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When copying page tables, added excluding common kernel entries.

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Normally common kernel entries in 2nd level page table need not get
copied to new tasks since those entries will be used commonly by all tasks.
On fork, we were copying those unnecessarily.
This commit is contained in:
Bahadir Balban
2008-09-01 17:26:49 +03:00
parent fb8d8f4bb9
commit a5fa48bc2f
1 changed files with 22 additions and 4 deletions
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26
src/arch/arm/v5/mm.c
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@@ -359,6 +359,23 @@ void remove_mapping(unsigned long vaddr)
remove_mapping_pgd(vaddr, current->pgd);
}
/*
* Tell if a pgd index is a common kernel index. This is used to distinguish
* common kernel entries in a pgd, when copying page tables.
*/
int is_kern_pgdi(int i)
{
if ((i >= PGD_INDEX(KERNEL_AREA_START) && i < PGD_INDEX(KERNEL_AREA_END)) ||
(i >= PGD_INDEX(IO_AREA_START) && i < PGD_INDEX(IO_AREA_END)) ||
(i == PGD_INDEX(USER_KIP_PAGE)) ||
(i == PGD_INDEX(ARM_HIGH_VECTOR)) ||
(i == PGD_INDEX(ARM_SYSCALL_VECTOR)) ||
(i == PGD_INDEX(USERSPACE_UART_BASE)))
return 1;
else
return 0;
}
/*
* Allocates and copies all levels of page tables from one task to another.
* Useful when forking.
@@ -368,14 +385,15 @@ pgd_table_t *copy_page_tables(pgd_table_t *from)
pmd_table_t *pmd, *orig;
pgd_table_t *pgd;
/* Allocate and copy pgd */
/* Allocate and copy pgd. This includes all kernel entries */
pgd = alloc_pgd();
memcpy(pgd, from, sizeof(pgd_table_t));
/* Allocate and copy all valid pmds */
/* Allocate and copy all pmds that will be exclusive to new task. */
for (int i = 0; i < PGD_ENTRY_TOTAL; i++) {
/* Detect a pmd entry in original pgd? */
if ((pgd->entry[i] & PGD_TYPE_MASK) == PGD_TYPE_COARSE) {
/* Detect a pmd entry that is not a kernel pmd? */
if (!is_kern_pgdi(i) &&
((pgd->entry[i] & PGD_TYPE_MASK) == PGD_TYPE_COARSE)) {
/* Allocate new pmd */
pmd = alloc_pmd();