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-rw-r--r--include/linux/module.h16
-rw-r--r--include/trace/events/module.h2
-rw-r--r--kernel/module.c170
-rw-r--r--kernel/params.c97
-rw-r--r--lib/bug.c20
5 files changed, 137 insertions, 168 deletions
diff --git a/include/linux/module.h b/include/linux/module.h
index 71f282a4e307..ebfb0e153c6a 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -210,20 +210,6 @@ enum module_state {
MODULE_STATE_UNFORMED, /* Still setting it up. */
};
-/**
- * struct module_ref - per cpu module reference counts
- * @incs: number of module get on this cpu
- * @decs: number of module put on this cpu
- *
- * We force an alignment on 8 or 16 bytes, so that alloc_percpu()
- * put @incs/@decs in same cache line, with no extra memory cost,
- * since alloc_percpu() is fine grained.
- */
-struct module_ref {
- unsigned long incs;
- unsigned long decs;
-} __attribute((aligned(2 * sizeof(unsigned long))));
-
struct module {
enum module_state state;
@@ -367,7 +353,7 @@ struct module {
/* Destruction function. */
void (*exit)(void);
- struct module_ref __percpu *refptr;
+ atomic_t refcnt;
#endif
#ifdef CONFIG_CONSTRUCTORS
diff --git a/include/trace/events/module.h b/include/trace/events/module.h
index 7c5cbfe3fc49..81c4c183d348 100644
--- a/include/trace/events/module.h
+++ b/include/trace/events/module.h
@@ -80,7 +80,7 @@ DECLARE_EVENT_CLASS(module_refcnt,
TP_fast_assign(
__entry->ip = ip;
- __entry->refcnt = __this_cpu_read(mod->refptr->incs) - __this_cpu_read(mod->refptr->decs);
+ __entry->refcnt = atomic_read(&mod->refcnt);
__assign_str(name, mod->name);
),
diff --git a/kernel/module.c b/kernel/module.c
index e52a8739361a..3965511ae133 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -42,7 +42,6 @@
#include <linux/vermagic.h>
#include <linux/notifier.h>
#include <linux/sched.h>
-#include <linux/stop_machine.h>
#include <linux/device.h>
#include <linux/string.h>
#include <linux/mutex.h>
@@ -98,7 +97,7 @@
* 1) List of modules (also safely readable with preempt_disable),
* 2) module_use links,
* 3) module_addr_min/module_addr_max.
- * (delete uses stop_machine/add uses RCU list operations). */
+ * (delete and add uses RCU list operations). */
DEFINE_MUTEX(module_mutex);
EXPORT_SYMBOL_GPL(module_mutex);
static LIST_HEAD(modules);
@@ -158,13 +157,13 @@ static BLOCKING_NOTIFIER_HEAD(module_notify_list);
* Protected by module_mutex. */
static unsigned long module_addr_min = -1UL, module_addr_max = 0;
-int register_module_notifier(struct notifier_block * nb)
+int register_module_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_register(&module_notify_list, nb);
}
EXPORT_SYMBOL(register_module_notifier);
-int unregister_module_notifier(struct notifier_block * nb)
+int unregister_module_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_unregister(&module_notify_list, nb);
}
@@ -628,18 +627,23 @@ static char last_unloaded_module[MODULE_NAME_LEN+1];
EXPORT_TRACEPOINT_SYMBOL(module_get);
+/* MODULE_REF_BASE is the base reference count by kmodule loader. */
+#define MODULE_REF_BASE 1
+
/* Init the unload section of the module. */
static int module_unload_init(struct module *mod)
{
- mod->refptr = alloc_percpu(struct module_ref);
- if (!mod->refptr)
- return -ENOMEM;
+ /*
+ * Initialize reference counter to MODULE_REF_BASE.
+ * refcnt == 0 means module is going.
