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[PATCH] kprobes: changed from using spinlock to mutex

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Since Kprobes runtime exception handlers is now lock free as this code path is
now using RCU to walk through the list, there is no need for the
register/unregister{_kprobe} to use spin_{lock/unlock}_isr{save/restore}.  The
serialization during registration/unregistration is now possible using just a
mutex.

In the above process, this patch also fixes a minor memory leak for x86_64 and
powerpc.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Anil S Keshavamurthy 2006-01-09 20:52:43 -08:00 committed by Linus Torvalds
parent 41dead49cc
commit 49a2a1b83b
7 changed files with 53 additions and 77 deletions
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6
arch/i386/kernel/kprobes.c
View File

@ -57,14 +57,10 @@ static inline int is_IF_modifier(kprobe_opcode_t opcode)
}
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
return 0;
}
void __kprobes arch_copy_kprobe(struct kprobe *p)
{
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
p->opcode = *p->addr;
return 0;
}
void __kprobes arch_arm_kprobe(struct kprobe *p)

14
arch/powerpc/kernel/kprobes.c
View File

@ -60,13 +60,13 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
if (!p->ainsn.insn)
ret = -ENOMEM;
}
return ret;
}
void __kprobes arch_copy_kprobe(struct kprobe *p)
{
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
p->opcode = *p->addr;
if (!ret) {
memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
p->opcode = *p->addr;
}
return ret;
}
void __kprobes arch_arm_kprobe(struct kprobe *p)
@ -85,9 +85,7 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p)
void __kprobes arch_remove_kprobe(struct kprobe *p)
{
down(&kprobe_mutex);
free_insn_slot(p->ainsn.insn);
up(&kprobe_mutex);
}
static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)

6
arch/sparc64/kernel/kprobes.c
View File

@ -42,15 +42,11 @@ DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
return 0;
}
void __kprobes arch_copy_kprobe(struct kprobe *p)
{
p->ainsn.insn[0] = *p->addr;
p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
p->opcode = *p->addr;
return 0;
}
void __kprobes arch_arm_kprobe(struct kprobe *p)

7
arch/x86_64/kernel/kprobes.c
View File

@ -42,8 +42,8 @@
#include <asm/pgtable.h>
#include <asm/kdebug.h>
static DECLARE_MUTEX(kprobe_mutex);
void jprobe_return_end(void);
void __kprobes arch_copy_kprobe(struct kprobe *p);
DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@ -69,12 +69,11 @@ static inline int is_IF_modifier(kprobe_opcode_t *insn)
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
/* insn: must be on special executable page on x86_64. */
down(&kprobe_mutex);
p->ainsn.insn = get_insn_slot();
up(&kprobe_mutex);
if (!p->ainsn.insn) {
return -ENOMEM;
}
arch_copy_kprobe(p);
return 0;
}
@ -223,9 +222,7 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p)
void __kprobes arch_remove_kprobe(struct kprobe *p)
{
down(&kprobe_mutex);
free_insn_slot(p->ainsn.insn);
up(&kprobe_mutex);
}
static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)

5
include/asm-ia64/kprobes.h
View File

@ -110,11 +110,6 @@ struct arch_specific_insn {
unsigned short target_br_reg;
};
/* ia64 does not need this */
static inline void arch_copy_kprobe(struct kprobe *p)
{
}
extern int kprobe_exceptions_notify(struct notifier_block *self,
unsigned long val, void *data);

1
include/linux/kprobes.h
View File

@ -150,7 +150,6 @@ struct kretprobe_instance {
extern spinlock_t kretprobe_lock;
extern int arch_prepare_kprobe(struct kprobe *p);
extern void arch_copy_kprobe(struct kprobe *p);
extern void arch_arm_kprobe(struct kprobe *p);
extern void arch_disarm_kprobe(struct kprobe *p);
extern void arch_remove_kprobe(struct kprobe *p);

