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linux/arch/mips/include/asm/pgtable-64.h
David Daney c8f3cc0b65 MIPS: Don't vmap things at address zero. 
In the 64-bit kernel we use swapper_pg_dir for three different things.

1) xuseg mappings for kernel threads.

2) vmap mappings for all kernel-space accesses in xkseg.

3) vmap mappings for kernel modules in ksseg (kseg2).

Due to how the TLB refill handlers work, any mapping established in
xkseg or ksseg will also establish a xuseg mapping that should never
be used by the kernel.

In order to be able to use exceptions to trap NULL pointer
dereferences, we need to ensure that nothing is mapped at address
zero.  Since vmap mappings in xkseg are reflected in xuseg, this means
we need to ensure that there are no vmap mappings established at the
start of xkseg.  So we move back VMALLOC_START to avoid establishing
vmap mappings at the start of xkseg.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
To: linux-mips@linux-mips.org
Patchwork: http://patchwork.linux-mips.org/patch/1129/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2010-04-30 20:52:41 +01:00

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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 1994, 95, 96, 97, 98, 99, 2000, 2003 Ralf Baechle
* Copyright (C) 1999, 2000, 2001 Silicon Graphics, Inc.
*/
#ifndef _ASM_PGTABLE_64_H
#define _ASM_PGTABLE_64_H
#include <linux/linkage.h>
#include <asm/addrspace.h>
#include <asm/page.h>
#include <asm/cachectl.h>
#include <asm/fixmap.h>
#ifdef CONFIG_PAGE_SIZE_64KB
#include <asm-generic/pgtable-nopmd.h>
#else
#include <asm-generic/pgtable-nopud.h>
#endif
/*
* Each address space has 2 4K pages as its page directory, giving 1024
* (== PTRS_PER_PGD) 8 byte pointers to pmd tables. Each pmd table is a
* single 4K page, giving 512 (== PTRS_PER_PMD) 8 byte pointers to page
* tables. Each page table is also a single 4K page, giving 512 (==
* PTRS_PER_PTE) 8 byte ptes. Each pud entry is initialized to point to
* invalid_pmd_table, each pmd entry is initialized to point to
* invalid_pte_table, each pte is initialized to 0. When memory is low,
* and a pmd table or a page table allocation fails, empty_bad_pmd_table
* and empty_bad_page_table is returned back to higher layer code, so
* that the failure is recognized later on. Linux does not seem to
* handle these failures very well though. The empty_bad_page_table has
* invalid pte entries in it, to force page faults.
*
* Kernel mappings: kernel mappings are held in the swapper_pg_table.
* The layout is identical to userspace except it's indexed with the
* fault address - VMALLOC_START.
*/
/* PGDIR_SHIFT determines what a third-level page table entry can map */
#ifdef __PAGETABLE_PMD_FOLDED
#define PGDIR_SHIFT (PAGE_SHIFT + PAGE_SHIFT + PTE_ORDER - 3)
#else
/* PMD_SHIFT determines the size of the area a second-level page table can map */
#define PMD_SHIFT (PAGE_SHIFT + (PAGE_SHIFT + PTE_ORDER - 3))
#define PMD_SIZE (1UL << PMD_SHIFT)
#define PMD_MASK (~(PMD_SIZE-1))
#define PGDIR_SHIFT (PMD_SHIFT + (PAGE_SHIFT + PMD_ORDER - 3))
#endif
#define PGDIR_SIZE (1UL << PGDIR_SHIFT)
#define PGDIR_MASK (~(PGDIR_SIZE-1))
/*
* For 4kB page size we use a 3 level page tree and an 8kB pud, which
* permits us mapping 40 bits of virtual address space.
*
* We used to implement 41 bits by having an order 1 pmd level but that seemed
* rather pointless.
*
