1 files changed, 61 insertions, 18 deletions

diff --git a/arch/ppc64/kernel/kprobes.c b/arch/ppc64/kernel/kprobes.c
index 103daaf73573..782ce3efa2c1 100644
--- a/arch/ppc64/kernel/kprobes.c
+++ b/arch/ppc64/kernel/kprobes.c
@@ -32,40 +32,53 @@
 #include <linux/ptrace.h>
 #include <linux/spinlock.h>
 #include <linux/preempt.h>
+#include <asm/cacheflush.h>
 #include <asm/kdebug.h>
 #include <asm/sstep.h>
 
-/* kprobe_status settings */
-#define KPROBE_HIT_ACTIVE	0x00000001
-#define KPROBE_HIT_SS		0x00000002
-
 static struct kprobe *current_kprobe;
 static unsigned long kprobe_status, kprobe_saved_msr;
+static struct kprobe *kprobe_prev;
+static unsigned long kprobe_status_prev, kprobe_saved_msr_prev;
 static struct pt_regs jprobe_saved_regs;
 
 int arch_prepare_kprobe(struct kprobe *p)
 {
+	int ret = 0;
 	kprobe_opcode_t insn = *p->addr;
 
-	if (IS_MTMSRD(insn) || IS_RFID(insn))
-		/* cannot put bp on RFID/MTMSRD */
-		return 1;
-	return 0;
+	if ((unsigned long)p->addr & 0x03) {
+		printk("Attempt to register kprobe at an unaligned address\n");
+		ret = -EINVAL;
+	} else if (IS_MTMSRD(insn) || IS_RFID(insn)) {
+		printk("Cannot register a kprobe on rfid or mtmsrd\n");
+		ret = -EINVAL;
+	}
+	return ret;
 }
 
 void arch_copy_kprobe(struct kprobe *p)
 {
 	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+	p->opcode = *p->addr;
 }
 
-void arch_remove_kprobe(struct kprobe *p)
+void arch_arm_kprobe(struct kprobe *p)
 {
+	*p->addr = BREAKPOINT_INSTRUCTION;
+	flush_icache_range((unsigned long) p->addr,
+			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
 }
 
-static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
+void arch_disarm_kprobe(struct kprobe *p)
 {
 	*p->addr = p->opcode;
-	regs->nip = (unsigned long)p->addr;
+	flush_icache_range((unsigned long) p->addr,
+			   (unsigned long) p->addr + sizeof(kprobe_opcode_t));
+}
+
+void arch_remove_kprobe(struct kprobe *p)
+{
 }
 
 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
@@ -78,6 +91,20 @@ static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 		regs->nip = (unsigned long)&p->ainsn.insn;
 }
 
+static inline void save_previous_kprobe(void)
+{
+	kprobe_prev = current_kprobe;
+	kprobe_status_prev = kprobe_status;
+	kprobe_saved_msr_prev = kprobe_saved_msr;
+}
+
+static inline void restore_previous_kprobe(void)
+{
+	current_kprobe = kprobe_prev;
+	kprobe_status = kprobe_status_prev;
+	kprobe_saved_msr = kprobe_saved_msr_prev;
+}
+
 static inline int kprobe_handler(struct pt_regs *regs)
 {
 	struct kprobe *p;
@@ -96,8 +123,19 @@ static inline int kprobe_handler(struct pt_regs *regs)
 				unlock_kprobes();
 				goto no_kprobe;
 			}
-			disarm_kprobe(p, regs);
-			ret = 1;
+			/* We have reentered the kprobe_handler(), since
+			 * another probe was hit while within the handler.
+			 * We here save the original kprobes variables and
+			 * just single step on the instruction of the new probe
+			 * without calling any user handlers.
+			 */
+			save_previous_kprobe();
+			current_kprobe = p;
+			kprobe_saved_msr = regs->msr;
+			p->nmissed++;
+			prepare_singlestep(p, regs);
+			kprobe_status = KPROBE_REENTER;
+			return 1;
 		} else {
 			p = current_kprobe;
 			if (p->break_handler && p->break_handler(p, regs)) {
@@ -172,8 +210,6 @@ static void resume_execution(struct kprobe *p, struct pt_regs *regs)
 	ret = emulate_step(regs, p->ainsn.insn[0]);
 	if (ret == 0)
 		regs->nip = (unsigned long)p->addr + 4;
-
-	regs->msr &= ~MSR_SE;
 }
 
 static inline int post_kprobe_handler(struct pt_regs *regs)
@@ -181,13 +217,21 @@ static inline int post_kprobe_handler(struct pt_regs *regs)
 	if (!kprobe_running())
 		return 0;
 
-	if (current_kprobe->post_handler)
+	if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
+		kprobe_status = KPROBE_HIT_SSDONE;
 		current_kprobe->post_handler(current_kprobe, regs, 0);
+	}
 
 	resume_execution(current_kprobe, regs);
 	regs->msr |= kprobe_saved_msr;
 
+	/*Restore back the original saved kprobes variables and continue. */
+	if (kprobe_status == KPROBE_REENTER) {
+		restore_previous_kprobe();
+		goto out;
+	}
 	unlock_kprobes();
+out:
 	preempt_enable_no_resched();
 
 	/*
@@ -210,6 +254,7 @@ static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 
 	if (kprobe_status & KPROBE_HIT_SS) {
 		resume_execution(current_kprobe, regs);
+		regs->msr &= ~MSR_SE;
 		regs->msr |= kprobe_saved_msr;
 
 		unlock_kprobes();
@@ -233,8 +278,6 @@ int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
 	 */
 	preempt_disable();
 	switch (val) {
-	case DIE_IABR_MATCH:
-	case DIE_DABR_MATCH:
 	case DIE_BPT:
 		if (kprobe_handler(args->regs))
 			ret = NOTIFY_STOP;