3 files changed, 94 insertions, 26 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 47fff3b63cbf..30e74dd6d01b 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -269,8 +269,11 @@ out_release:
 
 int __ref cpu_down(unsigned int cpu)
 {
-        int err = 0;
+        int err;
 
+        err = stop_machine_create();
+        if (err)
+                return err;
         cpu_maps_update_begin();
 
         if (cpu_hotplug_disabled) {
@@ -297,6 +300,7 @@ int __ref cpu_down(unsigned int cpu)
 
 out:
         cpu_maps_update_done();
+        stop_machine_destroy();
         return err;
 }
 EXPORT_SYMBOL(cpu_down);
diff --git a/kernel/module.c b/kernel/module.c
index dd2a54155b54..f47cce910f25 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -757,8 +757,16 @@ sys_delete_module(const char __user *name_user, unsigned int flags)
                 return -EFAULT;
         name[MODULE_NAME_LEN-1] = '\0';
 
-        if (mutex_lock_interruptible(&module_mutex) != 0)
-                return -EINTR;
+        /* Create stop_machine threads since free_module relies on
+         * a non-failing stop_machine call. */
+        ret = stop_machine_create();
+        if (ret)
+                return ret;
+
+        if (mutex_lock_interruptible(&module_mutex) != 0) {
+                ret = -EINTR;
+                goto out_stop;
+        }
 
         mod = find_module(name);
         if (!mod) {
@@ -817,10 +825,12 @@ sys_delete_module(const char __user *name_user, unsigned int flags)
 
  out:
         mutex_unlock(&module_mutex);
+out_stop:
+        stop_machine_destroy();
         return ret;
 }
 
-static void print_unload_info(struct seq_file *m, struct module *mod)
+static inline void print_unload_info(struct seq_file *m, struct module *mod)
 {
         struct module_use *use;
         int printed_something = 0;
@@ -893,7 +903,7 @@ void module_put(struct module *module)
 EXPORT_SYMBOL(module_put);
 
 #else /* !CONFIG_MODULE_UNLOAD */
-static void print_unload_info(struct seq_file *m, struct module *mod)
+static inline void print_unload_info(struct seq_file *m, struct module *mod)
 {
         /* We don't know the usage count, or what modules are using. */
         seq_printf(m, " - -");
@@ -1578,11 +1588,21 @@ static int simplify_symbols(Elf_Shdr *sechdrs,
         return ret;
 }
 
+/* Additional bytes needed by arch in front of individual sections */
+unsigned int __weak arch_mod_section_prepend(struct module *mod,
+                                             unsigned int section)
+{
+        /* default implementation just returns zero */
+        return 0;
+}
+
 /* Update size with this section: return offset. */
-static long get_offset(unsigned int *size, Elf_Shdr *sechdr)
+static long get_offset(struct module *mod, unsigned int *size,
+                       Elf_Shdr *sechdr, unsigned int section)
 {
         long ret;
 
+        *size += arch_mod_section_prepend(mod, section);
         ret = ALIGN(*size, sechdr->sh_addralign ?: 1);
         *size = ret + sechdr->sh_size;
         return ret;
@@ -1622,7 +1642,7 @@ static void layout_sections(struct module *mod,
                             || strncmp(secstrings + s->sh_name,
                                        ".init", 5) == 0)
                                 continue;
-                        s->sh_entsize = get_offset(&mod->core_size, s);
+                        s->sh_entsize = get_offset(mod, &mod->core_size, s, i);
                         DEBUGP("\t%s\n", secstrings + s->sh_name);
                 }
                 if (m == 0)
@@ -1640,7 +1660,7 @@ static void layout_sections(struct module *mod,
                             || strncmp(secstrings + s->sh_name,
                                        ".init", 5) != 0)
                                 continue;
-                        s->sh_entsize = (get_offset(&mod->init_size, s)
+                        s->sh_entsize = (get_offset(mod, &mod->init_size, s, i)
                                          | INIT_OFFSET_MASK);
                         DEBUGP("\t%s\n", secstrings + s->sh_name);
                 }
@@ -1725,15 +1745,15 @@ static const struct kernel_symbol *lookup_symbol(const char *name,
         return NULL;
 }
 
