Blackfin arch: Fix bug - skip single step in high priority interrupt handler instead of disabling all interrupts in single step debugging.

Skip single step if event priority of current instruction is higher than
that of the first instruction, from which gdb starts single step.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

arch/blackfin/kernel/kgdb.c

@@ -203,6 +203,8 @@ struct hw_breakpoint {
 
 int kgdb_arch_init(void)
 {
+	debugger_step = 0;
+
 	kgdb_remove_all_hw_break();
 	return 0;
 }
@@ -368,6 +370,7 @@ int kgdb_arch_handle_exception(int exceptionVector, int signo,
 	char *ptr;
 	int newPC;
 	int wp_status;
+	int i;
 
 	switch (remcom_in_buffer[0]) {
 	case 'c':
@@ -392,7 +395,18 @@ int kgdb_arch_handle_exception(int exceptionVector, int signo,
 		/* set the trace bit if we're stepping */
 		if (remcom_in_buffer[0] == 's') {
 			linux_regs->syscfg |= 0x1;
-			debugger_step = 1;
+			debugger_step = linux_regs->ipend;
+			debugger_step >>= 6;
+			for (i = 10; i > 0; i--, debugger_step >>= 1)
+				if (debugger_step & 1)
+					break;
+			/* i indicate event priority of current stopped instruction
+			 * user space instruction is 0, IVG15 is 1, IVTMR is 10.
+			 * debugger_step > 0 means in single step mode
+			 */
+			debugger_step = i + 1;
+		} else {
+			debugger_step = 0;
 		}
 
 		wp_status = bfin_read_WPSTAT();

arch/blackfin/mach-common/entry.S

@@ -158,23 +158,45 @@ ENTRY(_ex_single_step)
 	cc = r7 == r6;
 	if cc jump _bfin_return_from_exception;
 
+	/* Don't do single step in hardware exception handler */
+        p5.l = lo(IPEND);
+        p5.h = hi(IPEND);
+	r6 = [p5];
+	cc = bittst(r6, 5);
+	if cc jump _bfin_return_from_exception;
+
+#ifdef CONFIG_KGDB
+	/* skip single step if current interrupt priority is higher than
+	 * that of the first instruction, from which gdb starts single step */
+	r6 >>= 6;
+	r7 = 10;
+.Lfind_priority_start:
+	cc = bittst(r6, 0);
+	if cc jump .Lfind_priority_done;
+	r6 >>= 1;
+	r7 += -1;
+	cc = r7 == 0;
+	if cc jump .Lfind_priority_done;
+	jump.s .Lfind_priority_start;
+.Lfind_priority_done:
+	p4.l = _debugger_step;
+	p4.h = _debugger_step;
+	r6 = [p4];
+	cc = r6 == 0;
+	if cc jump .Ldo_single_step;
+	r6 += -1;
+	cc = r6 < r7;
+	if cc jump _bfin_return_from_exception;
+.Ldo_single_step:
+#endif
+
 	/* If we were in user mode, do the single step normally.  */
-	p5.l = lo(IPEND);
-	p5.h = hi(IPEND);
 	r6 = [p5];
 	r7 = 0xffe0 (z);
 	r7 = r7 & r6;
 	cc = r7 == 0;
-	if !cc jump 1f;
-
-	/* Single stepping only a single instruction, so clear the trace
-	 * bit here.  */
-	r7 = syscfg;
-	bitclr (r7, 0);
-	syscfg = R7;
-	jump _ex_trap_c;
+	if cc jump 1f;
 
-1:
 	/*
 	 * We were in an interrupt handler.  By convention, all of them save
 	 * SYSCFG with their first instruction, so by checking whether our
@@ -202,11 +224,15 @@ ENTRY(_ex_single_step)
 	cc = R7 == R6;
 	if !cc jump _bfin_return_from_exception;
 
+1:
+	/* Single stepping only a single instruction, so clear the trace
+	 * bit here.  */
 	r7 = syscfg;
 	bitclr (r7, 0);
 	syscfg = R7;
 
-	/* Fall through to _bfin_return_from_exception.  */
+	jump _ex_trap_c;
+
 ENDPROC(_ex_single_step)
 
 ENTRY(_bfin_return_from_exception)