arch/arm/mm/idmap.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/module.h>
   3 #include <linux/kernel.h>
   4 #include <linux/slab.h>
   5 #include <linux/mm_types.h>
   6
   7 #include <asm/cputype.h>
   8 #include <asm/idmap.h>
   9 #include <asm/pgalloc.h>
  10 #include <asm/pgtable.h>
  11 #include <asm/sections.h>
  12 #include <asm/system_info.h>
  13
  14 /*
  15  * Note: accesses outside of the kernel image and the identity map area
  16  * are not supported on any CPU using the idmap tables as its current
  17  * page tables.
  18  */
  19 pgd_t *idmap_pgd __ro_after_init;
  20 long long arch_phys_to_idmap_offset __ro_after_init;
  21
  22 #ifdef CONFIG_ARM_LPAE
  23 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
  24         unsigned long prot)
  25 {
  26         pmd_t *pmd;
  27         unsigned long next;
  28
  29         if (pud_none_or_clear_bad(pud) || (pud_val(*pud) & L_PGD_SWAPPER)) {
  30                 pmd = pmd_alloc_one(&init_mm, addr);
  31                 if (!pmd) {
  32                         pr_warn("Failed to allocate identity pmd.\n");
  33                         return;
  34                 }
  35                 /*
  36                  * Copy the original PMD to ensure that the PMD entries for
  37                  * the kernel image are preserved.
  38                  */
  39                 if (!pud_none(*pud))
  40                         memcpy(pmd, pmd_offset(pud, 0),
  41                                PTRS_PER_PMD * sizeof(pmd_t));
  42                 pud_populate(&init_mm, pud, pmd);
  43                 pmd += pmd_index(addr);
  44         } else
  45                 pmd = pmd_offset(pud, addr);
  46
  47         do {
  48                 next = pmd_addr_end(addr, end);
  49                 *pmd = __pmd((addr & PMD_MASK) | prot);
  50                 flush_pmd_entry(pmd);
  51         } while (pmd++, addr = next, addr != end);
  52 }
  53 #else   /* !CONFIG_ARM_LPAE */
  54 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
  55         unsigned long prot)
  56 {
  57         pmd_t *pmd = pmd_offset(pud, addr);
  58
  59         addr = (addr & PMD_MASK) | prot;
  60         pmd[0] = __pmd(addr);
  61         addr += SECTION_SIZE;
  62         pmd[1] = __pmd(addr);
  63         flush_pmd_entry(pmd);
  64 }
  65 #endif  /* CONFIG_ARM_LPAE */
  66
  67 static void idmap_add_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
  68         unsigned long prot)
  69 {
  70         pud_t *pud = pud_offset(pgd, addr);
  71         unsigned long next;
  72
  73         do {
  74                 next = pud_addr_end(addr, end);
  75                 idmap_add_pmd(pud, addr, next, prot);
  76         } while (pud++, addr = next, addr != end);
  77 }
  78
  79 static void identity_mapping_add(pgd_t *pgd, const char *text_start,
  80                                  const char *text_end, unsigned long prot)
  81 {
  82         unsigned long addr, end;
  83         unsigned long next;
  84
  85         addr = virt_to_idmap(text_start);
  86         end = virt_to_idmap(text_end);
  87         pr_info("Setting up static identity map for 0x%lx - 0x%lx\n", addr, end);
  88
  89         prot |= PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AF;
  90
  91         if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ && !cpu_is_xscale_family())
  92                 prot |= PMD_BIT4;
  93
  94         pgd += pgd_index(addr);
  95         do {
  96                 next = pgd_addr_end(addr, end);
  97                 idmap_add_pud(pgd, addr, next, prot);
  98         } while (pgd++, addr = next, addr != end);
  99 }
 100
 101 extern char  __idmap_text_start[], __idmap_text_end[];
 102
 103 static int __init init_static_idmap(void)
 104 {
 105         idmap_pgd = pgd_alloc(&init_mm);
 106         if (!idmap_pgd)
 107                 return -ENOMEM;
 108
 109         identity_mapping_add(idmap_pgd, __idmap_text_start,
 110                              __idmap_text_end, 0);
 111
 112         /* Flush L1 for the hardware to see this page table content */
 113         flush_cache_louis();
 114
 115         return 0;
 116 }
 117 early_initcall(init_static_idmap);
 118
 119 /*
 120  * In order to soft-boot, we need to switch to a 1:1 mapping for the
 121  * cpu_reset functions. This will then ensure that we have predictable
 122  * results when turning off the mmu.
 123  */
 124 void setup_mm_for_reboot(void)
 125 {
 126         /* Switch to the identity mapping. */
 127         cpu_switch_mm(idmap_pgd, &init_mm);
 128         local_flush_bp_all();
 129
 130 #ifdef CONFIG_CPU_HAS_ASID
 131         /*
 132          * We don't have a clean ASID for the identity mapping, which
 133          * may clash with virtual addresses of the previous page tables
 134          * and therefore potentially in the TLB.
 135          */
 136         local_flush_tlb_all();
 137 #endif
 138 }