2 files changed, 18 insertions, 2 deletions

diff --git a/arch/mn10300/Kconfig.debug b/arch/mn10300/Kconfig.debug
index ce83c74b3fd7..a1b8620f65ae 100644
--- a/arch/mn10300/Kconfig.debug
+++ b/arch/mn10300/Kconfig.debug
@@ -54,6 +54,14 @@ config GDBSTUB_IMMEDIATE
           possible, leaving the program counter at the beginning of
           start_kernel() in init/main.c.
 
+config GDBSTUB_ALLOW_SINGLE_STEP
+        bool "Allow software single-stepping in GDB stub"
+        depends on GDBSTUB && !SMP && !PREEMPT
+        help
+          Allow GDB stub to perform software single-stepping through the
+          kernel.  This doesn't work very well on SMP or preemptible kernels as
+          it uses temporary breakpoints to emulate single-stepping.
+
 config GDB_CONSOLE
         bool "Console output to GDB"
         depends on GDBSTUB
diff --git a/arch/mn10300/kernel/gdb-stub.c b/arch/mn10300/kernel/gdb-stub.c
index b169d99d9f20..a9c1e916687f 100644
--- a/arch/mn10300/kernel/gdb-stub.c
+++ b/arch/mn10300/kernel/gdb-stub.c
@@ -405,6 +405,7 @@ static int hexToInt(char **ptr, int *intValue)
         return (numChars);
 }
 
+#ifdef CONFIG_GDBSTUB_ALLOW_SINGLE_STEP
 /*
  * We single-step by setting breakpoints. When an exception
  * is handled, we need to restore the instructions hoisted
@@ -729,6 +730,7 @@ static int gdbstub_single_step(struct pt_regs *regs)
         __gdbstub_restore_bp();
         return -EFAULT;
 }
+#endif /* CONFIG_GDBSTUB_ALLOW_SINGLE_STEP */
 
 #ifdef CONFIG_GDBSTUB_CONSOLE
 
@@ -1208,11 +1210,13 @@ static int gdbstub(struct pt_regs *regs, enum exception_code excep)
         /* if we were single stepping, restore the opcodes hoisted for the
          * breakpoint[s] */
         broke = 0;
+#ifdef CONFIG_GDBSTUB_ALLOW_SINGLE_STEP
         if ((step_bp[0].addr && step_bp[0].addr == (u8 *) regs->pc) ||
             (step_bp[1].addr && step_bp[1].addr == (u8 *) regs->pc))
                 broke = 1;
 
         __gdbstub_restore_bp();
+#endif
 
         if (gdbstub_rx_unget) {
                 sigval = SIGINT;
@@ -1548,17 +1552,21 @@ packet_waiting:
                          * Step to next instruction
                          */
                 case 's':
-                        /*
-                         * using the T flag doesn't seem to perform single
+                        /* Using the T flag doesn't seem to perform single
                          * stepping (it seems to wind up being caught by the
                          * JTAG unit), so we have to use breakpoints and
                          * continue instead.
                          */
+#ifdef CONFIG_GDBSTUB_ALLOW_SINGLE_STEP
                         if (gdbstub_single_step(regs) < 0)
                                 /* ignore any fault error for now */
                                 gdbstub_printk("unable to set single-step"
                                                " bp\n");
                         goto done;
+#else
+                        gdbstub_strcpy(output_buffer, "E01");
+                        break;
+#endif
 
                         /*
                          * Set baud rate (bBB)