arch/s390/mm/kasan_init.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/kasan.h>
 #include <linux/sched/task.h>
 #include <linux/memblock.h>
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
 #include <asm/kasan.h>
 #include <asm/mem_detect.h>
 #include <asm/processor.h>
 #include <asm/sclp.h>
 #include <asm/facility.h>
 #include <asm/sections.h>
 #include <asm/setup.h>

 static unsigned long segment_pos __initdata;
 static unsigned long segment_low __initdata;
 static unsigned long pgalloc_pos __initdata;
 static unsigned long pgalloc_low __initdata;
 static unsigned long pgalloc_freeable __initdata;
 static bool has_edat __initdata;
 static bool has_nx __initdata;

 #define __sha(x) ((unsigned long)kasan_mem_to_shadow((void *)x))

 static pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);

 static void __init kasan_early_panic(const char *reason)
 {
 	sclp_early_printk("The Linux kernel failed to boot with the KernelAddressSanitizer:\n");
 	sclp_early_printk(reason);
 	disabled_wait();
 }

 static void * __init kasan_early_alloc_segment(void)
 {
 	segment_pos -= _SEGMENT_SIZE;

 	if (segment_pos < segment_low)
 		kasan_early_panic("out of memory during initialisation\n");

 	return (void *)segment_pos;
 }

 static void * __init kasan_early_alloc_pages(unsigned int order)
 {
 	pgalloc_pos -= (PAGE_SIZE << order);

 	if (pgalloc_pos < pgalloc_low)
 		kasan_early_panic("out of memory during initialisation\n");

 	return (void *)pgalloc_pos;
 }

 static void * __init kasan_early_crst_alloc(unsigned long val)
 {
 	unsigned long *table;

 	table = kasan_early_alloc_pages(CRST_ALLOC_ORDER);
 	if (table)
 		crst_table_init(table, val);
 	return table;
 }

 static pte_t * __init kasan_early_pte_alloc(void)
 {
 	static void *pte_leftover;
 	pte_t *pte;

 	BUILD_BUG_ON(_PAGE_TABLE_SIZE * 2 != PAGE_SIZE);

 	if (!pte_leftover) {
 		pte_leftover = kasan_early_alloc_pages(0);
 		pte = pte_leftover + _PAGE_TABLE_SIZE;
 	} else {
 		pte = pte_leftover;
 		pte_leftover = NULL;
 	}
 	memset64((u64 *)pte, _PAGE_INVALID, PTRS_PER_PTE);
 	return pte;
 }

 enum populate_mode {
 	POPULATE_ONE2ONE,
 	POPULATE_MAP,
 	POPULATE_ZERO_SHADOW
 };
 static void __init kasan_early_vmemmap_populate(unsigned long address,
 						unsigned long end,
 						enum populate_mode mode)
 {
 	unsigned long pgt_prot_zero, pgt_prot, sgt_prot;
 	pgd_t *pg_dir;
 	p4d_t *p4_dir;
 	pud_t *pu_dir;
 	pmd_t *pm_dir;
 	pte_t *pt_dir;

 	pgt_prot_zero = pgprot_val(PAGE_KERNEL_RO);
 	if (!has_nx)
 		pgt_prot_zero &= ~_PAGE_NOEXEC;
 	pgt_prot = pgprot_val(PAGE_KERNEL_EXEC);
 	sgt_prot = pgprot_val(SEGMENT_KERNEL_EXEC);

 	while (address < end) {
 		pg_dir = pgd_offset_k(address);
 		if (pgd_none(*pg_dir)) {
 			if (mode == POPULATE_ZERO_SHADOW &&
 			    IS_ALIGNED(address, PGDIR_SIZE) &&
 			    end - address >= PGDIR_SIZE) {
 				pgd_populate(&init_mm, pg_dir,
 						kasan_early_shadow_p4d);
 				address = (address + PGDIR_SIZE) & PGDIR_MASK;
 				continue;
 			}
 			p4_dir = kasan_early_crst_alloc(_REGION2_ENTRY_EMPTY);
 			pgd_populate(&init_mm, pg_dir, p4_dir);
 		}

