Commit d217d545 authored by Ananth N Mavinakayanahalli's avatar Ananth N Mavinakayanahalli Committed by Linus Torvalds
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[PATCH] Kprobes: preempt_disable/enable() simplification



Reorganize the preempt_disable/enable calls to eliminate the extra preempt
depth.  Changes based on Paul McKenney's review suggestions for the kprobes
RCU changeset.
Signed-off-by: default avatarAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: default avatarAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 991a51d8
......@@ -153,7 +153,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
int ret = 0;
kprobe_opcode_t *addr = NULL;
unsigned long *lp;
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
struct kprobe_ctlblk *kcb;
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
/* Check if the application is using LDT entry for its code segment and
* calculate the address by reading the base address from the LDT entry.
......@@ -221,11 +228,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
goto no_kprobe;
}
/*
* This preempt_disable() matches the preempt_enable_no_resched()
* in post_kprobe_handler()
*/
preempt_disable();
set_current_kprobe(p, regs, kcb);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
......@@ -239,6 +241,7 @@ ss_probe:
return 1;
no_kprobe:
preempt_enable_no_resched();
return ret;
}
......@@ -310,8 +313,8 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
/*
* By returning a non-zero value, we are telling
* kprobe_handler() that we have handled unlocking
* and re-enabling preemption
* kprobe_handler() that we don't want the post_handler
* to run (and have re-enabled preemption)
*/
return 1;
}
......@@ -455,7 +458,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
rcu_read_lock();
switch (val) {
case DIE_INT3:
if (kprobe_handler(args->regs))
......@@ -467,14 +469,16 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
break;
case DIE_GPF:
case DIE_PAGE_FAULT:
/* kprobe_running() needs smp_processor_id() */
preempt_disable();
if (kprobe_running() &&
kprobe_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
preempt_enable();
break;
default:
break;
}
rcu_read_unlock();
return ret;
}
......@@ -537,6 +541,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
*regs = kcb->jprobe_saved_regs;
memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
MIN_STACK_SIZE(stack_addr));
preempt_enable_no_resched();
return 1;
}
return 0;
......
......@@ -389,11 +389,11 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
spin_unlock_irqrestore(&kretprobe_lock, flags);
preempt_enable_no_resched();
/*
* By returning a non-zero value, we are telling
* kprobe_handler() that we have handled unlocking
* and re-enabling preemption
*/
/*
* By returning a non-zero value, we are telling
* kprobe_handler() that we don't want the post_handler
* to run (and have re-enabled preemption)
*/
return 1;
}
......@@ -604,7 +604,14 @@ static int __kprobes pre_kprobes_handler(struct die_args *args)
int ret = 0;
struct pt_regs *regs = args->regs;
kprobe_opcode_t *addr = (kprobe_opcode_t *)instruction_pointer(regs);
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
struct kprobe_ctlblk *kcb;
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
/* Handle recursion cases */
if (kprobe_running()) {
......@@ -659,11 +666,6 @@ static int __kprobes pre_kprobes_handler(struct die_args *args)
goto no_kprobe;
}
/*
* This preempt_disable() matches the preempt_enable_no_resched()
* in post_kprobes_handler()
*/
preempt_disable();
set_current_kprobe(p, kcb);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
......@@ -681,6 +683,7 @@ ss_probe:
return 1;
no_kprobe:
preempt_enable_no_resched();
return ret;
}
......@@ -716,9 +719,6 @@ static int __kprobes kprobes_fault_handler(struct pt_regs *regs, int trapnr)
struct kprobe *cur = kprobe_running();
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
if (!cur)
return 0;
if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
return 1;
......@@ -737,7 +737,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
rcu_read_lock();
switch(val) {
case DIE_BREAK:
if (pre_kprobes_handler(args))
......@@ -748,12 +747,15 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
ret = NOTIFY_STOP;
break;
case DIE_PAGE_FAULT:
if (kprobes_fault_handler(args->regs, args->trapnr))
/* kprobe_running() needs smp_processor_id() */
preempt_disable();
if (kprobe_running() &&
kprobes_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
preempt_enable();
default:
break;
}
rcu_read_unlock();
return ret;
}
......@@ -785,6 +787,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
*regs = kcb->jprobe_saved_regs;
preempt_enable_no_resched();
return 1;
}
......
......@@ -148,7 +148,14 @@ static inline int kprobe_handler(struct pt_regs *regs)
struct kprobe *p;
int ret = 0;
unsigned int *addr = (unsigned int *)regs->nip;
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
struct kprobe_ctlblk *kcb;
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
/* Check we're not actually recursing */
if (kprobe_running()) {
......@@ -207,11 +214,6 @@ static inline int kprobe_handler(struct pt_regs *regs)
goto no_kprobe;
}
/*
* This preempt_disable() matches the preempt_enable_no_resched()
* in post_kprobe_handler().
*/
preempt_disable();
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
set_current_kprobe(p, regs, kcb);
if (p->pre_handler && p->pre_handler(p, regs))
......@@ -224,6 +226,7 @@ ss_probe:
return 1;
no_kprobe:
preempt_enable_no_resched();
return ret;
}
......@@ -296,8 +299,8 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
/*
* By returning a non-zero value, we are telling
* kprobe_handler() that we have handled unlocking
* and re-enabling preemption.