+ */
+ atomic_set(&mod->refcnt, MODULE_REF_BASE);
INIT_LIST_HEAD(&mod->source_list);
INIT_LIST_HEAD(&mod->target_list);
/* Hold reference count during initialization. */
- raw_cpu_write(mod->refptr->incs, 1);
+ atomic_inc(&mod->refcnt);
return 0;
}
@@ -721,8 +725,6 @@ static void module_unload_free(struct module *mod)
kfree(use);
}
mutex_unlock(&module_mutex);
-
- free_percpu(mod->refptr);
}
#ifdef CONFIG_MODULE_FORCE_UNLOAD
@@ -740,60 +742,39 @@ static inline int try_force_unload(unsigned int flags)
}
#endif /* CONFIG_MODULE_FORCE_UNLOAD */
-struct stopref
+/* Try to release refcount of module, 0 means success. */
+static int try_release_module_ref(struct module *mod)
{
- struct module *mod;
- int flags;
- int *forced;
-};
+ int ret;
-/* Whole machine is stopped with interrupts off when this runs. */
-static int __try_stop_module(void *_sref)
-{
- struct stopref *sref = _sref;
+ /* Try to decrement refcnt which we set at loading */
+ ret = atomic_sub_return(MODULE_REF_BASE, &mod->refcnt);
+ BUG_ON(ret < 0);
+ if (ret)
+ /* Someone can put this right now, recover with checking */
+ ret = atomic_add_unless(&mod->refcnt, MODULE_REF_BASE, 0);
+
+ return ret;
+}
+static int try_stop_module(struct module *mod, int flags, int *forced)
+{
/* If it's not unused, quit unless we're forcing. */
- if (module_refcount(sref->mod) != 0) {
- if (!(*sref->forced = try_force_unload(sref->flags)))
+ if (try_release_module_ref(mod) != 0) {
+ *forced = try_force_unload(flags);
+ if (!(*forced))
return -EWOULDBLOCK;
}
/* Mark it as dying. */
- sref->mod->state = MODULE_STATE_GOING;
- return 0;
-}
-
-static int try_stop_module(struct module *mod, int flags, int *forced)
-{
- struct stopref sref = { mod, flags, forced };
+ mod->state = MODULE_STATE_GOING;
- return stop_machine(__try_stop_module, &sref, NULL);
+ return 0;
}
unsigned long module_refcount(struct module *mod)
{
- unsigned long incs = 0, decs = 0;
- int cpu;
-
- for_each_possible_cpu(cpu)
- decs += per_cpu_ptr(mod->refptr, cpu)->decs;
- /*
- * ensure the incs are added up after the decs.
- * module_put ensures incs are visible before decs with smp_wmb.
- *
- * This 2-count scheme avoids the situation where the refcount
- * for CPU0 is read, then CPU0 increments the module refcount,
- * then CPU1 drops that refcount, then the refcount for CPU1 is
- * read. We would record a decrement but not its corresponding
- * increment so we would see a low count (disaster).
- *
- * Rare situation? But module_refcount can be preempted, and we
- * might be tallying up 4096+ CPUs. So it is not impossible.
- */
- smp_rmb();
- for_each_possible_cpu(cpu)
- incs += per_cpu_ptr(mod->refptr, cpu)->incs;
- return incs - decs;
+ return (unsigned long)atomic_read(&mod->refcnt) - MODULE_REF_BASE;
}
EXPORT_SYMBOL(module_refcount);
@@ -877,8 +858,10 @@ static inline void print_unload_info(struct seq_file *m, struct module *mod)
seq_printf(m, " %lu ", module_refcount(mod));
- /* Always include a trailing , so userspace can differentiate
- between this and the old multi-field proc format. */
+ /*
+ * Always include a trailing , so userspace can differentiate
+ * between this and the old multi-field proc format.
