Commit de35cab0 authored May 21, 2014 by Shiraz Hashim

arm: mm: fix pte allocation with CONFIG_FORCE_PAGES feature



CONFIG_FORCE_PAGES introduces a debug option to mark free
pages as read only in order to trigger a fault if any code
attempts to write to a page on the buddy list.

In order to achieve this it splits all section mappings in
to PAGE_SIZE pages during boot. While doing this split, it
wrongly allocates a pte (of page size) for each pmd. Linux
however in armv7 short descriptor format, uses same second
level pte for 2 consecutive pmds offset by the actual second
level table size. Refer comments in kernel file
arch/arm/include/asm/pgtable-2level.h for details.

Fix this by allocating pte for a section mapped pmd while
providing required offset if pte already exists.

Change-Id: Iadbaa5e71e4b220208a7275bf039a2a413349e42
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>

parent e80004be

arch/arm/mm/mmu.c

+18 −1

Original line number	Diff line number	Diff line
		@@ -1600,8 +1600,25 @@ static noinline void __init split_pmd(pmd_t *pmd, unsigned long addr,
		const struct mem_type *type)
		{
		pte_t pte, start_pte;
		pmd_t *base_pmd;

		base_pmd = pmd_offset(
		pud_offset(pgd_offset(&init_mm, addr), addr), addr);

		if (pmd_none(base_pmd) \|\| pmd_bad(base_pmd)) {
		start_pte = early_alloc(PTE_HWTABLE_OFF + PTE_HWTABLE_SIZE);
		#ifndef CONFIG_ARM_LPAE
		/*
		* Following is needed when new pte is allocated for pmd[1]
		* cases, which may happen when base (start) address falls
		* under pmd[1].
		*/
		if (addr & SECTION_SIZE)
		start_pte += pte_index(addr);
		#endif
		} else {
		start_pte = pte_offset_kernel(base_pmd, addr);
		}

		pte = start_pte;