There are cases where normal kernel pages tables, i.e. idmap_pg_dir
and swapper_pg_dir are not sufficient because they may be overwritten.
This happens when we transition from one world to another: for example
during kexec kernel relocation transition, and also during hibernate
kernel restore transition.
In these cases, if MMU is needed, the page table memory must be allocated
from a safe place. Transitional tables is intended to allow just that.
Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
---
arch/arm64/Kconfig | 4 +
arch/arm64/include/asm/pgtable-hwdef.h | 1 +
arch/arm64/include/asm/trans_table.h | 68 ++++++
arch/arm64/mm/Makefile | 1 +
arch/arm64/mm/trans_table.c | 273 +++++++++++++++++++++++++
5 files changed, 347 insertions(+)
create mode 100644 arch/arm64/include/asm/trans_table.h
create mode 100644 arch/arm64/mm/trans_table.c
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 3adcec05b1f6..91a7416ffe4e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -999,6 +999,10 @@ config CRASH_DUMP
For more details see Documentation/admin-guide/kdump/kdump.rst
+config TRANS_TABLE
+ def_bool y
+ depends on HIBERNATION || KEXEC_CORE
+
config XEN_DOM0
def_bool y
depends on XEN
diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
index db92950bb1a0..dcb4f13c7888 100644
--- a/arch/arm64/include/asm/pgtable-hwdef.h
+++ b/arch/arm64/include/asm/pgtable-hwdef.h
@@ -110,6 +110,7 @@
#define PUD_TABLE_BIT (_AT(pudval_t, 1) << 1)
#define PUD_TYPE_MASK (_AT(pudval_t, 3) << 0)
#define PUD_TYPE_SECT (_AT(pudval_t, 1) << 0)
+#define PUD_SECT_RDONLY (_AT(pudval_t, 1) << 7) /* AP[2] */
/*
* Level 2 descriptor (PMD).
diff --git a/arch/arm64/include/asm/trans_table.h b/arch/arm64/include/asm/trans_table.h
new file mode 100644
index 000000000000..c7aef70587a1
--- /dev/null
+++ b/arch/arm64/include/asm/trans_table.h
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Copyright (c) 2019, Microsoft Corporation.
+ * Pavel Tatashin <patatash@xxxxxxxxxxxxxxxxxxx>
+ */
+
+#ifndef _ASM_TRANS_TABLE_H
+#define _ASM_TRANS_TABLE_H
+
+#include <linux/bits.h>
+#include <asm/pgtable-types.h>
+
+/*
+ * trans_alloc_page
+ * - Allocator that should return exactly one uninitilaized page, if this
+ * allocator fails, trans_table returns -ENOMEM error.
+ *
+ * trans_alloc_arg
+ * - Passed to trans_alloc_page as an argument
+ *
+ * trans_flags
+ * - bitmap with flags that control how page table is filled.
+ * TRANS_MKWRITE: during page table copy make PTE, PME, and PUD page
+ * writeable by removing RDONLY flag from PTE.
+ * TRANS_MKVALID: during page table copy, if PTE present, but not valid,
+ * make it valid.
+ * TRANS_CHECKPFN: During page table copy, for every PTE entry check that
+ * PFN that this PTE points to is valid. Otherwise return
+ * -ENXIO
+ * TRANS_FORCEMAP: During page map, if translation exists, force
+ * overwrite it. Otherwise -ENXIO may be returned by
+ * trans_table_map_* functions if conflict is detected.
+ */
+
+#define TRANS_MKWRITE BIT(0)
+#define TRANS_MKVALID BIT(1)
+#define TRANS_CHECKPFN BIT(2)
+#define TRANS_FORCEMAP BIT(3)
+
+struct trans_table_info {
+ void * (*trans_alloc_page)(void *arg);
+ void *trans_alloc_arg;
+ unsigned long trans_flags;
+};
+
+/* Create and empty trans table. */
+int trans_table_create_empty(struct trans_table_info *info,
+ pgd_t **trans_table);
+
+/*
+ * Create trans table and copy entries from from_table to trans_table in range
+ * [start, end)
+ */
+int trans_table_create_copy(struct trans_table_info *info, pgd_t **trans_table,
+ pgd_t *from_table, unsigned long start,
+ unsigned long end);
+
+/*
+ * Add map entry to trans_table for a base-size page at PTE level.
+ * page: page to be mapped.
+ * dst_addr: new VA address for the pages
+ * pgprot: protection for the page.
+ */
+int trans_table_map_page(struct trans_table_info *info, pgd_t *trans_table,
+ void *page, unsigned long dst_addr, pgprot_t pgprot);
+
+#endif /* _ASM_TRANS_TABLE_H */
diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
index 849c1df3d214..3794fff18659 100644
--- a/arch/arm64/mm/Makefile
+++ b/arch/arm64/mm/Makefile
@@ -6,6 +6,7 @@ obj-y := dma-mapping.o extable.o fault.o init.o \
obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
obj-$(CONFIG_ARM64_PTDUMP_CORE) += dump.o
obj-$(CONFIG_ARM64_PTDUMP_DEBUGFS) += ptdump_debugfs.o
+obj-$(CONFIG_TRANS_TABLE) += trans_table.o
obj-$(CONFIG_NUMA) += numa.o
obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o
KASAN_SANITIZE_physaddr.o += n
diff --git a/arch/arm64/mm/trans_table.c b/arch/arm64/mm/trans_table.c
new file mode 100644
index 000000000000..e3b8d4a2fa15
--- /dev/null
+++ b/arch/arm64/mm/trans_table.c
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (c) 2019, Microsoft Corporation.
