powerpc, hw_breakpoint: Cooperate better with other single-steppers
The code we had to clear the MSR_SE bit was not doing anything because
the caller (ultimately single_step_exception() in traps.c) had already
cleared. Instead of trying to leave MSR_SE set if the TIF_SINGLESTEP
flag is set (which indicates that the process is being single-stepped
by ptrace), we instead return NOTIFY_DONE in that case, which means
the caller will generate a SIGTRAP for the process.
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
index 241e097..5a1d55d 100644
--- a/arch/powerpc/kernel/hw_breakpoint.c
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -304,15 +304,16 @@
if (!bp_info->extraneous_interrupt)
perf_bp_event(bp, regs);
- /*
- * Do not disable MSR_SE if the process was already in
- * single-stepping mode.
- */
- if (!test_thread_flag(TIF_SINGLESTEP))
- regs->msr &= ~MSR_SE;
-
set_dabr(bp_info->address | bp_info->type | DABR_TRANSLATION);
current->thread.last_hit_ubp = NULL;
+
+ /*
+ * If the process was being single-stepped by ptrace, let the
+ * other single-step actions occur (e.g. generate SIGTRAP).
+ */
+ if (test_thread_flag(TIF_SINGLESTEP))
+ return NOTIFY_DONE;
+
return NOTIFY_STOP;
}