alistair23-linux/arch/riscv/mm/init.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 Regents of the University of California
 * Copyright (C) 2019 Western Digital Corporation or its affiliates.
 */

#include <linux/init.h>
#include <linux/mm.h>
#include <linux/memblock.h>
#include <linux/initrd.h>
#include <linux/swap.h>
#include <linux/sizes.h>
#include <linux/of_fdt.h>

#include <asm/fixmap.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>
#include <asm/pgtable.h>
#include <asm/io.h>

unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
							__page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);

extern char _start[];

static void __init zone_sizes_init(void)
{
	unsigned long max_zone_pfns[MAX_NR_ZONES] = { 0, };

#ifdef CONFIG_ZONE_DMA32
	max_zone_pfns[ZONE_DMA32] = PFN_DOWN(min(4UL * SZ_1G,
			(unsigned long) PFN_PHYS(max_low_pfn)));
#endif
	max_zone_pfns[ZONE_NORMAL] = max_low_pfn;

	free_area_init_nodes(max_zone_pfns);
}

void setup_zero_page(void)
{
	memset((void *)empty_zero_page, 0, PAGE_SIZE);
}

void __init mem_init(void)
{
#ifdef CONFIG_FLATMEM
	BUG_ON(!mem_map);
#endif /* CONFIG_FLATMEM */

	high_memory = (void *)(__va(PFN_PHYS(max_low_pfn)));
	memblock_free_all();

	mem_init_print_info(NULL);
}

#ifdef CONFIG_BLK_DEV_INITRD
static void __init setup_initrd(void)
{
	unsigned long size;

	if (initrd_start >= initrd_end) {
		pr_info("initrd not found or empty");
		goto disable;
	}
	if (__pa(initrd_end) > PFN_PHYS(max_low_pfn)) {
		pr_err("initrd extends beyond end of memory");
		goto disable;
	}

	size = initrd_end - initrd_start;
	memblock_reserve(__pa(initrd_start), size);
	initrd_below_start_ok = 1;

	pr_info("Initial ramdisk at: 0x%p (%lu bytes)\n",
		(void *)(initrd_start), size);
	return;
disable:
	pr_cont(" - disabling initrd\n");
	initrd_start = 0;
	initrd_end = 0;
}
#endif /* CONFIG_BLK_DEV_INITRD */

void __init setup_bootmem(void)
{
	struct memblock_region *reg;
	phys_addr_t mem_size = 0;
	phys_addr_t vmlinux_end = __pa(&_end);
	phys_addr_t vmlinux_start = __pa(&_start);

	/* Find the memory region containing the kernel */
	for_each_memblock(memory, reg) {
		phys_addr_t end = reg->base + reg->size;

		if (reg->base <= vmlinux_end && vmlinux_end <= end) {
			mem_size = min(reg->size, (phys_addr_t)-PAGE_OFFSET);

			/*
			 * Remove memblock from the end of usable area to the
			 * end of region
			 */
			if (reg->base + mem_size < end)
				memblock_remove(reg->base + mem_size,
						end - reg->base - mem_size);
		}
	}
	BUG_ON(mem_size == 0);

	/* Reserve from the start of the kernel to the end of the kernel */
	memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);

	set_max_mapnr(PFN_DOWN(mem_size));
	max_low_pfn = PFN_DOWN(memblock_end_of_DRAM());

#ifdef CONFIG_BLK_DEV_INITRD
	setup_initrd();
#endif /* CONFIG_BLK_DEV_INITRD */

	early_init_fdt_reserve_self();
	early_init_fdt_scan_reserved_mem();
	memblock_allow_resize();
	memblock_dump_all();

	for_each_memblock(memory, reg) {
		unsigned long start_pfn = memblock_region_memory_base_pfn(reg);
		unsigned long end_pfn = memblock_region_memory_end_pfn(reg);

		memblock_set_node(PFN_PHYS(start_pfn),
				  PFN_PHYS(end_pfn - start_pfn),
				  &memblock.memory, 0);
	}
}

unsigned long va_pa_offset;
EXPORT_SYMBOL(va_pa_offset);
unsigned long pfn_base;
EXPORT_SYMBOL(pfn_base);

void *dtb_early_va;
pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
static bool mmu_enabled;

#define MAX_EARLY_MAPPING_SIZE	SZ_128M

pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);

void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
{
	unsigned long addr = __fix_to_virt(idx);
	pte_t *ptep;

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

	ptep = &fixmap_pte[pte_index(addr)];

	if (pgprot_val(prot)) {
		set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, prot));
	} else {
		pte_clear(&init_mm, addr, ptep);
		local_flush_tlb_page(addr);
	}
}

static pte_t *__init get_pte_virt(phys_addr_t pa)
{
	if (mmu_enabled) {
		clear_fixmap(FIX_PTE);
		return (pte_t *)set_fixmap_offset(FIX_PTE, pa);
	} else {
		return (pte_t *)((uintptr_t)pa);
	}
}

static phys_addr_t __init alloc_pte(uintptr_t va)
{
	/*
	 * We only create PMD or PGD early mappings so we
	 * should never reach here with MMU disabled.
	 */
	BUG_ON(!mmu_enabled);

	return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
}

static void __init create_pte_mapping(pte_t *ptep,
				      uintptr_t va, phys_addr_t pa,
				      phys_addr_t sz, pgprot_t prot)
{
	uintptr_t pte_index = pte_index(va);

