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 #define NR_BM_PTE_TABLES \
20 SPAN_NR_ENTRIES(FIXADDR_TOT_START, FIXADDR_TOP, PMD_SHIFT)
21 #define NR_BM_PMD_TABLES \
22 SPAN_NR_ENTRIES(FIXADDR_TOT_START, FIXADDR_TOP, PUD_SHIFT)
23
24 static_assert(NR_BM_PMD_TABLES == 1);
25
26 #define __BM_TABLE_IDX(addr, shift) \
27 (((addr) >> (shift)) - (FIXADDR_TOT_START >> (shift)))
28
29 #define BM_PTE_TABLE_IDX(addr) __BM_TABLE_IDX(addr, PMD_SHIFT)
30
31 static pte_t bm_pte[NR_BM_PTE_TABLES][PTRS_PER_PTE] __page_aligned_bss;
32 static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
33 static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;
34
fixmap_pte(unsigned long addr)35 static inline pte_t *fixmap_pte(unsigned long addr)
36 {
37 return &bm_pte[BM_PTE_TABLE_IDX(addr)][pte_index(addr)];
38 }
39
early_fixmap_init_pte(pmd_t * pmdp,unsigned long addr)40 static void __init early_fixmap_init_pte(pmd_t *pmdp, unsigned long addr)
41 {
42 pmd_t pmd = READ_ONCE(*pmdp);
43 pte_t *ptep;
44
45 if (pmd_none(pmd)) {
46 ptep = bm_pte[BM_PTE_TABLE_IDX(addr)];
47 __pmd_populate(pmdp, __pa_symbol(ptep), PMD_TYPE_TABLE);
48 }
49 }
50
early_fixmap_init_pmd(pud_t * pudp,unsigned long addr,unsigned long end)51 static void __init early_fixmap_init_pmd(pud_t *pudp, unsigned long addr,
52 unsigned long end)
53 {
54 unsigned long next;
55 pud_t pud = READ_ONCE(*pudp);
56 pmd_t *pmdp;
57
58 if (pud_none(pud))
59 __pud_populate(pudp, __pa_symbol(bm_pmd), PUD_TYPE_TABLE);
60
61 pmdp = pmd_offset_kimg(pudp, addr);
62 do {
63 next = pmd_addr_end(addr, end);
64 early_fixmap_init_pte(pmdp, addr);
65 } while (pmdp++, addr = next, addr != end);
66 }
67
68
early_fixmap_init_pud(p4d_t * p4dp,unsigned long addr,unsigned long end)69 static void __init early_fixmap_init_pud(p4d_t *p4dp, unsigned long addr,
70 unsigned long end)
71 {
72 p4d_t p4d = READ_ONCE(*p4dp);
73 pud_t *pudp;
74
75 if (CONFIG_PGTABLE_LEVELS > 3 && !p4d_none(p4d) &&
76 p4d_page_paddr(p4d) != __pa_symbol(bm_pud)) {
77 /*
78 * We only end up here if the kernel mapping and the fixmap
79 * share the top level pgd entry, which should only happen on
80 * 16k/4 levels configurations.
81 */
82 BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
83 }
84
85 if (p4d_none(p4d))
86 __p4d_populate(p4dp, __pa_symbol(bm_pud), P4D_TYPE_TABLE);
87
88 pudp = pud_offset_kimg(p4dp, addr);
89 early_fixmap_init_pmd(pudp, addr, end);
90 }
91
92 /*
93 * The p*d_populate functions call virt_to_phys implicitly so they can't be used
94 * directly on kernel symbols (bm_p*d). This function is called too early to use
95 * lm_alias so __p*d_populate functions must be used to populate with the
96 * physical address from __pa_symbol.
