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>

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 3fbef28..b6a9d64 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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 850ee87..6fc623e 100644 (file)
--- 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,
                                        struct pt_regs *regs)
@@ -209,8 +210,6 @@ void jprobe_return(void);
 int register_kretprobe(struct kretprobe *rp);
 void unregister_kretprobe(struct kretprobe *rp);
 
-struct kretprobe_instance *get_free_rp_inst(struct kretprobe *rp);
-void add_rp_inst(struct kretprobe_instance *ri);
 void kprobe_flush_task(struct task_struct *tk);
 void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);
 #else /* CONFIG_KPROBES */

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2285700..f58f171 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -357,46 +357,6 @@ void __kprobes kprobes_inc_nmissed_count(struct kprobe *p)
        return;
 }
 
-/* Called with kretprobe_lock held */
-struct kretprobe_instance __kprobes *get_free_rp_inst(struct kretprobe *rp)
-{
-       struct hlist_node *node;
-       struct kretprobe_instance *ri;
-       hlist_for_each_entry(ri, node, &rp->free_instances, uflist)
-               return ri;
-       return NULL;
-}
-
-/* Called with kretprobe_lock held */
-static struct kretprobe_instance __kprobes *get_used_rp_inst(struct kretprobe
-                                                             *rp)
-{
-       struct hlist_node *node;
-       struct kretprobe_instance *ri;
-       hlist_for_each_entry(ri, node, &rp->used_instances, uflist)
-               return ri;
-       return NULL;
-}
-
-/* Called with kretprobe_lock held */
-void __kprobes add_rp_inst(struct kretprobe_instance *ri)
-{
-       /*
-        * Remove rp inst off the free list -
-        * Add it back when probed function returns
-        */
-       hlist_del(&ri->uflist);
-
-       /* Add rp inst onto table */
-       INIT_HLIST_NODE(&ri->hlist);
-       hlist_add_head(&ri->hlist,
-                       &kretprobe_inst_table[hash_ptr(ri->task, KPROBE_HASH_BITS)]);
-
-       /* Also add this rp inst to the used list. */
-       INIT_HLIST_NODE(&ri->uflist);
-       hlist_add_head(&ri->uflist, &ri->rp->used_instances);
-}
-
 /* Called with kretprobe_lock held */
 void __kprobes recycle_rp_inst(struct kretprobe_instance *ri,
                                struct hlist_head *head)
@@ -450,7 +410,9 @@ void __kprobes kprobe_flush_task(struct task_struct *tk)
 static inline void free_rp_inst(struct kretprobe *rp)
 {
        struct kretprobe_instance *ri;
-       while ((ri = get_free_rp_inst(rp)) != NULL) {
+       struct hlist_node *pos, *next;
+
+       hlist_for_each_entry_safe(ri, pos, next, &rp->free_instances, uflist) {
                hlist_del(&ri->uflist);
                kfree(ri);
        }
@@ -732,7 +694,21 @@ static int __kprobes pre_handler_kretprobe(struct kprobe *p,
 
        /*TODO: consider to only swap the RA after the last pre_handler fired */
        spin_lock_irqsave(&kretprobe_lock, flags);
-       arch_prepare_kretprobe(rp, regs);
+       if (!hlist_empty(&rp->free_instances)) {
+               struct kretprobe_instance *ri;
+
+               ri = hlist_entry(rp->free_instances.first,
+                                struct kretprobe_instance, uflist);
+               ri->rp = rp;
+               ri->task = current;
+               arch_prepare_kretprobe(ri, regs);
+
+               /* XXX(hch): why is there no hlist_move_head? */
+               hlist_del(&ri->uflist);
+               hlist_add_head(&ri->uflist, &ri->rp->used_instances);
+               hlist_add_head(&ri->hlist, kretprobe_inst_table_head(ri->task));
+       } else
+               rp->nmissed++;
        spin_unlock_irqrestore(&kretprobe_lock, flags);
        return 0;
 }
@@ -795,11 +771,13 @@ void __kprobes unregister_kretprobe(struct kretprobe *rp)
 {
        unsigned long flags;
        struct kretprobe_instance *ri;
+       struct hlist_node *pos, *next;
 
        unregister_kprobe(&rp->kp);
+
        /* No race here */
        spin_lock_irqsave(&kretprobe_lock, flags);
-       while ((ri = get_used_rp_inst(rp)) != NULL) {
+       hlist_for_each_entry_safe(ri, pos, next, &rp->used_instances, uflist) {
                ri->rp = NULL;
                hlist_del(&ri->uflist);
        }