 		p4_dir = p4d_offset(pg_dir, address);
 		if (p4d_none(*p4_dir)) {
 			if (mode == POPULATE_ZERO_SHADOW &&
 			    IS_ALIGNED(address, P4D_SIZE) &&
 			    end - address >= P4D_SIZE) {
 				p4d_populate(&init_mm, p4_dir,
 						kasan_early_shadow_pud);
 				address = (address + P4D_SIZE) & P4D_MASK;
 				continue;
 			}
 			pu_dir = kasan_early_crst_alloc(_REGION3_ENTRY_EMPTY);
 			p4d_populate(&init_mm, p4_dir, pu_dir);
 		}

 		pu_dir = pud_offset(p4_dir, address);
 		if (pud_none(*pu_dir)) {
 			if (mode == POPULATE_ZERO_SHADOW &&
 			    IS_ALIGNED(address, PUD_SIZE) &&
 			    end - address >= PUD_SIZE) {
 				pud_populate(&init_mm, pu_dir,
 						kasan_early_shadow_pmd);
 				address = (address + PUD_SIZE) & PUD_MASK;
 				continue;
 			}
 			pm_dir = kasan_early_crst_alloc(_SEGMENT_ENTRY_EMPTY);
 			pud_populate(&init_mm, pu_dir, pm_dir);
 		}

 		pm_dir = pmd_offset(pu_dir, address);
 		if (pmd_none(*pm_dir)) {
 			if (mode == POPULATE_ZERO_SHADOW &&
 			    IS_ALIGNED(address, PMD_SIZE) &&
 			    end - address >= PMD_SIZE) {
 				pmd_populate(&init_mm, pm_dir,
 						kasan_early_shadow_pte);
 				address = (address + PMD_SIZE) & PMD_MASK;
 				continue;
 			}
 			/* the first megabyte of 1:1 is mapped with 4k pages */
 			if (has_edat && address && end - address >= PMD_SIZE &&
 			    mode != POPULATE_ZERO_SHADOW) {
 				void *page;

 				if (mode == POPULATE_ONE2ONE) {
 					page = (void *)address;
 				} else {
 					page = kasan_early_alloc_segment();
 					memset(page, 0, _SEGMENT_SIZE);
 				}
 				pmd_val(*pm_dir) = __pa(page) | sgt_prot;
 				address = (address + PMD_SIZE) & PMD_MASK;
 				continue;
 			}

 			pt_dir = kasan_early_pte_alloc();
 			pmd_populate(&init_mm, pm_dir, pt_dir);
 		} else if (pmd_large(*pm_dir)) {
 			address = (address + PMD_SIZE) & PMD_MASK;
 			continue;
 		}

 		pt_dir = pte_offset_kernel(pm_dir, address);
 		if (pte_none(*pt_dir)) {
 			void *page;

 			switch (mode) {
 			case POPULATE_ONE2ONE:
 				page = (void *)address;
 				pte_val(*pt_dir) = __pa(page) | pgt_prot;
 				break;
 			case POPULATE_MAP:
 				page = kasan_early_alloc_pages(0);
 				memset(page, 0, PAGE_SIZE);
 				pte_val(*pt_dir) = __pa(page) | pgt_prot;
 				break;
 			case POPULATE_ZERO_SHADOW:
 				page = kasan_early_shadow_page;
 				pte_val(*pt_dir) = __pa(page) | pgt_prot_zero;
 				break;
 			}
 		}
 		address += PAGE_SIZE;
 	}
 }

 static void __init kasan_set_pgd(pgd_t *pgd, unsigned long asce_type)
 {
 	unsigned long asce_bits;

 	asce_bits = asce_type | _ASCE_TABLE_LENGTH;
 	S390_lowcore.kernel_asce = (__pa(pgd) & PAGE_MASK) | asce_bits;
 	S390_lowcore.user_asce = S390_lowcore.kernel_asce;

