 7c 05 48 00 cmpw r5,r9 <== r9 has value 0xc0011518 here

So if static_call_update() is called with one of the other instances of
__static_call_return0(), arch_static_call_transform() won't recognise it.

In order to work properly, global single instance of __static_call_return0() is required.

Fixes: 3f2a8fc4b15d ("static_call/x86: Add __static_call_return0()")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/30821468a0e7d28251954b578e5051dc09300d04.1647258493.git.christophe.leroy@csgroup.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/static_call.h | 5
kernel/Makefile | 3
kernel/static_call.c | 542 -------------------------------------------
kernel/static_call_inline.c | 543 ++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 547 insertions(+), 546 deletions(-)
create mode 100644 kernel/static_call_inline.c

--- a/include/linux/static_call.h
+++ b/include/linux/static_call.h
@@ -248,10 +248,7 @@ static inline int static_call_text_reser
return 0;
}

-static inline long __static_call_return0(void)
-{
- return 0;
-}
+extern long __static_call_return0(void);

#define EXPORT_STATIC_CALL(name) \
EXPORT_SYMBOL(STATIC_CALL_KEY(name)); \
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -112,7 +112,8 @@ obj-$(CONFIG_CPU_PM) += cpu_pm.o
obj-$(CONFIG_BPF) += bpf/
obj-$(CONFIG_KCSAN) += kcsan/
obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o
-obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call.o
+obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o
+obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call_inline.o
obj-$(CONFIG_CFI_CLANG) += cfi.o

obj-$(CONFIG_PERF_EVENTS) += events/
--- a/kernel/static_call.c
+++ b/kernel/static_call.c
@@ -1,548 +1,8 @@
// SPDX-License-Identifier: GPL-2.0
-#include <linux/init.h>
#include <linux/static_call.h>
-#include <linux/bug.h>
-#include <linux/smp.h>
-#include <linux/sort.h>
-#include <linux/slab.h>
-#include <linux/module.h>
-#include <linux/cpu.h>
-#include <linux/processor.h>
-#include <asm/sections.h>
-
-extern struct static_call_site __start_static_call_sites[],
- __stop_static_call_sites[];
-extern struct static_call_tramp_key __start_static_call_tramp_key[],
- __stop_static_call_tramp_key[];
-
-static bool static_call_initialized;
-
-/* mutex to protect key modules/sites */
-static DEFINE_MUTEX(static_call_mutex);
-
-static void static_call_lock(void)
-{
- mutex_lock(&static_call_mutex);
-}
-
-static void static_call_unlock(void)
-{
- mutex_unlock(&static_call_mutex);
-}
-
-static inline void *static_call_addr(struct static_call_site *site)
-{
- return (void *)((long)site->addr + (long)&site->addr);
-}
-
-static inline unsigned long __static_call_key(const struct static_call_site *site)
-{
- return (long)site->key + (long)&site->key;
-}
-
-static inline struct static_call_key *static_call_key(const struct static_call_site *site)
-{
- return (void *)(__static_call_key(site) & ~STATIC_CALL_SITE_FLAGS);
-}
-
-/* These assume the key is word-aligned. */
-static inline bool static_call_is_init(struct static_call_site *site)
-{
- return __static_call_key(site) & STATIC_CALL_SITE_INIT;
-}
-
-static inline bool static_call_is_tail(struct static_call_site *site)
-{
- return __static_call_key(site) & STATIC_CALL_SITE_TAIL;
-}
-
-static inline void static_call_set_init(struct static_call_site *site)
-{
- site->key = (__static_call_key(site) | STATIC_CALL_SITE_INIT) -
- (long)&site->key;
-}
-
-static int static_call_site_cmp(const void *_a, const void *_b)
-{
- const struct static_call_site *a = _a;
- const struct static_call_site *b = _b;
- const struct static_call_key *key_a = static_call_key(a);
- const struct static_call_key *key_b = static_call_key(b);
-
- if (key_a < key_b)
- return -1;
-
- if (key_a > key_b)
- return 1;
-
- return 0;
-}
-
-static void static_call_site_swap(void *_a, void *_b, int size)
