linux/arch/s390/mm/kasan_init.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/kasan.h>
#include <linux/sched/task.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 bool has_edat __initdata;
static bool has_nx __initdata;

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

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 __va(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 __va(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_MAP,
	POPULATE_ZERO_SHADOW,
	POPULATE_SHALLOW
};

static inline pgprot_t pgprot_clear_bit(pgprot_t pgprot, unsigned long bit)
{
	return __pgprot(pgprot_val(pgprot) & ~bit);
}

static void __init kasan_early_pgtable_populate(unsigned long address,
						unsigned long end,
						enum populate_mode mode)
{
	pgprot_t pgt_prot_zero = PAGE_KERNEL_RO;
	pgprot_t pgt_prot = PAGE_KERNEL;
	pgprot_t sgt_prot = SEGMENT_KERNEL;
	pgd_t *pg_dir;
	p4d_t *p4_dir;
	pud_t *pu_dir;
	pmd_t *pm_dir;
	pte_t *pt_dir;
	pmd_t pmd;
	pte_t pte;

	if (!has_nx) {
		pgt_prot_zero = pgprot_clear_bit(pgt_prot_zero, _PAGE_NOEXEC);
		pgt_prot = pgprot_clear_bit(pgt_prot, _PAGE_NOEXEC);
		sgt_prot = pgprot_clear_bit(sgt_prot, _SEGMENT_ENTRY_NOEXEC);
	}

	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) {
					void *page = kasan_early_alloc_segment();

					memset(page, 0, _SEGMENT_SIZE);
					pmd = __pmd(__pa(page));
					pmd = set_pmd_bit(pmd, sgt_prot);
					set_pmd(pm_dir, pmd);
					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_MAP:
				page = kasan_early_alloc_pages(0);
				memset(page, 0, PAGE_SIZE);
				pte = __pte(__pa(page));
				pte = set_pte_bit(pte, pgt_prot);
				set_pte(pt_dir, pte);
				break;
			case POPULATE_ZERO_SHADOW:
				page = kasan_early_shadow_page;
				pte = __pte(__pa(page));
				pte = set_pte_bit(pte, pgt_prot_zero);
				set_pte(pt_dir, pte);
				break;
			case POPULATE_SHALLOW:
				/* should never happen */
				break;
			}
		}
		address += PAGE_SIZE;
	}
}

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)
{
	pte_t pte_z = __pte(__pa(kasan_early_shadow_page) | pgprot_val(PAGE_KERNEL_RO));
	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);
	unsigned long untracked_end = MODULES_VADDR;
	unsigned long shadow_alloc_size;
	unsigned long memsize;

	kasan_early_detect_facilities();
	if (!has_nx)
		pte_z = clear_pte_bit(pte_z, __pgprot(_PAGE_NOEXEC));

	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.
	 * [__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));

	/* 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;

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

	if (has_edat) {
		segment_pos = round_down(pgalloc_pos, _SEGMENT_SIZE);
		segment_low = segment_pos - shadow_alloc_size;
		segment_low = round_down(segment_low, _SEGMENT_SIZE);
		pgalloc_pos = segment_low;
	}
	/*
	 * 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)) {
		untracked_end = VMALLOC_START;
		/* 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), __sha(untracked_end),
				     POPULATE_ZERO_SHADOW);
	kasan_early_pgtable_populate(__sha(MODULES_END), __sha(_REGION1_SIZE),
				     POPULATE_ZERO_SHADOW);
	/* enable kasan */
	init_task.kasan_depth = 0;
	sclp_early_printk("KernelAddressSanitizer initialized\n");
}