 	__ctl_load(S390_lowcore.kernel_asce, 1, 1);
 	__ctl_load(S390_lowcore.kernel_asce, 7, 7);
 	__ctl_load(S390_lowcore.kernel_asce, 13, 13);
 }

 static void __init kasan_enable_dat(void)
 {
 	psw_t psw;

 	psw.mask = __extract_psw();
 	psw_bits(psw).dat = 1;
 	psw_bits(psw).as = PSW_BITS_AS_HOME;
 	__load_psw_mask(psw.mask);
 }

 static void __init kasan_early_detect_facilities(void)
 {
 	if (test_facility(8)) {
 		has_edat = true;
 		__ctl_set_bit(0, 23);
 	}
 	if (!noexec_disabled && test_facility(130)) {
 		has_nx = true;
 		__ctl_set_bit(0, 20);
 	}
 }

 static unsigned long __init get_mem_detect_end(void)
 {
 	unsigned long start;
 	unsigned long end;

 	if (mem_detect.count) {
 		__get_mem_detect_block(mem_detect.count - 1, &start, &end);
 		return end;
 	}
 	return 0;
 }

 void __init kasan_early_init(void)
 {
 	unsigned long untracked_mem_end;
 	unsigned long shadow_alloc_size;
 	unsigned long initrd_end;
 	unsigned long asce_type;
 	unsigned long memsize;
 	unsigned long vmax;
 	unsigned long pgt_prot = pgprot_val(PAGE_KERNEL_RO);
 	pte_t pte_z;
 	pmd_t pmd_z = __pmd(__pa(kasan_early_shadow_pte) | _SEGMENT_ENTRY);
 	pud_t pud_z = __pud(__pa(kasan_early_shadow_pmd) | _REGION3_ENTRY);
 	p4d_t p4d_z = __p4d(__pa(kasan_early_shadow_pud) | _REGION2_ENTRY);

 	kasan_early_detect_facilities();
 	if (!has_nx)
 		pgt_prot &= ~_PAGE_NOEXEC;
 	pte_z = __pte(__pa(kasan_early_shadow_page) | pgt_prot);

 	memsize = get_mem_detect_end();
 	if (!memsize)
 		kasan_early_panic("cannot detect physical memory size\n");
 	/* respect mem= cmdline parameter */
 	if (memory_end_set && memsize > memory_end)
 		memsize = memory_end;
 	memsize = min(memsize, KASAN_SHADOW_START);

 	if (IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING)) {
 		/* 4 level paging */
 		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, P4D_SIZE));
 		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, P4D_SIZE));
 		crst_table_init((unsigned long *)early_pg_dir,
 				_REGION2_ENTRY_EMPTY);
 		untracked_mem_end = vmax = _REGION1_SIZE;
 		asce_type = _ASCE_TYPE_REGION2;
 	} else {
 		/* 3 level paging */
 		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PUD_SIZE));
 		BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PUD_SIZE));
 		crst_table_init((unsigned long *)early_pg_dir,
 				_REGION3_ENTRY_EMPTY);
 		untracked_mem_end = vmax = _REGION2_SIZE;
 		asce_type = _ASCE_TYPE_REGION3;
 	}

 	/* init kasan zero shadow */
 	crst_table_init((unsigned long *)kasan_early_shadow_p4d,
 				p4d_val(p4d_z));
 	crst_table_init((unsigned long *)kasan_early_shadow_pud,
 				pud_val(pud_z));
 	crst_table_init((unsigned long *)kasan_early_shadow_pmd,
 				pmd_val(pmd_z));
 	memset64((u64 *)kasan_early_shadow_pte, pte_val(pte_z), PTRS_PER_PTE);

 	shadow_alloc_size = memsize >> KASAN_SHADOW_SCALE_SHIFT;
 	pgalloc_low = round_up((unsigned long)_end, _SEGMENT_SIZE);
 	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD)) {
 		initrd_end =
 		    round_up(INITRD_START + INITRD_SIZE, _SEGMENT_SIZE);
 		pgalloc_low = max(pgalloc_low, initrd_end);
 	}