	BUG_ON(sz != PAGE_SIZE);

	if (pte_none(ptep[pte_index]))
		ptep[pte_index] = pfn_pte(PFN_DOWN(pa), prot);
}

#ifndef __PAGETABLE_PMD_FOLDED

pmd_t trampoline_pmd[PTRS_PER_PMD] __page_aligned_bss;
pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;

#if MAX_EARLY_MAPPING_SIZE < PGDIR_SIZE
#define NUM_EARLY_PMDS		1UL
#else
#define NUM_EARLY_PMDS		(1UL + MAX_EARLY_MAPPING_SIZE / PGDIR_SIZE)
#endif
pmd_t early_pmd[PTRS_PER_PMD * NUM_EARLY_PMDS] __initdata __aligned(PAGE_SIZE);

static pmd_t *__init get_pmd_virt(phys_addr_t pa)
{
	if (mmu_enabled) {
		clear_fixmap(FIX_PMD);
		return (pmd_t *)set_fixmap_offset(FIX_PMD, pa);
	} else {
		return (pmd_t *)((uintptr_t)pa);
	}
}

static phys_addr_t __init alloc_pmd(uintptr_t va)
{
	uintptr_t pmd_num;

	if (mmu_enabled)
		return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);

	pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT;
	BUG_ON(pmd_num >= NUM_EARLY_PMDS);
	return (uintptr_t)&early_pmd[pmd_num * PTRS_PER_PMD];
}

static void __init create_pmd_mapping(pmd_t *pmdp,
				      uintptr_t va, phys_addr_t pa,
				      phys_addr_t sz, pgprot_t prot)
{
	pte_t *ptep;
	phys_addr_t pte_phys;
	uintptr_t pmd_index = pmd_index(va);

	if (sz == PMD_SIZE) {
		if (pmd_none(pmdp[pmd_index]))
			pmdp[pmd_index] = pfn_pmd(PFN_DOWN(pa), prot);
		return;
	}

	if (pmd_none(pmdp[pmd_index])) {
		pte_phys = alloc_pte(va);
		pmdp[pmd_index] = pfn_pmd(PFN_DOWN(pte_phys), PAGE_TABLE);
		ptep = get_pte_virt(pte_phys);
		memset(ptep, 0, PAGE_SIZE);
	} else {
		pte_phys = PFN_PHYS(_pmd_pfn(pmdp[pmd_index]));
		ptep = get_pte_virt(pte_phys);
	}

	create_pte_mapping(ptep, va, pa, sz, prot);
}

#define pgd_next_t		pmd_t
#define alloc_pgd_next(__va)	alloc_pmd(__va)
#define get_pgd_next_virt(__pa)	get_pmd_virt(__pa)
#define create_pgd_next_mapping(__nextp, __va, __pa, __sz, __prot)	\
	create_pmd_mapping(__nextp, __va, __pa, __sz, __prot)
#define PTE_PARENT_SIZE		PMD_SIZE
#define fixmap_pgd_next		fixmap_pmd
#else
#define pgd_next_t		pte_t
#define alloc_pgd_next(__va)	alloc_pte(__va)
#define get_pgd_next_virt(__pa)	get_pte_virt(__pa)
#define create_pgd_next_mapping(__nextp, __va, __pa, __sz, __prot)	\
	create_pte_mapping(__nextp, __va, __pa, __sz, __prot)
#define PTE_PARENT_SIZE		PGDIR_SIZE
#define fixmap_pgd_next		fixmap_pte
#endif

static void __init create_pgd_mapping(pgd_t *pgdp,
				      uintptr_t va, phys_addr_t pa,
				      phys_addr_t sz, pgprot_t prot)
{
	pgd_next_t *nextp;
	phys_addr_t next_phys;
	uintptr_t pgd_index = pgd_index(va);

	if (sz == PGDIR_SIZE) {
		if (pgd_val(pgdp[pgd_index]) == 0)
			pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pa), prot);
		return;
	}

	if (pgd_val(pgdp[pgd_index]) == 0) {
		next_phys = alloc_pgd_next(va);
		pgdp[pgd_index] = pfn_pgd(PFN_DOWN(next_phys), PAGE_TABLE);
		nextp = get_pgd_next_virt(next_phys);
		memset(nextp, 0, PAGE_SIZE);
	} else {
		next_phys = PFN_PHYS(_pgd_pfn(pgdp[pgd_index]));
		nextp = get_pgd_next_virt(next_phys);
	}

	create_pgd_next_mapping(nextp, va, pa, sz, prot);
}

static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
{
	uintptr_t map_size = PAGE_SIZE;