-static int is_exported(const char *name, const struct module *mod)
+static int is_exported(const char *name, unsigned long value,
+                       const struct module *mod)
 {
-        if (!mod && lookup_symbol(name, __start___ksymtab, __stop___ksymtab))
-                return 1;
+        const struct kernel_symbol *ks;
+        if (!mod)
+                ks = lookup_symbol(name, __start___ksymtab, __stop___ksymtab);
         else
-                if (mod && lookup_symbol(name, mod->syms, mod->syms + mod->num_syms))
-                        return 1;
-                else
-                        return 0;
+                ks = lookup_symbol(name, mod->syms, mod->syms + mod->num_syms);
+        return ks != NULL && ks->value == value;
 }
 
 /* As per nm */
@@ -1865,6 +1885,13 @@ static noinline struct module *load_module(void __user *umod,
         /* vmalloc barfs on "unusual" numbers.  Check here */
         if (len > 64 * 1024 * 1024 || (hdr = vmalloc(len)) == NULL)
                 return ERR_PTR(-ENOMEM);
+
+        /* Create stop_machine threads since the error path relies on
+         * a non-failing stop_machine call. */
+        err = stop_machine_create();
+        if (err)
+                goto free_hdr;
+
         if (copy_from_user(hdr, umod, len) != 0) {
                 err = -EFAULT;
                 goto free_hdr;
@@ -2248,6 +2275,7 @@ static noinline struct module *load_module(void __user *umod,
         /* Get rid of temporary copy */
         vfree(hdr);
 
+        stop_machine_destroy();
         /* Done! */
         return mod;
 
@@ -2270,6 +2298,7 @@ static noinline struct module *load_module(void __user *umod,
         kfree(args);
  free_hdr:
         vfree(hdr);
+        stop_machine_destroy();
         return ERR_PTR(err);
 
  truncated:
@@ -2504,7 +2533,7 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
                         strlcpy(name, mod->strtab + mod->symtab[symnum].st_name,
                                 KSYM_NAME_LEN);
                         strlcpy(module_name, mod->name, MODULE_NAME_LEN);
-                        *exported = is_exported(name, mod);
+                        *exported = is_exported(name, *value, mod);
                         preempt_enable();
                         return 0;
                 }
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 286c41722e8c..0cd415ee62a2 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -38,7 +38,10 @@ struct stop_machine_data {
 static unsigned int num_threads;
 static atomic_t thread_ack;
 static DEFINE_MUTEX(lock);
-
+/* setup_lock protects refcount, stop_machine_wq and stop_machine_work. */
+static DEFINE_MUTEX(setup_lock);
+/* Users of stop_machine. */
+static int refcount;
 static struct workqueue_struct *stop_machine_wq;
 static struct stop_machine_data active, idle;
 static const cpumask_t *active_cpus;
@@ -109,6 +112,43 @@ static int chill(void *unused)
         return 0;
 }
 
+int stop_machine_create(void)
+{
+        mutex_lock(&setup_lock);
+        if (refcount)
+                goto done;
+        stop_machine_wq = create_rt_workqueue("kstop");
+        if (!stop_machine_wq)
+                goto err_out;
+        stop_machine_work = alloc_percpu(struct work_struct);
+        if (!stop_machine_work)
+                goto err_out;
+done:
+        refcount++;
+        mutex_unlock(&setup_lock);
+        return 0;
+
+err_out:
+        if (stop_machine_wq)
+                destroy_workqueue(stop_machine_wq);
+        mutex_unlock(&setup_lock);
+        return -ENOMEM;
+}
+EXPORT_SYMBOL_GPL(stop_machine_create);
+
+void stop_machine_destroy(void)
+{
+        mutex_lock(&setup_lock);
+        refcount--;
+        if (refcount)
+                goto done;
+        destroy_workqueue(stop_machine_wq);
+        free_percpu(stop_machine_work);
+done:
+        mutex_unlock(&setup_lock);
+}
+EXPORT_SYMBOL_GPL(stop_machine_destroy);
+
 int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
 {
         struct work_struct *sm_work;
@@ -146,19 +186,14 @@ int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus)
 {
         int ret;
 
+        ret = stop_machine_create();
+        if (ret)
+                return ret;
         /* No CPUs can come up or down during this. */
         get_online_cpus();
         ret = __stop_machine(fn, data, cpus);
         put_online_cpus();
-
+        stop_machine_destroy();
         return ret;
 }
 EXPORT_SYMBOL_GPL(stop_machine);
-
-static int __init stop_machine_init(void)
-{
-        stop_machine_wq = create_rt_workqueue("kstop");
-        stop_machine_work = alloc_percpu(struct work_struct);
-        return 0;
-}
-core_initcall(stop_machine_init);