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-rw-r--r--arch/arm64/mm/trans_pgd.c292
1 files changed, 292 insertions, 0 deletions
diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
new file mode 100644
index 0000000000..7b14df3c64
--- /dev/null
+++ b/arch/arm64/mm/trans_pgd.c
@@ -0,0 +1,292 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Transitional page tables for kexec and hibernate
+ *
+ * This file derived from: arch/arm64/kernel/hibernate.c
+ *
+ * Copyright (c) 2021, Microsoft Corporation.
+ * Pasha Tatashin <pasha.tatashin@soleen.com>
+ *
+ */
+
+/*
+ * 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. This is because
+ * hibernate and kexec can overwrite the current page tables during transition.
+ */
+
+#include <asm/trans_pgd.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <linux/suspend.h>
+#include <linux/bug.h>
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/kfence.h>
+
+static void *trans_alloc(struct trans_pgd_info *info)
+{
+ return info->trans_alloc_page(info->trans_alloc_arg);
+}
+
+static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr)
+{
+ pte_t pte = READ_ONCE(*src_ptep);
+
+ if (pte_valid(pte)) {
+ /*
+ * Resume will overwrite areas that may be marked
+ * read only (code, rodata). Clear the RDONLY bit from
+ * the temporary mappings we use during restore.
+ */
+ set_pte(dst_ptep, pte_mkwrite_novma(pte));
+ } else if ((debug_pagealloc_enabled() ||
+ is_kfence_address((void *)addr)) && !pte_none(pte)) {
+ /*
+ * debug_pagealloc will removed the PTE_VALID bit if
+ * the page isn't in use by the resume kernel. It may have
+ * been in use by the original kernel, in which case we need
+ * to put it back in our copy to do the restore.
+ *
+ * Before marking this entry valid, check the pfn should
+ * be mapped.
+ */
+ BUG_ON(!pfn_valid(pte_pfn(pte)));
+
+ set_pte(dst_ptep, pte_mkpresent(pte_mkwrite_novma(pte)));
+ }
+}
+
+static int copy_pte(struct trans_pgd_info *info, pmd_t *dst_pmdp,
+ pmd_t *src_pmdp, unsigned long start, unsigned long end)
+{
+ pte_t *src_ptep;
+ pte_t *dst_ptep;
+ unsigned long addr = start;
+
+ dst_ptep = trans_alloc(info);
+ if (!dst_ptep)
+ return -ENOMEM;
+ pmd_populate_kernel(NULL, dst_pmdp, dst_ptep);
+ dst_ptep = pte_offset_kernel(dst_pmdp, start);
+
+ src_ptep = pte_offset_kernel(src_pmdp, start);
+ do {
+ _copy_pte(dst_ptep, src_ptep, addr);
+ } while (dst_ptep++, src_ptep++, addr += PAGE_SIZE, addr != end);
+
+ return 0;
+}
+
+static int copy_pmd(struct trans_pgd_info *info, pud_t *dst_pudp,
+ pud_t *src_pudp, unsigned long start, unsigned long end)
+{
+ pmd_t *src_pmdp;
+ pmd_t *dst_pmdp;
+ unsigned long next;
+ unsigned long addr = start;
+
+ if (pud_none(READ_ONCE(*dst_pudp))) {
+ dst_pmdp = trans_alloc(info);
+ if (!dst_pmdp)
+ return -ENOMEM;
+ pud_populate(NULL, dst_pudp, dst_pmdp);
+ }
+ dst_pmdp = pmd_offset(dst_pudp, start);
+
+ src_pmdp = pmd_offset(src_pudp, start);
+ do {
+ pmd_t pmd = READ_ONCE(*src_pmdp);
+
+ next = pmd_addr_end(addr, end);
+ if (pmd_none(pmd))
+ continue;
+ if (pmd_table(pmd)) {
+ if (copy_pte(info, dst_pmdp, src_pmdp, addr, next))
+ return -ENOMEM;
+ } else {
+ set_pmd(dst_pmdp,
+ __pmd(pmd_val(pmd) & ~PMD_SECT_RDONLY));
+ }
+ } while (dst_pmdp++, src_pmdp++, addr = next, addr != end);
+
+ return 0;
+}
+
+static int copy_pud(struct trans_pgd_info *info, p4d_t *dst_p4dp,
+ p4d_t *src_p4dp, unsigned long start,
+ unsigned long end)
+{
+ pud_t *dst_pudp;
+ pud_t *src_pudp;
+ unsigned long next;
+ unsigned long addr = start;
+
+ if (p4d_none(READ_ONCE(*dst_p4dp))) {
+ dst_pudp = trans_alloc(info);
+ if (!dst_pudp)
+ return -ENOMEM;
+ p4d_populate(NULL, dst_p4dp, dst_pudp);
+ }
+ dst_pudp = pud_offset(dst_p4dp, start);
+
+ src_pudp = pud_offset(src_p4dp, start);
+ do {
+ pud_t pud = READ_ONCE(*src_pudp);
+
+ next = pud_addr_end(addr, end);
+ if (pud_none(pud))
+ continue;
+ if (pud_table(pud)) {
+ if (copy_pmd(info, dst_pudp, src_pudp, addr, next))
+ return -ENOMEM;
+ } else {
+ set_pud(dst_pudp,
+ __pud(pud_val(pud) & ~PUD_SECT_RDONLY));
+ }
+ } while (dst_pudp++, src_pudp++, addr = next, addr != end);
+
+ return 0;
+}
+
+static int copy_p4d(struct trans_pgd_info *info, pgd_t *dst_pgdp,
+ pgd_t *src_pgdp, unsigned long start,
+ unsigned long end)
+{
+ p4d_t *dst_p4dp;
+ p4d_t *src_p4dp;
+ unsigned long next;
+ unsigned long addr = start;
+
+ dst_p4dp = p4d_offset(dst_pgdp, start);
+ src_p4dp = p4d_offset(src_pgdp, start);
+ do {
+ next = p4d_addr_end(addr, end);
+ if (p4d_none(READ_ONCE(*src_p4dp)))
+ continue;
+ if (copy_pud(info, dst_p4dp, src_p4dp, addr, next))
+ return -ENOMEM;
+ } while (dst_p4dp++, src_p4dp++, addr = next, addr != end);
+
+ return 0;
+}
+
+static int copy_page_tables(struct trans_pgd_info *info, pgd_t *dst_pgdp,
+ unsigned long start, unsigned long end)
+{
+ unsigned long next;
+ unsigned long addr = start;
+ pgd_t *src_pgdp = pgd_offset_k(start);
+
+ dst_pgdp = pgd_offset_pgd(dst_pgdp, start);
+ do {
+ next = pgd_addr_end(addr, end);
+ if (pgd_none(READ_ONCE(*src_pgdp)))
+ continue;
+ if (copy_p4d(info, dst_pgdp, src_pgdp, addr, next))
+ return -ENOMEM;
+ } while (dst_pgdp++, src_pgdp++, addr = next, addr != end);
+
+ return 0;
+}
+
+/*
+ * Create trans_pgd and copy linear map.
