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linux/arch/s390/boot/vmem.c
Vasily Gorbik 327899674e s390/kasan: handle DCSS mapping in memory holes 
When physical memory is defined under z/VM using DEF STOR CONFIG, there
may be memory holes that are not hotpluggable memory. In such cases,
DCSS mapping could be placed in one of these memory holes. Subsequently,
attempting memory access to such DCSS mapping would result in a kasan
failure because there is no shadow memory mapping for it.

To maintain consistency with cases where DCSS mapping is positioned after
the kernel identity mapping, which is then covered by kasan zero shadow
mapping, handle the scenario above by populating zero shadow mapping
for memory holes where DCSS mapping could potentially be placed.

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
2023-10-16 13:03:05 +02:00

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// SPDX-License-Identifier: GPL-2.0
#include <linux/sched/task.h>
#include <linux/pgtable.h>
#include <linux/kasan.h>
#include <asm/pgalloc.h>
#include <asm/facility.h>
#include <asm/sections.h>
#include <asm/physmem_info.h>
#include <asm/maccess.h>
#include <asm/abs_lowcore.h>
#include "decompressor.h"
#include "boot.h"
unsigned long __bootdata_preserved(s390_invalid_asce);
#ifdef CONFIG_PROC_FS
atomic_long_t __bootdata_preserved(direct_pages_count[PG_DIRECT_MAP_MAX]);
#endif
#define init_mm (*(struct mm_struct *)vmlinux.init_mm_off)
#define swapper_pg_dir vmlinux.swapper_pg_dir_off
#define invalid_pg_dir vmlinux.invalid_pg_dir_off
enum populate_mode {
POPULATE_NONE,
POPULATE_DIRECT,
POPULATE_ABS_LOWCORE,
#ifdef CONFIG_KASAN
POPULATE_KASAN_MAP_SHADOW,
POPULATE_KASAN_ZERO_SHADOW,
POPULATE_KASAN_SHALLOW
#endif
};
static void pgtable_populate(unsigned long addr, unsigned long end, enum populate_mode mode);
#ifdef CONFIG_KASAN
#define kasan_early_shadow_page vmlinux.kasan_early_shadow_page_off
#define kasan_early_shadow_pte ((pte_t *)vmlinux.kasan_early_shadow_pte_off)
#define kasan_early_shadow_pmd ((pmd_t *)vmlinux.kasan_early_shadow_pmd_off)
#define kasan_early_shadow_pud ((pud_t *)vmlinux.kasan_early_shadow_pud_off)
#define kasan_early_shadow_p4d ((p4d_t *)vmlinux.kasan_early_shadow_p4d_off)
#define __sha(x) ((unsigned long)kasan_mem_to_shadow((void *)x))
static pte_t pte_z;
static inline void kasan_populate(unsigned long start, unsigned long end, enum populate_mode mode)
{
start = PAGE_ALIGN_DOWN(__sha(start));
end = PAGE_ALIGN(__sha(end));
pgtable_populate(start, end, mode);
}
static void kasan_populate_shadow(void)
{
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 memgap_start = 0;
unsigned long untracked_end;
unsigned long start, end;
int i;
pte_z = __pte(__pa(kasan_early_shadow_page) | pgprot_val(PAGE_KERNEL_RO));
if (!machine.has_nx)
pte_z = clear_pte_bit(pte_z, __pgprot(_PAGE_NOEXEC));
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);
/*
* 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 ---+