 	if (pgalloc_low + shadow_alloc_size > memsize)
 		kasan_early_panic("out of memory during initialisation\n");

 	if (has_edat) {
 		segment_pos = round_down(memsize, _SEGMENT_SIZE);
 		segment_low = segment_pos - shadow_alloc_size;
 		pgalloc_pos = segment_low;
 	} else {
 		pgalloc_pos = memsize;
 	}
 	init_mm.pgd = early_pg_dir;
 	/*
 	 * Current memory layout:
 	 * +- 0 -------------+	 +- shadow start -+
 	 * | 1:1 ram mapping |	/| 1/8 ram	  |
 	 * +- end of ram ----+ / +----------------+
 	 * | ... gap ...     |/  |	kasan	  |
 	 * +- shadow start --+	 |	zero	  |
 	 * | 1/8 addr space  |	 |	page	  |
 	 * +- shadow end    -+	 |	mapping	  |
 	 * | ... gap ...     |\  |    (untracked) |
 	 * +- modules vaddr -+ \ +----------------+
 	 * | 2Gb	     |	\|	unmapped  | allocated per module
 	 * +-----------------+	 +- shadow end ---+
 	 */
 	/* populate kasan shadow (for identity mapping and zero page mapping) */
 	kasan_early_vmemmap_populate(__sha(0), __sha(memsize), POPULATE_MAP);
 	if (IS_ENABLED(CONFIG_MODULES))
 		untracked_mem_end = vmax - MODULES_LEN;
 	kasan_early_vmemmap_populate(__sha(max_physmem_end),
 				     __sha(untracked_mem_end),
 				     POPULATE_ZERO_SHADOW);
 	/* memory allocated for identity mapping structs will be freed later */
 	pgalloc_freeable = pgalloc_pos;
 	/* populate identity mapping */
 	kasan_early_vmemmap_populate(0, memsize, POPULATE_ONE2ONE);
 	kasan_set_pgd(early_pg_dir, asce_type);
 	kasan_enable_dat();
 	/* enable kasan */
 	init_task.kasan_depth = 0;
 	memblock_reserve(pgalloc_pos, memsize - pgalloc_pos);
 	sclp_early_printk("KernelAddressSanitizer initialized\n");
 }

 void __init kasan_copy_shadow(pgd_t *pg_dir)
 {
 	/*
 	 * At this point we are still running on early pages setup early_pg_dir,
 	 * while swapper_pg_dir has just been initialized with identity mapping.
 	 * Carry over shadow memory region from early_pg_dir to swapper_pg_dir.
 	 */

 	pgd_t *pg_dir_src;
 	pgd_t *pg_dir_dst;
 	p4d_t *p4_dir_src;
 	p4d_t *p4_dir_dst;
 	pud_t *pu_dir_src;
 	pud_t *pu_dir_dst;

 	pg_dir_src = pgd_offset_raw(early_pg_dir, KASAN_SHADOW_START);
 	pg_dir_dst = pgd_offset_raw(pg_dir, KASAN_SHADOW_START);
 	p4_dir_src = p4d_offset(pg_dir_src, KASAN_SHADOW_START);
 	p4_dir_dst = p4d_offset(pg_dir_dst, KASAN_SHADOW_START);
 	if (!p4d_folded(*p4_dir_src)) {
 		/* 4 level paging */
 		memcpy(p4_dir_dst, p4_dir_src,
 		       (KASAN_SHADOW_SIZE >> P4D_SHIFT) * sizeof(p4d_t));
 		return;
 	}
 	/* 3 level paging */
 	pu_dir_src = pud_offset(p4_dir_src, KASAN_SHADOW_START);
 	pu_dir_dst = pud_offset(p4_dir_dst, KASAN_SHADOW_START);
 	memcpy(pu_dir_dst, pu_dir_src,
 	       (KASAN_SHADOW_SIZE >> PUD_SHIFT) * sizeof(pud_t));
 }

