diff options
Diffstat (limited to 'include/asm-alpha')
| -rw-r--r-- | include/asm-alpha/pgtable.h | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/include/asm-alpha/pgtable.h b/include/asm-alpha/pgtable.h index 05ce5fba43e..3f0c59f6d8a 100644 --- a/include/asm-alpha/pgtable.h +++ b/include/asm-alpha/pgtable.h @@ -287,17 +287,34 @@ extern inline pte_t pte_mkspecial(pte_t pte) { return pte; } #define pgd_index(address) (((address) >> PGDIR_SHIFT) & (PTRS_PER_PGD-1)) #define pgd_offset(mm, address) ((mm)->pgd+pgd_index(address)) +/* + * The smp_read_barrier_depends() in the following functions are required to + * order the load of *dir (the pointer in the top level page table) with any + * subsequent load of the returned pmd_t *ret (ret is data dependent on *dir). + * + * If this ordering is not enforced, the CPU might load an older value of + * *ret, which may be uninitialized data. See mm/memory.c:__pte_alloc for + * more details. + * + * Note that we never change the mm->pgd pointer after the task is running, so + * pgd_offset does not require such a barrier. + */ + /* Find an entry in the second-level page table.. */ extern inline pmd_t * pmd_offset(pgd_t * dir, unsigned long address) { - return (pmd_t *) pgd_page_vaddr(*dir) + ((address >> PMD_SHIFT) & (PTRS_PER_PAGE - 1)); + pmd_t *ret = (pmd_t *) pgd_page_vaddr(*dir) + ((address >> PMD_SHIFT) & (PTRS_PER_PAGE - 1)); + smp_read_barrier_depends(); /* see above */ + return ret; } /* Find an entry in the third-level page table.. */ extern inline pte_t * pte_offset_kernel(pmd_t * dir, unsigned long address) { - return (pte_t *) pmd_page_vaddr(*dir) + pte_t *ret = (pte_t *) pmd_page_vaddr(*dir) + ((address >> PAGE_SHIFT) & (PTRS_PER_PAGE - 1)); + smp_read_barrier_depends(); /* see above */ + return ret; } #define pte_offset_map(dir,addr) pte_offset_kernel((dir),(addr)) |