*/
for_each_physmem_usable_range(i, &start, &end) {
kasan_populate(start, end, POPULATE_KASAN_MAP_SHADOW);
if (memgap_start && physmem_info.info_source == MEM_DETECT_DIAG260)
kasan_populate(memgap_start, start, POPULATE_KASAN_ZERO_SHADOW);
memgap_start = end;
}
if (IS_ENABLED(CONFIG_KASAN_VMALLOC)) {
untracked_end = VMALLOC_START;
/* shallowly populate kasan shadow for vmalloc and modules */
kasan_populate(VMALLOC_START, MODULES_END, POPULATE_KASAN_SHALLOW);
} else {
untracked_end = MODULES_VADDR;
}
/* populate kasan shadow for untracked memory */
kasan_populate(ident_map_size, untracked_end, POPULATE_KASAN_ZERO_SHADOW);
kasan_populate(MODULES_END, _REGION1_SIZE, POPULATE_KASAN_ZERO_SHADOW);
}
static bool kasan_pgd_populate_zero_shadow(pgd_t *pgd, unsigned long addr,
unsigned long end, enum populate_mode mode)
{
if (mode == POPULATE_KASAN_ZERO_SHADOW &&
IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
pgd_populate(&init_mm, pgd, kasan_early_shadow_p4d);
return true;
}
return false;
}
static bool kasan_p4d_populate_zero_shadow(p4d_t *p4d, unsigned long addr,
unsigned long end, enum populate_mode mode)
{
if (mode == POPULATE_KASAN_ZERO_SHADOW &&
IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
p4d_populate(&init_mm, p4d, kasan_early_shadow_pud);
return true;
}
return false;
}
static bool kasan_pud_populate_zero_shadow(pud_t *pud, unsigned long addr,
unsigned long end, enum populate_mode mode)
{
if (mode == POPULATE_KASAN_ZERO_SHADOW &&
IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
pud_populate(&init_mm, pud, kasan_early_shadow_pmd);
return true;
}
return false;
}
static bool kasan_pmd_populate_zero_shadow(pmd_t *pmd, unsigned long addr,
unsigned long end, enum populate_mode mode)
{
if (mode == POPULATE_KASAN_ZERO_SHADOW &&
IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
pmd_populate(&init_mm, pmd, kasan_early_shadow_pte);
return true;
}
return false;
}
static bool kasan_pte_populate_zero_shadow(pte_t *pte, enum populate_mode mode)
{
pte_t entry;
if (mode == POPULATE_KASAN_ZERO_SHADOW) {
set_pte(pte, pte_z);
return true;
}
return false;
}
#else
static inline void kasan_populate_shadow(void) {}
static inline bool kasan_pgd_populate_zero_shadow(pgd_t *pgd, unsigned long addr,
unsigned long end, enum populate_mode mode)
{
return false;
}
static inline bool kasan_p4d_populate_zero_shadow(p4d_t *p4d, unsigned long addr,
unsigned long end, enum populate_mode mode)
{
return false;
}
static inline bool kasan_pud_populate_zero_shadow(pud_t *pud, unsigned long addr,
unsigned long end, enum populate_mode mode)
{
return false;
}
static inline bool kasan_pmd_populate_zero_shadow(pmd_t *pmd, unsigned long addr,
unsigned long end, enum populate_mode mode)
{
return false;
}
static bool kasan_pte_populate_zero_shadow(pte_t *pte, enum populate_mode mode)
{
return false;
}
#endif
/*
* Mimic virt_to_kpte() in lack of init_mm symbol. Skip pmd NULL check though.
