[ARM] nommu: fixups for the exception vectors

The high page vector (0xFFFF0000) does not supported in nommu mode.
This patch allows the vectors to be 0x00000000 or the begining of DRAM
in nommu mode.
Signed-off-by: Hyok S. Choi <hyok.choi@samsung.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -72,6 +72,14 @@ config FIQ
 config ARCH_MTD_XIP
 	bool
 
+config VECTORS_BASE
+	hex
+	default 0xffff0000 if MMU
+	default DRAM_BASE if REMAP_VECTORS_TO_RAM
+	default 0x00000000
+	help
+	  The base address of exception vectors.
+
 source "init/Kconfig"
 
 menu "System Type"

arch/arm/Kconfig-nommu

@@ -25,3 +25,20 @@ config FLASH_SIZE
 	hex 'FLASH Size' if SET_MEM_PARAM
 	default 0x00400000
 
+config REMAP_VECTORS_TO_RAM
+	bool 'Install vectors to the begining of RAM' if DRAM_BASE
+	depends on DRAM_BASE
+	help
+	  The kernel needs to change the hardware exception vectors.
+	  In nommu mode, the hardware exception vectors are normally
+	  placed at address 0x00000000. However, this region may be
+	  occupied by read-only memory depending on H/W design.
+
+	  If the region contains read-write memory, say 'n' here.
+
+	  If your CPU provides a remap facility which allows the exception
+	  vectors to be mapped to writable memory, say 'n' here.
+
+	  Otherwise, say 'y' here.  In this case, the kernel will require
+	  external support to redirect the hardware exception vectors to
+	  the writable versions located at DRAM_BASE.

arch/arm/kernel/signal.h

@@ -7,6 +7,6 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
-#define KERN_SIGRETURN_CODE	0xffff0500
+#define KERN_SIGRETURN_CODE	(CONFIG_VECTORS_BASE + 0x00000500)
 
 extern const unsigned long sigreturn_codes[7];

arch/arm/kernel/traps.c

@@ -688,6 +688,7 @@ EXPORT_SYMBOL(abort);
 
 void __init trap_init(void)
 {
+	unsigned long vectors = CONFIG_VECTORS_BASE;
 	extern char __stubs_start[], __stubs_end[];
 	extern char __vectors_start[], __vectors_end[];
 	extern char __kuser_helper_start[], __kuser_helper_end[];
@@ -698,9 +699,9 @@ void __init trap_init(void)
 	 * into the vector page, mapped at 0xffff0000, and ensure these
 	 * are visible to the instruction stream.
 	 */
-	memcpy((void *)0xffff0000, __vectors_start, __vectors_end - __vectors_start);
-	memcpy((void *)0xffff0200, __stubs_start, __stubs_end - __stubs_start);
-	memcpy((void *)0xffff1000 - kuser_sz, __kuser_helper_start, kuser_sz);
+	memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start);
+	memcpy((void *)vectors + 0x200, __stubs_start, __stubs_end - __stubs_start);
+	memcpy((void *)vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz);
 
 	/*
 	 * Copy signal return handlers into the vector page, and
@@ -709,6 +710,6 @@ void __init trap_init(void)
 	memcpy((void *)KERN_SIGRETURN_CODE, sigreturn_codes,
 	       sizeof(sigreturn_codes));
 
-	flush_icache_range(0xffff0000, 0xffff0000 + PAGE_SIZE);
+	flush_icache_range(vectors, vectors + PAGE_SIZE);
 	modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
 }