[PATCH 1/1] arm: mmu: catch NULL pointer dereferences

[Jean-Christophe PLAGNIOL-VILLARD]

For high vectors if memory start at 0x0. We have to
live without being able to catch NULL pointer dereferences.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagn...@jcrosoft.com>
---
 arch/arm/cpu/mmu.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/arch/arm/cpu/mmu.c b/arch/arm/cpu/mmu.c
index e3ea3b6..2e69b16 100644
--- a/arch/arm/cpu/mmu.c
+++ b/arch/arm/cpu/mmu.c
@@ -218,9 +218,9 @@ static int arm_mmu_remap_sdram(struct memory_bank *bank)
 /*
  * Map vectors and zero page
  */
-static void vectors_init(void)
+static void vectors_init(bool zero_valid_addr)
 {
-       u32 *exc, *zero = NULL;
+       u32 *exc;
        void *vectors;
        u32 cr;
 
@@ -235,10 +235,19 @@ static void vectors_init(void)
                 * page table for the high vectors and zero page
                 */
                exc = arm_create_pte(0xfff00000);
-               zero = arm_create_pte(0x0);
 
-               /* Set the zero page to faulting */
-               zero[0] = 0;
+               /*
+                * Memory start at 0x0. We have to
+                * live without being able to catch NULL pointer dereferences
+                */
+               if (!zero_valid_addr) {
+                       u32 *zero = NULL;
+
+                       zero = arm_create_pte(0x0);
+
+                       /* Set the zero page to faulting */
+                       zero[0] = 0;
+               }
        } else {
                /*
                 * Otherwise map the vectors to the zero page. We have to
@@ -267,6 +276,7 @@ static int mmu_init(void)
 {
        struct memory_bank *bank;
        int i;
+       bool is_start_zero = 0;
 
        arm_set_cache_functions();
 
@@ -303,7 +313,12 @@ static int mmu_init(void)
        create_sections(0, 0, PAGE_SIZE, PMD_SECT_AP_WRITE | PMD_SECT_AP_READ |
                        PMD_TYPE_SECT);
 
-       vectors_init();
+       for_each_memory_bank(bank) {
+               if (bank->start == 0x0)
+                       is_start_zero = 1;
+       }
+
+       vectors_init(is_start_zero);
 
        /*
         * First remap sdram cached using sections.
-- 
1.8.4.rc1


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