-{
- long delta = (unsigned long)_a - (unsigned long)_b;
- struct static_call_site *a = _a;
- struct static_call_site *b = _b;
- struct static_call_site tmp = *a;
-
- a->addr = b->addr - delta;
- a->key = b->key - delta;
-
- b->addr = tmp.addr + delta;
- b->key = tmp.key + delta;
-}
-
-static inline void static_call_sort_entries(struct static_call_site *start,
- struct static_call_site *stop)
-{
- sort(start, stop - start, sizeof(struct static_call_site),
- static_call_site_cmp, static_call_site_swap);
-}
-
-static inline bool static_call_key_has_mods(struct static_call_key *key)
-{
- return !(key->type & 1);
-}
-
-static inline struct static_call_mod *static_call_key_next(struct static_call_key *key)
-{
- if (!static_call_key_has_mods(key))
- return NULL;
-
- return key->mods;
-}
-
-static inline struct static_call_site *static_call_key_sites(struct static_call_key *key)
-{
- if (static_call_key_has_mods(key))
- return NULL;
-
- return (struct static_call_site *)(key->type & ~1);
-}
-
-void __static_call_update(struct static_call_key *key, void *tramp, void *func)
-{
- struct static_call_site *site, *stop;
- struct static_call_mod *site_mod, first;
-
- cpus_read_lock();
- static_call_lock();
-
- if (key->func == func)
- goto done;
-
- key->func = func;
-
- arch_static_call_transform(NULL, tramp, func, false);
-
- /*
- * If uninitialized, we'll not update the callsites, but they still
- * point to the trampoline and we just patched that.
- */
- if (WARN_ON_ONCE(!static_call_initialized))
- goto done;
-
- first = (struct static_call_mod){
- .next = static_call_key_next(key),
- .mod = NULL,
- .sites = static_call_key_sites(key),
- };
-
- for (site_mod = &first; site_mod; site_mod = site_mod->next) {
- bool init = system_state < SYSTEM_RUNNING;
- struct module *mod = site_mod->mod;
-
- if (!site_mod->sites) {
- /*
- * This can happen if the static call key is defined in
- * a module which doesn't use it.
- *
- * It also happens in the has_mods case, where the
- * 'first' entry has no sites associated with it.
- */
- continue;
- }
-
- stop = __stop_static_call_sites;
-
- if (mod) {
-#ifdef CONFIG_MODULES
- stop = mod->static_call_sites +
- mod->num_static_call_sites;
- init = mod->state == MODULE_STATE_COMING;
-#endif
- }
-
- for (site = site_mod->sites;
- site < stop && static_call_key(site) == key; site++) {
- void *site_addr = static_call_addr(site);
-
- if (!init && static_call_is_init(site))
- continue;
-
- if (!kernel_text_address((unsigned long)site_addr)) {
- /*
- * This skips patching built-in __exit, which
- * is part of init_section_contains() but is
- * not part of kernel_text_address().
- *
- * Skipping built-in __exit is fine since it
- * will never be executed.
- */
- WARN_ONCE(!static_call_is_init(site),
- "can't patch static call site at %pS",
- site_addr);
- continue;
- }
-
- arch_static_call_transform(site_addr, NULL, func,
- static_call_is_tail(site));
- }
- }
-
-done:
- static_call_unlock();
- cpus_read_unlock();
-}
-EXPORT_SYMBOL_GPL(__static_call_update);
-
-static int __static_call_init(struct module *mod,
- struct static_call_site *start,
- struct static_call_site *stop)
-{
- struct static_call_site *site;
- struct static_call_key *key, *prev_key = NULL;
- struct static_call_mod *site_mod;
-
- if (start == stop)
- return 0;
-
- static_call_sort_entries(start, stop);
-
- for (site = start; site < stop; site++) {
- void *site_addr = static_call_addr(site);
-
- if ((mod && within_module_init((unsigned long)site_addr, mod)) ||
- (!mod && init_section_contains(site_addr, 1)))
- static_call_set_init(site);
-
- key = static_call_key(site);
- if (key != prev_key) {
- prev_key = key;
-
- /*
- * For vmlinux (!mod) avoid the allocation by storing
- * the sites pointer in the key itself. Also see
- * __static_call_update()'s @first.
