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Linux/arch/arm/mm/idmap.c

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  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 }
137 

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