linux/arch/arm64/mm/init.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Based on arch/arm/mm/init.c
 *
 * Copyright (C) 1995-2005 Russell King
 * Copyright (C) 2012 ARM Ltd.
 */

#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/errno.h>
#include <linux/swap.h>
#include <linux/init.h>
#include <linux/cache.h>
#include <linux/mman.h>
#include <linux/nodemask.h>
#include <linux/initrd.h>
#include <linux/gfp.h>
#include <linux/math.h>
#include <linux/memblock.h>
#include <linux/sort.h>
#include <linux/of.h>
#include <linux/of_fdt.h>
#include <linux/dma-direct.h>
#include <linux/dma-map-ops.h>
#include <linux/efi.h>
#include <linux/swiotlb.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/kexec.h>
#include <linux/crash_dump.h>
#include <linux/hugetlb.h>
#include <linux/acpi_iort.h>
#include <linux/kmemleak.h>
#include <linux/execmem.h>

#include <asm/boot.h>
#include <asm/fixmap.h>
#include <asm/kasan.h>
#include <asm/kernel-pgtable.h>
#include <asm/kvm_host.h>
#include <asm/memory.h>
#include <asm/numa.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <linux/sizes.h>
#include <asm/tlb.h>
#include <asm/alternative.h>
#include <asm/xen/swiotlb-xen.h>

/*
 * We need to be able to catch inadvertent references to memstart_addr
 * that occur (potentially in generic code) before arm64_memblock_init()
 * executes, which assigns it its actual value. So use a default value
 * that cannot be mistaken for a real physical address.
 */
s64 memstart_addr __ro_after_init = -1;
EXPORT_SYMBOL(memstart_addr);

/*
 * If the corresponding config options are enabled, we create both ZONE_DMA
 * and ZONE_DMA32. By default ZONE_DMA covers the 32-bit addressable memory
 * unless restricted on specific platforms (e.g. 30-bit on Raspberry Pi 4).
 * In such case, ZONE_DMA32 covers the rest of the 32-bit addressable memory,
 * otherwise it is empty.
 */
phys_addr_t __ro_after_init arm64_dma_phys_limit;

/*
 * To make optimal use of block mappings when laying out the linear
 * mapping, round down the base of physical memory to a size that can
 * be mapped efficiently, i.e., either PUD_SIZE (4k granule) or PMD_SIZE
 * (64k granule), or a multiple that can be mapped using contiguous bits
 * in the page tables: 32 * PMD_SIZE (16k granule)
 */
#if defined(CONFIG_ARM64_4K_PAGES)
#define ARM64_MEMSTART_SHIFT		PUD_SHIFT
#elif defined(CONFIG_ARM64_16K_PAGES)
#define ARM64_MEMSTART_SHIFT		CONT_PMD_SHIFT
#else
#define ARM64_MEMSTART_SHIFT		PMD_SHIFT
#endif

/*
 * sparsemem vmemmap imposes an additional requirement on the alignment of
 * memstart_addr, due to the fact that the base of the vmemmap region
 * has a direct correspondence, and needs to appear sufficiently aligned
 * in the virtual address space.
 */
#if ARM64_MEMSTART_SHIFT < SECTION_SIZE_BITS
#define ARM64_MEMSTART_ALIGN	(1UL << SECTION_SIZE_BITS)
#else
#define ARM64_MEMSTART_ALIGN	(1UL << ARM64_MEMSTART_SHIFT)
#endif

static void __init arch_reserve_crashkernel(void)
{
	unsigned long long low_size = 0;
	unsigned long long crash_base, crash_size;
	char *cmdline = boot_command_line;
	bool high = false;
	int ret;

	if (!IS_ENABLED(CONFIG_CRASH_RESERVE))
		return;

	ret = parse_crashkernel(cmdline, memblock_phys_mem_size(),
				&crash_size, &crash_base,
				&low_size, &high);
	if (ret)
		return;

	reserve_crashkernel_generic(cmdline, crash_size, crash_base,
				    low_size, high);
}