* For 8kB page size we use a 3 level page tree which permits a total of
* 8TB of address space. Alternatively a 33-bit / 8GB organization using
* two levels would be easy to implement.
*
* For 16kB page size we use a 2 level page tree which permits a total of
* 36 bits of virtual address space. We could add a third level but it seems
* like at the moment there's no need for this.
*
* For 64kB page size we use a 2 level page table tree for a total of 42 bits
* of virtual address space.
*/
#ifdef CONFIG_PAGE_SIZE_4KB
#define PGD_ORDER 1
#define PUD_ORDER aieeee_attempt_to_allocate_pud
#define PMD_ORDER 0
#define PTE_ORDER 0
#endif
#ifdef CONFIG_PAGE_SIZE_8KB
#define PGD_ORDER 0
#define PUD_ORDER aieeee_attempt_to_allocate_pud
#define PMD_ORDER 0
#define PTE_ORDER 0
#endif
#ifdef CONFIG_PAGE_SIZE_16KB
#define PGD_ORDER 0
#define PUD_ORDER aieeee_attempt_to_allocate_pud
#define PMD_ORDER 0
#define PTE_ORDER 0
#endif
#ifdef CONFIG_PAGE_SIZE_32KB
#define PGD_ORDER 0
#define PUD_ORDER aieeee_attempt_to_allocate_pud
#define PMD_ORDER 0
#define PTE_ORDER 0
#endif
#ifdef CONFIG_PAGE_SIZE_64KB
#define PGD_ORDER 0
#define PUD_ORDER aieeee_attempt_to_allocate_pud
#define PMD_ORDER aieeee_attempt_to_allocate_pmd
#define PTE_ORDER 0
#endif
#define PTRS_PER_PGD ((PAGE_SIZE << PGD_ORDER) / sizeof(pgd_t))
#ifndef __PAGETABLE_PMD_FOLDED
#define PTRS_PER_PMD ((PAGE_SIZE << PMD_ORDER) / sizeof(pmd_t))
#endif
#define PTRS_PER_PTE ((PAGE_SIZE << PTE_ORDER) / sizeof(pte_t))
#if PGDIR_SIZE >= TASK_SIZE
#define USER_PTRS_PER_PGD (1)
#else
#define USER_PTRS_PER_PGD (TASK_SIZE / PGDIR_SIZE)
#endif
#define FIRST_USER_ADDRESS 0UL
/*
* TLB refill handlers also map the vmalloc area into xuseg. Avoid
* the first couple of pages so NULL pointer dereferences will still
* reliably trap.
*/
#define VMALLOC_START (MAP_BASE + (2 * PAGE_SIZE))
#define VMALLOC_END \
(MAP_BASE + \
min(PTRS_PER_PGD * PTRS_PER_PMD * PTRS_PER_PTE * PAGE_SIZE, \
(1UL << cpu_vmbits)) - (1UL << 32))
#if defined(CONFIG_MODULES) && defined(KBUILD_64BIT_SYM32) && \
VMALLOC_START != CKSSEG
/* Load modules into 32bit-compatible segment. */
#define MODULE_START CKSSEG
#define MODULE_END (FIXADDR_START-2*PAGE_SIZE)
#endif
#define pte_ERROR(e) \
printk("%s:%d: bad pte %016lx.\n", __FILE__, __LINE__, pte_val(e))
#ifndef __PAGETABLE_PMD_FOLDED
#define pmd_ERROR(e) \
printk("%s:%d: bad pmd %016lx.\n", __FILE__, __LINE__, pmd_val(e))
#endif
#define pgd_ERROR(e) \
printk("%s:%d: bad pgd %016lx.\n", __FILE__, __LINE__, pgd_val(e))
extern pte_t invalid_pte_table[PTRS_PER_PTE];
extern pte_t empty_bad_page_table[PTRS_PER_PTE];
#ifndef __PAGETABLE_PMD_FOLDED
/*
* For 3-level pagetables we defines these ourselves, for 2-level the
* definitions are supplied by <asm-generic/pgtable-nopmd.h>.
*/
typedef struct { unsigned long pmd; } pmd_t;
#define pmd_val(x) ((x).pmd)
#define __pmd(x) ((pmd_t) { (x) } )
extern pmd_t invalid_pmd_table[PTRS_PER_PMD];
extern pmd_t empty_bad_pmd_table[PTRS_PER_PMD];
#endif
/*
* Empty pgd/pmd entries point to the invalid_pte_table.
*/
static inline int pmd_none(pmd_t pmd)
{
return pmd_val(pmd) == (unsigned long) invalid_pte_table;
}
#define pmd_bad(pmd) (pmd_val(pmd) & ~PAGE_MASK)
static inline int pmd_present(pmd_t pmd)
{
return pmd_val(pmd) != (unsigned long) invalid_pte_table;
}
static inline void pmd_clear(pmd_t *pmdp)
{
pmd_val(*pmdp) = ((unsigned long) invalid_pte_table);
}
#ifndef __PAGETABLE_PMD_FOLDED
/*
* Empty pud entries point to the invalid_pmd_table.