+ * Pavel Tatashin <patatash@xxxxxxxxxxxxxxxxxxx>
+ */
+
+/*
+ * Transitional tables are used during system transferring from one world to
+ * another: such as during hibernate restore, and kexec reboots. During these
+ * phases one cannot rely on page table not being overwritten.
+ *
+ */
+
+#include <asm/trans_table.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+
+static void *trans_alloc(struct trans_table_info *info)
+{
+ void *page = info->trans_alloc_page(info->trans_alloc_arg);
+
+ if (page)
+ clear_page(page);
+
+ return page;
+}
+
+static int trans_table_copy_pte(struct trans_table_info *info, pte_t *dst_ptep,
+ pte_t *src_ptep, unsigned long start,
+ unsigned long end)
+{
+ unsigned long addr = start;
+ int i = pgd_index(addr);
+
+ do {
+ pte_t src_pte = READ_ONCE(src_ptep[i]);
+
+ if (pte_none(src_pte))
+ continue;
+ if (info->trans_flags & TRANS_MKWRITE)
+ src_pte = pte_mkwrite(src_pte);
+ if (info->trans_flags & TRANS_MKVALID)
+ src_pte = pte_mkpresent(src_pte);
+ if (info->trans_flags & TRANS_CHECKPFN) {
+ if (!pfn_valid(pte_pfn(src_pte)))
+ return -ENXIO;
+ }
+ set_pte(&dst_ptep[i], src_pte);
+ } while (addr += PAGE_SIZE, i++, addr != end && i < PTRS_PER_PTE);
+
+ return 0;
+}
+
+static int trans_table_copy_pmd(struct trans_table_info *info, pmd_t *dst_pmdp,
+ pmd_t *src_pmdp, unsigned long start,
+ unsigned long end)
+{
+ unsigned long next;
+ unsigned long addr = start;
+ int i = pgd_index(addr);
+ int rc;
+
+ do {
+ pmd_t src_pmd = READ_ONCE(src_pmdp[i]);
+ pmd_t dst_pmd = READ_ONCE(dst_pmdp[i]);
+ pte_t *dst_ptep, *src_ptep;
+
+ next = pmd_addr_end(addr, end);
+ if (pmd_none(src_pmd))
+ continue;
+
+ if (!pmd_table(src_pmd)) {
+ if (info->trans_flags & TRANS_MKWRITE)
+ pmd_val(src_pmd) &= ~PMD_SECT_RDONLY;
+ set_pmd(&dst_pmdp[i], src_pmd);
+ continue;
+ }
+
+ if (pmd_none(dst_pmd)) {
+ pte_t *t = trans_alloc(info);
+
+ if (!t)
+ return -ENOMEM;
+
+ __pmd_populate(&dst_pmdp[i], __pa(t), PTE_TYPE_PAGE);
+ dst_pmd = READ_ONCE(dst_pmdp[i]);
+ }
+
+ src_ptep = __va(pmd_page_paddr(src_pmd));
+ dst_ptep = __va(pmd_page_paddr(dst_pmd));
+
+ rc = trans_table_copy_pte(info, dst_ptep, src_ptep, addr, next);
+ if (rc)
+ return rc;
+ } while (addr = next, i++, addr != end && i < PTRS_PER_PMD);
+
+ return 0;
+}
+
+static int trans_table_copy_pud(struct trans_table_info *info, pud_t *dst_pudp,
+ pud_t *src_pudp, unsigned long start,
+ unsigned long end)
+{
+ unsigned long next;
+ unsigned long addr = start;
+ int i = pgd_index(addr);
+ int rc;
+
+ do {
+ pud_t src_pud = READ_ONCE(src_pudp[i]);
+ pud_t dst_pud = READ_ONCE(dst_pudp[i]);
+ pmd_t *dst_pmdp, *src_pmdp;
+
+ next = pud_addr_end(addr, end);
+ if (pud_none(src_pud))
+ continue;
+
+ if (!pud_table(src_pud)) {
+ if (info->trans_flags & TRANS_MKWRITE)
+ pud_val(src_pud) &= ~PUD_SECT_RDONLY;
+ set_pud(&dst_pudp[i], src_pud);
+ continue;
+ }
+
+ if (pud_none(dst_pud)) {
+ pmd_t *t = trans_alloc(info);
+
+ if (!t)
+ return -ENOMEM;
+
+ __pud_populate(&dst_pudp[i], __pa(t), PMD_TYPE_TABLE);
+ dst_pud = READ_ONCE(dst_pudp[i]);
+ }
+
+ src_pmdp = __va(pud_page_paddr(src_pud));
+ dst_pmdp = __va(pud_page_paddr(dst_pud));
+
