arch/arm/mm/idmap.c

   1 #include <linux/module.h>
   2 #include <linux/kernel.h>
   3 #include <linux/slab.h>
   4
   5 #include <asm/cputype.h>
   6 #include <asm/idmap.h>
   7 #include <asm/pgalloc.h>
   8 #include <asm/pgtable.h>
   9 #include <asm/sections.h>
  10 #include <asm/system_info.h>
  11
  12 /*
  13  * Note: accesses outside of the kernel image and the identity map area
  14  * are not supported on any CPU using the idmap tables as its current
  15  * page tables.
  16  */
  17 pgd_t *idmap_pgd;
  18 phys_addr_t (*arch_virt_to_idmap) (unsigned long x);
  19
  20 #ifdef CONFIG_ARM_LPAE
  21 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
  22         unsigned long prot)
  23 {
  24         pmd_t *pmd;
  25         unsigned long next;
  26
  27         if (pud_none_or_clear_bad(pud) || (pud_val(*pud) & L_PGD_SWAPPER)) {
  28                 pmd = pmd_alloc_one(&init_mm, addr);
  29                 if (!pmd) {
  30                         pr_warn("Failed to allocate identity pmd.\n");
  31                         return;
  32                 }
  33                 /*
  34                  * Copy the original PMD to ensure that the PMD entries for
  35                  * the kernel image are preserved.
  36                  */
  37                 if (!pud_none(*pud))
  38                         memcpy(pmd, pmd_offset(pud, 0),
  39                                PTRS_PER_PMD * sizeof(pmd_t));
  40                 pud_populate(&init_mm, pud, pmd);
  41                 pmd += pmd_index(addr);
  42         } else
  43                 pmd = pmd_offset(pud, addr);
  44
  45         do {
  46                 next = pmd_addr_end(addr, end);
  47                 *pmd = __pmd((addr & PMD_MASK) | prot);
  48                 flush_pmd_entry(pmd);
  49         } while (pmd++, addr = next, addr != end);
  50 }
  51 #else   /* !CONFIG_ARM_LPAE */
  52 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
  53         unsigned long prot)
  54 {
  55         pmd_t *pmd = pmd_offset(pud, addr);
  56
  57         addr = (addr & PMD_MASK) | prot;
  58         pmd[0] = __pmd(addr);
  59         addr += SECTION_SIZE;
  60         pmd[1] = __pmd(addr);
  61         flush_pmd_entry(pmd);
  62 }
  63 #endif  /* CONFIG_ARM_LPAE */
  64
  65 static void idmap_add_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
  66         unsigned long prot)
  67 {
  68         pud_t *pud = pud_offset(pgd, addr);
  69         unsigned long next;
  70
  71         do {
  72                 next = pud_addr_end(addr, end);
  73                 idmap_add_pmd(pud, addr, next, prot);
  74         } while (pud++, addr = next, addr != end);
  75 }
  76
  77 static void identity_mapping_add(pgd_t *pgd, const char *text_start,
  78                                  const char *text_end, unsigned long prot)
  79 {
  80         unsigned long addr, end;
  81         unsigned long next;
  82
  83         addr = virt_to_idmap(text_start);
  84         end = virt_to_idmap(text_end);
  85         pr_info("Setting up static identity map for 0x%lx - 0x%lx\n", addr, end);
  86
  87         prot |= PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AF;
  88
  89         if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ && !cpu_is_xscale())
  90                 prot |= PMD_BIT4;
  91
  92         pgd += pgd_index(addr);
  93         do {
  94                 next = pgd_addr_end(addr, end);
  95                 idmap_add_pud(pgd, addr, next, prot);
  96         } while (pgd++, addr = next, addr != end);
  97 }
  98
  99 extern char  __idmap_text_start[], __idmap_text_end[];
 100
 101 static int __init init_static_idmap(void)
 102 {
 103         idmap_pgd = pgd_alloc(&init_mm);
 104         if (!idmap_pgd)
 105                 return -ENOMEM;
 106
 107         identity_mapping_add(idmap_pgd, __idmap_text_start,
 108                              __idmap_text_end, 0);
 109
 110         /* Flush L1 for the hardware to see this page table content */
 111         flush_cache_louis();
 112
 113         return 0;
 114 }
 115 early_initcall(init_static_idmap);
 116
 117 /*
 118  * In order to soft-boot, we need to switch to a 1:1 mapping for the
 119  * cpu_reset functions. This will then ensure that we have predictable
 120  * results when turning off the mmu.
 121  */
 122 void setup_mm_for_reboot(void)
 123 {
 124         /* Switch to the identity mapping. */
 125         cpu_switch_mm(idmap_pgd, &init_mm);
 126         local_flush_bp_all();
 127
 128 #ifdef CONFIG_CPU_HAS_ASID
 129         /*
 130          * We don't have a clean ASID for the identity mapping, which
 131          * may clash with virtual addresses of the previous page tables
 132          * and therefore potentially in the TLB.
 133          */
 134         local_flush_tlb_all();
 135 #endif
 136 }