[PATCH] Kprobes: preempt_disable/enable() reordering redux
From: Ananth N Mavinakayanahalli
Date: Mon Oct 24 2005 - 10:58:16 EST
From: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
This patch (over 2.6.14-rc4-mm1) reorganizes 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: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@xxxxxxxxx>
---
arch/i386/kernel/kprobes.c | 25 +++++++++++++++----------
arch/ia64/kernel/kprobes.c | 37 ++++++++++++++++++++-----------------
arch/ppc64/kernel/kprobes.c | 25 +++++++++++++++----------
arch/sparc64/kernel/kprobes.c | 21 +++++++++++++--------
arch/x86_64/kernel/kprobes.c | 29 +++++++++++++++--------------
include/linux/kprobes.h | 2 +-
kernel/kprobes.c | 2 +-
7 files changed, 80 insertions(+), 61 deletions(-)
Index: linux-2.6.14-rc4/arch/i386/kernel/kprobes.c
===================================================================
--- linux-2.6.14-rc4.orig/arch/i386/kernel/kprobes.c 2005-10-17 18:59:51.000000000 -0400
+++ linux-2.6.14-rc4/arch/i386/kernel/kprobes.c 2005-10-21 11:02:52.000000000 -0400
@@ -153,7 +153,14 @@ static int __kprobes kprobe_handler(stru
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(stru
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(s
/*
* 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(s
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(s
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(stru
*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;
Index: linux-2.6.14-rc4/include/linux/kprobes.h
===================================================================
--- linux-2.6.14-rc4.orig/include/linux/kprobes.h 2005-10-17 19:00:01.000000000 -0400
+++ linux-2.6.14-rc4/include/linux/kprobes.h 2005-10-19 10:56:35.000000000 -0400
@@ -159,7 +159,7 @@ extern void show_registers(struct pt_reg
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);
Index: linux-2.6.14-rc4/kernel/kprobes.c
===================================================================
--- linux-2.6.14-rc4.orig/kernel/kprobes.c 2005-10-17 19:00:02.000000000 -0400
+++ linux-2.6.14-rc4/kernel/kprobes.c 2005-10-18 14:19:01.000000000 -0400
@@ -167,7 +167,7 @@ static inline void reset_kprobe_instance
* 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)
{
Index: linux-2.6.14-rc4/arch/ia64/kernel/kprobes.c
===================================================================
--- linux-2.6.14-rc4.orig/arch/ia64/kernel/kprobes.c 2005-10-17 18:59:52.000000000 -0400
+++ linux-2.6.14-rc4/arch/ia64/kernel/kprobes.c 2005-10-21 13:50:10.000000000 -0400
@@ -389,11 +389,11 @@ int __kprobes trampoline_probe_handler(s
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
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
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_handl
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(s
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(s
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(stru
struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
*regs = kcb->jprobe_saved_regs;
+ preempt_enable_no_resched();
return 1;
}
Index: linux-2.6.14-rc4/arch/ppc64/kernel/kprobes.c
===================================================================
--- linux-2.6.14-rc4.orig/arch/ppc64/kernel/kprobes.c 2005-10-17 18:59:52.000000000 -0400
+++ linux-2.6.14-rc4/arch/ppc64/kernel/kprobes.c 2005-10-19 11:00:02.000000000 -0400
@@ -148,7 +148,14 @@ static inline int kprobe_handler(struct
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
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(s
/*
* 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(s
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))
@@ -397,14 +399,16 @@ int __kprobes kprobe_exceptions_notify(s
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;
}
@@ -441,6 +445,7 @@ int __kprobes longjmp_break_handler(stru
* saved regs...
*/
memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
+ preempt_enable_no_resched();
return 1;
}
Index: linux-2.6.14-rc4/arch/sparc64/kernel/kprobes.c
===================================================================
--- linux-2.6.14-rc4.orig/arch/sparc64/kernel/kprobes.c 2005-10-17 18:59:53.000000000 -0400
+++ linux-2.6.14-rc4/arch/sparc64/kernel/kprobes.c 2005-10-19 11:00:21.000000000 -0400
@@ -113,7 +113,14 @@ static int __kprobes kprobe_handler(stru
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(stru
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(s
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(s
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(stru
&(kcb->jprobe_saved_stack),
sizeof(kcb->jprobe_saved_stack));
+ preempt_enable_no_resched();
return 1;
}
return 0;
Index: linux-2.6.14-rc4/arch/x86_64/kernel/kprobes.c
===================================================================
--- linux-2.6.14-rc4.orig/arch/x86_64/kernel/kprobes.c 2005-10-17 18:59:53.000000000 -0400
+++ linux-2.6.14-rc4/arch/x86_64/kernel/kprobes.c 2005-10-19 11:01:31.000000000 -0400
@@ -286,16 +286,19 @@ void __kprobes arch_prepare_kretprobe(st
}
}
-/*
- * 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_r
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(s
/*
* 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(s
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(s
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(stru
*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;
-
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