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Message-Id: <20180529043820.27948-1-yaojun8558363@gmail.com>
Date: Tue, 29 May 2018 12:38:20 +0800
From: YaoJun <yaojun8558363@...il.com>
To: kernel-hardening@...ts.openwall.com
Cc: linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org,
jmorris@...ei.org
Subject: [PATCH 4/4] migrate swapper_pg_dir
Migrate swapper_pg_dir and tramp_pg_dir. And its placement in
the virtual address space does not correlate with the placement
of the kernel.
---
arch/arm64/mm/mmu.c | 67 ++++++++++++++++++++++++++++++---------------
1 file changed, 45 insertions(+), 22 deletions(-)
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 26ba3e70a91c..0b1a77b8c757 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -55,6 +55,9 @@ u64 idmap_ptrs_per_pgd = PTRS_PER_PGD;
u64 kimage_voffset __ro_after_init;
EXPORT_SYMBOL(kimage_voffset);
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+pgd_t *new_tramp_pg_dir;
+#endif
phys_addr_t __pa_swapper_pg_dir;
pgd_t *new_swapper_pg_dir = swapper_pg_dir;
@@ -105,6 +108,25 @@ static phys_addr_t __init early_pgtable_alloc(void)
return phys;
}
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+static phys_addr_t __init early_pgtables_alloc(int num)
+{
+ int i;
+ phys_addr_t phys;
+ void *ptr;
+
+ phys = memblock_alloc(PAGE_SIZE * num, PAGE_SIZE);
+
+ for (i = 0; i < num; i++) {
+ ptr = pte_set_fixmap(phys + i * PAGE_SIZE);
+ memset(ptr, 0, PAGE_SIZE);
+ pte_clear_fixmap();
+ }
+
+ return phys;
+}
+#endif
+
static bool pgattr_change_is_safe(u64 old, u64 new)
{
/*
@@ -554,6 +576,10 @@ static int __init map_entry_trampoline(void)
__create_pgd_mapping(tramp_pg_dir, pa_start, TRAMP_VALIAS, PAGE_SIZE,
prot, pgd_pgtable_alloc, 0);
+ memcpy(new_tramp_pg_dir, tramp_pg_dir, PGD_SIZE);
+ memblock_free(__pa_symbol(tramp_pg_dir),
+ __pa_symbol(swapper_pg_dir) - __pa_symbol(tramp_pg_dir));
+
/* Map both the text and data into the kernel page table */
__set_fixmap(FIX_ENTRY_TRAMP_TEXT, pa_start, prot);
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
@@ -631,36 +657,33 @@ static void __init map_kernel(pgd_t *pgdp)
*/
void __init paging_init(void)
{
- phys_addr_t pgd_phys = early_pgtable_alloc();
- pgd_t *pgdp = pgd_set_fixmap(pgd_phys);
+ phys_addr_t pgd_phys;
+ pgd_t *pgdp;
- __pa_swapper_pg_dir = __pa_symbol(swapper_pg_dir);
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+ int pages;
+ pages = (__pa_symbol(swapper_pg_dir) - __pa_symbol(tramp_pg_dir) +
+ PAGE_SIZE) >> PAGE_SHIFT;
+ pgd_phys = early_pgtables_alloc(pages);
+ new_tramp_pg_dir = __va(pgd_phys);
+ __pa_swapper_pg_dir = pgd_phys + PAGE_SIZE;
+#else
+ pgd_phys = early_pgtable_alloc();
+ __pa_swapper_pg_dir = pgd_phys;
+#endif
+ new_swapper_pg_dir = __va(__pa_swapper_pg_dir);
+
+ pgdp = pgd_set_fixmap(__pa_swapper_pg_dir);
map_kernel(pgdp);
map_mem(pgdp);
- /*
- * We want to reuse the original swapper_pg_dir so we don't have to
- * communicate the new address to non-coherent secondaries in
- * secondary_entry, and so cpu_switch_mm can generate the address with
- * adrp+add rather than a load from some global variable.
- *
- * To do this we need to go via a temporary pgd.
- */
- cpu_replace_ttbr1(pgd_phys);
- memcpy(swapper_pg_dir, pgdp, PGD_SIZE);
cpu_replace_ttbr1(__pa_swapper_pg_dir);
+ init_mm.pgd = new_swapper_pg_dir;
pgd_clear_fixmap();
- memblock_free(pgd_phys, PAGE_SIZE);
-
- /*
- * We only reuse the PGD from the swapper_pg_dir, not the pud + pmd
- * allocated with it.
- */
- memblock_free(__pa_symbol(swapper_pg_dir) + PAGE_SIZE,
- __pa_symbol(swapper_pg_end) - __pa_symbol(swapper_pg_dir)
- - PAGE_SIZE);
+ memblock_free(__pa_symbol(swapper_pg_dir),
+ __pa_symbol(swapper_pg_end) - __pa_symbol(swapper_pg_dir));
}
/*
--
2.17.0
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