[PATCH 1/2] powerpc/hw_breakpoint: move instruction stepping out of hw_breakpoint_handler()

[Ravi Bangoria]

From: Christophe Leroy <christophe.le...@c-s.fr>

On 8xx, breakpoints stop after executing the instruction, so
stepping/emulation is not needed. Move it into a sub-function and
remove the #ifdefs.

Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
Reviewed-by: Ravi Bangoria <ravi.bango...@linux.ibm.com>
---
 arch/powerpc/kernel/hw_breakpoint.c | 60 ++++++++++++++++-------------
 1 file changed, 33 insertions(+), 27 deletions(-)

diff --git a/arch/powerpc/kernel/hw_breakpoint.c 
b/arch/powerpc/kernel/hw_breakpoint.c
index c8d1fa2e9d53..28ad3171bb82 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -198,15 +198,43 @@ void thread_change_pc(struct task_struct *tsk, struct 
pt_regs *regs)
 /*
  * Handle debug exception notifications.
  */
+static bool stepping_handler(struct pt_regs *regs, struct perf_event *bp,
+                            unsigned long addr)
+{
+       int stepped;
+       unsigned int instr;
+
+       /* Do not emulate user-space instructions, instead single-step them */
+       if (user_mode(regs)) {
+               current->thread.last_hit_ubp = bp;
+               regs->msr |= MSR_SE;
+               return false;
+       }
+
+       stepped = 0;
+       instr = 0;
+       if (!__get_user_inatomic(instr, (unsigned int *)regs->nip))
+               stepped = emulate_step(regs, instr);
+
+       /*
+        * emulate_step() could not execute it. We've failed in reliably
+        * handling the hw-breakpoint. Unregister it and throw a warning
+        * message to let the user know about it.
+        */
+       if (!stepped) {
+               WARN(1, "Unable to handle hardware breakpoint. Breakpoint at "
+                       "0x%lx will be disabled.", addr);
+               perf_event_disable_inatomic(bp);
+               return false;
+       }
+       return true;
+}
+
 int hw_breakpoint_handler(struct die_args *args)
 {
        int rc = NOTIFY_STOP;
        struct perf_event *bp;
        struct pt_regs *regs = args->regs;
-#ifndef CONFIG_PPC_8xx
-       int stepped = 1;
-       unsigned int instr;
-#endif
        struct arch_hw_breakpoint *info;
        unsigned long dar = regs->dar;
 
@@ -251,31 +279,9 @@ int hw_breakpoint_handler(struct die_args *args)
              (dar - bp->attr.bp_addr < bp->attr.bp_len)))
                info->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
 
-#ifndef CONFIG_PPC_8xx
-       /* Do not emulate user-space instructions, instead single-step them */
-       if (user_mode(regs)) {
-               current->thread.last_hit_ubp = bp;
-               regs->msr |= MSR_SE;
+       if (!IS_ENABLED(CONFIG_PPC_8xx) && !stepping_handler(regs, bp, 
info->address))
                goto out;
-       }
-
-       stepped = 0;
-       instr = 0;
-       if (!__get_user_inatomic(instr, (unsigned int *) regs->nip))
-               stepped = emulate_step(regs, instr);
 
-       /*
-        * emulate_step() could not execute it. We've failed in reliably
-        * handling the hw-breakpoint. Unregister it and throw a warning
-        * message to let the user know about it.
-        */
-       if (!stepped) {
-               WARN(1, "Unable to handle hardware breakpoint. Breakpoint at "
-                       "0x%lx will be disabled.", info->address);
-               perf_event_disable_inatomic(bp);
-               goto out;
-       }
-#endif
        /*
         * As a policy, the callback is invoked in a 'trigger-after-execute'
         * fashion
-- 
2.21.0