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[PATCH] Enable mprotect on huge pages
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2.6.16-rc3 uses hugetlb on-demand paging, but it doesn_t support hugetlb
mprotect.

From: David Gibson <david@gibson.dropbear.id.au>

  Remove a test from the mprotect() path which checks that the mprotect()ed
  range on a hugepage VMA is hugepage aligned (yes, really, the sense of
  is_aligned_hugepage_range() is the opposite of what you'd guess :-/).

  In fact, we don't need this test.  If the given addresses match the
  beginning/end of a hugepage VMA they must already be suitably aligned.  If
  they don't, then mprotect_fixup() will attempt to split the VMA.  The very
  first test in split_vma() will check for a badly aligned address on a
  hugepage VMA and return -EINVAL if necessary.

From: "Chen, Kenneth W" <kenneth.w.chen@intel.com>

  On i386 and x86-64, pte flag _PAGE_PSE collides with _PAGE_PROTNONE.  The
  identify of hugetlb pte is lost when changing page protection via mprotect.
  A page fault occurs later will trigger a bug check in huge_pte_alloc().

  The fix is to always make new pte a hugetlb pte and also to clean up
  legacy code where _PAGE_PRESENT is forced on in the pre-faulting day.

Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: William Lee Irwin III <wli@holomorphy.com>
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Zhang, Yanmin authored and Linus Torvalds committed Mar 22, 2006
1 parent aed75ff commit 8f86059
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Showing 6 changed files with 43 additions and 13 deletions.
5 changes: 2 additions & 3 deletions include/asm-i386/pgtable.h
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Original file line number Diff line number Diff line change
Expand Up @@ -219,13 +219,12 @@ extern unsigned long pg0[];
* The following only work if pte_present() is true.
* Undefined behaviour if not..
*/
#define __LARGE_PTE (_PAGE_PSE | _PAGE_PRESENT)
static inline int pte_user(pte_t pte) { return (pte).pte_low & _PAGE_USER; }
static inline int pte_read(pte_t pte) { return (pte).pte_low & _PAGE_USER; }
static inline int pte_dirty(pte_t pte) { return (pte).pte_low & _PAGE_DIRTY; }
static inline int pte_young(pte_t pte) { return (pte).pte_low & _PAGE_ACCESSED; }
static inline int pte_write(pte_t pte) { return (pte).pte_low & _PAGE_RW; }
static inline int pte_huge(pte_t pte) { return ((pte).pte_low & __LARGE_PTE) == __LARGE_PTE; }
static inline int pte_huge(pte_t pte) { return (pte).pte_low & _PAGE_PSE; }

/*
* The following only works if pte_present() is not true.
Expand All @@ -242,7 +241,7 @@ static inline pte_t pte_mkexec(pte_t pte) { (pte).pte_low |= _PAGE_USER; return
static inline pte_t pte_mkdirty(pte_t pte) { (pte).pte_low |= _PAGE_DIRTY; return pte; }
static inline pte_t pte_mkyoung(pte_t pte) { (pte).pte_low |= _PAGE_ACCESSED; return pte; }
static inline pte_t pte_mkwrite(pte_t pte) { (pte).pte_low |= _PAGE_RW; return pte; }
static inline pte_t pte_mkhuge(pte_t pte) { (pte).pte_low |= __LARGE_PTE; return pte; }
static inline pte_t pte_mkhuge(pte_t pte) { (pte).pte_low |= _PAGE_PSE; return pte; }

#ifdef CONFIG_X86_PAE
# include <asm/pgtable-3level.h>
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2 changes: 1 addition & 1 deletion include/asm-ia64/pgtable.h
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Original file line number Diff line number Diff line change
Expand Up @@ -314,7 +314,7 @@ ia64_phys_addr_valid (unsigned long addr)
#define pte_mkyoung(pte) (__pte(pte_val(pte) | _PAGE_A))
#define pte_mkclean(pte) (__pte(pte_val(pte) & ~_PAGE_D))
#define pte_mkdirty(pte) (__pte(pte_val(pte) | _PAGE_D))
#define pte_mkhuge(pte) (__pte(pte_val(pte) | _PAGE_P))
#define pte_mkhuge(pte) (__pte(pte_val(pte)))

