New patch to review for coreboot: 89848e3 exynos5420: Don't map low addresses that lead nowhere

[Isaac Christensen]

Isaac Christensen ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/6650

-gerrit

commit 89848e3bcb4a7d997b15d795741a9438f6207a03
Author: Julius Werner 
Date:   Thu Sep 19 20:15:45 2013 -0700

exynos5420: Don't map low addresses that lead nowhere

I just spent half a day (including the time to implement a stack dumper)
    to figure out that I am reading from a NULL pointer. A problem this
    simple should be more easy to catch. Let's mark the address range below
    SRAM as uncached so that the MMU can yell at you right away for being
    the bad programmer you are when you access a NULL pointer.

Change-Id: I4a3a13f75bf21b25732be2ecb69d47503eff1b53
    Signed-off-by: Julius Werner 
    Reviewed-on: https://chromium-review.googlesource.com/170112
    Reviewed-by: Ronald Minnich 
    (cherry picked from commit 7316732ea0ccdc0d607bde81dbb38ca9abd29fa9)
    Signed-off-by: Isaac Christensen 
---
 src/cpu/samsung/exynos5420/bootblock.c | 4 ++--
 src/cpu/samsung/exynos5420/cpu.h       | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/cpu/samsung/exynos5420/bootblock.c b/src/cpu/samsung/exynos5420/bootblock.c
index 2c42b03..97e85f1 100644
--- a/src/cpu/samsung/exynos5420/bootblock.c
+++ b/src/cpu/samsung/exynos5420/bootblock.c
@@ -24,7 +24,7 @@
 #include "cpu.h"

/* convenient shorthand (in MB) */
-#define SRAM_START	(0x02020000 >> 20)
+#define SRAM_START	(EXYNOS5_SRAM_BASE >> 20)
 #define SRAM_SIZE	1
 #define SRAM_END	(SRAM_START + SRAM_SIZE)	/* plus one... */

@@ -43,7 +43,7 @@ void bootblock_cpu_init(void)

/* set up dcache and MMU */
    mmu_init();
-	mmu_config_range(0, SRAM_START, DCACHE_OFF);
+	mmu_disable_range(0, SRAM_START);
    mmu_config_range(SRAM_START, SRAM_SIZE, DCACHE_WRITEBACK);
    mmu_config_range(SRAM_END, 4096 - SRAM_END, DCACHE_OFF);
    dcache_mmu_enable();
diff --git a/src/cpu/samsung/exynos5420/cpu.h b/src/cpu/samsung/exynos5420/cpu.h
index e3c7f1b..847800d 100644
--- a/src/cpu/samsung/exynos5420/cpu.h
+++ b/src/cpu/samsung/exynos5420/cpu.h
@@ -22,6 +22,8 @@

#include <arch/io.h>

+#define EXYNOS5_SRAM_BASE		0x02020000
+
 /* Base address registers */
 #define EXYNOS5420_GPIO_PART6_BASE	0x03860000 /* Z0 */
 #define EXYNOS5_PRO_ID			0x10000000