arch/arm/mm/idmap.c

   1 #include <linux/module.h>
   2 #include <linux/kernel.h>
   3 #include <linux/slab.h>
   4 #include <linux/mm_types.h>
   5
   6 #include <asm/cputype.h>
   7 #include <asm/idmap.h>
   8 #include <asm/pgalloc.h>
   9 #include <asm/pgtable.h>
  10 #include <asm/sections.h>
  11 #include <asm/system_info.h>
  12
  13 /*
  14  * Note: accesses outside of the kernel image and the identity map area
  15  * are not supported on any CPU using the idmap tables as its current
  16  * page tables.
  17  */
  18 pgd_t *idmap_pgd;
  19 long long arch_phys_to_idmap_offset;
  20
  21 #ifdef CONFIG_ARM_LPAE
  22 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
  23         unsigned long prot)
  24 {
  25         pmd_t *pmd;
  26         unsigned long next;
  27
  28         if (pud_none_or_clear_bad(pud) || (pud_val(*pud) & L_PGD_SWAPPER)) {
  29                 pmd = pmd_alloc_one(&init_mm, addr);
  30                 if (!pmd) {
  31                         pr_warn("Failed to allocate identity pmd.\n");
  32                         return;
  33                 }
  34                 /*
  35                  * Copy the original PMD to ensure that the PMD entries for
  36                  * the kernel image are preserved.
  37                  */
  38                 if (!pud_none(*pud))
  39                         memcpy(pmd, pmd_offset(pud, 0),
  40                                PTRS_PER_PMD * sizeof(pmd_t));
  41                 pud_populate(&init_mm, pud, pmd);
  42                 pmd += pmd_index(addr);
  43         } else
  44                 pmd = pmd_offset(pud, addr);
  45
  46         do {
  47                 next = pmd_addr_end(addr, end);
  48                 *pmd = __pmd((addr & PMD_MASK) | prot);
  49                 flush_pmd_entry(pmd);
  50         } while (pmd++, addr = next, addr != end);
  51 }
  52 #else   /* !CONFIG_ARM_LPAE */
  53 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
  54         unsigned long prot)
  55 {
  56         pmd_t *pmd = pmd_offset(pud, addr);
  57
  58         addr = (addr & PMD_MASK) | prot;
  59         pmd[0] = __pmd(addr);
  60         addr += SECTION_SIZE;
  61         pmd[1] = __pmd(addr);
  62         flush_pmd_entry(pmd);
  63 }
  64 #endif  /* CONFIG_ARM_LPAE */
  65
  66 static void idmap_add_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
  67         unsigned long prot)
  68 {
  69         pud_t *pud = pud_offset(pgd, addr);
  70         unsigned long next;
  71
  72         do {
  73                 next = pud_addr_end(addr, end);
  74                 idmap_add_pmd(pud, addr, next, prot);
  75         } while (pud++, addr = next, addr != end);
  76 }
  77
  78 static void identity_mapping_add(pgd_t *pgd, const char *text_start,
  79                                  const char *text_end, unsigned long prot)
  80 {
  81         unsigned long addr, end;
  82         unsigned long next;
  83
  84         addr = virt_to_idmap(text_start);
  85         end = virt_to_idmap(text_end);
  86         pr_info("Setting up static identity map for 0x%lx - 0x%lx\n", addr, end);
  87
  88         prot |= PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AF;
  89
  90         if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ && !cpu_is_xscale_family())
  91                 prot |= PMD_BIT4;
  92
  93         pgd += pgd_index(addr);
  94         do {
  95                 next = pgd_addr_end(addr, end);
  96                 idmap_add_pud(pgd, addr, next, prot);
  97         } while (pgd++, addr = next, addr != end);
  98 }
  99
 100 extern char  __idmap_text_start[], __idmap_text_end[];
 101
 102 static int __init init_static_idmap(void)
 103 {
 104         idmap_pgd = pgd_alloc(&init_mm);
 105         if (!idmap_pgd)
 106                 return -ENOMEM;
 107
 108         identity_mapping_add(idmap_pgd, __idmap_text_start,
 109                              __idmap_text_end, 0);
 110
 111         /* Flush L1 for the hardware to see this page table content */
 112         flush_cache_louis();
 113
 114         return 0;
 115 }
 116 early_initcall(init_static_idmap);
 117
 118 /*
 119  * In order to soft-boot, we need to switch to a 1:1 mapping for the
 120  * cpu_reset functions. This will then ensure that we have predictable
 121  * results when turning off the mmu.
 122  */
 123 void setup_mm_for_reboot(void)
 124 {
 125         /* Switch to the identity mapping. */
 126         cpu_switch_mm(idmap_pgd, &init_mm);
 127         local_flush_bp_all();
 128
 129 #ifdef CONFIG_CPU_HAS_ASID
 130         /*
 131          * We don't have a clean ASID for the identity mapping, which
 132          * may clash with virtual addresses of the previous page tables
 133          * and therefore potentially in the TLB.
 134          */
 135         local_flush_tlb_all();
 136 #endif
 137 }