arch/arm64/mm/fixmap.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Fixmap manipulation code
   4  */
   5
   6 #include <linux/bug.h>
   7 #include <linux/init.h>
   8 #include <linux/kernel.h>
   9 #include <linux/libfdt.h>
  10 #include <linux/memory.h>
  11 #include <linux/mm.h>
  12 #include <linux/sizes.h>
  13
  14 #include <asm/fixmap.h>
  15 #include <asm/kernel-pgtable.h>
  16 #include <asm/pgalloc.h>
  17 #include <asm/tlbflush.h>
  18
  19 /* ensure that the fixmap region does not grow down into the PCI I/O region */
  20 static_assert(FIXADDR_TOT_START > PCI_IO_END);
  21
  22 #define NR_BM_PTE_TABLES \
  23         SPAN_NR_ENTRIES(FIXADDR_TOT_START, FIXADDR_TOP, PMD_SHIFT)
  24 #define NR_BM_PMD_TABLES \
  25         SPAN_NR_ENTRIES(FIXADDR_TOT_START, FIXADDR_TOP, PUD_SHIFT)
  26
  27 static_assert(NR_BM_PMD_TABLES == 1);
  28
  29 #define __BM_TABLE_IDX(addr, shift) \
  30         (((addr) >> (shift)) - (FIXADDR_TOT_START >> (shift)))
  31
  32 #define BM_PTE_TABLE_IDX(addr)  __BM_TABLE_IDX(addr, PMD_SHIFT)
  33
  34 static pte_t bm_pte[NR_BM_PTE_TABLES][PTRS_PER_PTE] __page_aligned_bss;
  35 static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
  36 static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;
  37
  38 static inline pte_t *fixmap_pte(unsigned long addr)
  39 {
  40         return &bm_pte[BM_PTE_TABLE_IDX(addr)][pte_index(addr)];
  41 }
  42
  43 static void __init early_fixmap_init_pte(pmd_t *pmdp, unsigned long addr)
  44 {
  45         pmd_t pmd = READ_ONCE(*pmdp);
  46         pte_t *ptep;
  47
  48         if (pmd_none(pmd)) {
  49                 ptep = bm_pte[BM_PTE_TABLE_IDX(addr)];
  50                 __pmd_populate(pmdp, __pa_symbol(ptep), PMD_TYPE_TABLE);
  51         }
  52 }
  53
  54 static void __init early_fixmap_init_pmd(pud_t *pudp, unsigned long addr,
  55                                          unsigned long end)
  56 {
  57         unsigned long next;
  58         pud_t pud = READ_ONCE(*pudp);
  59         pmd_t *pmdp;
  60
  61         if (pud_none(pud))
  62                 __pud_populate(pudp, __pa_symbol(bm_pmd), PUD_TYPE_TABLE);
  63
  64         pmdp = pmd_offset_kimg(pudp, addr);
  65         do {
  66                 next = pmd_addr_end(addr, end);
  67                 early_fixmap_init_pte(pmdp, addr);
  68         } while (pmdp++, addr = next, addr != end);
  69 }
  70
  71
  72 static void __init early_fixmap_init_pud(p4d_t *p4dp, unsigned long addr,
  73                                          unsigned long end)
  74 {
  75         p4d_t p4d = READ_ONCE(*p4dp);
  76         pud_t *pudp;
  77
  78         if (CONFIG_PGTABLE_LEVELS > 3 && !p4d_none(p4d) &&
  79             p4d_page_paddr(p4d) != __pa_symbol(bm_pud)) {
  80                 /*
  81                  * We only end up here if the kernel mapping and the fixmap
  82                  * share the top level pgd entry, which should only happen on
  83                  * 16k/4 levels configurations.
  84                  */
  85                 BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
  86         }
  87
  88         if (p4d_none(p4d))
  89                 __p4d_populate(p4dp, __pa_symbol(bm_pud), P4D_TYPE_TABLE);
  90
  91         pudp = pud_offset_kimg(p4dp, addr);
  92         early_fixmap_init_pmd(pudp, addr, end);
  93 }
  94
  95 /*
  96  * The p*d_populate functions call virt_to_phys implicitly so they can't be used
  97  * directly on kernel symbols (bm_p*d). This function is called too early to use
  98  * lm_alias so __p*d_populate functions must be used to populate with the
  99  * physical address from __pa_symbol.
 100  */
 101 void __init early_fixmap_init(void)
 102 {
 103         unsigned long addr = FIXADDR_TOT_START;
 104         unsigned long end = FIXADDR_TOP;
 105
 106         pgd_t *pgdp = pgd_offset_k(addr);
 107         p4d_t *p4dp = p4d_offset_kimg(pgdp, addr);
 108
 109         early_fixmap_init_pud(p4dp, addr, end);
 110 }
 111
 112 /*
 113  * Unusually, this is also called in IRQ context (ghes_iounmap_irq) so if we
 114  * ever need to use IPIs for TLB broadcasting, then we're in trouble here.
 115  */
 116 void __set_fixmap(enum fixed_addresses idx,
 117                                phys_addr_t phys, pgprot_t flags)
 118 {
 119         unsigned long addr = __fix_to_virt(idx);
 120         pte_t *ptep;
 121
 122         BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
 123
 124         ptep = fixmap_pte(addr);
 125
 126         if (pgprot_val(flags)) {
 127                 __set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, flags));
 128         } else {
 129                 __pte_clear(&init_mm, addr, ptep);
 130                 flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
 131         }
 132 }
 133
 134 void *__init fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
 135 {
 136         const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
 137         phys_addr_t dt_phys_base;
 138         int offset;
 139         void *dt_virt;
 140
 141         /*
 142          * Check whether the physical FDT address is set and meets the minimum
 143          * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
 144          * at least 8 bytes so that we can always access the magic and size
 145          * fields of the FDT header after mapping the first chunk, double check
 146          * here if that is indeed the case.
 147          */
 148         BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
 149         if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
 150                 return NULL;
 151
 152         dt_phys_base = round_down(dt_phys, PAGE_SIZE);
 153         offset = dt_phys % PAGE_SIZE;
 154         dt_virt = (void *)dt_virt_base + offset;
 155
 156         /* map the first chunk so we can read the size from the header */
 157         create_mapping_noalloc(dt_phys_base, dt_virt_base, PAGE_SIZE, prot);
 158
 159         if (fdt_magic(dt_virt) != FDT_MAGIC)
 160                 return NULL;
 161
 162         *size = fdt_totalsize(dt_virt);
 163         if (*size > MAX_FDT_SIZE)
 164                 return NULL;
 165
 166         if (offset + *size > PAGE_SIZE) {
 167                 create_mapping_noalloc(dt_phys_base, dt_virt_base,
 168                                        offset + *size, prot);
 169         }
 170
 171         return dt_virt;
 172 }