arch/s390/mm/kasan_init.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/kasan.h>
#include <linux/sched/task.h>
#include <linux/memblock.h>
#include <linux/pgtable.h>
#include <asm/pgalloc.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>
#include <asm/uv.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,
	POPULATE_SHALLOW
};
static void __init kasan_early_pgtable_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);
	sgt_prot = pgprot_val(SEGMENT_KERNEL);
	if (!has_nx || mode == POPULATE_ONE2ONE) {
		pgt_prot &= ~_PAGE_NOEXEC;
		sgt_prot &= ~_SEGMENT_ENTRY_NOEXEC;
	}

	/*
	 * The first 1MB of 1:1 mapping is mapped with 4KB pages
	 */
	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);
		}

		if (mode == POPULATE_SHALLOW) {
			address = (address + P4D_SIZE) & P4D_MASK;
			continue;
		}

		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 (IS_ALIGNED(address, PMD_SIZE) &&
			    end - address >= PMD_SIZE) {
				if (mode == POPULATE_ZERO_SHADOW) {
					pmd_populate(&init_mm, pm_dir, kasan_early_shadow_pte);
					address = (address + PMD_SIZE) & PMD_MASK;
					continue;
				} else if (has_edat && address) {
					void *page;

					if (mode == POPULATE_ONE2ONE) {
						page = (void *)address;
					} else {
						page = kasan_early_alloc_segment();
						memset(page, 0, _SEGMENT_SIZE);
					}
					set_pmd(pm_dir, __pmd(__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;
				set_pte(pt_dir, __pte(__pa(page) | pgt_prot));
				break;
			case POPULATE_MAP:
				page = kasan_early_alloc_pages(0);
				memset(page, 0, PAGE_SIZE);
				set_pte(pt_dir, __pte(__pa(page) | pgt_prot));
				break;
			case POPULATE_ZERO_SHADOW:
				page = kasan_early_shadow_page;
				set_pte(pt_dir, __pte(__pa(page) | pgt_prot_zero));
				break;
			case POPULATE_SHALLOW:
				/* should never happen */
				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);
	}
}

void __init kasan_early_init(void)
{
	unsigned long shadow_alloc_size;
	unsigned long initrd_end;
	unsigned long memsize;
	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");
	/*
	 * Kasan currently supports standby memory but only if it follows
	 * online memory (default allocation), i.e. no memory holes.
	 * - memsize represents end of online memory
	 * - ident_map_size represents online + standby and memory limits
	 *   accounted.
	 * Kasan maps "memsize" right away.
	 * [0, memsize]			- as identity mapping
	 * [__sha(0), __sha(memsize)]	- shadow memory for identity mapping
	 * The rest [memsize, ident_map_size] if memsize < ident_map_size
	 * could be mapped/unmapped dynamically later during memory hotplug.
	 */
	memsize = min(memsize, ident_map_size);

	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);

	/* 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_data.start + initrd_data.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)   |
	 * +- vmalloc area  -+ \   |		    |
	 * | vmalloc_size    |	\  |		    |
	 * +- modules vaddr -+	 \ +----------------+
	 * | 2Gb	     |	  \|	  unmapped  | allocated per module
	 * +-----------------+	   +- shadow end ---+
	 *
	 * Current memory layout (KASAN_VMALLOC):
	 * +- 0 -------------+	   +- shadow start -+
	 * | 1:1 ram mapping |	  /| 1/8 ram	    |
	 * |		     |	 / |		    |
	 * +- end of ram ----+	/  +----------------+
	 * | ... gap ...     | /   |	kasan	    |
	 * |		     |/    |	zero	    |
	 * +- shadow start --+	   |	page	    |
	 * | 1/8 addr space  |	   |	mapping     |
	 * +- shadow end    -+	   |  (untracked)   |
	 * | ... gap ...     |\    |		    |
	 * +- vmalloc area  -+ \   +- vmalloc area -+
	 * | vmalloc_size    |	\  |shallow populate|
	 * +- modules vaddr -+	 \ +- modules area -+
	 * | 2Gb	     |	  \|shallow populate|
	 * +-----------------+	   +- shadow end ---+
	 */
	/* populate kasan shadow (for identity mapping and zero page mapping) */
	kasan_early_pgtable_populate(__sha(0), __sha(memsize), POPULATE_MAP);
	if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
		/* shallowly populate kasan shadow for vmalloc and modules */
		kasan_early_pgtable_populate(__sha(VMALLOC_START), __sha(MODULES_END),
					     POPULATE_SHALLOW);
	}
	/* populate kasan shadow for untracked memory */
	kasan_early_pgtable_populate(__sha(ident_map_size),
				     IS_ENABLED(CONFIG_KASAN_VMALLOC) ?
						   __sha(VMALLOC_START) :
						   __sha(MODULES_VADDR),
				     POPULATE_ZERO_SHADOW);
	kasan_early_pgtable_populate(__sha(MODULES_END), __sha(_REGION1_SIZE),
				     POPULATE_ZERO_SHADOW);
	/* memory allocated for identity mapping structs will be freed later */
	pgalloc_freeable = pgalloc_pos;
	/* populate identity mapping */
	kasan_early_pgtable_populate(0, memsize, POPULATE_ONE2ONE);
	kasan_set_pgd(early_pg_dir, _ASCE_TYPE_REGION2);
	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_mapping(void)
{
	/*
	 * 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;

	pg_dir_src = pgd_offset_raw(early_pg_dir, KASAN_SHADOW_START);
	pg_dir_dst = pgd_offset_raw(init_mm.pgd, 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);
	memcpy(p4_dir_dst, p4_dir_src,
	       (KASAN_SHADOW_SIZE >> P4D_SHIFT) * sizeof(p4d_t));
}

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