 void __init kasan_free_early_identity(void)
 {
 	memblock_free(pgalloc_pos, pgalloc_freeable - pgalloc_pos);
 }
	// SPDX-License-Identifier: GPL-2.0
	#include <linux/kasan.h>
	#include <linux/sched/task.h>
	#include <linux/memblock.h>
	#include <asm/pgalloc.h>
	#include <asm/pgtable.h>
	#include <asm/kasan.h>
	#include <asm/mem_detect.h>
	#include <asm/processor.h>
	#include <asm/sclp.h>
	#include <asm/facility.h>
	#include <asm/sections.h>
	#include <asm/setup.h>

	static unsigned long segment_pos __initdata;
	static unsigned long segment_low __initdata;
	static unsigned long pgalloc_pos __initdata;
	static unsigned long pgalloc_low __initdata;
	static unsigned long pgalloc_freeable __initdata;
	static bool has_edat __initdata;
	static bool has_nx __initdata;

	#define __sha(x) ((unsigned long)kasan_mem_to_shadow((void *)x))

	static pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);

	static void __init kasan_early_panic(const char *reason)
	{
	sclp_early_printk("The Linux kernel failed to boot with the KernelAddressSanitizer:\n");
	sclp_early_printk(reason);
	disabled_wait();
	}

	static void * __init kasan_early_alloc_segment(void)
	{
	segment_pos -= _SEGMENT_SIZE;

	if (segment_pos < segment_low)
	kasan_early_panic("out of memory during initialisation\n");

	return (void *)segment_pos;
	}

	static void * __init kasan_early_alloc_pages(unsigned int order)
	{
	pgalloc_pos -= (PAGE_SIZE << order);

	if (pgalloc_pos < pgalloc_low)
	kasan_early_panic("out of memory during initialisation\n");

	return (void *)pgalloc_pos;
	}

	static void * __init kasan_early_crst_alloc(unsigned long val)
	{
	unsigned long *table;

	table = kasan_early_alloc_pages(CRST_ALLOC_ORDER);
	if (table)
	crst_table_init(table, val);
	return table;
	}

	static pte_t * __init kasan_early_pte_alloc(void)
	{
	static void *pte_leftover;
	pte_t *pte;

	BUILD_BUG_ON(_PAGE_TABLE_SIZE * 2 != PAGE_SIZE);

	if (!pte_leftover) {
	pte_leftover = kasan_early_alloc_pages(0);
	pte = pte_leftover + _PAGE_TABLE_SIZE;
	} else {
	pte = pte_leftover;
	pte_leftover = NULL;
	}
	memset64((u64 *)pte, _PAGE_INVALID, PTRS_PER_PTE);
	return pte;
	}

	enum populate_mode {
	POPULATE_ONE2ONE,
	POPULATE_MAP,
	POPULATE_ZERO_SHADOW
	};
	static void __init kasan_early_vmemmap_populate(unsigned long address,
	unsigned long end,
	enum populate_mode mode)
	{
	unsigned long pgt_prot_zero, pgt_prot, sgt_prot;
	pgd_t *pg_dir;
	p4d_t *p4_dir;
	pud_t *pu_dir;
	pmd_t *pm_dir;
	pte_t *pt_dir;

	pgt_prot_zero = pgprot_val(PAGE_KERNEL_RO);
	if (!has_nx)
	pgt_prot_zero &= ~_PAGE_NOEXEC;
	pgt_prot = pgprot_val(PAGE_KERNEL_EXEC);
	sgt_prot = pgprot_val(SEGMENT_KERNEL_EXEC);