- *
- * This allows architectures (eg. x86) to call
- * static_call_init() before memory allocation works.
- */
- if (!mod) {
- key->sites = site;
- key->type |= 1;
- goto do_transform;
- }
-
- site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
- if (!site_mod)
- return -ENOMEM;
-
- /*
- * When the key has a direct sites pointer, extract
- * that into an explicit struct static_call_mod, so we
- * can have a list of modules.
- */
- if (static_call_key_sites(key)) {
- site_mod->mod = NULL;
- site_mod->next = NULL;
- site_mod->sites = static_call_key_sites(key);
-
- key->mods = site_mod;
-
- site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
- if (!site_mod)
- return -ENOMEM;
- }
-
- site_mod->mod = mod;
- site_mod->sites = site;
- site_mod->next = static_call_key_next(key);
- key->mods = site_mod;
- }
-
-do_transform:
- arch_static_call_transform(site_addr, NULL, key->func,
- static_call_is_tail(site));
- }
-
- return 0;
-}
-
-static int addr_conflict(struct static_call_site *site, void *start, void *end)
-{
- unsigned long addr = (unsigned long)static_call_addr(site);
-
- if (addr <= (unsigned long)end &&
- addr + CALL_INSN_SIZE > (unsigned long)start)
- return 1;
-
- return 0;
-}
-
-static int __static_call_text_reserved(struct static_call_site *iter_start,
- struct static_call_site *iter_stop,
- void *start, void *end, bool init)
-{
- struct static_call_site *iter = iter_start;
-
- while (iter < iter_stop) {
- if (init || !static_call_is_init(iter)) {
- if (addr_conflict(iter, start, end))
- return 1;
- }
- iter++;
- }
-
- return 0;
-}
-
-#ifdef CONFIG_MODULES
-
-static int __static_call_mod_text_reserved(void *start, void *end)
-{
- struct module *mod;
- int ret;
-
- preempt_disable();
- mod = __module_text_address((unsigned long)start);
- WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
- if (!try_module_get(mod))
- mod = NULL;
- preempt_enable();
-
- if (!mod)
- return 0;
-
- ret = __static_call_text_reserved(mod->static_call_sites,
- mod->static_call_sites + mod->num_static_call_sites,
- start, end, mod->state == MODULE_STATE_COMING);
-
- module_put(mod);
-
- return ret;
-}
-
-static unsigned long tramp_key_lookup(unsigned long addr)
-{
- struct static_call_tramp_key *start = __start_static_call_tramp_key;
- struct static_call_tramp_key *stop = __stop_static_call_tramp_key;
- struct static_call_tramp_key *tramp_key;
-
- for (tramp_key = start; tramp_key != stop; tramp_key++) {
- unsigned long tramp;
-
- tramp = (long)tramp_key->tramp + (long)&tramp_key->tramp;
- if (tramp == addr)
- return (long)tramp_key->key + (long)&tramp_key->key;
- }
-
- return 0;
-}
-
-static int static_call_add_module(struct module *mod)
-{
- struct static_call_site *start = mod->static_call_sites;
- struct static_call_site *stop = start + mod->num_static_call_sites;
- struct static_call_site *site;
-
- for (site = start; site != stop; site++) {
- unsigned long s_key = __static_call_key(site);
- unsigned long addr = s_key & ~STATIC_CALL_SITE_FLAGS;
- unsigned long key;
-
- /*
- * Is the key is exported, 'addr' points to the key, which
- * means modules are allowed to call static_call_update() on
- * it.
