arch/arm/mm/idmap.c

#include <linux/kernel.h>

#include <asm/cputype.h>
#include <asm/idmap.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/sections.h>

pgd_t *idmap_pgd;

static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
	unsigned long prot)
{
	pmd_t *pmd = pmd_offset(pud, addr);

	addr = (addr & PMD_MASK) | prot;
	pmd[0] = __pmd(addr);
	addr += SECTION_SIZE;
	pmd[1] = __pmd(addr);
	flush_pmd_entry(pmd);
}

static void idmap_add_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
	unsigned long prot)
{
	pud_t *pud = pud_offset(pgd, addr);
	unsigned long next;

	do {
		next = pud_addr_end(addr, end);
		idmap_add_pmd(pud, addr, next, prot);
	} while (pud++, addr = next, addr != end);
}

void identity_mapping_add(pgd_t *pgd, unsigned long addr, unsigned long end)
{
	unsigned long prot, next;

	prot = PMD_TYPE_SECT | PMD_SECT_AP_WRITE;
	if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ && !cpu_is_xscale())
		prot |= PMD_BIT4;

	pgd += pgd_index(addr);
	do {
		next = pgd_addr_end(addr, end);
		idmap_add_pud(pgd, addr, next, prot);
	} while (pgd++, addr = next, addr != end);
}

#ifdef CONFIG_SMP
static void idmap_del_pmd(pud_t *pud, unsigned long addr, unsigned long end)
{
	pmd_t *pmd = pmd_offset(pud, addr);
	pmd_clear(pmd);
}

static void idmap_del_pud(pgd_t *pgd, unsigned long addr, unsigned long end)
{
	pud_t *pud = pud_offset(pgd, addr);
	unsigned long next;

	do {
		next = pud_addr_end(addr, end);
		idmap_del_pmd(pud, addr, next);
	} while (pud++, addr = next, addr != end);
}

void identity_mapping_del(pgd_t *pgd, unsigned long addr, unsigned long end)
{
	unsigned long next;

	pgd += pgd_index(addr);
	do {
		next = pgd_addr_end(addr, end);
		idmap_del_pud(pgd, addr, next);
	} while (pgd++, addr = next, addr != end);
}
#endif

extern char  __idmap_text_start[], __idmap_text_end[];

static int __init init_static_idmap(void)
{
	phys_addr_t idmap_start, idmap_end;

	idmap_pgd = pgd_alloc(&init_mm);
	if (!idmap_pgd)
		return -ENOMEM;

	/* Add an identity mapping for the physical address of the section. */
	idmap_start = virt_to_phys((void *)__idmap_text_start);
	idmap_end = virt_to_phys((void *)__idmap_text_end);

	pr_info("Setting up static identity map for 0x%llx - 0x%llx\n",
		(long long)idmap_start, (long long)idmap_end);
	identity_mapping_add(idmap_pgd, idmap_start, idmap_end);

	return 0;
}
arch_initcall(init_static_idmap);

/*
 * In order to soft-boot, we need to insert a 1:1 mapping in place of
 * the user-mode pages.  This will then ensure that we have predictable
 * results when turning the mmu off
 */
void setup_mm_for_reboot(void)
{
	/*
	 * We need to access to user-mode page tables here. For kernel threads
	 * we don't have any user-mode mappings so we use the context that we
	 * "borrowed".
	 */
	identity_mapping_add(current->active_mm->pgd, 0, TASK_SIZE);
	local_flush_tlb_all();
}