91
kernel/kprobes.c
View File

@ -48,7 +48,7 @@
static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
static DEFINE_SPINLOCK(kprobe_lock); /* Protects kprobe_table */
static DECLARE_MUTEX(kprobe_mutex); /* Protects kprobe_table */
DEFINE_SPINLOCK(kretprobe_lock); /* Protects kretprobe_inst_table */
static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
@ -167,7 +167,7 @@ static inline void reset_kprobe_instance(void)
/*
* This routine is called either:
* - under the kprobe_lock spinlock - during kprobe_[un]register()
* - under the kprobe_mutex - during kprobe_[un]register()
* OR
* - with preemption disabled - from arch/xxx/kernel/kprobes.c
*/
@ -420,7 +420,6 @@ static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
/*
* This is the second or subsequent kprobe at the address - handle
* the intricacies
* TODO: Move kcalloc outside the spin_lock
*/
static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
struct kprobe *p)
@ -442,25 +441,6 @@ static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
return ret;
}
/* kprobe removal house-keeping routines */
static inline void cleanup_kprobe(struct kprobe *p, unsigned long flags)
{
arch_disarm_kprobe(p);
hlist_del_rcu(&p->hlist);
spin_unlock_irqrestore(&kprobe_lock, flags);
arch_remove_kprobe(p);
}
static inline void cleanup_aggr_kprobe(struct kprobe *old_p,
struct kprobe *p, unsigned long flags)
{
list_del_rcu(&p->list);
if (list_empty(&old_p->list))
cleanup_kprobe(old_p, flags);
else
spin_unlock_irqrestore(&kprobe_lock, flags);
}
static int __kprobes in_kprobes_functions(unsigned long addr)
{
if (addr >= (unsigned long)__kprobes_text_start
@ -472,7 +452,6 @@ static int __kprobes in_kprobes_functions(unsigned long addr)
int __kprobes register_kprobe(struct kprobe *p)
{
int ret = 0;
unsigned long flags = 0;
struct kprobe *old_p;
struct module *mod;
@ -484,18 +463,17 @@ int __kprobes register_kprobe(struct kprobe *p)
(unlikely(!try_module_get(mod))))
return -EINVAL;
if ((ret = arch_prepare_kprobe(p)) != 0)
goto rm_kprobe;
p->nmissed = 0;
spin_lock_irqsave(&kprobe_lock, flags);
down(&kprobe_mutex);
old_p = get_kprobe(p->addr);
if (old_p) {
ret = register_aggr_kprobe(old_p, p);
goto out;
}
arch_copy_kprobe(p);
if ((ret = arch_prepare_kprobe(p)) != 0)
goto out;
INIT_HLIST_NODE(&p->hlist);
hlist_add_head_rcu(&p->hlist,
&kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
@ -503,10 +481,8 @@ int __kprobes register_kprobe(struct kprobe *p)
arch_arm_kprobe(p);
out:
spin_unlock_irqrestore(&kprobe_lock, flags);
rm_kprobe:
if (ret == -EEXIST)
arch_remove_kprobe(p);
up(&kprobe_mutex);
if (ret && mod)
module_put(mod);
return ret;
@ -514,29 +490,48 @@ int __kprobes register_kprobe(struct kprobe *p)
void __kprobes unregister_kprobe(struct kprobe *p)
{
unsigned long flags;
struct kprobe *old_p;
struct module *mod;
struct kprobe *old_p, *cleanup_p;
spin_lock_irqsave(&kprobe_lock, flags);
down(&kprobe_mutex);
old_p = get_kprobe(p->addr);
if (old_p) {
/* cleanup_*_kprobe() does the spin_unlock_irqrestore */
if (old_p->pre_handler == aggr_pre_handler)
cleanup_aggr_kprobe(old_p, p, flags);
else
cleanup_kprobe(p, flags);
if (unlikely(!old_p)) {
up(&kprobe_mutex);
return;
}
synchronize_sched();
if ((old_p->pre_handler == aggr_pre_handler) &&
(p->list.next == &old_p->list) &&
(p->list.prev == &old_p->list)) {
/* Only one element in the aggregate list */
arch_disarm_kprobe(p);
hlist_del_rcu(&old_p->hlist);
cleanup_p = old_p;
} else if (old_p == p) {
/* Only one kprobe element in the hash list */
arch_disarm_kprobe(p);
hlist_del_rcu(&p->hlist);
cleanup_p = p;
} else {
list_del_rcu(&p->list);
cleanup_p = NULL;
}
if ((mod = module_text_address((unsigned long)p->addr)))
module_put(mod);
up(&kprobe_mutex);
if (old_p->pre_handler == aggr_pre_handler &&
list_empty(&old_p->list))
synchronize_sched();
if ((mod = module_text_address((unsigned long)p->addr)))
module_put(mod);
if (cleanup_p) {
if (cleanup_p->pre_handler == aggr_pre_handler) {
list_del_rcu(&p->list);
kfree(old_p);
} else
spin_unlock_irqrestore(&kprobe_lock, flags);
}
down(&kprobe_mutex);
arch_remove_kprobe(p);
up(&kprobe_mutex);
}
}
static struct notifier_block kprobe_exceptions_nb = {