paging_init

void __init paging_init(void)
{
	pgd_t *pgdp = pgd_set_fixmap(__pa_symbol(swapper_pg_dir));
	extern pgd_t init_idmap_pg_dir[];

	idmap_t0sz = 63UL - __fls(__pa_symbol(_end) | GENMASK(VA_BITS_MIN - 1, 0));

	map_kernel(pgdp);
	map_mem(pgdp);

	pgd_clear_fixmap();

	cpu_replace_ttbr1(lm_alias(swapper_pg_dir), init_idmap_pg_dir);
	init_mm.pgd = swapper_pg_dir;

	memblock_phys_free(__pa_symbol(init_pg_dir),
			   __pa_symbol(init_pg_end) - __pa_symbol(init_pg_dir));

	memblock_allow_resize();

	create_idmap();
}

static void __init map_kernel(pgd_t *pgdp)
{
	static struct vm_struct vmlinux_text, vmlinux_rodata, vmlinux_inittext,
				vmlinux_initdata, vmlinux_data;

	/*
	 * External debuggers may need to write directly to the text
	 * mapping to install SW breakpoints. Allow this (only) when
	 * explicitly requested with rodata=off.
	 */
	pgprot_t text_prot = kernel_exec_prot();

	/*
	 * If we have a CPU that supports BTI and a kernel built for
	 * BTI then mark the kernel executable text as guarded pages
	 * now so we don't have to rewrite the page tables later.
	 */
	if (arm64_early_this_cpu_has_bti())
		text_prot = __pgprot_modify(text_prot, PTE_GP, PTE_GP);

	/*
	 * Only rodata will be remapped with different permissions later on,
	 * all other segments are allowed to use contiguous mappings.
	 */
	map_kernel_segment(pgdp, _stext, _etext, text_prot, &vmlinux_text, 0,
			   VM_NO_GUARD);
	map_kernel_segment(pgdp, __start_rodata, __inittext_begin, PAGE_KERNEL,
			   &vmlinux_rodata, NO_CONT_MAPPINGS, VM_NO_GUARD);
	map_kernel_segment(pgdp, __inittext_begin, __inittext_end, text_prot,
			   &vmlinux_inittext, 0, VM_NO_GUARD);
	map_kernel_segment(pgdp, __initdata_begin, __initdata_end, PAGE_KERNEL,
			   &vmlinux_initdata, 0, VM_NO_GUARD);
	map_kernel_segment(pgdp, _data, _end, PAGE_KERNEL, &vmlinux_data, 0, 0);

	fixmap_copy(pgdp);
	kasan_copy_shadow(pgdp);
}

static void __init map_mem(pgd_t *pgdp)
{
	static const u64 direct_map_end = _PAGE_END(VA_BITS_MIN);
	phys_addr_t kernel_start = __pa_symbol(_stext);
	phys_addr_t kernel_end = __pa_symbol(__init_begin);
	phys_addr_t start, end;
	phys_addr_t early_kfence_pool;
	int flags = NO_EXEC_MAPPINGS;
	u64 i;

	/*
	 * Setting hierarchical PXNTable attributes on table entries covering
	 * the linear region is only possible if it is guaranteed that no table
	 * entries at any level are being shared between the linear region and
	 * the vmalloc region. Check whether this is true for the PGD level, in
	 * which case it is guaranteed to be true for all other levels as well.
	 */
	BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end));

	early_kfence_pool = arm64_kfence_alloc_pool();

	if (can_set_direct_map())
		flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;

	/*
	 * Take care not to create a writable alias for the
	 * read-only text and rodata sections of the kernel image.
	 * So temporarily mark them as NOMAP to skip mappings in
	 * the following for-loop
	 */
	memblock_mark_nomap(kernel_start, kernel_end - kernel_start);

	/* map all the memory banks */
	for_each_mem_range(i, &start, &end) {
		if (start >= end)
			break;
		/*
		 * The linear map must allow allocation tags reading/writing
		 * if MTE is present. Otherwise, it has the same attributes as
		 * PAGE_KERNEL.
		 */
		__map_memblock(pgdp, start, end, pgprot_tagged(PAGE_KERNEL),
			       flags);
	}

	/*
	 * Map the linear alias of the [_stext, __init_begin) interval
	 * as non-executable now, and remove the write permission in
	 * mark_linear_text_alias_ro() below (which will be called after
	 * alternative patching has completed). This makes the contents
	 * of the region accessible to subsystems such as hibernate,
	 * but protects it from inadvertent modification or execution.
	 * Note that contiguous mappings cannot be remapped in this way,
	 * so we should avoid them here.
	 */
	__map_memblock(pgdp, kernel_start, kernel_end,
		       PAGE_KERNEL, NO_CONT_MAPPINGS);
	memblock_clear_nomap(kernel_start, kernel_end - kernel_start);
	arm64_kfence_map_pool(early_kfence_pool, pgdp);
}