/*
 * Return the maximum physical address for a zone accessible by the given bits
 * limit. If DRAM starts above 32-bit, expand the zone to the maximum
 * available memory, otherwise cap it at 32-bit.
 */
static phys_addr_t __init max_zone_phys(unsigned int zone_bits)
{
	phys_addr_t zone_mask = DMA_BIT_MASK(zone_bits);
	phys_addr_t phys_start = memblock_start_of_DRAM();

	if (phys_start > U32_MAX)
		zone_mask = PHYS_ADDR_MAX;
	else if (phys_start > zone_mask)
		zone_mask = U32_MAX;

	return min(zone_mask, memblock_end_of_DRAM() - 1) + 1;
}

static void __init zone_sizes_init(void)
{
	unsigned long max_zone_pfns[MAX_NR_ZONES]  = {0};
	unsigned int __maybe_unused acpi_zone_dma_bits;
	unsigned int __maybe_unused dt_zone_dma_bits;
	phys_addr_t __maybe_unused dma32_phys_limit = max_zone_phys(32);

#ifdef CONFIG_ZONE_DMA
	acpi_zone_dma_bits = fls64(acpi_iort_dma_get_max_cpu_address());
	dt_zone_dma_bits = fls64(of_dma_get_max_cpu_address(NULL));
	zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_zone_dma_bits);
	arm64_dma_phys_limit = max_zone_phys(zone_dma_bits);
	max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit);
#endif
#ifdef CONFIG_ZONE_DMA32
	max_zone_pfns[ZONE_DMA32] = PFN_DOWN(dma32_phys_limit);
	if (!arm64_dma_phys_limit)
		arm64_dma_phys_limit = dma32_phys_limit;
#endif
	if (!arm64_dma_phys_limit)
		arm64_dma_phys_limit = PHYS_MASK + 1;
	max_zone_pfns[ZONE_NORMAL] = max_pfn;

	free_area_init(max_zone_pfns);
}

int pfn_is_map_memory(unsigned long pfn)
{
	phys_addr_t addr = PFN_PHYS(pfn);

	/* avoid false positives for bogus PFNs, see comment in pfn_valid() */
	if (PHYS_PFN(addr) != pfn)
		return 0;

	return memblock_is_map_memory(addr);
}
EXPORT_SYMBOL(pfn_is_map_memory);

static phys_addr_t memory_limit __ro_after_init = PHYS_ADDR_MAX;

/*
 * Limit the memory size that was specified via FDT.
 */
static int __init early_mem(char *p)
{
	if (!p)
		return 1;

	memory_limit = memparse(p, &p) & PAGE_MASK;
	pr_notice("Memory limited to %lldMB\n", memory_limit >> 20);

	return 0;
}
early_param("mem", early_mem);

void __init arm64_memblock_init(void)
{
	s64 linear_region_size = PAGE_END - _PAGE_OFFSET(vabits_actual);

	/*
	 * Corner case: 52-bit VA capable systems running KVM in nVHE mode may
	 * be limited in their ability to support a linear map that exceeds 51
	 * bits of VA space, depending on the placement of the ID map. Given
	 * that the placement of the ID map may be randomized, let's simply
	 * limit the kernel's linear map to 51 bits as well if we detect this
	 * configuration.
	 */
	if (IS_ENABLED(CONFIG_KVM) && vabits_actual == 52 &&
	    is_hyp_mode_available() && !is_kernel_in_hyp_mode()) {
		pr_info("Capping linear region to 51 bits for KVM in nVHE mode on LVA capable hardware.\n");
		linear_region_size = min_t(u64, linear_region_size, BIT(51));
	}

	/* Remove memory above our supported physical address size */
	memblock_remove(1ULL << PHYS_MASK_SHIFT, ULLONG_MAX);

	/*
	 * Select a suitable value for the base of physical memory.
	 */
	memstart_addr = round_down(memblock_start_of_DRAM(),
				   ARM64_MEMSTART_ALIGN);

	if ((memblock_end_of_DRAM() - memstart_addr) > linear_region_size)
		pr_warn("Memory doesn't fit in the linear mapping, VA_BITS too small\n");