/*
* Macro to a page protection value as "uncacheable". Note that "protection" is really a
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4 changes: 2 additions & 2 deletions include/asm-x86_64/pgtable.h
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Original file line number Diff line number Diff line change
Expand Up @@ -273,7 +273,7 @@ static inline int pte_dirty(pte_t pte) { return pte_val(pte) & _PAGE_DIRTY; }
static inline int pte_young(pte_t pte) { return pte_val(pte) & _PAGE_ACCESSED; }
static inline int pte_write(pte_t pte) { return pte_val(pte) & _PAGE_RW; }
static inline int pte_file(pte_t pte) { return pte_val(pte) & _PAGE_FILE; }
static inline int pte_huge(pte_t pte) { return (pte_val(pte) & __LARGE_PTE) == __LARGE_PTE; }
static inline int pte_huge(pte_t pte) { return pte_val(pte) & _PAGE_PSE; }

static inline pte_t pte_rdprotect(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_USER)); return pte; }
static inline pte_t pte_exprotect(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_USER)); return pte; }
Expand All @@ -285,7 +285,7 @@ static inline pte_t pte_mkexec(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | _
static inline pte_t pte_mkdirty(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | _PAGE_DIRTY)); return pte; }
static inline pte_t pte_mkyoung(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | _PAGE_ACCESSED)); return pte; }
static inline pte_t pte_mkwrite(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | _PAGE_RW)); return pte; }
static inline pte_t pte_mkhuge(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | __LARGE_PTE)); return pte; }
static inline pte_t pte_mkhuge(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | _PAGE_PSE)); return pte; }

struct vm_area_struct;

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4 changes: 4 additions & 0 deletions include/linux/hugetlb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,8 @@ struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
pmd_t *pmd, int write);
int is_aligned_hugepage_range(unsigned long addr, unsigned long len);
int pmd_huge(pmd_t pmd);
void hugetlb_change_protection(struct vm_area_struct *vma,
unsigned long address, unsigned long end, pgprot_t newprot);

#ifndef ARCH_HAS_HUGEPAGE_ONLY_RANGE
#define is_hugepage_only_range(mm, addr, len) 0
Expand Down Expand Up @@ -101,6 +103,8 @@ static inline unsigned long hugetlb_total_pages(void)
#define free_huge_page(p) ({ (void)(p); BUG(); })
#define hugetlb_fault(mm, vma, addr, write) ({ BUG(); 0; })

#define hugetlb_change_protection(vma, address, end, newprot)

#ifndef HPAGE_MASK
#define HPAGE_MASK PAGE_MASK /* Keep the compiler happy */
#define HPAGE_SIZE PAGE_SIZE
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29 changes: 29 additions & 0 deletions mm/hugetlb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -565,3 +565,32 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,

return i;
}

void hugetlb_change_protection(struct vm_area_struct *vma,
unsigned long address, unsigned long end, pgprot_t newprot)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long start = address;
pte_t *ptep;
pte_t pte;

BUG_ON(address >= end);
flush_cache_range(vma, address, end);

spin_lock(&mm->page_table_lock);
for (; address < end; address += HPAGE_SIZE) {
ptep = huge_pte_offset(mm, address);
if (!ptep)
continue;
if (!pte_none(*ptep)) {
pte = huge_ptep_get_and_clear(mm, address, ptep);
pte = pte_mkhuge(pte_modify(pte, newprot));
set_huge_pte_at(mm, address, ptep, pte);
lazy_mmu_prot_update(pte);
}
}
spin_unlock(&mm->page_table_lock);

flush_tlb_range(vma, start, end);
}

12 changes: 5 additions & 7 deletions mm/mprotect.c
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Original file line number Diff line number Diff line change
Expand Up @@ -124,7 +124,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
* a MAP_NORESERVE private mapping to writable will now reserve.
*/
if (newflags & VM_WRITE) {
if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED|VM_HUGETLB))) {
if (!(oldflags & (VM_ACCOUNT|VM_WRITE|VM_SHARED))) {
charged = nrpages;
if (security_vm_enough_memory(charged))
return -ENOMEM;
Expand Down Expand Up @@ -166,7 +166,10 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
*/
vma->vm_flags = newflags;
vma->vm_page_prot = newprot;
change_protection(vma, start, end, newprot);
if (is_vm_hugetlb_page(vma))
hugetlb_change_protection(vma, start, end, newprot);
else
change_protection(vma, start, end, newprot);
vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
vm_stat_account(mm, newflags, vma->vm_file, nrpages);
return 0;
Expand Down Expand Up @@ -240,11 +243,6 @@ sys_mprotect(unsigned long start, size_t len, unsigned long prot)

/* Here we know that vma->vm_start <= nstart < vma->vm_end. */

if (is_vm_hugetlb_page(vma)) {
error = -EACCES;
goto out;
}

newflags = vm_flags | (vma->vm_flags & ~(VM_READ | VM_WRITE | VM_EXEC));

/* newflags >> 4 shift VM_MAY% in place of VM_% */
Expand Down

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