1 files changed, 29 insertions, 7 deletions

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index c176c513566b..4ba2af125450 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -34,6 +34,13 @@
 #include <asm/cacheflush.h>
 #include <asm/sstep.h>
 #include <asm/uaccess.h>
+#include <asm/system.h>
+
+#ifdef CONFIG_BOOKE
+#define MSR_SINGLESTEP  (MSR_DE)
+#else
+#define MSR_SINGLESTEP  (MSR_SE)
+#endif
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -53,7 +60,8 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
                 ret = -EINVAL;
         }
 
-        /* insn must be on a special executable page on ppc64 */
+        /* insn must be on a special executable page on ppc64.  This is
+         * not explicitly required on ppc32 (right now), but it doesn't hurt */
         if (!ret) {
                 p->ainsn.insn = get_insn_slot();
                 if (!p->ainsn.insn)
@@ -95,7 +103,16 @@ void __kprobes arch_remove_kprobe(struct kprobe *p)
 
 static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
 {
-        regs->msr |= MSR_SE;
+        /* We turn off async exceptions to ensure that the single step will
+         * be for the instruction we have the kprobe on, if we dont its
+         * possible we'd get the single step reported for an exception handler
+         * like Decrementer or External Interrupt */
+        regs->msr &= ~MSR_EE;
+        regs->msr |= MSR_SINGLESTEP;
+#ifdef CONFIG_BOOKE
+        regs->msr &= ~MSR_CE;
+        mtspr(SPRN_DBCR0, mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
+#endif
 
         /*
          * On powerpc we should single step on the original
@@ -158,7 +175,8 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
                         kprobe_opcode_t insn = *p->ainsn.insn;
                         if (kcb->kprobe_status == KPROBE_HIT_SS &&
                                         is_trap(insn)) {
-                                regs->msr &= ~MSR_SE;
+                                /* Turn off 'trace' bits */
+                                regs->msr &= ~MSR_SINGLESTEP;
                                 regs->msr |= kcb->kprobe_saved_msr;
                                 goto no_kprobe;
                         }
@@ -376,6 +394,10 @@ static int __kprobes post_kprobe_handler(struct pt_regs *regs)
         if (!cur)
                 return 0;
 
+        /* make sure we got here for instruction we have a kprobe on */
+        if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
+                return 0;
+
         if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
                 cur->post_handler(cur, regs, 0);
@@ -395,10 +417,10 @@ out:
 
         /*
          * if somebody else is singlestepping across a probe point, msr
-         * will have SE set, in which case, continue the remaining processing
+         * will have DE/SE set, in which case, continue the remaining processing
          * of do_debug, as if this is not a probe hit.
          */
-        if (regs->msr & MSR_SE)
+        if (regs->msr & MSR_SINGLESTEP)
                 return 0;
 
         return 1;
@@ -421,7 +443,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
                  * normal page fault.
                  */
                 regs->nip = (unsigned long)cur->addr;
-                regs->msr &= ~MSR_SE;
+                regs->msr &= ~MSR_SINGLESTEP; /* Turn off 'trace' bits */
                 regs->msr |= kcb->kprobe_saved_msr;
                 if (kcb->kprobe_status == KPROBE_REENTER)
                         restore_previous_kprobe(kcb);
@@ -498,7 +520,7 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 #ifdef CONFIG_PPC64
 unsigned long arch_deref_entry_point(void *entry)
 {
-        return (unsigned long)(((func_descr_t *)entry)->entry);
+        return ((func_descr_t *)entry)->entry;
 }
 #endif