	/*
	 * Remove the memory that we will not be able to cover with the
	 * linear mapping. Take care not to clip the kernel which may be
	 * high in memory.
	 */
	memblock_remove(max_t(u64, memstart_addr + linear_region_size,
			__pa_symbol(_end)), ULLONG_MAX);
	if (memstart_addr + linear_region_size < memblock_end_of_DRAM()) {
		/* ensure that memstart_addr remains sufficiently aligned */
		memstart_addr = round_up(memblock_end_of_DRAM() - linear_region_size,
					 ARM64_MEMSTART_ALIGN);
		memblock_remove(0, memstart_addr);
	}

	/*
	 * If we are running with a 52-bit kernel VA config on a system that
	 * does not support it, we have to place the available physical
	 * memory in the 48-bit addressable part of the linear region, i.e.,
	 * we have to move it upward. Since memstart_addr represents the
	 * physical address of PAGE_OFFSET, we have to *subtract* from it.
	 */
	if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52))
		memstart_addr -= _PAGE_OFFSET(vabits_actual) - _PAGE_OFFSET(52);

	/*
	 * Apply the memory limit if it was set. Since the kernel may be loaded
	 * high up in memory, add back the kernel region that must be accessible
	 * via the linear mapping.
	 */
	if (memory_limit != PHYS_ADDR_MAX) {
		memblock_mem_limit_remove_map(memory_limit);
		memblock_add(__pa_symbol(_text), (u64)(_end - _text));
	}

	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
		/*
		 * Add back the memory we just removed if it results in the
		 * initrd to become inaccessible via the linear mapping.
		 * Otherwise, this is a no-op
		 */
		u64 base = phys_initrd_start & PAGE_MASK;
		u64 size = PAGE_ALIGN(phys_initrd_start + phys_initrd_size) - base;

		/*
		 * We can only add back the initrd memory if we don't end up
		 * with more memory than we can address via the linear mapping.
		 * It is up to the bootloader to position the kernel and the
		 * initrd reasonably close to each other (i.e., within 32 GB of
		 * each other) so that all granule/#levels combinations can
		 * always access both.
		 */
		if (WARN(base < memblock_start_of_DRAM() ||
			 base + size > memblock_start_of_DRAM() +
				       linear_region_size,
			"initrd not fully accessible via the linear mapping -- please check your bootloader ...\n")) {
			phys_initrd_size = 0;
		} else {
			memblock_add(base, size);
			memblock_clear_nomap(base, size);
			memblock_reserve(base, size);
		}
	}

	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
		extern u16 memstart_offset_seed;
		u64 mmfr0 = read_cpuid(ID_AA64MMFR0_EL1);
		int parange = cpuid_feature_extract_unsigned_field(
					mmfr0, ID_AA64MMFR0_EL1_PARANGE_SHIFT);
		s64 range = linear_region_size -
			    BIT(id_aa64mmfr0_parange_to_phys_shift(parange));

		/*
		 * If the size of the linear region exceeds, by a sufficient
		 * margin, the size of the region that the physical memory can
		 * span, randomize the linear region as well.
		 */
		if (memstart_offset_seed > 0 && range >= (s64)ARM64_MEMSTART_ALIGN) {
			range /= ARM64_MEMSTART_ALIGN;
			memstart_addr -= ARM64_MEMSTART_ALIGN *
					 ((range * memstart_offset_seed) >> 16);
		}
	}

	/*
	 * Register the kernel text, kernel data, initrd, and initial
	 * pagetables with memblock.
	 */
	memblock_reserve(__pa_symbol(_stext), _end - _stext);
	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {
		/* the generic initrd code expects virtual addresses */
		initrd_start = __phys_to_virt(phys_initrd_start);
		initrd_end = initrd_start + phys_initrd_size;
	}

	early_init_fdt_scan_reserved_mem();

	high_memory = __va(memblock_end_of_DRAM() - 1) + 1;
}

void __init bootmem_init(void)
{
	unsigned long min, max;

	min = PFN_UP(memblock_start_of_DRAM());
	max = PFN_DOWN(memblock_end_of_DRAM());

	early_memtest(min << PAGE_SHIFT, max << PAGE_SHIFT);

	max_pfn = max_low_pfn = max;
	min_low_pfn = min;

	arch_numa_init();

