1 files changed, 301 insertions, 0 deletions
diff --git a/arch/s390/mm/kasan_init.c b/arch/s390/mm/kasan_init.c
new file mode 100644
index 000000000..ef89a5f26
--- /dev/null
+++ b/arch/s390/mm/kasan_init.c
@@ -0,0 +1,301 @@
+// 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 start, end;
+	int i;
+
+	kasan_early_detect_facilities();
+	if (!has_nx)
+		pte_z = clear_pte_bit(pte_z, __pgprot(_PAGE_NOEXEC));
+
+	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);
+
+	if (has_edat) {
+		shadow_alloc_size = get_mem_detect_usable_total() >> KASAN_SHADOW_SCALE_SHIFT;
+		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 ident mapping|	      /|1/8 of ident map|
+	 * |		     |	     / |		|
+	 * +-end of ident map+	    /  +----------------+
+	 * | ... gap ...     |	   /   |    kasan	|
+	 * |		     |	  /    |  zero page	|
+	 * +- vmalloc area  -+	 /     |   mapping	|
+	 * | vmalloc_size    |	/      | (untracked)	|
+	 * +- modules vaddr -+ /       +----------------+
+	 * | 2Gb	     |/        |    unmapped	| allocated per module
+	 * +- shadow start  -+	       +----------------+
+	 * | 1/8 addr space  |	       | zero pg mapping| (untracked)
+	 * +- shadow end ----+---------+- shadow end ---+
+	 *
+	 * Current memory layout (KASAN_VMALLOC):
+	 * +- 0 -------------+	       +- shadow start -+
+	 * |1:1 ident mapping|	      /|1/8 of ident map|
+	 * |		     |	     / |		|
+	 * +-end of ident map+	    /  +----------------+
+	 * | ... gap ...     |	   /   | kasan zero page| (untracked)
+	 * |		     |	  /    | mapping	|
+	 * +- vmalloc area  -+	 /     +----------------+
+	 * | vmalloc_size    |	/      |shallow populate|
+	 * +- modules vaddr -+ /       +----------------+
+	 * | 2Gb	     |/        |shallow populate|
+	 * +- shadow start  -+	       +----------------+
+	 * | 1/8 addr space  |	       | zero pg mapping| (untracked)
+	 * +- shadow end ----+---------+- shadow end ---+
+	 */
+	/* populate kasan shadow (for identity mapping and zero page mapping) */
+	for_each_mem_detect_usable_block(i, &start, &end)
+		kasan_early_pgtable_populate(__sha(start), __sha(end), 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");
+}