[PATCH] kprobes: x86_64 memory allocation changes

Minor changes to the kprobes code to provide memory allocation for x86_64
architecture outside kprobes spin lock.
Signed-off-by: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/kprobes.c

@@ -62,10 +62,14 @@ static inline int is_IF_modifier(kprobe_opcode_t opcode)
 
 int arch_prepare_kprobe(struct kprobe *p)
 {
-	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
 	return 0;
 }
 
+void arch_copy_kprobe(struct kprobe *p)
+{
+	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+}
+
 void arch_remove_kprobe(struct kprobe *p)
 {
 }

arch/ppc64/kernel/kprobes.c

@@ -45,13 +45,19 @@ static struct pt_regs jprobe_saved_regs;
 
 int arch_prepare_kprobe(struct kprobe *p)
 {
-	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
-	if (IS_MTMSRD(p->ainsn.insn[0]) || IS_RFID(p->ainsn.insn[0]))
+	kprobe_opcode_t insn = *p->addr;
+
+	if (IS_MTMSRD(insn) || IS_RFID(insn))
 		/* cannot put bp on RFID/MTMSRD */
 		return 1;
 	return 0;
 }
 
+void arch_copy_kprobe(struct kprobe *p)
+{
+	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+}
+
 void arch_remove_kprobe(struct kprobe *p)
 {
 }

arch/sparc64/kernel/kprobes.c

@@ -39,10 +39,14 @@
  */
 
 int arch_prepare_kprobe(struct kprobe *p)
+{
+	return 0;
+}
+
+void arch_copy_kprobe(struct kprobe *p)
 {
 	p->ainsn.insn[0] = *p->addr;
 	p->ainsn.insn[1] = BREAKPOINT_INSTRUCTION_2;
-	return 0;
 }
 
 void arch_remove_kprobe(struct kprobe *p)

arch/x86_64/kernel/kprobes.c

@@ -39,6 +39,8 @@
 #include <asm/pgtable.h>
 #include <asm/kdebug.h>
 
+static DECLARE_MUTEX(kprobe_mutex);
+
 /* kprobe_status settings */
 #define KPROBE_HIT_ACTIVE	0x00000001
 #define KPROBE_HIT_SS		0x00000002
@@ -75,17 +77,25 @@ static inline int is_IF_modifier(kprobe_opcode_t *insn)
 int arch_prepare_kprobe(struct kprobe *p)
 {
 	/* insn: must be on special executable page on x86_64. */
+	up(&kprobe_mutex);
 	p->ainsn.insn = get_insn_slot();
+	down(&kprobe_mutex);
 	if (!p->ainsn.insn) {
 		return -ENOMEM;
 	}
-	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
 	return 0;
 }
 
+void arch_copy_kprobe(struct kprobe *p)
+{
+	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
+}
+
 void arch_remove_kprobe(struct kprobe *p)
 {
+	up(&kprobe_mutex);
 	free_insn_slot(p->ainsn.insn);
+	down(&kprobe_mutex);
 }
 
 static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
@@ -425,12 +435,12 @@ static kprobe_opcode_t *get_insn_slot(void)
 	}
 
 	/* All out of space.  Need to allocate a new page. Use slot 0.*/
-	kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_ATOMIC);
+	kip = kmalloc(sizeof(struct kprobe_insn_page), GFP_KERNEL);
 	if (!kip) {
 		return NULL;
 	}
 	kip->insns = (kprobe_opcode_t*) __vmalloc(PAGE_SIZE,
-		GFP_ATOMIC|__GFP_HIGHMEM, __pgprot(__PAGE_KERNEL_EXEC));
+		GFP_KERNEL|__GFP_HIGHMEM, __pgprot(__PAGE_KERNEL_EXEC));
 	if (!kip->insns) {
 		kfree(kip);
 		return NULL;

include/linux/kprobes.h

@@ -95,6 +95,7 @@ static inline int kprobe_running(void)
 }
 
 extern int arch_prepare_kprobe(struct kprobe *p);
+extern void arch_copy_kprobe(struct kprobe *p);
 extern void arch_remove_kprobe(struct kprobe *p);
 extern void show_registers(struct pt_regs *regs);
 

kernel/kprobes.c

@@ -76,18 +76,19 @@ struct kprobe *get_kprobe(void *addr)
 int register_kprobe(struct kprobe *p)
 {
 	int ret = 0;
-	unsigned long flags;
+	unsigned long flags = 0;
 
+	if ((ret = arch_prepare_kprobe(p)) != 0) {
+		goto out;
+	}
 	spin_lock_irqsave(&kprobe_lock, flags);
 	INIT_HLIST_NODE(&p->hlist);
 	if (get_kprobe(p->addr)) {
 		ret = -EEXIST;
 		goto out;
 	}
+	arch_copy_kprobe(p);
 
-	if ((ret = arch_prepare_kprobe(p)) != 0) {
-		goto out;
-	}
 	hlist_add_head(&p->hlist,
 		       &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
 
@@ -97,14 +98,16 @@ int register_kprobe(struct kprobe *p)
 			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
       out:
 	spin_unlock_irqrestore(&kprobe_lock, flags);
+	if (ret == -EEXIST)
+		arch_remove_kprobe(p);
 	return ret;
 }
 
 void unregister_kprobe(struct kprobe *p)
 {
 	unsigned long flags;
-	spin_lock_irqsave(&kprobe_lock, flags);
 	arch_remove_kprobe(p);
+	spin_lock_irqsave(&kprobe_lock, flags);
 	*p->addr = p->opcode;
 	hlist_del(&p->hlist);
 	flush_icache_range((unsigned long) p->addr,