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Kprobes - Increment kprobe missed count for multiprobes

PATCH In review Keshavamurthy Anil S 2 participants 2 messages Dec 9, 2005 – Dec 10, 2005

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PowerPC kprobes
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Keshavamurthy Anil S

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#0 lore raw

PATCH 1/1 Kprobes - Increment kprobe missed count for multiprobes

[BUG][PATCH] Kprobes - Increment kprobe missed count for multiprobes

When multiple probes are registered at the same address and if due to some recursion (probe getting triggered within a probe handler), we skip calling pre_handlers and just increment nmissed field.

The below patch make sure it walks the list for multiple probes case. Without the below patch we get incorrect results of nmissed count for multiple probe case.

Signed-off-by Anil S Keshavamurthy <[email protected]>

-----------------------------------------------------

 arch/i386/kernel/kprobes.c    |    2 +-
 arch/ia64/kernel/kprobes.c    |    2 +-
 arch/powerpc/kernel/kprobes.c |    2 +-
 arch/sparc64/kernel/kprobes.c |    2 +-
 arch/x86_64/kernel/kprobes.c  |    2 +-
 include/linux/kprobes.h       |    1 +
 kernel/kprobes.c              |   13 +++++++++++++
 7 files changed, 19 insertions(+), 5 deletions(-)
arch/i386/kernel/kprobes.c +1 -1
Index: linux-2.6.15-rc5-mm1/arch/i386/kernel/kprobes.c
===================================================================
@@ -191,7 +191,7 @@ static int __kprobes kprobe_handler(stru
 			 */
 			save_previous_kprobe(kcb);
 			set_current_kprobe(p, regs, kcb);
-			p->nmissed++;
+			inc_nmissed_count(p);
 			prepare_singlestep(p, regs);
 			kcb->kprobe_status = KPROBE_REENTER;
 			return 1;
arch/ia64/kernel/kprobes.c +1 -1
Index: linux-2.6.15-rc5-mm1/arch/ia64/kernel/kprobes.c
===================================================================
@@ -630,7 +630,7 @@ static int __kprobes pre_kprobes_handler
 			 */
 			save_previous_kprobe(kcb);
 			set_current_kprobe(p, kcb);
-			p->nmissed++;
+			inc_nmissed_count(p);
 			prepare_ss(p, regs);
 			kcb->kprobe_status = KPROBE_REENTER;
 			return 1;
arch/powerpc/kernel/kprobes.c +1 -1
Index: linux-2.6.15-rc5-mm1/arch/powerpc/kernel/kprobes.c
===================================================================
@@ -174,7 +174,7 @@ static inline int kprobe_handler(struct 
 			save_previous_kprobe(kcb);
 			set_current_kprobe(p, regs, kcb);
 			kcb->kprobe_saved_msr = regs->msr;
-			p->nmissed++;
+			inc_nmissed_count(p);
 			prepare_singlestep(p, regs);
 			kcb->kprobe_status = KPROBE_REENTER;
 			return 1;
arch/sparc64/kernel/kprobes.c +1 -1
Index: linux-2.6.15-rc5-mm1/arch/sparc64/kernel/kprobes.c
===================================================================
@@ -138,7 +138,7 @@ static int __kprobes kprobe_handler(stru
 			 */
 			save_previous_kprobe(kcb);
 			set_current_kprobe(p, regs, kcb);
-			p->nmissed++;
+			inc_nmissed_count(p);
 			kcb->kprobe_status = KPROBE_REENTER;
 			prepare_singlestep(p, regs, kcb);
 			return 1;
arch/x86_64/kernel/kprobes.c +1 -1
Index: linux-2.6.15-rc5-mm1/arch/x86_64/kernel/kprobes.c
===================================================================
@@ -329,7 +329,7 @@ int __kprobes kprobe_handler(struct pt_r
 				 */
 				save_previous_kprobe(kcb);
 				set_current_kprobe(p, regs, kcb);
-				p->nmissed++;
+				inc_nmissed_count(p);
 				prepare_singlestep(p, regs);
 				kcb->kprobe_status = KPROBE_REENTER;
 				return 1;
include/linux/kprobes.h +1 -0
Index: linux-2.6.15-rc5-mm1/include/linux/kprobes.h
===================================================================
@@ -158,6 +158,7 @@ extern int arch_init_kprobes(void);
 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);
+extern void inc_nmissed_count(struct kprobe *p);
 
 /* Get the kprobe at this addr (if any) - called with preemption disabled */
 struct kprobe *get_kprobe(void *addr);
kernel/kprobes.c +13 -0
Index: linux-2.6.15-rc5-mm1/kernel/kprobes.c
===================================================================
@@ -246,6 +246,19 @@ static int __kprobes aggr_break_handler(
 	return ret;
 }
 
+/* Walks the list and increments nmissed count for multiprobe case */
+void __kprobes inc_nmissed_count(struct kprobe *p)
+{
+	struct kprobe *kp;
+	if (p->pre_handler != aggr_pre_handler) {
+		p->nmissed++;
+	} else {
+		list_for_each_entry_rcu(kp, &p->list, list)
+			kp->nmissed++;
+	}
+	return;
+}
+
 /* Called with kretprobe_lock held */
 struct kretprobe_instance __kprobes *get_free_rp_inst(struct kretprobe *rp)
 {
#1 lore raw
Quoted 2 lines · Keshavamurthy Anil S

+void __kprobes inc_nmissed_count(struct kprobe *p)

That's not a good name for a global identifier. I renamed it to kprobes_inc_nmissed_count().