+ */
list_for_each_entry(use, &mod->source_list, source_list) {
printed_something = 1;
seq_printf(m, "%s,", use->source->name);
@@ -886,11 +869,11 @@ static inline void print_unload_info(struct seq_file *m, struct module *mod)
if (mod->init != NULL && mod->exit == NULL) {
printed_something = 1;
- seq_printf(m, "[permanent],");
+ seq_puts(m, "[permanent],");
}
if (!printed_something)
- seq_printf(m, "-");
+ seq_puts(m, "-");
}
void __symbol_put(const char *symbol)
@@ -935,7 +918,7 @@ void __module_get(struct module *module)
{
if (module) {
preempt_disable();
- __this_cpu_inc(module->refptr->incs);
+ atomic_inc(&module->refcnt);
trace_module_get(module, _RET_IP_);
preempt_enable();
}
@@ -948,11 +931,11 @@ bool try_module_get(struct module *module)
if (module) {
preempt_disable();
-
- if (likely(module_is_live(module))) {
- __this_cpu_inc(module->refptr->incs);
+ /* Note: here, we can fail to get a reference */
+ if (likely(module_is_live(module) &&
+ atomic_inc_not_zero(&module->refcnt) != 0))
trace_module_get(module, _RET_IP_);
- } else
+ else
ret = false;
preempt_enable();
@@ -963,11 +946,12 @@ EXPORT_SYMBOL(try_module_get);
void module_put(struct module *module)
{
+ int ret;
+
if (module) {
preempt_disable();
- smp_wmb(); /* see comment in module_refcount */
- __this_cpu_inc(module->refptr->decs);
-
+ ret = atomic_dec_if_positive(&module->refcnt);
+ WARN_ON(ret < 0); /* Failed to put refcount */
trace_module_put(module, _RET_IP_);
preempt_enable();
}
@@ -978,7 +962,7 @@ EXPORT_SYMBOL(module_put);
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, " - -");
+ seq_puts(m, " - -");
}
static inline void module_unload_free(struct module *mod)
@@ -1131,7 +1115,7 @@ static unsigned long maybe_relocated(unsigned long crc,
static int check_version(Elf_Shdr *sechdrs,
unsigned int versindex,
const char *symname,
- struct module *mod,
+ struct module *mod,
const unsigned long *crc,
const struct module *crc_owner)
{
@@ -1165,7 +1149,7 @@ static int check_version(Elf_Shdr *sechdrs,
return 0;
bad_version:
- printk("%s: disagrees about version of symbol %s\n",
+ pr_warn("%s: disagrees about version of symbol %s\n",
mod->name, symname);
return 0;
}
@@ -1200,7 +1184,7 @@ static inline int same_magic(const char *amagic, const char *bmagic,
static inline int check_version(Elf_Shdr *sechdrs,
unsigned int versindex,
const char *symname,
- struct module *mod,
+ struct module *mod,
const unsigned long *crc,
const struct module *crc_owner)
{
@@ -1288,15 +1272,13 @@ static inline bool sect_empty(const Elf_Shdr *sect)
return !(sect->sh_flags & SHF_ALLOC) || sect->sh_size == 0;
}
-struct module_sect_attr
-{
+struct module_sect_attr {
struct module_attribute mattr;
char *name;
unsigned long address;
};
-struct module_sect_attrs
-{
+struct module_sect_attrs {
struct attribute_group grp;
unsigned int nsections;
struct module_sect_attr attrs[0];