+ * info: contains allocator and its argument
+ * dst_pgdp: new page table that is created, and to which map is copied.
+ * start: Start of the interval (inclusive).
+ * end: End of the interval (exclusive).
+ *
+ * Returns 0 on success, and -ENOMEM on failure.
+ */
+int trans_pgd_create_copy(struct trans_pgd_info *info, pgd_t **dst_pgdp,
+ unsigned long start, unsigned long end)
+{
+ int rc;
+ pgd_t *trans_pgd = trans_alloc(info);
+
+ if (!trans_pgd) {
+ pr_err("Failed to allocate memory for temporary page tables.\n");
+ return -ENOMEM;
+ }
+
+ rc = copy_page_tables(info, trans_pgd, start, end);
+ if (!rc)
+ *dst_pgdp = trans_pgd;
+
+ return rc;
+}
+
+/*
+ * The page we want to idmap may be outside the range covered by VA_BITS that
+ * can be built using the kernel's p?d_populate() helpers. As a one off, for a
+ * single page, we build these page tables bottom up and just assume that will
+ * need the maximum T0SZ.
+ *
+ * Returns 0 on success, and -ENOMEM on failure.
+ * On success trans_ttbr0 contains page table with idmapped page, t0sz is set to
+ * maximum T0SZ for this page.
+ */
+int trans_pgd_idmap_page(struct trans_pgd_info *info, phys_addr_t *trans_ttbr0,
+ unsigned long *t0sz, void *page)
+{
+ phys_addr_t dst_addr = virt_to_phys(page);
+ unsigned long pfn = __phys_to_pfn(dst_addr);
+ int max_msb = (dst_addr & GENMASK(52, 48)) ? 51 : 47;
+ int bits_mapped = PAGE_SHIFT - 4;
+ unsigned long level_mask, prev_level_entry, *levels[4];
+ int this_level, index, level_lsb, level_msb;
+
+ dst_addr &= PAGE_MASK;
+ prev_level_entry = pte_val(pfn_pte(pfn, PAGE_KERNEL_ROX));
+
+ for (this_level = 3; this_level >= 0; this_level--) {
+ levels[this_level] = trans_alloc(info);
+ if (!levels[this_level])
+ return -ENOMEM;
+
+ level_lsb = ARM64_HW_PGTABLE_LEVEL_SHIFT(this_level);
+ level_msb = min(level_lsb + bits_mapped, max_msb);
+ level_mask = GENMASK_ULL(level_msb, level_lsb);
+
+ index = (dst_addr & level_mask) >> level_lsb;
+ *(levels[this_level] + index) = prev_level_entry;
+
+ pfn = virt_to_pfn(levels[this_level]);
+ prev_level_entry = pte_val(pfn_pte(pfn,
+ __pgprot(PMD_TYPE_TABLE)));
+
+ if (level_msb == max_msb)
+ break;
+ }
+
+ *trans_ttbr0 = phys_to_ttbr(__pfn_to_phys(pfn));
+ *t0sz = TCR_T0SZ(max_msb + 1);
+
+ return 0;
+}
+
+/*
+ * Create a copy of the vector table so we can call HVC_SET_VECTORS or
+ * HVC_SOFT_RESTART from contexts where the table may be overwritten.
+ */
+int trans_pgd_copy_el2_vectors(struct trans_pgd_info *info,
+ phys_addr_t *el2_vectors)
+{
+ void *hyp_stub = trans_alloc(info);
+
+ if (!hyp_stub)
+ return -ENOMEM;
+ *el2_vectors = virt_to_phys(hyp_stub);
+ memcpy(hyp_stub, &trans_pgd_stub_vectors, ARM64_VECTOR_TABLE_LEN);
+ caches_clean_inval_pou((unsigned long)hyp_stub,
+ (unsigned long)hyp_stub +
+ ARM64_VECTOR_TABLE_LEN);
+ dcache_clean_inval_poc((unsigned long)hyp_stub,
+ (unsigned long)hyp_stub +
+ ARM64_VECTOR_TABLE_LEN);
+
+ return 0;
+}