	/*
	 * must be done after arch_numa_init() which calls numa_init() to
	 * initialize node_online_map that gets used in hugetlb_cma_reserve()
	 * while allocating required CMA size across online nodes.
	 */
#if defined(CONFIG_HUGETLB_PAGE) && defined(CONFIG_CMA)
	arm64_hugetlb_cma_reserve();
#endif

	kvm_hyp_reserve();

	/*
	 * sparse_init() tries to allocate memory from memblock, so must be
	 * done after the fixed reservations
	 */
	sparse_init();
	zone_sizes_init();

	/*
	 * Reserve the CMA area after arm64_dma_phys_limit was initialised.
	 */
	dma_contiguous_reserve(arm64_dma_phys_limit);

	/*
	 * request_standard_resources() depends on crashkernel's memory being
	 * reserved, so do it here.
	 */
	arch_reserve_crashkernel();

	memblock_dump_all();
}

/*
 * mem_init() marks the free areas in the mem_map and tells us how much memory
 * is free.  This is done after various parts of the system have claimed their
 * memory after the kernel image.
 */
void __init mem_init(void)
{
	bool swiotlb = max_pfn > PFN_DOWN(arm64_dma_phys_limit);

	if (IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC) && !swiotlb) {
		/*
		 * If no bouncing needed for ZONE_DMA, reduce the swiotlb
		 * buffer for kmalloc() bouncing to 1MB per 1GB of RAM.
		 */
		unsigned long size =
			DIV_ROUND_UP(memblock_phys_mem_size(), 1024);
		swiotlb_adjust_size(min(swiotlb_size_or_default(), size));
		swiotlb = true;
	}

	swiotlb_init(swiotlb, SWIOTLB_VERBOSE);

	/* this will put all unused low memory onto the freelists */
	memblock_free_all();

	/*
	 * Check boundaries twice: Some fundamental inconsistencies can be
	 * detected at build time already.
	 */
#ifdef CONFIG_COMPAT
	BUILD_BUG_ON(TASK_SIZE_32 > DEFAULT_MAP_WINDOW_64);
#endif

	/*
	 * Selected page table levels should match when derived from
	 * scratch using the virtual address range and page size.
	 */
	BUILD_BUG_ON(ARM64_HW_PGTABLE_LEVELS(CONFIG_ARM64_VA_BITS) !=
		     CONFIG_PGTABLE_LEVELS);

	if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
		extern int sysctl_overcommit_memory;
		/*
		 * On a machine this small we won't get anywhere without
		 * overcommit, so turn it on by default.
		 */
		sysctl_overcommit_memory = OVERCOMMIT_ALWAYS;
	}
}

void free_initmem(void)
{
	free_reserved_area(lm_alias(__init_begin),
			   lm_alias(__init_end),
			   POISON_FREE_INITMEM, "unused kernel");
	/*
	 * Unmap the __init region but leave the VM area in place. This
	 * prevents the region from being reused for kernel modules, which
	 * is not supported by kallsyms.
	 */
	vunmap_range((u64)__init_begin, (u64)__init_end);
}

void dump_mem_limit(void)
{
	if (memory_limit != PHYS_ADDR_MAX) {
		pr_emerg("Memory Limit: %llu MB\n", memory_limit >> 20);
	} else {
		pr_emerg("Memory Limit: none\n");
	}
}

#ifdef CONFIG_EXECMEM
static u64 module_direct_base __ro_after_init = 0;
static u64 module_plt_base __ro_after_init = 0;