- *
- * Otherwise, the key isn't exported, and 'addr' points to the
- * trampoline so we need to lookup the key.
- *
- * We go through this dance to prevent crazy modules from
- * abusing sensitive static calls.
- */
- if (!kernel_text_address(addr))
- continue;
-
- key = tramp_key_lookup(addr);
- if (!key) {
- pr_warn("Failed to fixup __raw_static_call() usage at: %ps\n",
- static_call_addr(site));
- return -EINVAL;
- }
-
- key |= s_key & STATIC_CALL_SITE_FLAGS;
- site->key = key - (long)&site->key;
- }
-
- return __static_call_init(mod, start, stop);
-}
-
-static void static_call_del_module(struct module *mod)
-{
- struct static_call_site *start = mod->static_call_sites;
- struct static_call_site *stop = mod->static_call_sites +
- mod->num_static_call_sites;
- struct static_call_key *key, *prev_key = NULL;
- struct static_call_mod *site_mod, **prev;
- struct static_call_site *site;
-
- for (site = start; site < stop; site++) {
- key = static_call_key(site);
- if (key == prev_key)
- continue;
-
- prev_key = key;
-
- for (prev = &key->mods, site_mod = key->mods;
- site_mod && site_mod->mod != mod;
- prev = &site_mod->next, site_mod = site_mod->next)
- ;
-
- if (!site_mod)
- continue;
-
- *prev = site_mod->next;
- kfree(site_mod);
- }
-}
-
-static int static_call_module_notify(struct notifier_block *nb,
- unsigned long val, void *data)
-{
- struct module *mod = data;
- int ret = 0;
-
- cpus_read_lock();
- static_call_lock();
-
- switch (val) {
- case MODULE_STATE_COMING:
- ret = static_call_add_module(mod);
- if (ret) {
- WARN(1, "Failed to allocate memory for static calls");
- static_call_del_module(mod);
- }
- break;
- case MODULE_STATE_GOING:
- static_call_del_module(mod);
- break;
- }
-
- static_call_unlock();
- cpus_read_unlock();
-
- return notifier_from_errno(ret);
-}
-
-static struct notifier_block static_call_module_nb = {
- .notifier_call = static_call_module_notify,
-};
-
-#else
-
-static inline int __static_call_mod_text_reserved(void *start, void *end)
-{
- return 0;
-}
-
-#endif /* CONFIG_MODULES */
-
-int static_call_text_reserved(void *start, void *end)
-{
- bool init = system_state < SYSTEM_RUNNING;
- int ret = __static_call_text_reserved(__start_static_call_sites,
- __stop_static_call_sites, start, end, init);
-
- if (ret)
- return ret;
-
- return __static_call_mod_text_reserved(start, end);
-}
-
-int __init static_call_init(void)
-{
- int ret;
-
- if (static_call_initialized)
- return 0;
-
- cpus_read_lock();
- static_call_lock();
- ret = __static_call_init(NULL, __start_static_call_sites,
- __stop_static_call_sites);
- static_call_unlock();
- cpus_read_unlock();
-
- if (ret) {
- pr_err("Failed to allocate memory for static_call!\n");
- BUG();
- }
-
- static_call_initialized = true;
-
-#ifdef CONFIG_MODULES
- register_module_notifier(&static_call_module_nb);
-#endif
- return 0;
-}
-early_initcall(static_call_init);

long __static_call_return0(void)
{
return 0;
}
-
-#ifdef CONFIG_STATIC_CALL_SELFTEST
-
-static int func_a(int x)
-{
- return x+1;
-}
-
-static int func_b(int x)
-{
- return x+2;
-}
-
-DEFINE_STATIC_CALL(sc_selftest, func_a);
-
-static struct static_call_data {
- int (*func)(int);
- int val;
- int expect;
-} static_call_data [] __initdata = {
- { NULL, 2, 3 },
- { func_b, 2, 4 },
- { func_a, 2, 3 }
-};
-
-static int __init test_static_call_init(void)
-{
- int i;
-
- for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) {
- struct static_call_data *scd = &static_call_data[i];
-
- if (scd->func)
- static_call_update(sc_selftest, scd->func);
-
- WARN_ON(static_call(sc_selftest)(scd->val) != scd->expect);
- }
-
- return 0;
-}
-early_initcall(test_static_call_init);
-