	while (address < end) {
	pg_dir = pgd_offset_k(address);
	if (pgd_none(*pg_dir)) {
	if (mode == POPULATE_ZERO_SHADOW &&
	IS_ALIGNED(address, PGDIR_SIZE) &&
	end - address >= PGDIR_SIZE) {
	pgd_populate(&init_mm, pg_dir,
	kasan_early_shadow_p4d);
	address = (address + PGDIR_SIZE) & PGDIR_MASK;
	continue;
	}
	p4_dir = kasan_early_crst_alloc(_REGION2_ENTRY_EMPTY);
	pgd_populate(&init_mm, pg_dir, p4_dir);
	}

	p4_dir = p4d_offset(pg_dir, address);
	if (p4d_none(*p4_dir)) {
	if (mode == POPULATE_ZERO_SHADOW &&
	IS_ALIGNED(address, P4D_SIZE) &&
	end - address >= P4D_SIZE) {
	p4d_populate(&init_mm, p4_dir,
	kasan_early_shadow_pud);
	address = (address + P4D_SIZE) & P4D_MASK;
	continue;
	}
	pu_dir = kasan_early_crst_alloc(_REGION3_ENTRY_EMPTY);
	p4d_populate(&init_mm, p4_dir, pu_dir);
	}

	pu_dir = pud_offset(p4_dir, address);
	if (pud_none(*pu_dir)) {
	if (mode == POPULATE_ZERO_SHADOW &&
	IS_ALIGNED(address, PUD_SIZE) &&
	end - address >= PUD_SIZE) {
	pud_populate(&init_mm, pu_dir,
	kasan_early_shadow_pmd);
	address = (address + PUD_SIZE) & PUD_MASK;
	continue;
	}
	pm_dir = kasan_early_crst_alloc(_SEGMENT_ENTRY_EMPTY);
	pud_populate(&init_mm, pu_dir, pm_dir);
	}

	pm_dir = pmd_offset(pu_dir, address);
	if (pmd_none(*pm_dir)) {
	if (mode == POPULATE_ZERO_SHADOW &&
	IS_ALIGNED(address, PMD_SIZE) &&
	end - address >= PMD_SIZE) {
	pmd_populate(&init_mm, pm_dir,
	kasan_early_shadow_pte);
	address = (address + PMD_SIZE) & PMD_MASK;
	continue;
	}
	/* the first megabyte of 1:1 is mapped with 4k pages */
	if (has_edat && address && end - address >= PMD_SIZE &&
	mode != POPULATE_ZERO_SHADOW) {
	void *page;

	if (mode == POPULATE_ONE2ONE) {
	page = (void *)address;
	} else {
	page = kasan_early_alloc_segment();
	memset(page, 0, _SEGMENT_SIZE);
	}
	pmd_val(*pm_dir) = __pa(page) \| sgt_prot;
	address = (address + PMD_SIZE) & PMD_MASK;
	continue;
	}

	pt_dir = kasan_early_pte_alloc();
	pmd_populate(&init_mm, pm_dir, pt_dir);
	} else if (pmd_large(*pm_dir)) {
	address = (address + PMD_SIZE) & PMD_MASK;
	continue;
	}

	pt_dir = pte_offset_kernel(pm_dir, address);
	if (pte_none(*pt_dir)) {
	void *page;

	switch (mode) {
	case POPULATE_ONE2ONE:
	page = (void *)address;
	pte_val(*pt_dir) = __pa(page) \| pgt_prot;
	break;
	case POPULATE_MAP:
	page = kasan_early_alloc_pages(0);
	memset(page, 0, PAGE_SIZE);
	pte_val(*pt_dir) = __pa(page) \| pgt_prot;
	break;
	case POPULATE_ZERO_SHADOW:
	page = kasan_early_shadow_page;
	pte_val(*pt_dir) = __pa(page) \| pgt_prot_zero;
	break;
	}
	}
	address += PAGE_SIZE;
	}
	}

	static void __init kasan_set_pgd(pgd_t *pgd, unsigned long asce_type)
	{
	unsigned long asce_bits;

	asce_bits = asce_type \| _ASCE_TABLE_LENGTH;
	S390_lowcore.kernel_asce = (__pa(pgd) & PAGE_MASK) \| asce_bits;
	S390_lowcore.user_asce = S390_lowcore.kernel_asce;