*/
static inline int pud_none(pud_t pud)
{
return pud_val(pud) == (unsigned long) invalid_pmd_table;
}
static inline int pud_bad(pud_t pud)
{
return pud_val(pud) & ~PAGE_MASK;
}
static inline int pud_present(pud_t pud)
{
return pud_val(pud) != (unsigned long) invalid_pmd_table;
}
static inline void pud_clear(pud_t *pudp)
{
pud_val(*pudp) = ((unsigned long) invalid_pmd_table);
}
#endif
#define pte_page(x) pfn_to_page(pte_pfn(x))
#ifdef CONFIG_CPU_VR41XX
#define pte_pfn(x) ((unsigned long)((x).pte >> (PAGE_SHIFT + 2)))
#define pfn_pte(pfn, prot) __pte(((pfn) << (PAGE_SHIFT + 2)) | pgprot_val(prot))
#else
#define pte_pfn(x) ((unsigned long)((x).pte >> _PFN_SHIFT))
#define pfn_pte(pfn, prot) __pte(((pfn) << _PFN_SHIFT) | pgprot_val(prot))
#endif
#define __pgd_offset(address) pgd_index(address)
#define __pud_offset(address) (((address) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
#define __pmd_offset(address) pmd_index(address)
/* to find an entry in a kernel page-table-directory */
#define pgd_offset_k(address) pgd_offset(&init_mm, address)
#define pgd_index(address) (((address) >> PGDIR_SHIFT) & (PTRS_PER_PGD-1))
#define pmd_index(address) (((address) >> PMD_SHIFT) & (PTRS_PER_PMD-1))
/* to find an entry in a page-table-directory */
#define pgd_offset(mm, addr) ((mm)->pgd + pgd_index(addr))
#ifndef __PAGETABLE_PMD_FOLDED
static inline unsigned long pud_page_vaddr(pud_t pud)
{
return pud_val(pud);
}
#define pud_phys(pud) virt_to_phys((void *)pud_val(pud))
#define pud_page(pud) (pfn_to_page(pud_phys(pud) >> PAGE_SHIFT))
/* Find an entry in the second-level page table.. */
static inline pmd_t *pmd_offset(pud_t * pud, unsigned long address)
{
return (pmd_t *) pud_page_vaddr(*pud) + pmd_index(address);
}
#endif
/* Find an entry in the third-level page table.. */
#define __pte_offset(address) \
(((address) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))
#define pte_offset(dir, address) \
((pte_t *) pmd_page_vaddr(*(dir)) + __pte_offset(address))
#define pte_offset_kernel(dir, address) \
((pte_t *) pmd_page_vaddr(*(dir)) + __pte_offset(address))
#define pte_offset_map(dir, address) \
((pte_t *)page_address(pmd_page(*(dir))) + __pte_offset(address))
#define pte_offset_map_nested(dir, address) \
((pte_t *)page_address(pmd_page(*(dir))) + __pte_offset(address))
#define pte_unmap(pte) ((void)(pte))
#define pte_unmap_nested(pte) ((void)(pte))
/*
* Initialize a new pgd / pmd table with invalid pointers.
*/
extern void pgd_init(unsigned long page);
extern void pmd_init(unsigned long page, unsigned long pagetable);
/*
* Non-present pages: high 24 bits are offset, next 8 bits type,
* low 32 bits zero.
*/
static inline pte_t mk_swap_pte(unsigned long type, unsigned long offset)
{ pte_t pte; pte_val(pte) = (type << 32) | (offset << 40); return pte; }
#define __swp_type(x) (((x).val >> 32) & 0xff)
#define __swp_offset(x) ((x).val >> 40)
#define __swp_entry(type, offset) ((swp_entry_t) { pte_val(mk_swap_pte((type), (offset))) })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x) ((pte_t) { (x).val })
/*
* Bits 0, 4, 6, and 7 are taken. Let's leave bits 1, 2, 3, and 5 alone to
* make things easier, and only use the upper 56 bits for the page offset...
*/
#define PTE_FILE_MAX_BITS 56
#define pte_to_pgoff(_pte) ((_pte).pte >> 8)
#define pgoff_to_pte(off) ((pte_t) { ((off) << 8) | _PAGE_FILE })
#endif /* _ASM_PGTABLE_64_H */
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