*/
static inline pte_t *__virt_to_kpte(unsigned long va)
{
return pte_offset_kernel(pmd_offset(pud_offset(p4d_offset(pgd_offset_k(va), va), va), va), va);
}
static void *boot_crst_alloc(unsigned long val)
{
unsigned long size = PAGE_SIZE << CRST_ALLOC_ORDER;
unsigned long *table;
table = (unsigned long *)physmem_alloc_top_down(RR_VMEM, size, size);
crst_table_init(table, val);
return table;
}
static pte_t *boot_pte_alloc(void)
{
static void *pte_leftover;
pte_t *pte;
/*
* handling pte_leftovers this way helps to avoid memory fragmentation
* during POPULATE_KASAN_MAP_SHADOW when EDAT is off
*/
if (!pte_leftover) {
pte_leftover = (void *)physmem_alloc_top_down(RR_VMEM, PAGE_SIZE, PAGE_SIZE);
pte = pte_leftover + _PAGE_TABLE_SIZE;
} else {
pte = pte_leftover;
pte_leftover = NULL;
}
memset64((u64 *)pte, _PAGE_INVALID, PTRS_PER_PTE);
return pte;
}
static unsigned long _pa(unsigned long addr, unsigned long size, enum populate_mode mode)
{
switch (mode) {
case POPULATE_NONE:
return -1;
case POPULATE_DIRECT:
return addr;
case POPULATE_ABS_LOWCORE:
return __abs_lowcore_pa(addr);
#ifdef CONFIG_KASAN
case POPULATE_KASAN_MAP_SHADOW:
addr = physmem_alloc_top_down(RR_VMEM, size, size);
memset((void *)addr, 0, size);
return addr;
#endif
default:
return -1;
}
}
static bool can_large_pud(pud_t *pu_dir, unsigned long addr, unsigned long end)
{
return machine.has_edat2 &&
IS_ALIGNED(addr, PUD_SIZE) && (end - addr) >= PUD_SIZE;
}
static bool can_large_pmd(pmd_t *pm_dir, unsigned long addr, unsigned long end)
{
return machine.has_edat1 &&
IS_ALIGNED(addr, PMD_SIZE) && (end - addr) >= PMD_SIZE;
}
static void pgtable_pte_populate(pmd_t *pmd, unsigned long addr, unsigned long end,
enum populate_mode mode)
{
unsigned long pages = 0;
pte_t *pte, entry;
pte = pte_offset_kernel(pmd, addr);
for (; addr < end; addr += PAGE_SIZE, pte++) {
if (pte_none(*pte)) {
if (kasan_pte_populate_zero_shadow(pte, mode))
continue;
entry = __pte(_pa(addr, PAGE_SIZE, mode));
entry = set_pte_bit(entry, PAGE_KERNEL);
if (!machine.has_nx)
entry = clear_pte_bit(entry, __pgprot(_PAGE_NOEXEC));
set_pte(pte, entry);
pages++;
}
}
if (mode == POPULATE_DIRECT)
update_page_count(PG_DIRECT_MAP_4K, pages);
}
static void pgtable_pmd_populate(pud_t *pud, unsigned long addr, unsigned long end,
enum populate_mode mode)
{
unsigned long next, pages = 0;
pmd_t *pmd, entry;
pte_t *pte;
pmd = pmd_offset(pud, addr);
for (; addr < end; addr = next, pmd++) {
next = pmd_addr_end(addr, end);
if (pmd_none(*pmd)) {
if (kasan_pmd_populate_zero_shadow(pmd, addr, next, mode))
continue;
if (can_large_pmd(pmd, addr, next)) {
entry = __pmd(_pa(addr, _SEGMENT_SIZE, mode));
entry = set_pmd_bit(entry, SEGMENT_KERNEL);
if (!machine.has_nx)
entry = clear_pmd_bit(entry, __pgprot(_SEGMENT_ENTRY_NOEXEC));
set_pmd(pmd, entry);
pages++;
continue;
}
pte = boot_pte_alloc();
pmd_populate(&init_mm, pmd, pte);
} else if (pmd_large(*pmd)) {
continue;
}
pgtable_pte_populate(pmd, addr, next, mode);
}
if (mode == POPULATE_DIRECT)
update_page_count(PG_DIRECT_MAP_1M, pages);
}
static void pgtable_pud_populate(p4d_t *p4d, unsigned long addr, unsigned long end,
enum populate_mode mode)
{
unsigned long next, pages = 0;
pud_t *pud, entry;
pmd_t *pmd;
pud = pud_offset(p4d, addr);
