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ARM: expand fixmap region to 3MB
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With commit a05e54c ("ARM: 8031/2: change fixmap mapping region to
support 32 CPUs"), the fixmap region was expanded to 2MB, but it
precluded any other uses of the fixmap region. In order to support other
uses the fixmap region needs to be expanded beyond 2MB. Fortunately, the
adjacent 1MB range 0xffe00000-0xfff00000 is availabe.

Remove fixmap_page_table ptr and lookup the page table via the virtual
address so that the fixmap region can span more that one pmd. The 2nd
pmd is already created since it is shared with the vector page.

Signed-off-by: Rob Herring <robh@kernel.org>
[kees: fixed CONFIG_DEBUG_HIGHMEM get_fixmap() calls]
[kees: moved pte allocation outside of CONFIG_HIGHMEM]
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
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Rob Herring authored and Kees Cook committed Oct 16, 2014
1 parent b615bbb commit 836a241
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Showing 4 changed files with 13 additions and 12 deletions.
2 changes: 1 addition & 1 deletion Documentation/arm/memory.txt
Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ fffe8000 fffeffff DTCM mapping area for platforms with
fffe0000 fffe7fff ITCM mapping area for platforms with
ITCM mounted inside the CPU.

ffc00000 ffdfffff Fixmap mapping region. Addresses provided
ffc00000 ffefffff Fixmap mapping region. Addresses provided
by fix_to_virt() will be located here.

fee00000 feffffff Mapping of PCI I/O space. This is a static
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2 changes: 1 addition & 1 deletion arch/arm/include/asm/fixmap.h
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
#define _ASM_FIXMAP_H

#define FIXADDR_START 0xffc00000UL
#define FIXADDR_END 0xffe00000UL
#define FIXADDR_END 0xfff00000UL
#define FIXADDR_TOP (FIXADDR_END - PAGE_SIZE)

#include <asm/kmap_types.h>
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15 changes: 8 additions & 7 deletions arch/arm/mm/highmem.c
Original file line number Diff line number Diff line change
Expand Up @@ -18,19 +18,20 @@
#include <asm/tlbflush.h>
#include "mm.h"

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 *ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);

set_pte_ext(ptep, 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 *ptep = pte_offset_kernel(pmd_off_k(vaddr), vaddr);

return *ptep;
}

void *kmap(struct page *page)
Expand Down Expand Up @@ -84,7 +85,7 @@ void *kmap_atomic(struct page *page)
* With debugging enabled, kunmap_atomic forces that entry to 0.
* Make sure it was indeed properly unmapped.
*/
BUG_ON(!pte_none(*(fixmap_page_table + idx)));
BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
#endif
/*
* When debugging is off, kunmap_atomic leaves the previous mapping
Expand Down Expand Up @@ -134,7 +135,7 @@ void *kmap_atomic_pfn(unsigned long pfn)
idx = type + KM_TYPE_NR * smp_processor_id();
vaddr = __fix_to_virt(idx);
#ifdef CONFIG_DEBUG_HIGHMEM
BUG_ON(!pte_none(*(fixmap_page_table + idx)));
BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
#endif
set_fixmap_pte(idx, pfn_pte(pfn, kmap_prot));

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6 changes: 3 additions & 3 deletions arch/arm/mm/mmu.c
Original file line number Diff line number Diff line change
Expand Up @@ -1326,10 +1326,10 @@ static void __init kmap_init(void)
#ifdef CONFIG_HIGHMEM
pkmap_page_table = early_pte_alloc(pmd_off_k(PKMAP_BASE),
PKMAP_BASE, _PAGE_KERNEL_TABLE);

fixmap_page_table = early_pte_alloc(pmd_off_k(FIXADDR_START),
FIXADDR_START, _PAGE_KERNEL_TABLE);
#endif

early_pte_alloc(pmd_off_k(FIXADDR_START), FIXADDR_START,
_PAGE_KERNEL_TABLE);
}

static void __init map_lowmem(void)
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