-#endif /* CONFIG_STATIC_CALL_SELFTEST */
+EXPORT_SYMBOL_GPL(__static_call_return0);
--- /dev/null
+++ b/kernel/static_call_inline.c
@@ -0,0 +1,543 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/static_call.h>
+#include <linux/bug.h>
+#include <linux/smp.h>
+#include <linux/sort.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/cpu.h>
+#include <linux/processor.h>
+#include <asm/sections.h>
+
+extern struct static_call_site __start_static_call_sites[],
+ __stop_static_call_sites[];
+extern struct static_call_tramp_key __start_static_call_tramp_key[],
+ __stop_static_call_tramp_key[];
+
+static bool static_call_initialized;
+
+/* mutex to protect key modules/sites */
+static DEFINE_MUTEX(static_call_mutex);
+
+static void static_call_lock(void)
+{
+ mutex_lock(&static_call_mutex);
+}
+
+static void static_call_unlock(void)
+{
+ mutex_unlock(&static_call_mutex);
+}
+
+static inline void *static_call_addr(struct static_call_site *site)
+{
+ return (void *)((long)site->addr + (long)&site->addr);
+}
+
+static inline unsigned long __static_call_key(const struct static_call_site *site)
+{
+ return (long)site->key + (long)&site->key;
+}
+
+static inline struct static_call_key *static_call_key(const struct static_call_site *site)
+{
+ return (void *)(__static_call_key(site) & ~STATIC_CALL_SITE_FLAGS);
+}
+
+/* These assume the key is word-aligned. */
+static inline bool static_call_is_init(struct static_call_site *site)
+{
+ return __static_call_key(site) & STATIC_CALL_SITE_INIT;
+}
+
+static inline bool static_call_is_tail(struct static_call_site *site)
+{
+ return __static_call_key(site) & STATIC_CALL_SITE_TAIL;
+}
+
+static inline void static_call_set_init(struct static_call_site *site)
+{
+ site->key = (__static_call_key(site) | STATIC_CALL_SITE_INIT) -
+ (long)&site->key;
+}
+
+static int static_call_site_cmp(const void *_a, const void *_b)
+{
+ const struct static_call_site *a = _a;
+ const struct static_call_site *b = _b;
+ const struct static_call_key *key_a = static_call_key(a);
+ const struct static_call_key *key_b = static_call_key(b);
+
+ if (key_a < key_b)
+ return -1;
+
+ if (key_a > key_b)
+ return 1;
+
+ return 0;
+}
+
+static void static_call_site_swap(void *_a, void *_b, int size)
+{
+ long delta = (unsigned long)_a - (unsigned long)_b;
+ struct static_call_site *a = _a;
+ struct static_call_site *b = _b;
+ struct static_call_site tmp = *a;
+
+ a->addr = b->addr - delta;
+ a->key = b->key - delta;
+
+ b->addr = tmp.addr + delta;
+ b->key = tmp.key + delta;
+}
+
+static inline void static_call_sort_entries(struct static_call_site *start,
+ struct static_call_site *stop)
+{
+ sort(start, stop - start, sizeof(struct static_call_site),
+ static_call_site_cmp, static_call_site_swap);
+}
+
+static inline bool static_call_key_has_mods(struct static_call_key *key)
+{
+ return !(key->type & 1);
+}
+
+static inline struct static_call_mod *static_call_key_next(struct static_call_key *key)
+{
+ if (!static_call_key_has_mods(key))
+ return NULL;
+
+ return key->mods;
+}
+
+static inline struct static_call_site *static_call_key_sites(struct static_call_key *key)
+{
+ if (static_call_key_has_mods(key))
+ return NULL;
+
+ return (struct static_call_site *)(key->type & ~1);
+}
+
+void __static_call_update(struct static_call_key *key, void *tramp, void *func)
+{
+ struct static_call_site *site, *stop;
+ struct static_call_mod *site_mod, first;
+
+ cpus_read_lock();
+ static_call_lock();
+
+ if (key->func == func)
+ goto done;
+
+ key->func = func;
+
+ arch_static_call_transform(NULL, tramp, func, false);
+
+ /*
+ * If uninitialized, we'll not update the callsites, but they still
+ * point to the trampoline and we just patched that.
