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
 24static_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
 31static pte_t bm_pte[NR_BM_PTE_TABLES][PTRS_PER_PTE] __page_aligned_bss;
 32static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss __maybe_unused;
 33static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss __maybe_unused;
 34
 35static inline pte_t *fixmap_pte(unsigned long addr)
 36{
 37	return &bm_pte[BM_PTE_TABLE_IDX(addr)][pte_index(addr)];
 38}
 39
 40static 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
 51static 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
 69static 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 */
 98void __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 */
113void __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
131void *__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 */
174void __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}