@@ -1550,7 +1532,8 @@ static int module_add_modinfo_attrs(struct module *mod)
(attr->test && attr->test(mod))) {
memcpy(temp_attr, attr, sizeof(*temp_attr));
sysfs_attr_init(&temp_attr->attr);
- error = sysfs_create_file(&mod->mkobj.kobj,&temp_attr->attr);
+ error = sysfs_create_file(&mod->mkobj.kobj,
+ &temp_attr->attr);
++temp_attr;
}
}
@@ -1566,7 +1549,7 @@ static void module_remove_modinfo_attrs(struct module *mod)
/* pick a field to test for end of list */
if (!attr->attr.name)
break;
- sysfs_remove_file(&mod->mkobj.kobj,&attr->attr);
+ sysfs_remove_file(&mod->mkobj.kobj, &attr->attr);
if (attr->free)
attr->free(mod);
}
@@ -1697,18 +1680,6 @@ static void mod_sysfs_teardown(struct module *mod)
mod_sysfs_fini(mod);
}
-/*
- * unlink the module with the whole machine is stopped with interrupts off
- * - this defends against kallsyms not taking locks
- */
-static int __unlink_module(void *_mod)
-{
- struct module *mod = _mod;
- list_del(&mod->list);
- module_bug_cleanup(mod);
- return 0;
-}
-
#ifdef CONFIG_DEBUG_SET_MODULE_RONX
/*
* LKM RO/NX protection: protect module's text/ro-data
@@ -1860,7 +1831,12 @@ static void free_module(struct module *mod)
/* Now we can delete it from the lists */
mutex_lock(&module_mutex);
- stop_machine(__unlink_module, mod, NULL);
+ /* Unlink carefully: kallsyms could be walking list. */
+ list_del_rcu(&mod->list);
+ /* Remove this module from bug list, this uses list_del_rcu */
+ module_bug_cleanup(mod);
+ /* Wait for RCU synchronizing before releasing mod->list and buglist. */
+ synchronize_rcu();
mutex_unlock(&module_mutex);
/* This may be NULL, but that's OK */
@@ -1955,7 +1931,7 @@ static int simplify_symbols(struct module *mod, const struct load_info *info)
/* We compiled with -fno-common. These are not
supposed to happen. */
pr_debug("Common symbol: %s\n", name);
- printk("%s: please compile with -fno-common\n",
+ pr_warn("%s: please compile with -fno-common\n",
mod->name);
ret = -ENOEXEC;
break;
@@ -2259,7 +2235,7 @@ static char elf_type(const Elf_Sym *sym, const struct load_info *info)
}
static bool is_core_symbol(const Elf_Sym *src, const Elf_Shdr *sechdrs,
- unsigned int shnum)
+ unsigned int shnum)
{
const Elf_Shdr *sec;
@@ -2735,7 +2711,7 @@ static int find_module_sections(struct module *mod, struct load_info *info)
* This shouldn't happen with same compiler and binutils
* building all parts of the module.
*/
- printk(KERN_WARNING "%s: has both .ctors and .init_array.\n",
+ pr_warn("%s: has both .ctors and .init_array.\n",
mod->name);
return -EINVAL;
}
@@ -3023,8 +2999,10 @@ static int do_init_module(struct module *mod)
if (mod->init != NULL)
ret = do_one_initcall(mod->init);
if (ret < 0) {
- /* Init routine failed: abort. Try to protect us from
- buggy refcounters. */
+ /*
+ * Init routine failed: abort. Try to protect us from
+ * buggy refcounters.