+ */
+ if (WARN_ON_ONCE(!static_call_initialized))
+ goto done;
+
+ first = (struct static_call_mod){
+ .next = static_call_key_next(key),
+ .mod = NULL,
+ .sites = static_call_key_sites(key),
+ };
+
+ for (site_mod = &first; site_mod; site_mod = site_mod->next) {
+ bool init = system_state < SYSTEM_RUNNING;
+ struct module *mod = site_mod->mod;
+
+ if (!site_mod->sites) {
+ /*
+ * This can happen if the static call key is defined in
+ * a module which doesn't use it.
+ *
+ * It also happens in the has_mods case, where the
+ * 'first' entry has no sites associated with it.
+ */
+ continue;
+ }
+
+ stop = __stop_static_call_sites;
+
+ if (mod) {
+#ifdef CONFIG_MODULES
+ stop = mod->static_call_sites +
+ mod->num_static_call_sites;
+ init = mod->state == MODULE_STATE_COMING;
+#endif
+ }
+
+ for (site = site_mod->sites;
+ site < stop && static_call_key(site) == key; site++) {
+ void *site_addr = static_call_addr(site);
+
+ if (!init && static_call_is_init(site))
+ continue;
+
+ if (!kernel_text_address((unsigned long)site_addr)) {
+ /*
+ * This skips patching built-in __exit, which
+ * is part of init_section_contains() but is
+ * not part of kernel_text_address().
+ *
+ * Skipping built-in __exit is fine since it
+ * will never be executed.
+ */
+ WARN_ONCE(!static_call_is_init(site),
+ "can't patch static call site at %pS",
+ site_addr);
+ continue;
+ }
+
+ arch_static_call_transform(site_addr, NULL, func,
+ static_call_is_tail(site));
+ }
+ }
+
+done:
+ static_call_unlock();
+ cpus_read_unlock();
+}
+EXPORT_SYMBOL_GPL(__static_call_update);
+
+static int __static_call_init(struct module *mod,
+ struct static_call_site *start,
+ struct static_call_site *stop)
+{
+ struct static_call_site *site;
+ struct static_call_key *key, *prev_key = NULL;
+ struct static_call_mod *site_mod;
+
+ if (start == stop)
+ return 0;
+
+ static_call_sort_entries(start, stop);
+
+ for (site = start; site < stop; site++) {
+ void *site_addr = static_call_addr(site);
+
+ if ((mod && within_module_init((unsigned long)site_addr, mod)) ||
+ (!mod && init_section_contains(site_addr, 1)))
+ static_call_set_init(site);
+
+ key = static_call_key(site);
+ if (key != prev_key) {
+ prev_key = key;
+
+ /*
+ * For vmlinux (!mod) avoid the allocation by storing
+ * the sites pointer in the key itself. Also see
+ * __static_call_update()'s @first.
+ *
+ * This allows architectures (eg. x86) to call
+ * static_call_init() before memory allocation works.
+ */
+ if (!mod) {
+ key->sites = site;
+ key->type |= 1;
+ goto do_transform;
+ }
+
+ site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
+ if (!site_mod)
+ return -ENOMEM;
+
+ /*
+ * When the key has a direct sites pointer, extract
+ * that into an explicit struct static_call_mod, so we
+ * can have a list of modules.