for (; addr < end; addr = next, pud++) {
next = pud_addr_end(addr, end);
if (pud_none(*pud)) {
if (kasan_pud_populate_zero_shadow(pud, addr, next, mode))
continue;
if (can_large_pud(pud, addr, next)) {
entry = __pud(_pa(addr, _REGION3_SIZE, mode));
entry = set_pud_bit(entry, REGION3_KERNEL);
if (!machine.has_nx)
entry = clear_pud_bit(entry, __pgprot(_REGION_ENTRY_NOEXEC));
set_pud(pud, entry);
pages++;
continue;
}
pmd = boot_crst_alloc(_SEGMENT_ENTRY_EMPTY);
pud_populate(&init_mm, pud, pmd);
} else if (pud_large(*pud)) {
continue;
}
pgtable_pmd_populate(pud, addr, next, mode);
}
if (mode == POPULATE_DIRECT)
update_page_count(PG_DIRECT_MAP_2G, pages);
}
static void pgtable_p4d_populate(pgd_t *pgd, unsigned long addr, unsigned long end,
enum populate_mode mode)
{
unsigned long next;
p4d_t *p4d;
pud_t *pud;
p4d = p4d_offset(pgd, addr);
for (; addr < end; addr = next, p4d++) {
next = p4d_addr_end(addr, end);
if (p4d_none(*p4d)) {
if (kasan_p4d_populate_zero_shadow(p4d, addr, next, mode))
continue;
pud = boot_crst_alloc(_REGION3_ENTRY_EMPTY);
p4d_populate(&init_mm, p4d, pud);
}
pgtable_pud_populate(p4d, addr, next, mode);
}
}
static void pgtable_populate(unsigned long addr, unsigned long end, enum populate_mode mode)
{
unsigned long next;
pgd_t *pgd;
p4d_t *p4d;
pgd = pgd_offset(&init_mm, addr);
for (; addr < end; addr = next, pgd++) {
next = pgd_addr_end(addr, end);
if (pgd_none(*pgd)) {
if (kasan_pgd_populate_zero_shadow(pgd, addr, next, mode))
continue;
p4d = boot_crst_alloc(_REGION2_ENTRY_EMPTY);
pgd_populate(&init_mm, pgd, p4d);
}
#ifdef CONFIG_KASAN
if (mode == POPULATE_KASAN_SHALLOW)
continue;
#endif
pgtable_p4d_populate(pgd, addr, next, mode);
}
}
void setup_vmem(unsigned long asce_limit)
{
unsigned long start, end;
unsigned long asce_type;
unsigned long asce_bits;
int i;
if (asce_limit == _REGION1_SIZE) {
asce_type = _REGION2_ENTRY_EMPTY;
asce_bits = _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
} else {
asce_type = _REGION3_ENTRY_EMPTY;
asce_bits = _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
}
s390_invalid_asce = invalid_pg_dir | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
crst_table_init((unsigned long *)swapper_pg_dir, asce_type);
crst_table_init((unsigned long *)invalid_pg_dir, _REGION3_ENTRY_EMPTY);
/*
* To allow prefixing the lowcore must be mapped with 4KB pages.
* To prevent creation of a large page at address 0 first map
* the lowcore and create the identity mapping only afterwards.
*/
pgtable_populate(0, sizeof(struct lowcore), POPULATE_DIRECT);
for_each_physmem_usable_range(i, &start, &end)
pgtable_populate(start, end, POPULATE_DIRECT);
pgtable_populate(__abs_lowcore, __abs_lowcore + sizeof(struct lowcore),
POPULATE_ABS_LOWCORE);
pgtable_populate(__memcpy_real_area, __memcpy_real_area + PAGE_SIZE,
POPULATE_NONE);
memcpy_real_ptep = __virt_to_kpte(__memcpy_real_area);
kasan_populate_shadow();
S390_lowcore.kernel_asce = swapper_pg_dir | asce_bits;
S390_lowcore.user_asce = s390_invalid_asce;
__ctl_load(S390_lowcore.kernel_asce, 1, 1);
__ctl_load(S390_lowcore.user_asce, 7, 7);
__ctl_load(S390_lowcore.kernel_asce, 13, 13);
init_mm.context.asce = S390_lowcore.kernel_asce;
}
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