arch/arm64/mm/fixmap.c

Source file repositories/reference/linux-study-clean/arch/arm64/mm/fixmap.c

File Facts

System
Linux kernel
Corpus path
arch/arm64/mm/fixmap.c
Extension
.c
Size
4776 bytes
Lines
176
Domain
Architecture Layer
Bucket
arch/arm64
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

p4d_page_paddr(p4d) != __pa_symbol(bm_pud)) {
		/*
		 * We only end up here if the kernel mapping and the fixmap
		 * share the top level pgd entry, which should only happen on
		 * 16k/4 levels configurations.
		 */
		BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
	}

	if (p4d_none(p4d))
		__p4d_populate(p4dp, __pa_symbol(bm_pud),
			       P4D_TYPE_TABLE | P4D_TABLE_AF);

	pudp = pud_offset_kimg(p4dp, addr);
	early_fixmap_init_pmd(pudp, addr, end);
}

/*
 * The p*d_populate functions call virt_to_phys implicitly so they can't be used
 * directly on kernel symbols (bm_p*d). This function is called too early to use
 * lm_alias so __p*d_populate functions must be used to populate with the
 * physical address from __pa_symbol.
 */
void __init early_fixmap_init(void)
{
	unsigned long addr = FIXADDR_TOT_START;
	unsigned long end = FIXADDR_TOP;

	pgd_t *pgdp = pgd_offset_k(addr);
	p4d_t *p4dp = p4d_offset_kimg(pgdp, addr);

	early_fixmap_init_pud(p4dp, addr, end);
}

/*
 * Unusually, this is also called in IRQ context (ghes_iounmap_irq) so if we
 * ever need to use IPIs for TLB broadcasting, then we're in trouble here.
 */
void __set_fixmap(enum fixed_addresses idx,
			       phys_addr_t phys, pgprot_t flags)
{
	unsigned long addr = __fix_to_virt(idx);
	pte_t *ptep;

	BUG_ON(idx <= FIX_HOLE || idx >= __end_of_fixed_addresses);

	ptep = fixmap_pte(addr);

	if (pgprot_val(flags)) {
		__set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, flags));
	} else {
		__pte_clear(&init_mm, addr, ptep);
		flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
	}
}

void *__init fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
{
	const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
	phys_addr_t dt_phys_base;
	int offset;
	void *dt_virt;

	/*
	 * Check whether the physical FDT address is set and meets the minimum
	 * alignment requirement. Since we are relying on MIN_FDT_ALIGN to be
	 * at least 8 bytes so that we can always access the magic and size
	 * fields of the FDT header after mapping the first chunk, double check
	 * here if that is indeed the case.
	 */
	BUILD_BUG_ON(MIN_FDT_ALIGN < 8);
	if (!dt_phys || dt_phys % MIN_FDT_ALIGN)
		return NULL;

	dt_phys_base = round_down(dt_phys, PAGE_SIZE);
	offset = dt_phys % PAGE_SIZE;
	dt_virt = (void *)dt_virt_base + offset;

	/* map the first chunk so we can read the size from the header */
	create_mapping_noalloc(dt_phys_base, dt_virt_base, PAGE_SIZE, prot);

	if (fdt_magic(dt_virt) != FDT_MAGIC)
		return NULL;

	*size = fdt_totalsize(dt_virt);
	if (*size > MAX_FDT_SIZE)
		return NULL;

	if (offset + *size > PAGE_SIZE) {
		create_mapping_noalloc(dt_phys_base, dt_virt_base,

Annotation

Implementation Notes