+ */
+ if (static_call_key_sites(key)) {
+ site_mod->mod = NULL;
+ site_mod->next = NULL;
+ site_mod->sites = static_call_key_sites(key);
+
+ key->mods = site_mod;
+
+ site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL);
+ if (!site_mod)
+ return -ENOMEM;
+ }
+
+ site_mod->mod = mod;
+ site_mod->sites = site;
+ site_mod->next = static_call_key_next(key);
+ key->mods = site_mod;
+ }
+
+do_transform:
+ arch_static_call_transform(site_addr, NULL, key->func,
+ static_call_is_tail(site));
+ }
+
+ return 0;
+}
+
+static int addr_conflict(struct static_call_site *site, void *start, void *end)
+{
+ unsigned long addr = (unsigned long)static_call_addr(site);
+
+ if (addr <= (unsigned long)end &&
+ addr + CALL_INSN_SIZE > (unsigned long)start)
+ return 1;
+
+ return 0;
+}
+
+static int __static_call_text_reserved(struct static_call_site *iter_start,
+ struct static_call_site *iter_stop,
+ void *start, void *end, bool init)
+{
+ struct static_call_site *iter = iter_start;
+
+ while (iter < iter_stop) {
+ if (init || !static_call_is_init(iter)) {
+ if (addr_conflict(iter, start, end))
+ return 1;
+ }
+ iter++;
+ }
+
+ return 0;
+}
+
+#ifdef CONFIG_MODULES
+
+static int __static_call_mod_text_reserved(void *start, void *end)
+{
+ struct module *mod;
+ int ret;
+
+ preempt_disable();
+ mod = __module_text_address((unsigned long)start);
+ WARN_ON_ONCE(__module_text_address((unsigned long)end) != mod);
+ if (!try_module_get(mod))
+ mod = NULL;
+ preempt_enable();
+
+ if (!mod)
+ return 0;
+
+ ret = __static_call_text_reserved(mod->static_call_sites,
+ mod->static_call_sites + mod->num_static_call_sites,
+ start, end, mod->state == MODULE_STATE_COMING);
+
+ module_put(mod);
+
+ return ret;
+}
+
+static unsigned long tramp_key_lookup(unsigned long addr)
+{
+ struct static_call_tramp_key *start = __start_static_call_tramp_key;
+ struct static_call_tramp_key *stop = __stop_static_call_tramp_key;
+ struct static_call_tramp_key *tramp_key;
+
+ for (tramp_key = start; tramp_key != stop; tramp_key++) {
+ unsigned long tramp;
+
+ tramp = (long)tramp_key->tramp + (long)&tramp_key->tramp;
+ if (tramp == addr)
+ return (long)tramp_key->key + (long)&tramp_key->key;
+ }
+
+ return 0;
+}
+
+static int static_call_add_module(struct module *mod)
+{
+ struct static_call_site *start = mod->static_call_sites;
+ struct static_call_site *stop = start + mod->num_static_call_sites;
+ struct static_call_site *site;
+
+ for (site = start; site != stop; site++) {
+ unsigned long s_key = __static_call_key(site);
+ unsigned long addr = s_key & ~STATIC_CALL_SITE_FLAGS;
+ unsigned long key;
+
+ /*
+ * Is the key is exported, 'addr' points to the key, which
+ * means modules are allowed to call static_call_update() on
+ * it.
+ *
+ * Otherwise, the key isn't exported, and 'addr' points to the
+ * trampoline so we need to lookup the key.
+ *
+ * We go through this dance to prevent crazy modules from
+ * abusing sensitive static calls.
