From 6ee8630e02be6dd89926ca0fbc21af68b23dc087 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 29 Apr 2013 15:07:44 -0700 Subject: mm: allow arch code to control the user page table ceiling On architectures where a pgd entry may be shared between user and kernel (e.g. ARM+LPAE), freeing page tables needs a ceiling other than 0. This patch introduces a generic USER_PGTABLES_CEILING that arch code can override. It is the responsibility of the arch code setting the ceiling to ensure the complete freeing of the page tables (usually in pgd_free()). [catalin.marinas@arm.com: commit log; shift_arg_pages(), asm-generic/pgtables.h changes] Signed-off-by: Hugh Dickins Signed-off-by: Catalin Marinas Cc: Russell King Cc: [3.3+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/pgtable.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/asm-generic/pgtable.h') diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index bfd87685fc1f..a59ff51b0166 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -7,6 +7,16 @@ #include #include +/* + * On almost all architectures and configurations, 0 can be used as the + * upper ceiling to free_pgtables(): on many architectures it has the same + * effect as using TASK_SIZE. However, there is one configuration which + * must impose a more careful limit, to avoid freeing kernel pgtables. + */ +#ifndef USER_PGTABLES_CEILING +#define USER_PGTABLES_CEILING 0UL +#endif + #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS extern int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, pte_t *ptep, -- cgit v1.2.3