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 */
20static_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
27static_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
34static pte_t bm_pte[NR_BM_PTE_TABLES][PTRS_PER_PTE] __page_aligned_bss;
35static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
36static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;
37
38static inline pte_t *fixmap_pte(unsigned long addr)
39{
40 return &bm_pte[BM_PTE_TABLE_IDX(addr)][pte_index(address: addr)];
41}
42
43static 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),
51 PMD_TYPE_TABLE | PMD_TABLE_AF);
52 }
53}
54
55static void __init early_fixmap_init_pmd(pud_t *pudp, unsigned long addr,
56 unsigned long end)
57{
58 unsigned long next;
59 pud_t pud = READ_ONCE(*pudp);
60 pmd_t *pmdp;
61
62 if (pud_none(pud))
63 __pud_populate(pudp, __pa_symbol(bm_pmd),
64 PUD_TYPE_TABLE | PUD_TABLE_AF);
65
66 pmdp = pmd_offset_kimg(pudp, addr);
67 do {
68 next = pmd_addr_end(addr, end);
69 early_fixmap_init_pte(pmdp, addr);
70 } while (pmdp++, addr = next, addr != end);
71}
72
73
74static void __init early_fixmap_init_pud(p4d_t *p4dp, unsigned long addr,
75 unsigned long end)
76{
77 p4d_t p4d = READ_ONCE(*p4dp);
78 pud_t *pudp;
79
80 if (CONFIG_PGTABLE_LEVELS > 3 && !p4d_none(p4d) &&
81 p4d_page_paddr(p4d) != __pa_symbol(bm_pud)) {
82 /*
83 * We only end up here if the kernel mapping and the fixmap
84 * share the top level pgd entry, which should only happen on
85 * 16k/4 levels configurations.
86 */
87 BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
88 }
89
90 if (p4d_none(p4d))
91 __p4d_populate(p4dp, __pa_symbol(bm_pud),
92 P4D_TYPE_TABLE | P4D_TABLE_AF);
93
94 pudp = pud_offset_kimg(p4dp, addr);
95 early_fixmap_init_pmd(pudp, addr, end);
96}
97
98/*
99 * The p*d_populate functions call virt_to_phys implicitly so they can't be used
100 * directly on kernel symbols (bm_p*d). This function is called too early to use
101 * lm_alias so __p*d_populate functions must be used to populate with the
102 * physical address from __pa_symbol.
103 */
104void __init early_fixmap_init(void)
105{
106 unsigned long addr = FIXADDR_TOT_START;
107 unsigned long end = FIXADDR_TOP;
108
109 pgd_t *pgdp = pgd_offset_k(addr);
110 p4d_t *p4dp = p4d_offset_kimg(pgdp, addr);
111
112 early_fixmap_init_pud(p4dp, addr, end);
113}
114
115/*
116 * Unusually, this is also called in IRQ context (ghes_iounmap_irq) so if we
117 * ever need to use IPIs for TLB broadcasting, then we're in trouble here.
118 */
119void __set_fixmap(enum fixed_addresses idx,
120 phys_addr_t phys, pgprot_t flags)
121{
122 unsigned long addr = __fix_to_virt(idx);
123 pte_t *ptep;
124
125 BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
126
127 ptep = fixmap_pte(addr);
128
129 if (pgprot_val(flags)) {
130 __set_pte(ptep, pfn_pte(page_nr: phys >> PAGE_SHIFT, pgprot: flags));
131 } else {
132 __pte_clear(&init_mm, addr, ptep);
133 flush_tlb_kernel_range(start: addr, end: addr+PAGE_SIZE);
134 }
135}
136
137void *__init fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
138{
139 const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
140 phys_addr_t dt_phys_base;
141 int offset;
142 void *dt_virt;
143
144 /*
145 * Check whether the physical FDT address is set and meets the minimum
146 * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
147 * at least 8 bytes so that we can always access the magic and size
148 * fields of the FDT header after mapping the first chunk, double check
149 * here if that is indeed the case.
150 */
151 BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
152 if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
153 return NULL;
154
155 dt_phys_base = round_down(dt_phys, PAGE_SIZE);
156 offset = dt_phys % PAGE_SIZE;
157 dt_virt = (void *)dt_virt_base + offset;
158
159 /* map the first chunk so we can read the size from the header */
160 create_mapping_noalloc(dt_phys_base, dt_virt_base, PAGE_SIZE, prot);
161
162 if (fdt_magic(dt_virt) != FDT_MAGIC)
163 return NULL;
164
165 *size = fdt_totalsize(dt_virt);
166 if (*size > MAX_FDT_SIZE)
167 return NULL;
168
169 if (offset + *size > PAGE_SIZE) {
170 create_mapping_noalloc(dt_phys_base, dt_virt_base,
171 offset + *size, prot);
172 }
173
174 return dt_virt;
175}
176

source code of linux/arch/arm64/mm/fixmap.c