1 files changed, 60 insertions, 11 deletions

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index cfab48566db1..ad7a90212204 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -1,6 +1,5 @@
 /*
  *  Kernel Probes (KProbes)
- *  arch/ppc64/kernel/kprobes.c
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -31,9 +30,11 @@
 #include <linux/kprobes.h>
 #include <linux/ptrace.h>
 #include <linux/preempt.h>
+#include <linux/module.h>
 #include <asm/cacheflush.h>
 #include <asm/kdebug.h>
 #include <asm/sstep.h>
+#include <asm/uaccess.h>
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -82,9 +83,9 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p)
 
 void __kprobes arch_remove_kprobe(struct kprobe *p)
 {
-        down(&kprobe_mutex);
+        mutex_lock(&kprobe_mutex);
         free_insn_slot(p->ainsn.insn);
-        up(&kprobe_mutex);
+        mutex_unlock(&kprobe_mutex);
 }
 
 static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
@@ -373,17 +374,62 @@ static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 {
         struct kprobe *cur = kprobe_running();
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
-
-        if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
-                return 1;
-
-        if (kcb->kprobe_status & KPROBE_HIT_SS) {
-                resume_execution(cur, regs);
+        const struct exception_table_entry *entry;
+
+        switch(kcb->kprobe_status) {
+        case KPROBE_HIT_SS:
+        case KPROBE_REENTER:
+                /*
+                 * We are here because the instruction being single
+                 * stepped caused a page fault. We reset the current
+                 * kprobe and the nip points back to the probe address
+                 * and allow the page fault handler to continue as a
+                 * normal page fault.
+                 */
+                regs->nip = (unsigned long)cur->addr;
                 regs->msr &= ~MSR_SE;
                 regs->msr |= kcb->kprobe_saved_msr;
-
-                reset_current_kprobe();
+                if (kcb->kprobe_status == KPROBE_REENTER)
+                        restore_previous_kprobe(kcb);
+                else
+                        reset_current_kprobe();
                 preempt_enable_no_resched();
+                break;
+        case KPROBE_HIT_ACTIVE:
+        case KPROBE_HIT_SSDONE:
+                /*
+                 * We increment the nmissed count for accounting,
+                 * we can also use npre/npostfault count for accouting
+                 * these specific fault cases.
+                 */
+                kprobes_inc_nmissed_count(cur);
+
+                /*
+                 * We come here because instructions in the pre/post
+                 * handler caused the page_fault, this could happen
+                 * if handler tries to access user space by
+                 * copy_from_user(), get_user() etc. Let the
+                 * user-specified handler try to fix it first.
+                 */
+                if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
+                        return 1;
+
+                /*
+                 * In case the user-specified fault handler returned
+                 * zero, try to fix up.
+                 */
+                if ((entry = search_exception_tables(regs->nip)) != NULL) {
+                        regs->nip = entry->fixup;
+                        return 1;
+                }
+
+                /*
+                 * fixup_exception() could not handle it,
+                 * Let do_page_fault() fix it.
+                 */
+                break;
+        default:
+                break;
         }
         return 0;
 }
@@ -397,6 +443,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
         struct die_args *args = (struct die_args *)data;
         int ret = NOTIFY_DONE;
 
+        if (args->regs && user_mode(args->regs))
+                return ret;
+
         switch (val) {
         case DIE_BPT:
                 if (kprobe_handler(args->regs))