	/* Upgrade to PMD/PGDIR mappings whenever possible */
	if (!(base & (PTE_PARENT_SIZE - 1)) &&
	    !(size & (PTE_PARENT_SIZE - 1)))
		map_size = PTE_PARENT_SIZE;

	return map_size;
}

/*
 * setup_vm() is called from head.S with MMU-off.
 *
 * Following requirements should be honoured for setup_vm() to work
 * correctly:
 * 1) It should use PC-relative addressing for accessing kernel symbols.
 *    To achieve this we always use GCC cmodel=medany.
 * 2) The compiler instrumentation for FTRACE will not work for setup_vm()
 *    so disable compiler instrumentation when FTRACE is enabled.
 *
 * Currently, the above requirements are honoured by using custom CFLAGS
 * for init.o in mm/Makefile.
 */

#ifndef __riscv_cmodel_medany
#error "setup_vm() is called from head.S before relocate so it should "
	"not use absolute addressing."
#endif

asmlinkage void __init setup_vm(uintptr_t dtb_pa)
{
	uintptr_t va, end_va;
	uintptr_t load_pa = (uintptr_t)(&_start);
	uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
	uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE);

	va_pa_offset = PAGE_OFFSET - load_pa;
	pfn_base = PFN_DOWN(load_pa);

	/*
	 * Enforce boot alignment requirements of RV32 and
	 * RV64 by only allowing PMD or PGD mappings.
	 */
	BUG_ON(map_size == PAGE_SIZE);

	/* Sanity check alignment and size */
	BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);
	BUG_ON((load_pa % map_size) != 0);
	BUG_ON(load_sz > MAX_EARLY_MAPPING_SIZE);

	/* Setup early PGD for fixmap */
	create_pgd_mapping(early_pg_dir, FIXADDR_START,
			   (uintptr_t)fixmap_pgd_next, PGDIR_SIZE, PAGE_TABLE);

#ifndef __PAGETABLE_PMD_FOLDED
	/* Setup fixmap PMD */
	create_pmd_mapping(fixmap_pmd, FIXADDR_START,
			   (uintptr_t)fixmap_pte, PMD_SIZE, PAGE_TABLE);
	/* Setup trampoline PGD and PMD */
	create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
			   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
	create_pmd_mapping(trampoline_pmd, PAGE_OFFSET,
			   load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
#else
	/* Setup trampoline PGD */
	create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
			   load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
#endif

	/*
	 * Setup early PGD covering entire kernel which will allows
	 * us to reach paging_init(). We map all memory banks later
	 * in setup_vm_final() below.
	 */
	end_va = PAGE_OFFSET + load_sz;
	for (va = PAGE_OFFSET; va < end_va; va += map_size)
		create_pgd_mapping(early_pg_dir, va,
				   load_pa + (va - PAGE_OFFSET),
				   map_size, PAGE_KERNEL_EXEC);

	/* Create fixed mapping for early FDT parsing */
	end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE;
	for (va = __fix_to_virt(FIX_FDT); va < end_va; va += PAGE_SIZE)
		create_pte_mapping(fixmap_pte, va,
				   dtb_pa + (va - __fix_to_virt(FIX_FDT)),
				   PAGE_SIZE, PAGE_KERNEL);

	/* Save pointer to DTB for early FDT parsing */
	dtb_early_va = (void *)fix_to_virt(FIX_FDT) + (dtb_pa & ~PAGE_MASK);
}

static void __init setup_vm_final(void)
{
	uintptr_t va, map_size;
	phys_addr_t pa, start, end;
	struct memblock_region *reg;

	/* Set mmu_enabled flag */
	mmu_enabled = true;

	/* Setup swapper PGD for fixmap */
	create_pgd_mapping(swapper_pg_dir, FIXADDR_START,
			   __pa(fixmap_pgd_next),
			   PGDIR_SIZE, PAGE_TABLE);

	/* Map all memory banks */
	for_each_memblock(memory, reg) {
		start = reg->base;
		end = start + reg->size;

		if (start >= end)
			break;
		if (memblock_is_nomap(reg))
			continue;
		if (start <= __pa(PAGE_OFFSET) &&
		    __pa(PAGE_OFFSET) < end)
			start = __pa(PAGE_OFFSET);

		map_size = best_map_size(start, end - start);
		for (pa = start; pa < end; pa += map_size) {
			va = (uintptr_t)__va(pa);
			create_pgd_mapping(swapper_pg_dir, va, pa,
					   map_size, PAGE_KERNEL_EXEC);
		}
	}

	/* Clear fixmap PTE and PMD mappings */
	clear_fixmap(FIX_PTE);
	clear_fixmap(FIX_PMD);

	/* Move to swapper page table */
	csr_write(CSR_SATP, PFN_DOWN(__pa(swapper_pg_dir)) | SATP_MODE);
	local_flush_tlb_all();
}

void __init paging_init(void)
{
	setup_vm_final();
	setup_zero_page();
	zone_sizes_init();
}