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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 <[email protected]>

  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" <[email protected]>

  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 <[email protected]>
Cc: David Gibson <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: William Lee Irwin III <[email protected]>
Signed-off-by: Ken Chen <[email protected]>
Signed-off-by: Nishanth Aravamudan <[email protected]>
Cc: Andi Kleen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Zhang, Yanmin 2006-03-22 00:08:50 -08:00 • committed by Linus Torvalds
commit 8f860591ff
6 changed files with 43 additions and 13 deletions
Download patch file Download diff file Expand all files Collapse all files

12
mm/mprotect.c
View file

@ -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;
@ -166,7 +166,10 @@ success:
*/
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;
@ -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_% */