* kprobe_handler() that we don't want the post_handler
* to run (and have re-enabled preemption)
*/
return 1;
}
......@@ -385,7 +388,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
rcu_read_lock();
switch (val) {
case DIE_BPT:
if (kprobe_handler(args->regs))
......@@ -396,14 +398,16 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
ret = NOTIFY_STOP;
break;
case DIE_PAGE_FAULT:
/* kprobe_running() needs smp_processor_id() */
preempt_disable();
if (kprobe_running() &&
kprobe_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
preempt_enable();
break;
default:
break;
}
rcu_read_unlock();
return ret;
}
......@@ -440,6 +444,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
* saved regs...
*/
memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
preempt_enable_no_resched();
return 1;
}
......
......@@ -113,7 +113,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
struct kprobe *p;
void *addr = (void *) regs->tpc;
int ret = 0;
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
struct kprobe_ctlblk *kcb;
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
if (kprobe_running()) {
p = get_kprobe(addr);
......@@ -159,11 +166,6 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
goto no_kprobe;
}
/*
* This preempt_disable() matches the preempt_enable_no_resched()
* in post_kprobes_handler()
*/
preempt_disable();
set_current_kprobe(p, regs, kcb);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
if (p->pre_handler && p->pre_handler(p, regs))
......@@ -175,6 +177,7 @@ ss_probe:
return 1;
no_kprobe:
preempt_enable_no_resched();
return ret;
}
......@@ -321,7 +324,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
rcu_read_lock();
switch (val) {
case DIE_DEBUG:
if (kprobe_handler(args->regs))
......@@ -333,14 +335,16 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
break;
case DIE_GPF:
case DIE_PAGE_FAULT:
/* kprobe_running() needs smp_processor_id() */
preempt_disable();
if (kprobe_running() &&
kprobe_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
preempt_enable();
break;
default:
break;
}
rcu_read_unlock();
return ret;
}
......@@ -426,6 +430,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
&(kcb->jprobe_saved_stack),
sizeof(kcb->jprobe_saved_stack));
preempt_enable_no_resched();
return 1;
}
return 0;
......
......@@ -286,16 +286,19 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
}
}
/*
* Interrupts are disabled on entry as trap3 is an interrupt gate and they
* remain disabled thorough out this function.
*/
int __kprobes kprobe_handler(struct pt_regs *regs)
{
struct kprobe *p;
int ret = 0;
kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
struct kprobe_ctlblk *kcb;
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
*/
preempt_disable();
kcb = get_kprobe_ctlblk();
/* Check we're not actually recursing */
if (kprobe_running()) {
......@@ -359,11 +362,6 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
goto no_kprobe;
}
/*
* This preempt_disable() matches the preempt_enable_no_resched()
* in post_kprobe_handler()
*/
preempt_disable();
set_current_kprobe(p, regs, kcb);
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
......@@ -377,6 +375,7 @@ ss_probe:
return 1;
no_kprobe:
preempt_enable_no_resched();
return ret;
}
......@@ -448,8 +447,8 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
/*
* By returning a non-zero value, we are telling
* kprobe_handler() that we have handled unlocking
* and re-enabling preemption
* kprobe_handler() that we don't want the post_handler
* to run (and have re-enabled preemption)
*/
return 1;
}
......@@ -594,7 +593,6 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
struct die_args *args = (struct die_args *)data;
int ret = NOTIFY_DONE;
rcu_read_lock();
switch (val) {
case DIE_INT3:
if (kprobe_handler(args->regs))
......@@ -606,14 +604,16 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
break;
case DIE_GPF:
case DIE_PAGE_FAULT:
/* kprobe_running() needs smp_processor_id() */
preempt_disable();
if (kprobe_running() &&
kprobe_fault_handler(args->regs, args->trapnr))
ret = NOTIFY_STOP;
preempt_enable();
break;
default:
break;
}
rcu_read_unlock();
return ret;
}
......@@ -675,6 +675,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
*regs = kcb->jprobe_saved_regs;
memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
MIN_STACK_SIZE(stack_addr));
preempt_enable_no_resched();
return 1;
}
return 0;
......
......@@ -159,7 +159,7 @@ extern void show_registers(struct pt_regs *regs);
extern kprobe_opcode_t *get_insn_slot(void);
extern void free_insn_slot(kprobe_opcode_t *slot);
/* Get the kprobe at this addr (if any) - called under a rcu_read_lock() */
/* Get the kprobe at this addr (if any) - called with preemption disabled */
struct kprobe *get_kprobe(void *addr);
struct hlist_head * kretprobe_inst_table_head(struct task_struct *tsk);
......
......@@ -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()
* OR
* - under an rcu_read_lock() - from arch/xxx/kernel/kprobes.c
* - with preemption disabled - from arch/xxx/kernel/kprobes.c
*/
struct kprobe __kprobes *get_kprobe(void *addr)
{
......
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