[PATCH 1/8] arm: use generic fixmap.h

[Kees Cook]

From: Mark Salter <msalter@xxxxxxxxxx>

ARM is different from other architectures in that fixmap pages are indexed
with a positive offset from FIXADDR_START.  Other architectures index with
a negative offset from FIXADDR_TOP.  In order to use the generic fixmap.h
definitions, this patch redefines FIXADDR_TOP to be inclusive of the
useable range.  That is, FIXADDR_TOP is the virtual address of the topmost
fixed page.  The newly defined FIXADDR_END is the first virtual address
past the fixed mappings.

Signed-off-by: Mark Salter <msalter@xxxxxxxxxx>
Reviewed-by: Doug Anderson <dianders@xxxxxxxxxxxx>
[update for "ARM: 8031/2: change fixmap mapping region to support 32 CPUs"]
[flipped highmem order, thanks to Laura Abbott]
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Laura Abbott <lauraa@xxxxxxxxxxxxxx>
---
 arch/arm/include/asm/fixmap.h | 27 +++++++++------------------
 arch/arm/mm/highmem.c         |  8 ++++++--
 arch/arm/mm/init.c            |  2 +-
 3 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index 74124b0d0d79..190142d174ee 100644
--- a/arch/arm/include/asm/fixmap.h
+++ b/arch/arm/include/asm/fixmap.h
@@ -2,27 +2,18 @@
 #define _ASM_FIXMAP_H
 
 #define FIXADDR_START		0xffc00000UL
-#define FIXADDR_TOP		0xffe00000UL
-#define FIXADDR_SIZE		(FIXADDR_TOP - FIXADDR_START)
+#define FIXADDR_END		0xffe00000UL
+#define FIXADDR_TOP		(FIXADDR_END - PAGE_SIZE)
+#define FIXADDR_SIZE		(FIXADDR_END - FIXADDR_START)
 
 #define FIX_KMAP_NR_PTES	(FIXADDR_SIZE >> PAGE_SHIFT)
 
-#define __fix_to_virt(x)	(FIXADDR_START + ((x) << PAGE_SHIFT))
-#define __virt_to_fix(x)	(((x) - FIXADDR_START) >> PAGE_SHIFT)
+enum fixed_addresses {
+	FIX_KMAP_BEGIN,
+	FIX_KMAP_END = FIX_KMAP_NR_PTES - 1,
+	__end_of_fixed_addresses
+};
 
-extern void __this_fixmap_does_not_exist(void);
-
-static inline unsigned long fix_to_virt(const unsigned int idx)
-{
-	if (idx >= FIX_KMAP_NR_PTES)
-		__this_fixmap_does_not_exist();
-	return __fix_to_virt(idx);
-}
-
-static inline unsigned int virt_to_fix(const unsigned long vaddr)
-{
-	BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
-	return __virt_to_fix(vaddr);
-}
+#include <asm-generic/fixmap.h>
 
 #endif
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
index 45aeaaca9052..a1241ee8425e 100644
--- a/arch/arm/mm/highmem.c
+++ b/arch/arm/mm/highmem.c
@@ -23,14 +23,18 @@ pte_t *fixmap_page_table;
 static inline void set_fixmap_pte(int idx, pte_t pte)
 {
 	unsigned long vaddr = __fix_to_virt(idx);
-	set_pte_ext(fixmap_page_table + idx, pte, 0);
+	pte_t *ppte = pte_offset_kernel(pmd_off_k(FIXADDR_START), vaddr);
+
+	set_pte_ext(ppte, pte, 0);
 	local_flush_tlb_kernel_page(vaddr);
 }
 
 static inline pte_t get_fixmap_pte(unsigned long vaddr)
 {
 	unsigned long idx = __virt_to_fix(vaddr);
-	return *(fixmap_page_table + idx);
+	pte_t *ppte = pte_offset_kernel(pmd_off_k(FIXADDR_START), vaddr);
+
+	return *ppte;
 }
 
 void *kmap(struct page *page)
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 659c75d808dc..ad82c05bfc3a 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -570,7 +570,7 @@ void __init mem_init(void)
 			MLK(DTCM_OFFSET, (unsigned long) dtcm_end),
 			MLK(ITCM_OFFSET, (unsigned long) itcm_end),
 #endif
-			MLK(FIXADDR_START, FIXADDR_TOP),
+			MLK(FIXADDR_START, FIXADDR_END),
 			MLM(VMALLOC_START, VMALLOC_END),
 			MLM(PAGE_OFFSET, (unsigned long)high_memory),
 #ifdef CONFIG_HIGHMEM
-- 
1.9.1

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