arm64: move kernel image to base of vmalloc area

This moves the module area to right before the vmalloc area, and moves
the kernel image to the base of the vmalloc area. This is an intermediate
step towards implementing KASLR, which allows the kernel image to be
located anywhere in the vmalloc area.

Since other subsystems such as hibernate may still need to refer to the
kernel text or data segments via their linears addresses, both are mapped
in the linear region as well. The linear alias of the text region is
mapped read-only/non-executable to prevent inadvertent modification or
execution.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 24 insertions, 3 deletions

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index cc569a38bc76..7f10cc91fa8a 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -17,9 +17,11 @@
 #include <linux/start_kernel.h>
 
 #include <asm/mmu_context.h>
+#include <asm/kernel-pgtable.h>
 #include <asm/page.h>
 #include <asm/pgalloc.h>
 #include <asm/pgtable.h>
+#include <asm/sections.h>
 #include <asm/tlbflush.h>
 
 static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
@@ -33,7 +35,7 @@ static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr,
 	if (pmd_none(*pmd))
 		pmd_populate_kernel(&init_mm, pmd, kasan_zero_pte);
 
-	pte = pte_offset_kernel(pmd, addr);
+	pte = pte_offset_kimg(pmd, addr);
 	do {
 		next = addr + PAGE_SIZE;
 		set_pte(pte, pfn_pte(virt_to_pfn(kasan_zero_page),
@@ -51,7 +53,7 @@ static void __init kasan_early_pmd_populate(pud_t *pud,
 	if (pud_none(*pud))
 		pud_populate(&init_mm, pud, kasan_zero_pmd);
 
-	pmd = pmd_offset(pud, addr);
+	pmd = pmd_offset_kimg(pud, addr);
 	do {
 		next = pmd_addr_end(addr, end);
 		kasan_early_pte_populate(pmd, addr, next);
@@ -68,7 +70,7 @@ static void __init kasan_early_pud_populate(pgd_t *pgd,
 	if (pgd_none(*pgd))
 		pgd_populate(&init_mm, pgd, kasan_zero_pud);
 
-	pud = pud_offset(pgd, addr);
+	pud = pud_offset_kimg(pgd, addr);
 	do {
 		next = pud_addr_end(addr, end);
 		kasan_early_pmd_populate(pud, addr, next);
@@ -126,9 +128,13 @@ static void __init clear_pgds(unsigned long start,
 
 void __init kasan_init(void)
 {
+	u64 kimg_shadow_start, kimg_shadow_end;
 	struct memblock_region *reg;
 	int i;
 
+	kimg_shadow_start = (u64)kasan_mem_to_shadow(_text);
+	kimg_shadow_end = (u64)kasan_mem_to_shadow(_end);
+
 	/*
 	 * We are going to perform proper setup of shadow memory.
 	 * At first we should unmap early shadow (clear_pgds() call bellow).
@@ -142,8 +148,23 @@ void __init kasan_init(void)
 
 	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 
+	vmemmap_populate(kimg_shadow_start, kimg_shadow_end, NUMA_NO_NODE);
+
+	/*
+	 * vmemmap_populate() has populated the shadow region that covers the
+	 * kernel image with SWAPPER_BLOCK_SIZE mappings, so we have to round
+	 * the start and end addresses to SWAPPER_BLOCK_SIZE as well, to prevent
+	 * kasan_populate_zero_shadow() from replacing the PMD block mappings
+	 * with PMD table mappings at the edges of the shadow region for the
+	 * kernel image.
+	 */
+	if (ARM64_SWAPPER_USES_SECTION_MAPS)
+		kimg_shadow_end = round_up(kimg_shadow_end, SWAPPER_BLOCK_SIZE);
+
 	kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 			kasan_mem_to_shadow((void *)MODULES_VADDR));
+	kasan_populate_zero_shadow((void *)kimg_shadow_end,
+			kasan_mem_to_shadow((void *)PAGE_OFFSET));
 
 	for_each_memblock(memory, reg) {
 		void *start = (void *)__phys_to_virt(reg->base);