Blackfin arch: add an option to allow people to stick exception stack…

… into L1 scratch

allow people to stick exception stack into L1 scratch
and make sure it gets placed into .bss sections rather than .data

Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

arch/blackfin/Kconfig

@@ -667,6 +667,17 @@ config APP_STACK_L1
 
 	  Currently only works with FLAT binaries.
 
+config EXCEPTION_L1_SCRATCH
+	bool "Locate exception stack in L1 Scratch Memory"
+	default n
+	depends on !APP_STACK_L1 && !SYSCALL_TAB_L1
+	help
+	  Whenever an exception occurs, use the L1 Scratch memory for
+	  stack storage.  You cannot place the stacks of FLAT binaries
+	  in L1 when using this option.
+
+	  If you don't use L1 Scratch, then you should say Y here.
+
 comment "Speed Optimizations"
 config BFIN_INS_LOWOVERHEAD
 	bool "ins[bwl] low overhead, higher interrupt latency"

arch/blackfin/mach-common/entry.S

@@ -1539,14 +1539,23 @@ ENTRY(_sys_call_table)
 	.endr
 END(_sys_call_table)
 
-_exception_stack:
-	.rept 1024
-	.long 0;
-	.endr
-_exception_stack_top:
-
 #if ANOMALY_05000261
 /* Used by the assembly entry point to work around an anomaly.  */
 _last_cplb_fault_retx:
 	.long 0;
 #endif
+
+#ifdef CONFIG_EXCEPTION_L1_SCRATCH
+/* .section .l1.bss.scratch */
+.set _exception_stack_top, L1_SCRATCH_START + L1_SCRATCH_LENGTH
+#else
+#ifdef CONFIG_SYSCALL_TAB_L1
+.section .l1.bss
+#else
+.bss
+#endif
+_exception_stack:
+.size _exception_stack, 1024 * 4
+.set _exception_stack_top, _exception_stack + 1024 * 4
+.size _exception_stack_top, 0
+#endif