	__ctl_load(S390_lowcore.kernel_asce, 1, 1);
	__ctl_load(S390_lowcore.kernel_asce, 7, 7);
	__ctl_load(S390_lowcore.kernel_asce, 13, 13);
	}

	static void __init kasan_enable_dat(void)
	{
	psw_t psw;

	psw.mask = __extract_psw();
	psw_bits(psw).dat = 1;
	psw_bits(psw).as = PSW_BITS_AS_HOME;
	__load_psw_mask(psw.mask);
	}

	static void __init kasan_early_detect_facilities(void)
	{
	if (test_facility(8)) {
	has_edat = true;
	__ctl_set_bit(0, 23);
	}
	if (!noexec_disabled && test_facility(130)) {
	has_nx = true;
	__ctl_set_bit(0, 20);
	}
	}

	static unsigned long __init get_mem_detect_end(void)
	{
	unsigned long start;
	unsigned long end;

	if (mem_detect.count) {
	__get_mem_detect_block(mem_detect.count - 1, &start, &end);
	return end;
	}
	return 0;
	}

	void __init kasan_early_init(void)
	{
	unsigned long untracked_mem_end;
	unsigned long shadow_alloc_size;
	unsigned long initrd_end;
	unsigned long asce_type;
	unsigned long memsize;
	unsigned long vmax;
	unsigned long pgt_prot = pgprot_val(PAGE_KERNEL_RO);
	pte_t pte_z;
	pmd_t pmd_z = __pmd(__pa(kasan_early_shadow_pte) \| _SEGMENT_ENTRY);
	pud_t pud_z = __pud(__pa(kasan_early_shadow_pmd) \| _REGION3_ENTRY);
	p4d_t p4d_z = __p4d(__pa(kasan_early_shadow_pud) \| _REGION2_ENTRY);

	kasan_early_detect_facilities();
	if (!has_nx)
	pgt_prot &= ~_PAGE_NOEXEC;
	pte_z = __pte(__pa(kasan_early_shadow_page) \| pgt_prot);

	memsize = get_mem_detect_end();
	if (!memsize)
	kasan_early_panic("cannot detect physical memory size\n");
	/* respect mem= cmdline parameter */
	if (memory_end_set && memsize > memory_end)
	memsize = memory_end;
	memsize = min(memsize, KASAN_SHADOW_START);

	if (IS_ENABLED(CONFIG_KASAN_S390_4_LEVEL_PAGING)) {
	/* 4 level paging */
	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, P4D_SIZE));
	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, P4D_SIZE));
	crst_table_init((unsigned long *)early_pg_dir,
	_REGION2_ENTRY_EMPTY);
	untracked_mem_end = vmax = _REGION1_SIZE;
	asce_type = _ASCE_TYPE_REGION2;
	} else {
	/* 3 level paging */
	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PUD_SIZE));
	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PUD_SIZE));
	crst_table_init((unsigned long *)early_pg_dir,
	_REGION3_ENTRY_EMPTY);
	untracked_mem_end = vmax = _REGION2_SIZE;
	asce_type = _ASCE_TYPE_REGION3;
	}

	/* init kasan zero shadow */
	crst_table_init((unsigned long *)kasan_early_shadow_p4d,
	p4d_val(p4d_z));
	crst_table_init((unsigned long *)kasan_early_shadow_pud,
	pud_val(pud_z));
	crst_table_init((unsigned long *)kasan_early_shadow_pmd,
	pmd_val(pmd_z));
	memset64((u64 *)kasan_early_shadow_pte, pte_val(pte_z), PTRS_PER_PTE);

	shadow_alloc_size = memsize >> KASAN_SHADOW_SCALE_SHIFT;
	pgalloc_low = round_up((unsigned long)_end, _SEGMENT_SIZE);
	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD)) {
	initrd_end =
	round_up(INITRD_START + INITRD_SIZE, _SEGMENT_SIZE);
	pgalloc_low = max(pgalloc_low, initrd_end);
	}

