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 #include <linux/pgtable.h>
   7
   8 #include <asm/cputype.h>
   9 #include <asm/idmap.h>
  10 #include <asm/hwcap.h>
  11 #include <asm/pgalloc.h>
  12 #include <asm/sections.h>
  13 #include <asm/system_info.h>
  14
  15 /*
  16  * Note: accesses outside of the kernel image and the identity map area
  17  * are not supported on any CPU using the idmap tables as its current
  18  * page tables.
  19  */
  20 pgd_t *idmap_pgd __ro_after_init;
  21 long long arch_phys_to_idmap_offset __ro_after_init;
  22
  23 #ifdef CONFIG_ARM_LPAE
  24 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
  25         unsigned long prot)
  26 {
  27         pmd_t *pmd;
  28         unsigned long next;
  29
  30         if (pud_none_or_clear_bad(pud) || (pud_val(*pud) & L_PGD_SWAPPER)) {
  31                 pmd = pmd_alloc_one(&init_mm, addr);
  32                 if (!pmd) {
  33                         pr_warn("Failed to allocate identity pmd.\n");
  34                         return;
  35                 }
  36                 /*
  37                  * Copy the original PMD to ensure that the PMD entries for
  38                  * the kernel image are preserved.
  39                  */
  40                 if (!pud_none(*pud))
  41                         memcpy(pmd, pmd_offset(pud, 0),
  42                                PTRS_PER_PMD * sizeof(pmd_t));
  43                 pud_populate(&init_mm, pud, pmd);
  44                 pmd += pmd_index(addr);
  45         } else
  46                 pmd = pmd_offset(pud, addr);
  47
  48         do {
  49                 next = pmd_addr_end(addr, end);
  50                 *pmd = __pmd((addr & PMD_MASK) | prot);
  51                 flush_pmd_entry(pmd);
  52         } while (pmd++, addr = next, addr != end);
  53 }
  54 #else   /* !CONFIG_ARM_LPAE */
  55 static void idmap_add_pmd(pud_t *pud, unsigned long addr, unsigned long end,
  56         unsigned long prot)
  57 {
  58         pmd_t *pmd = pmd_offset(pud, addr);
  59
  60         addr = (addr & PMD_MASK) | prot;
  61         pmd[0] = __pmd(addr);
  62         addr += SECTION_SIZE;
  63         pmd[1] = __pmd(addr);
  64         flush_pmd_entry(pmd);
  65 }
  66 #endif  /* CONFIG_ARM_LPAE */
  67
  68 static void idmap_add_pud(pgd_t *pgd, unsigned long addr, unsigned long end,
  69         unsigned long prot)
  70 {
  71         p4d_t *p4d = p4d_offset(pgd, addr);
  72         pud_t *pud = pud_offset(p4d, addr);
  73         unsigned long next;
  74
  75         do {
  76                 next = pud_addr_end(addr, end);
  77                 idmap_add_pmd(pud, addr, next, prot);
  78         } while (pud++, addr = next, addr != end);
  79 }
  80
  81 static void identity_mapping_add(pgd_t *pgd, const char *text_start,
  82                                  const char *text_end, unsigned long prot)
  83 {
  84         unsigned long addr, end;
  85         unsigned long next;
  86
  87 #ifdef CONFIG_XIP_KERNEL
  88         addr = (phys_addr_t)(text_start) - XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
  89                 + CONFIG_XIP_PHYS_ADDR;
  90         end = (phys_addr_t)(text_end) - XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
  91                 + CONFIG_XIP_PHYS_ADDR;
  92 #else
  93         addr = virt_to_idmap(text_start);
  94         end = virt_to_idmap(text_end);
  95 #endif
  96         pr_info("Setting up static identity map for 0x%lx - 0x%lx\n", addr, end);
  97
  98         prot |= PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_AF;
  99
 100         if (cpu_architecture() <= CPU_ARCH_ARMv5TEJ && !cpu_is_xscale_family())
 101                 prot |= PMD_BIT4;
 102
 103         pgd += pgd_index(addr);
 104         do {
 105                 next = pgd_addr_end(addr, end);
 106                 idmap_add_pud(pgd, addr, next, prot);
 107         } while (pgd++, addr = next, addr != end);
 108 }
 109
 110 extern char  __idmap_text_start[], __idmap_text_end[];
 111
 112 static int __init init_static_idmap(void)
 113 {
 114         idmap_pgd = pgd_alloc(&init_mm);
 115         if (!idmap_pgd)
 116                 return -ENOMEM;
 117
 118         identity_mapping_add(idmap_pgd, __idmap_text_start,
 119                              __idmap_text_end, 0);
 120
 121         /* Flush L1 for the hardware to see this page table content */
 122         if (!(elf_hwcap & HWCAP_LPAE))
 123                 flush_cache_louis();
 124
 125         return 0;
 126 }
 127 early_initcall(init_static_idmap);
 128
 129 /*
 130  * In order to soft-boot, we need to switch to a 1:1 mapping for the
 131  * cpu_reset functions. This will then ensure that we have predictable
 132  * results when turning off the mmu.
 133  */
 134 void setup_mm_for_reboot(void)
 135 {
 136         /* Switch to the identity mapping. */
 137         cpu_switch_mm(idmap_pgd, &init_mm);
 138         local_flush_bp_all();
 139
 140 #ifdef CONFIG_CPU_HAS_ASID
 141         /*
 142          * We don't have a clean ASID for the identity mapping, which
 143          * may clash with virtual addresses of the previous page tables
 144          * and therefore potentially in the TLB.
 145          */
 146         local_flush_tlb_all();
 147 #endif
 148 }