+ */
mod->state = MODULE_STATE_GOING;
synchronize_sched();
module_put(mod);
@@ -3202,7 +3180,7 @@ out:
static int unknown_module_param_cb(char *param, char *val, const char *modname)
{
- /* Check for magic 'dyndbg' arg */
+ /* Check for magic 'dyndbg' arg */
int ret = ddebug_dyndbg_module_param_cb(param, val, modname);
if (ret != 0)
pr_warn("%s: unknown parameter '%s' ignored\n", modname, param);
@@ -3352,6 +3330,8 @@ static int load_module(struct load_info *info, const char __user *uargs,
/* Unlink carefully: kallsyms could be walking list. */
list_del_rcu(&mod->list);
wake_up_all(&module_wq);
+ /* Wait for RCU synchronizing before releasing mod->list. */
+ synchronize_rcu();
mutex_unlock(&module_mutex);
free_module:
module_deallocate(mod, info);
@@ -3685,8 +3665,8 @@ static int m_show(struct seq_file *m, void *p)
/* Informative for users. */
seq_printf(m, " %s",
- mod->state == MODULE_STATE_GOING ? "Unloading":
- mod->state == MODULE_STATE_COMING ? "Loading":
+ mod->state == MODULE_STATE_GOING ? "Unloading" :
+ mod->state == MODULE_STATE_COMING ? "Loading" :
"Live");
/* Used by oprofile and other similar tools. */
seq_printf(m, " 0x%pK", mod->module_core);
@@ -3695,7 +3675,7 @@ static int m_show(struct seq_file *m, void *p)
if (mod->taints)
seq_printf(m, " %s", module_flags(mod, buf));
- seq_printf(m, "\n");
+ seq_puts(m, "\n");
return 0;
}
diff --git a/kernel/params.c b/kernel/params.c
index db97b791390f..0af9b2c4e56c 100644
--- a/kernel/params.c
+++ b/kernel/params.c
@@ -603,74 +603,67 @@ static __modinit int add_sysfs_param(struct module_kobject *mk,
const struct kernel_param *kp,
const char *name)
{
- struct module_param_attrs *new;
- struct attribute **attrs;
- int err, num;
+ struct module_param_attrs *new_mp;
+ struct attribute **new_attrs;
+ unsigned int i;
/* We don't bother calling this with invisible parameters. */
BUG_ON(!kp->perm);
if (!mk->mp) {
- num = 0;
- attrs = NULL;
- } else {
- num = mk->mp->num;
- attrs = mk->mp->grp.attrs;
+ /* First allocation. */
+ mk->mp = kzalloc(sizeof(*mk->mp), GFP_KERNEL);
+ if (!mk->mp)
+ return -ENOMEM;
+ mk->mp->grp.name = "parameters";
+ /* NULL-terminated attribute array. */
+ mk->mp->grp.attrs = kzalloc(sizeof(mk->mp->grp.attrs[0]),
+ GFP_KERNEL);
+ /* Caller will cleanup via free_module_param_attrs */
+ if (!mk->mp->grp.attrs)
+ return -ENOMEM;
}
- /* Enlarge. */
- new = krealloc(mk->mp,
- sizeof(*mk->mp) + sizeof(mk->mp->attrs[0]) * (num+1),
- GFP_KERNEL);
- if (!new) {
- kfree(attrs);
- err = -ENOMEM;
- goto fail;
- }
- /* Despite looking like the typical realloc() bug, this is safe.
- * We *want* the old 'attrs' to be freed either way, and we'll store
- * the new one in the success case. */
- attrs = krealloc(attrs, sizeof(new->grp.attrs[0])*(num+2), GFP_KERNEL);
- if (!attrs) {
- err = -ENOMEM;
- goto fail_free_new;
- }
+ /* Enlarge allocations. */
+ new_mp = krealloc(mk->mp,
+ sizeof(*mk->mp) +
+ sizeof(mk->mp->attrs[0]) * (mk->mp->num + 1),
+ GFP_KERNEL);
+ if (!new_mp)
+ return -ENOMEM;
+ mk->mp = new_mp;
- /* Sysfs wants everything zeroed. */
- memset(new, 0, sizeof(*new));
- memset(&new->attrs[num], 0, sizeof(new->attrs[num]));
- memset(&attrs[num], 0, sizeof(attrs[num]));
- new->grp.name = "parameters";
- new->grp.attrs = attrs;
+ /* Extra pointer for NULL terminator */