	if (pgalloc_low + shadow_alloc_size > memsize)
	kasan_early_panic("out of memory during initialisation\n");

	if (has_edat) {
	segment_pos = round_down(memsize, _SEGMENT_SIZE);
	segment_low = segment_pos - shadow_alloc_size;
	pgalloc_pos = segment_low;
	} else {
	pgalloc_pos = memsize;
	}
	init_mm.pgd = early_pg_dir;
	/*
	* Current memory layout:
	* +- 0 -------------+ +- shadow start -+
	* \| 1:1 ram mapping \| /\| 1/8 ram \|
	* +- end of ram ----+ / +----------------+
	* \| ... gap ... \|/ \| kasan \|
	* +- shadow start --+ \| zero \|
	* \| 1/8 addr space \| \| page \|
	* +- shadow end -+ \| mapping \|
	* \| ... gap ... \|\ \| (untracked) \|
	* +- modules vaddr -+ \ +----------------+
	* \| 2Gb \| \\| unmapped \| allocated per module
	* +-----------------+ +- shadow end ---+
	*/
	/* populate kasan shadow (for identity mapping and zero page mapping) */
	kasan_early_vmemmap_populate(__sha(0), __sha(memsize), POPULATE_MAP);
	if (IS_ENABLED(CONFIG_MODULES))
	untracked_mem_end = vmax - MODULES_LEN;
	kasan_early_vmemmap_populate(__sha(max_physmem_end),
	__sha(untracked_mem_end),
	POPULATE_ZERO_SHADOW);
	/* memory allocated for identity mapping structs will be freed later */
	pgalloc_freeable = pgalloc_pos;
	/* populate identity mapping */
	kasan_early_vmemmap_populate(0, memsize, POPULATE_ONE2ONE);
	kasan_set_pgd(early_pg_dir, asce_type);
	kasan_enable_dat();
	/* enable kasan */
	init_task.kasan_depth = 0;
	memblock_reserve(pgalloc_pos, memsize - pgalloc_pos);
	sclp_early_printk("KernelAddressSanitizer initialized\n");
	}

	void __init kasan_copy_shadow(pgd_t *pg_dir)
	{
	/*
	* At this point we are still running on early pages setup early_pg_dir,
	* while swapper_pg_dir has just been initialized with identity mapping.
	* Carry over shadow memory region from early_pg_dir to swapper_pg_dir.
	*/

	pgd_t *pg_dir_src;
	pgd_t *pg_dir_dst;
	p4d_t *p4_dir_src;
	p4d_t *p4_dir_dst;
	pud_t *pu_dir_src;
	pud_t *pu_dir_dst;

	pg_dir_src = pgd_offset_raw(early_pg_dir, KASAN_SHADOW_START);
	pg_dir_dst = pgd_offset_raw(pg_dir, KASAN_SHADOW_START);
	p4_dir_src = p4d_offset(pg_dir_src, KASAN_SHADOW_START);
	p4_dir_dst = p4d_offset(pg_dir_dst, KASAN_SHADOW_START);
	if (!p4d_folded(*p4_dir_src)) {
	/* 4 level paging */
	memcpy(p4_dir_dst, p4_dir_src,
	(KASAN_SHADOW_SIZE >> P4D_SHIFT) * sizeof(p4d_t));
	return;
	}
	/* 3 level paging */
	pu_dir_src = pud_offset(p4_dir_src, KASAN_SHADOW_START);
	pu_dir_dst = pud_offset(p4_dir_dst, KASAN_SHADOW_START);
	memcpy(pu_dir_dst, pu_dir_src,
	(KASAN_SHADOW_SIZE >> PUD_SHIFT) * sizeof(pud_t));
	}

	void __init kasan_free_early_identity(void)
	{
	memblock_free(pgalloc_pos, pgalloc_freeable - pgalloc_pos);
	}