+ */
+ if (!kernel_text_address(addr))
+ continue;
+
+ key = tramp_key_lookup(addr);
+ if (!key) {
+ pr_warn("Failed to fixup __raw_static_call() usage at: %ps\n",
+ static_call_addr(site));
+ return -EINVAL;
+ }
+
+ key |= s_key & STATIC_CALL_SITE_FLAGS;
+ site->key = key - (long)&site->key;
+ }
+
+ return __static_call_init(mod, start, stop);
+}
+
+static void static_call_del_module(struct module *mod)
+{
+ struct static_call_site *start = mod->static_call_sites;
+ struct static_call_site *stop = mod->static_call_sites +
+ mod->num_static_call_sites;
+ struct static_call_key *key, *prev_key = NULL;
+ struct static_call_mod *site_mod, **prev;
+ struct static_call_site *site;
+
+ for (site = start; site < stop; site++) {
+ key = static_call_key(site);
+ if (key == prev_key)
+ continue;
+
+ prev_key = key;
+
+ for (prev = &key->mods, site_mod = key->mods;
+ site_mod && site_mod->mod != mod;
+ prev = &site_mod->next, site_mod = site_mod->next)
+ ;
+
+ if (!site_mod)
+ continue;
+
+ *prev = site_mod->next;
+ kfree(site_mod);
+ }
+}
+
+static int static_call_module_notify(struct notifier_block *nb,
+ unsigned long val, void *data)
+{
+ struct module *mod = data;
+ int ret = 0;
+
+ cpus_read_lock();
+ static_call_lock();
+
+ switch (val) {
+ case MODULE_STATE_COMING:
+ ret = static_call_add_module(mod);
+ if (ret) {
+ WARN(1, "Failed to allocate memory for static calls");
+ static_call_del_module(mod);
+ }
+ break;
+ case MODULE_STATE_GOING:
+ static_call_del_module(mod);
+ break;
+ }
+
+ static_call_unlock();
+ cpus_read_unlock();
+
+ return notifier_from_errno(ret);
+}
+
+static struct notifier_block static_call_module_nb = {
+ .notifier_call = static_call_module_notify,
+};
+
+#else
+
+static inline int __static_call_mod_text_reserved(void *start, void *end)
+{
+ return 0;
+}
+
+#endif /* CONFIG_MODULES */
+
+int static_call_text_reserved(void *start, void *end)
+{
+ bool init = system_state < SYSTEM_RUNNING;
+ int ret = __static_call_text_reserved(__start_static_call_sites,
+ __stop_static_call_sites, start, end, init);
+
+ if (ret)
+ return ret;
+
+ return __static_call_mod_text_reserved(start, end);
+}
+
+int __init static_call_init(void)
+{
+ int ret;
+
+ if (static_call_initialized)
+ return 0;
+
+ cpus_read_lock();
+ static_call_lock();
+ ret = __static_call_init(NULL, __start_static_call_sites,
+ __stop_static_call_sites);
+ static_call_unlock();
+ cpus_read_unlock();
+
+ if (ret) {
+ pr_err("Failed to allocate memory for static_call!\n");
+ BUG();
+ }
+
+ static_call_initialized = true;
+
+#ifdef CONFIG_MODULES
+ register_module_notifier(&static_call_module_nb);
+#endif
+ return 0;
+}
+early_initcall(static_call_init);
+
+#ifdef CONFIG_STATIC_CALL_SELFTEST
+
+static int func_a(int x)
+{
+ return x+1;
+}
+
+static int func_b(int x)
+{
+ return x+2;
+}
+
+DEFINE_STATIC_CALL(sc_selftest, func_a);
+
+static struct static_call_data {
+ int (*func)(int);
+ int val;
+ int expect;
+} static_call_data [] __initdata = {
+ { NULL, 2, 3 },
+ { func_b, 2, 4 },
+ { func_a, 2, 3 }
+};
+
+static int __init test_static_call_init(void)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) {
+ struct static_call_data *scd = &static_call_data[i];
+
+ if (scd->func)
+ static_call_update(sc_selftest, scd->func);
+
+ WARN_ON(static_call(sc_selftest)(scd->val) != scd->expect);
+ }
+
+ return 0;
+}
+early_initcall(test_static_call_init);
+
+#endif /* CONFIG_STATIC_CALL_SELFTEST */