+ new_attrs = krealloc(mk->mp->grp.attrs,
+ sizeof(mk->mp->grp.attrs[0]) * (mk->mp->num + 2),
+ GFP_KERNEL);
+ if (!new_attrs)
+ return -ENOMEM;
+ mk->mp->grp.attrs = new_attrs;
/* Tack new one on the end. */
- sysfs_attr_init(&new->attrs[num].mattr.attr);
- new->attrs[num].param = kp;
- new->attrs[num].mattr.show = param_attr_show;
- new->attrs[num].mattr.store = param_attr_store;
- new->attrs[num].mattr.attr.name = (char *)name;
- new->attrs[num].mattr.attr.mode = kp->perm;
- new->num = num+1;
+ sysfs_attr_init(&mk->mp->attrs[mk->mp->num].mattr.attr);
+ mk->mp->attrs[mk->mp->num].param = kp;
+ mk->mp->attrs[mk->mp->num].mattr.show = param_attr_show;
+ /* Do not allow runtime DAC changes to make param writable. */
+ if ((kp->perm & (S_IWUSR | S_IWGRP | S_IWOTH)) != 0)
+ mk->mp->attrs[mk->mp->num].mattr.store = param_attr_store;
+ mk->mp->attrs[mk->mp->num].mattr.attr.name = (char *)name;
+ mk->mp->attrs[mk->mp->num].mattr.attr.mode = kp->perm;
+ mk->mp->num++;
/* Fix up all the pointers, since krealloc can move us */
- for (num = 0; num < new->num; num++)
- new->grp.attrs[num] = &new->attrs[num].mattr.attr;
- new->grp.attrs[num] = NULL;
-
- mk->mp = new;
+ for (i = 0; i < mk->mp->num; i++)
+ mk->mp->grp.attrs[i] = &mk->mp->attrs[i].mattr.attr;
+ mk->mp->grp.attrs[mk->mp->num] = NULL;
return 0;
-
-fail_free_new:
- kfree(new);
-fail:
- mk->mp = NULL;
- return err;
}
#ifdef CONFIG_MODULES
static void free_module_param_attrs(struct module_kobject *mk)
{
- kfree(mk->mp->grp.attrs);
+ if (mk->mp)
+ kfree(mk->mp->grp.attrs);
kfree(mk->mp);
mk->mp = NULL;
}
@@ -695,8 +688,10 @@ int module_param_sysfs_setup(struct module *mod,
if (kparam[i].perm == 0)
continue;
err = add_sysfs_param(&mod->mkobj, &kparam[i], kparam[i].name);
- if (err)
+ if (err) {
+ free_module_param_attrs(&mod->mkobj);
return err;
+ }
params = true;
}
diff --git a/lib/bug.c b/lib/bug.c
index d1d7c7878900..0c3bd9552b6f 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -64,16 +64,22 @@ static LIST_HEAD(module_bug_list);
static const struct bug_entry *module_find_bug(unsigned long bugaddr)
{
struct module *mod;
+ const struct bug_entry *bug = NULL;
- list_for_each_entry(mod, &module_bug_list, bug_list) {
- const struct bug_entry *bug = mod->bug_table;
+ rcu_read_lock();
+ list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
unsigned i;
+ bug = mod->bug_table;
for (i = 0; i < mod->num_bugs; ++i, ++bug)
if (bugaddr == bug_addr(bug))
- return bug;
+ goto out;
}
- return NULL;
+ bug = NULL;
+out:
+ rcu_read_unlock();
+
+ return bug;
}
void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
@@ -99,13 +105,15 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
* Strictly speaking this should have a spinlock to protect against
* traversals, but since we only traverse on BUG()s, a spinlock
* could potentially lead to deadlock and thus be counter-productive.
+ * Thus, this uses RCU to safely manipulate the bug list, since BUG
+ * must run in non-interruptive state.
*/
- list_add(&mod->bug_list, &module_bug_list);
+ list_add_rcu(&mod->bug_list, &module_bug_list);
}
void module_bug_cleanup(struct module *mod)
{
- list_del(&mod->bug_list);
+ list_del_rcu(&mod->bug_list);
}
#else
generated by cgit v1.2.3 (git 2.39.0) at 2024-11-29 00:59:38 +0300