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>

7 files changed, 44 insertions, 114 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 3fbef288c376..b6a9d64c2251 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 353689edebd5..0b72f0f94192 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 3d54ad7dd1f9..aed58e1cb91f 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 8516a94d8163..9d0f0d09d473 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 5841ba5f479b..f995bea6e2c1 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)
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 850ee871e353..6fc623e41fd8 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -123,7 +123,8 @@ DECLARE_PER_CPU(struct kprobe *, current_kprobe);
 DECLARE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
 #ifdef ARCH_SUPPORTS_KRETPROBES
-extern void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs);
+extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
+                                   struct pt_regs *regs);
 #else /* ARCH_SUPPORTS_KRETPROBES */
 static inline void arch_prepare_kretprobe(struct kretprobe *rp,