/*
 * Choose a random page-aligned base address for a window of 'size' bytes which
 * entirely contains the interval [start, end - 1].
 */
static u64 __init random_bounding_box(u64 size, u64 start, u64 end)
{
	u64 max_pgoff, pgoff;

	if ((end - start) >= size)
		return 0;

	max_pgoff = (size - (end - start)) / PAGE_SIZE;
	pgoff = get_random_u32_inclusive(0, max_pgoff);

	return start - pgoff * PAGE_SIZE;
}

/*
 * Modules may directly reference data and text anywhere within the kernel
 * image and other modules. References using PREL32 relocations have a +/-2G
 * range, and so we need to ensure that the entire kernel image and all modules
 * fall within a 2G window such that these are always within range.
 *
 * Modules may directly branch to functions and code within the kernel text,
 * and to functions and code within other modules. These branches will use
 * CALL26/JUMP26 relocations with a +/-128M range. Without PLTs, we must ensure
 * that the entire kernel text and all module text falls within a 128M window
 * such that these are always within range. With PLTs, we can expand this to a
 * 2G window.
 *
 * We chose the 128M region to surround the entire kernel image (rather than
 * just the text) as using the same bounds for the 128M and 2G regions ensures
 * by construction that we never select a 128M region that is not a subset of
 * the 2G region. For very large and unusual kernel configurations this means
 * we may fall back to PLTs where they could have been avoided, but this keeps
 * the logic significantly simpler.
 */
static int __init module_init_limits(void)
{
	u64 kernel_end = (u64)_end;
	u64 kernel_start = (u64)_text;
	u64 kernel_size = kernel_end - kernel_start;

	/*
	 * The default modules region is placed immediately below the kernel
	 * image, and is large enough to use the full 2G relocation range.
	 */
	BUILD_BUG_ON(KIMAGE_VADDR != MODULES_END);
	BUILD_BUG_ON(MODULES_VSIZE < SZ_2G);

	if (!kaslr_enabled()) {
		if (kernel_size < SZ_128M)
			module_direct_base = kernel_end - SZ_128M;
		if (kernel_size < SZ_2G)
			module_plt_base = kernel_end - SZ_2G;
	} else {
		u64 min = kernel_start;
		u64 max = kernel_end;

		if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
			pr_info("2G module region forced by RANDOMIZE_MODULE_REGION_FULL\n");
		} else {
			module_direct_base = random_bounding_box(SZ_128M, min, max);
			if (module_direct_base) {
				min = module_direct_base;
				max = module_direct_base + SZ_128M;
			}
		}

		module_plt_base = random_bounding_box(SZ_2G, min, max);
	}

	pr_info("%llu pages in range for non-PLT usage",
		module_direct_base ? (SZ_128M - kernel_size) / PAGE_SIZE : 0);
	pr_info("%llu pages in range for PLT usage",
		module_plt_base ? (SZ_2G - kernel_size) / PAGE_SIZE : 0);

	return 0;
}

static struct execmem_info execmem_info __ro_after_init;

struct execmem_info __init *execmem_arch_setup(void)
{
	unsigned long fallback_start = 0, fallback_end = 0;
	unsigned long start = 0, end = 0;

	module_init_limits();

	/*
	 * Where possible, prefer to allocate within direct branch range of the
	 * kernel such that no PLTs are necessary.
	 */
	if (module_direct_base) {
		start = module_direct_base;
		end = module_direct_base + SZ_128M;

		if (module_plt_base) {
			fallback_start = module_plt_base;
			fallback_end = module_plt_base + SZ_2G;
		}
	} else if (module_plt_base) {
		start = module_plt_base;
		end = module_plt_base + SZ_2G;
	}

	execmem_info = (struct execmem_info){
		.ranges = {
			[EXECMEM_DEFAULT] = {
				.start	= start,
				.end	= end,
				.pgprot	= PAGE_KERNEL,
				.alignment = 1,
				.fallback_start	= fallback_start,
				.fallback_end	= fallback_end,
			},
			[EXECMEM_KPROBES] = {
				.start	= VMALLOC_START,
				.end	= VMALLOC_END,
				.pgprot	= PAGE_KERNEL_ROX,
				.alignment = 1,
			},
			[EXECMEM_BPF] = {
				.start	= VMALLOC_START,
				.end	= VMALLOC_END,
				.pgprot	= PAGE_KERNEL,
				.alignment = 1,
			},
		},
	};

	return &execmem_info;
}
#endif /* CONFIG_EXECMEM */