kprobes: kretprobes simplifications

 - consolidate duplicate code in all arch_prepare_kretprobe instances
   into common code
 - replace various odd helpers that use hlist_for_each_entry to get
   the first elemenet of a list with either a hlist_for_each_entry_save
   or an opencoded access to the first element in the caller
 - inline add_rp_inst into it's only remaining caller
 - use kretprobe_inst_table_head instead of opencoding it

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 21 insertions, 68 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 3fbef28..b6a9d64 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -226,24 +226,15 @@ static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 }
 
 /* Called with kretprobe_lock held */
-void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 				      struct pt_regs *regs)
 {
 	unsigned long *sara = (unsigned long *)&regs->esp;
 
-	struct kretprobe_instance *ri;
+	ri->ret_addr = (kprobe_opcode_t *) *sara;
 
-	if ((ri = get_free_rp_inst(rp)) != NULL) {
-		ri->rp = rp;
-		ri->task = current;
-		ri->ret_addr = (kprobe_opcode_t *) *sara;
-
-		/* Replace the return addr with trampoline addr */
-		*sara = (unsigned long) &kretprobe_trampoline;
-		add_rp_inst(ri);
-	} else {
-		rp->nmissed++;
-	}
+	/* Replace the return addr with trampoline addr */
+	*sara = (unsigned long) &kretprobe_trampoline;
 }
 
 /*
diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 353689e..0b72f0f 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -465,23 +465,13 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 }
 
 /* Called with kretprobe_lock held */
-void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 				      struct pt_regs *regs)
 {
-	struct kretprobe_instance *ri;
+	ri->ret_addr = (kprobe_opcode_t *)regs->b0;
 
-	if ((ri = get_free_rp_inst(rp)) != NULL) {
-		ri->rp = rp;
-		ri->task = current;
-		ri->ret_addr = (kprobe_opcode_t *)regs->b0;
-
-		/* Replace the return addr with trampoline addr */
-		regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;
-
-		add_rp_inst(ri);
-	} else {
-		rp->nmissed++;
-	}
+	/* Replace the return addr with trampoline addr */
+	regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;
 }
 
 int __kprobes arch_prepare_kprobe(struct kprobe *p)
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 3d54ad7..aed58e1 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -126,22 +126,13 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 }
 
 /* Called with kretprobe_lock held */
-void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 				      struct pt_regs *regs)
 {
-	struct kretprobe_instance *ri;
-
-	if ((ri = get_free_rp_inst(rp)) != NULL) {
-		ri->rp = rp;
-		ri->task = current;
-		ri->ret_addr = (kprobe_opcode_t *)regs->link;
-
-		/* Replace the return addr with trampoline addr */
-		regs->link = (unsigned long)kretprobe_trampoline;
-		add_rp_inst(ri);
-	} else {
-		rp->nmissed++;
-	}
+	ri->ret_addr = (kprobe_opcode_t *)regs->link;
+
+	/* Replace the return addr with trampoline addr */
+	regs->link = (unsigned long)kretprobe_trampoline;
 }
 
 static int __kprobes kprobe_handler(struct pt_regs *regs)
diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index 8516a94..9d0f0d0 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -271,23 +271,13 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
 }
 
 /* Called with kretprobe_lock held */
-void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 					struct pt_regs *regs)
 {
-	struct kretprobe_instance *ri;
+	ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 
-	if ((ri = get_free_rp_inst(rp)) != NULL) {
-		ri->rp = rp;
-		ri->task = current;
-		ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
-
-		/* Replace the return addr with trampoline addr */
-		regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
-
-		add_rp_inst(ri);
-	} else {
-		rp->nmissed++;
-	}
+	/* Replace the return addr with trampoline addr */
+	regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
 }
 
 static int __kprobes kprobe_handler(struct pt_regs *regs)
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 5841ba5..f995bea 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -266,23 +266,14 @@ static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 }
 
 /* Called with kretprobe_lock held */
-void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
 				      struct pt_regs *regs)
 {
 	unsigned long *sara = (unsigned long *)regs->rsp;
-	struct kretprobe_instance *ri;
 
-	if ((ri = get_free_rp_inst(rp)) != NULL) {
-		ri->rp = rp;
-		ri->task = current;
-		ri->ret_addr = (kprobe_opcode_t *) *sara;
-
-		/* Replace the return addr with trampoline addr */
-		*sara = (unsigned long) &kretprobe_trampoline;
-		add_rp_inst(ri);
-	} else {
-		rp->nmissed++;
-	}
+	ri->ret_addr = (kprobe_opcode_t *) *sara;
+	/* Replace the return addr with trampoline addr */
+	*sara = (unsigned long) &kretprobe_trampoline;
 }
 
 int __kprobes kprobe_handler(struct pt_regs *regs)