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// SPDX-License-Identifier: GPL-2.0
/*
* Transitional page tables for kexec and hibernate
*
* This file derived from: arch/arm64/kernel/hibernate.c
*
* Copyright (c) 2020, Microsoft Corporation.
* Pavel 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>
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(pte));
} else if (debug_pagealloc_enabled() && !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(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;
}
/*
* Add map entry to trans_pgd for a base-size page at PTE level.
* info: contains allocator and its argument
* trans_pgd: page table in which new map is added.
* page: page to be mapped.
* dst_addr: new VA address for the page
* pgprot: protection for the page.
*
* Returns 0 on success, and -ENOMEM on failure.
*/
int trans_pgd_map_page(struct trans_pgd_info *info, pgd_t *trans_pgd,
void *page, unsigned long dst_addr, pgprot_t pgprot)
{
pgd_t *pgdp;
p4d_t *p4dp;
pud_t *pudp;
pmd_t *pmdp;
pte_t *ptep;
pgdp = pgd_offset_pgd(trans_pgd, dst_addr);
if (pgd_none(READ_ONCE(*pgdp))) {
p4dp = trans_alloc(info);
if (!pgdp)
return -ENOMEM;
pgd_populate(NULL, pgdp, p4dp);
}
p4dp = p4d_offset(pgdp, dst_addr);
if (p4d_none(READ_ONCE(*p4dp))) {
pudp = trans_alloc(info);
if (!pudp)
return -ENOMEM;
p4d_populate(NULL, p4dp, pudp);
}
pudp = pud_offset(p4dp, dst_addr);
if (pud_none(READ_ONCE(*pudp))) {
pmdp = trans_alloc(info);
if (!pmdp)
return -ENOMEM;
pud_populate(NULL, pudp, pmdp);
}
pmdp = pmd_offset(pudp, dst_addr);
if (pmd_none(READ_ONCE(*pmdp))) {
ptep = trans_alloc(info);
if (!ptep)
return -ENOMEM;
pmd_populate_kernel(NULL, pmdp, ptep);
}
ptep = pte_offset_kernel(pmdp, dst_addr);
set_pte(ptep, pfn_pte(virt_to_pfn(page), pgprot));
return 0;
}
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