On Thu, Aug 7, 2014 at 10:38 AM, Leif Lindholm [off-list ref] wrote:

On Thu, Aug 07, 2014 at 08:01:46AM -0700, Kees Cook wrote:

quoted

From: Mark Salter <redacted>

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 <redacted>
Reviewed-by: Doug Anderson <dianders@chromium.org>
[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 <redacted>
Cc: Laura Abbott <redacted>
---
 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);

idx is now "unused variable".

Ah! Yes, thanks. I'll add HIGHMEM to my build cycles.

quoted

-     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

Apart from that, verified with early_ioremap/UEFI patches on TC2.

Tested-by: Leif Lindholm <redacted>

Thanks! I've added this and fixed idx above for the future v3 of this series.

-Kees

-- 
Kees Cook
Chrome OS Security