97 */
early_fixmap_init(void)98 void __init early_fixmap_init(void)
99 {
100 unsigned long addr = FIXADDR_TOT_START;
101 unsigned long end = FIXADDR_TOP;
102
103 pgd_t *pgdp = pgd_offset_k(addr);
104 p4d_t *p4dp = p4d_offset(pgdp, addr);
105
106 early_fixmap_init_pud(p4dp, addr, end);
107 }
108
109 /*
110 * Unusually, this is also called in IRQ context (ghes_iounmap_irq) so if we
111 * ever need to use IPIs for TLB broadcasting, then we're in trouble here.
112 */
__set_fixmap(enum fixed_addresses idx,phys_addr_t phys,pgprot_t flags)113 void __set_fixmap(enum fixed_addresses idx,
114 phys_addr_t phys, pgprot_t flags)
115 {
116 unsigned long addr = __fix_to_virt(idx);
117 pte_t *ptep;
118
119 BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);
120
121 ptep = fixmap_pte(addr);
122
123 if (pgprot_val(flags)) {
124 set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, flags));
125 } else {
126 pte_clear(&init_mm, addr, ptep);
127 flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
128 }
129 }
130
fixmap_remap_fdt(phys_addr_t dt_phys,int * size,pgprot_t prot)131 void *__init fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
132 {
133 const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
134 phys_addr_t dt_phys_base;
135 int offset;
136 void *dt_virt;
137
138 /*
139 * Check whether the physical FDT address is set and meets the minimum
140 * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
141 * at least 8 bytes so that we can always access the magic and size
142 * fields of the FDT header after mapping the first chunk, double check
143 * here if that is indeed the case.
144 */
145 BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
146 if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
147 return NULL;
148
149 dt_phys_base = round_down(dt_phys, PAGE_SIZE);
150 offset = dt_phys % PAGE_SIZE;
151 dt_virt = (void *)dt_virt_base + offset;
152
153 /* map the first chunk so we can read the size from the header */
154 create_mapping_noalloc(dt_phys_base, dt_virt_base, PAGE_SIZE, prot);
155
156 if (fdt_magic(dt_virt) != FDT_MAGIC)
157 return NULL;
158
159 *size = fdt_totalsize(dt_virt);
160 if (*size > MAX_FDT_SIZE)
161 return NULL;
162
163 if (offset + *size > PAGE_SIZE) {
164 create_mapping_noalloc(dt_phys_base, dt_virt_base,
165 offset + *size, prot);
166 }
167
168 return dt_virt;
169 }
170
171 /*
172 * Copy the fixmap region into a new pgdir.
173 */
fixmap_copy(pgd_t * pgdir)174 void __init fixmap_copy(pgd_t *pgdir)
175 {
176 if (!READ_ONCE(pgd_val(*pgd_offset_pgd(pgdir, FIXADDR_TOT_START)))) {
177 /*
178 * The fixmap falls in a separate pgd to the kernel, and doesn't
179 * live in the carveout for the swapper_pg_dir. We can simply
180 * re-use the existing dir for the fixmap.
181 */
182 set_pgd(pgd_offset_pgd(pgdir, FIXADDR_TOT_START),
183 READ_ONCE(*pgd_offset_k(FIXADDR_TOT_START)));
184 } else if (CONFIG_PGTABLE_LEVELS > 3) {
185 pgd_t *bm_pgdp;
186 p4d_t *bm_p4dp;
187 pud_t *bm_pudp;
188 /*
189 * The fixmap shares its top level pgd entry with the kernel
190 * mapping. This can really only occur when we are running
191 * with 16k/4 levels, so we can simply reuse the pud level
192 * entry instead.
193 */
194 BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
195 bm_pgdp = pgd_offset_pgd(pgdir, FIXADDR_TOT_START);
196 bm_p4dp = p4d_offset(bm_pgdp, FIXADDR_TOT_START);
197 bm_pudp = pud_set_fixmap_offset(bm_p4dp, FIXADDR_TOT_START);
198 pud_populate(&init_mm, bm_pudp, lm_alias(bm_pmd));
199 pud_clear_fixmap();
200 } else {
201 BUG();
202 }
203 }
204