[OpenBIOS] [PATCH] Remove zero page mapping from all architectures to allow detection of NULL pointer dereferences.

[Mark Cave-Ayland]

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland at ilande.co.uk>
---
 openbios-devel/arch/ppc/qemu/ofmem.c        |    7 ++++---
 openbios-devel/arch/sparc32/lib.c           |    6 +++---
 openbios-devel/arch/sparc64/ofmem_sparc64.c |    4 ++--
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/openbios-devel/arch/ppc/qemu/ofmem.c b/openbios-devel/arch/ppc/qemu/ofmem.c
index 0161a17..429f43b 100644
--- a/openbios-devel/arch/ppc/qemu/ofmem.c
+++ b/openbios-devel/arch/ppc/qemu/ofmem.c
@@ -549,9 +549,10 @@ ofmem_init(void)
 {
     ofmem_t *ofmem = ofmem_arch_get_private();
 
-    ofmem_claim_phys(0, get_ram_bottom(), 0);
-    ofmem_claim_virt(0, get_ram_bottom(), 0);
-    ofmem_map(0, 0, get_ram_bottom(), 0);
+    /* Map the memory (don't map page 0 to allow catching of NULL dereferences) */
+    ofmem_claim_phys(PAGE_SIZE, get_ram_bottom() - PAGE_SIZE, 0);
+    ofmem_claim_virt(PAGE_SIZE, get_ram_bottom() - PAGE_SIZE, 0);
+    ofmem_map(PAGE_SIZE, PAGE_SIZE, get_ram_bottom() - PAGE_SIZE, 0);
 
     /* Map everything at the top of physical RAM 1:1, minus the OpenBIOS ROM in RAM copy */
     ofmem_claim_phys(get_ram_top(), get_hash_base() + HASH_SIZE - get_ram_top(), 0);
diff --git a/openbios-devel/arch/sparc32/lib.c b/openbios-devel/arch/sparc32/lib.c
index c0df654..4ff3619 100644
--- a/openbios-devel/arch/sparc32/lib.c
+++ b/openbios-devel/arch/sparc32/lib.c
@@ -403,9 +403,9 @@ init_mmu_swift(void)
     ofmem_arch_map_pages(pa, va, size, ofmem_arch_default_translation_mode(pa));
     ofmem_map_page_range(pa, va, size, ofmem_arch_default_translation_mode(pa));
 
-    // 1:1 mapping for RAM
-    ofmem_arch_map_pages(0, 0, LOWMEMSZ, ofmem_arch_default_translation_mode(0));
-    ofmem_map_page_range(0, 0, LOWMEMSZ, ofmem_arch_default_translation_mode(0));
+    // 1:1 mapping for RAM (don't map page 0 to allow catching of NULL dereferences)
+    ofmem_arch_map_pages(PAGE_SIZE, PAGE_SIZE, LOWMEMSZ - PAGE_SIZE, ofmem_arch_default_translation_mode(0));
+    ofmem_map_page_range(PAGE_SIZE, PAGE_SIZE, LOWMEMSZ - PAGE_SIZE, ofmem_arch_default_translation_mode(0));
 
     /*
      * Flush cache
diff --git a/openbios-devel/arch/sparc64/ofmem_sparc64.c b/openbios-devel/arch/sparc64/ofmem_sparc64.c
index 50224e6..ece51f9 100644
--- a/openbios-devel/arch/sparc64/ofmem_sparc64.c
+++ b/openbios-devel/arch/sparc64/ofmem_sparc64.c
@@ -365,8 +365,8 @@ void ofmem_init( void )
 	/* inherit translations set up by entry.S */
 	ofmem_walk_boot_map(remap_page_range);
 
-        /* Map the memory */
-        ofmem_map_page_range(0, 0, qemu_mem_size, 0x36);
+        /* Map the memory (don't map page 0 to allow catching of NULL dereferences) */
+        ofmem_map_page_range(PAGE_SIZE, PAGE_SIZE, qemu_mem_size - PAGE_SIZE, 0x36);
 
 	if (!(retained->magic == RETAIN_MAGIC)) {
 		OFMEM_TRACE("ofmem_init: no retained magic found, creating\n");
-- 
1.7.10.4