+ rc = trans_table_copy_pmd(info, dst_pmdp, src_pmdp, addr, next);
+ if (rc)
+ return rc;
+ } while (addr = next, i++, addr != end && i < PTRS_PER_PUD);
+
+ return 0;
+}
+
+static int trans_table_copy_pgd(struct trans_table_info *info, pgd_t *dst_pgdp,
+ pgd_t *src_pgdp, unsigned long start,
+ unsigned long end)
+{
+ unsigned long next;
+ unsigned long addr = start;
+ int i = pgd_index(addr);
+ int rc;
+
+ do {
+ pgd_t src_pgd;
+ pgd_t dst_pgd;
+ pud_t *dst_pudp, *src_pudp;
+
+ src_pgd = READ_ONCE(src_pgdp[i]);
+ dst_pgd = READ_ONCE(dst_pgdp[i]);
+ next = pgd_addr_end(addr, end);
+ if (pgd_none(src_pgd))
+ continue;
+
+ if (pgd_none(dst_pgd)) {
+ pud_t *t = trans_alloc(info);
+
+ if (!t)
+ return -ENOMEM;
+
+ __pgd_populate(&dst_pgdp[i], __pa(t), PUD_TYPE_TABLE);
+ dst_pgd = READ_ONCE(dst_pgdp[i]);
+ }
+
+ src_pudp = __va(pgd_page_paddr(src_pgd));
+ dst_pudp = __va(pgd_page_paddr(dst_pgd));
+
+ rc = trans_table_copy_pud(info, dst_pudp, src_pudp, addr, next);
+ if (rc)
+ return rc;
+ } while (addr = next, i++, addr != end && i < PTRS_PER_PGD);
+
+ return 0;
+}
+
+int trans_table_create_empty(struct trans_table_info *info, pgd_t **trans_table)
+{
+ pgd_t *dst_pgdp = trans_alloc(info);
+
+ if (!dst_pgdp)
+ return -ENOMEM;
+
+ *trans_table = dst_pgdp;
+
+ return 0;
+}
+
+int trans_table_create_copy(struct trans_table_info *info, pgd_t **trans_table,
+ pgd_t *from_table, unsigned long start,
+ unsigned long end)
+{
+ int rc;
+
+ rc = trans_table_create_empty(info, trans_table);
+ if (rc)
+ return rc;
+
+ return trans_table_copy_pgd(info, *trans_table, from_table, start, end);
+}
+
+int trans_table_map_page(struct trans_table_info *info, pgd_t *trans_table,
+ void *page, unsigned long dst_addr, pgprot_t pgprot)
+{
+ int pgd_idx = pgd_index(dst_addr);
+ int pud_idx = pud_index(dst_addr);
+ int pmd_idx = pmd_index(dst_addr);
+ int pte_idx = pte_index(dst_addr);
+ pgd_t *pgdp = trans_table;
+ pgd_t pgd = READ_ONCE(pgdp[pgd_idx]);
+ pud_t *pudp, pud;
+ pmd_t *pmdp, pmd;
+ pte_t *ptep, pte;
+
+ if (pgd_none(pgd)) {
+ pud_t *t = trans_alloc(info);
+
+ if (!t)
+ return -ENOMEM;
+
+ __pgd_populate(&pgdp[pgd_idx], __pa(t), PUD_TYPE_TABLE);
+ pgd = READ_ONCE(pgdp[pgd_idx]);
+ }
+
+ pudp = __va(pgd_page_paddr(pgd));
+ pud = READ_ONCE(pudp[pud_idx]);
+ if (pud_sect(pud) && !(info->trans_flags & TRANS_FORCEMAP)) {
+ return -ENXIO;
+ } else if (pud_none(pud) || pud_sect(pud)) {
+ pmd_t *t = trans_alloc(info);
+
+ if (!t)
+ return -ENOMEM;
+
+ __pud_populate(&pudp[pud_idx], __pa(t), PMD_TYPE_TABLE);
+ pud = READ_ONCE(pudp[pud_idx]);
+ }
+
+ pmdp = __va(pud_page_paddr(pud));
+ pmd = READ_ONCE(pmdp[pmd_idx]);
+ if (pmd_sect(pmd) && !(info->trans_flags & TRANS_FORCEMAP)) {
+ return -ENXIO;
+ } else if (pmd_none(pmd) || pmd_sect(pmd)) {
+ pte_t *t = trans_alloc(info);
+
+ if (!t)
+ return -ENOMEM;
+
+ __pmd_populate(&pmdp[pmd_idx], __pa(t), PTE_TYPE_PAGE);
+ pmd = READ_ONCE(pmdp[pmd_idx]);
+ }
+
+ ptep = __va(pmd_page_paddr(pmd));
+ pte = READ_ONCE(ptep[pte_idx]);
+
+ if (!pte_none(pte) && !(info->trans_flags & TRANS_FORCEMAP))
+ return -ENXIO;
+
+ set_pte(&ptep[pte_idx], pfn_pte(virt_to_pfn(page), pgprot));
+
+ return 0;
+}
--
2.22.0
