[PATCH v3 07/21] arm64: move kernel image to base of vmalloc area

Ard Biesheuvel
2016-01-11T13:19:56Z

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, where the kernel
image can be located anywhere in the vmalloc area.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm64/include/asm/kasan.h | 20 ++++---
arch/arm64/include/asm/kernel-pgtable.h | 5 +-
arch/arm64/include/asm/memory.h | 18 ++++--
arch/arm64/include/asm/pgtable.h | 7 ---
arch/arm64/kernel/setup.c | 12 ++++
arch/arm64/mm/dump.c | 12 ++--
arch/arm64/mm/init.c | 20 +++----
arch/arm64/mm/kasan_init.c | 21 +++++--
arch/arm64/mm/mmu.c | 62 ++++++++++++++------
9 files changed, 118 insertions(+), 59 deletions(-)

diff --git a/arch/arm64/include/asm/kasan.h b/arch/arm64/include/asm/kasan.h
index de0d21211c34..2c583dbf4746 100644
--- a/arch/arm64/include/asm/kasan.h
+++ b/arch/arm64/include/asm/kasan.h
@@ -1,20 +1,16 @@
#ifndef __ASM_KASAN_H
#define __ASM_KASAN_H

-#ifndef __ASSEMBLY__
-
#ifdef CONFIG_KASAN

#include <linux/linkage.h>
-#include <asm/memory.h>
-#include <asm/pgtable-types.h>

/*
* KASAN_SHADOW_START: beginning of the kernel virtual addresses.
* KASAN_SHADOW_END: KASAN_SHADOW_START + 1/8 of kernel virtual addresses.
*/
-#define KASAN_SHADOW_START (VA_START)
-#define KASAN_SHADOW_END (KASAN_SHADOW_START + (1UL << (VA_BITS - 3)))
+#define KASAN_SHADOW_START (VA_START)
+#define KASAN_SHADOW_END (KASAN_SHADOW_START + (_AC(1, UL) << (VA_BITS - 3)))

/*
* This value is used to map an address to the corresponding shadow
@@ -26,16 +22,22 @@
* should satisfy the following equation:
* KASAN_SHADOW_OFFSET = KASAN_SHADOW_END - (1ULL << 61)
*/
-#define KASAN_SHADOW_OFFSET (KASAN_SHADOW_END - (1ULL << (64 - 3)))
+#define KASAN_SHADOW_OFFSET (KASAN_SHADOW_END - (_AC(1, ULL) << (64 - 3)))
+
+#ifndef __ASSEMBLY__
+#include <asm/pgtable-types.h>

void kasan_init(void);
void kasan_copy_shadow(pgd_t *pgdir);
asmlinkage void kasan_early_init(void);
+#endif

#else
+
+#ifndef __ASSEMBLY__
static inline void kasan_init(void) { }
static inline void kasan_copy_shadow(pgd_t *pgdir) { }
#endif

-#endif
-#endif
+#endif /* CONFIG_KASAN */
+#endif /* __ASM_KASAN_H */
diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index a459714ee29e..daa8a7b9917a 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -70,8 +70,9 @@
/*
* Initial memory map attributes.
*/
-#define SWAPPER_PTE_FLAGS (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED)
-#define SWAPPER_PMD_FLAGS (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S)
+#define SWAPPER_PTE_FLAGS (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED | PTE_UXN)
+#define SWAPPER_PMD_FLAGS (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S | \
+ PMD_SECT_UXN)

#if ARM64_SWAPPER_USES_SECTION_MAPS
#define SWAPPER_MM_MMUFLAGS (PMD_ATTRINDX(MT_NORMAL) | SWAPPER_PMD_FLAGS)
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index bea9631b34a8..e45d3141ad98 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -51,14 +51,24 @@
#define VA_BITS (CONFIG_ARM64_VA_BITS)
#define VA_START (UL(0xffffffffffffffff) << VA_BITS)
#define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS - 1))
-#define KIMAGE_VADDR (PAGE_OFFSET)
-#define MODULES_END (KIMAGE_VADDR)
-#define MODULES_VADDR (MODULES_END - SZ_64M)
-#define PCI_IO_END (MODULES_VADDR - SZ_2M)
+#define PCI_IO_END (PAGE_OFFSET - SZ_2M)
#define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE)
#define FIXADDR_TOP (PCI_IO_START - SZ_2M)
#define TASK_SIZE_64 (UL(1) << VA_BITS)

+#ifndef CONFIG_KASAN
+#define MODULES_VADDR (VA_START)
+#else
+#include <asm/kasan.h>
+#define MODULES_VADDR (KASAN_SHADOW_END)
+#endif
+
+#define MODULES_VSIZE (SZ_64M)
+#define MODULES_END (MODULES_VADDR + MODULES_VSIZE)
+
+#define KIMAGE_VADDR (MODULES_END)
+#define VMALLOC_START (MODULES_END)
+
#ifdef CONFIG_COMPAT
#define TASK_SIZE_32 UL(0x100000000)
#define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 7b4e16068c9f..a910a44d7ab3 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -42,13 +42,6 @@
*/
#define VMEMMAP_SIZE ALIGN((1UL << (VA_BITS - PAGE_SHIFT)) * sizeof(struct page), PUD_SIZE)

-#ifndef CONFIG_KASAN
-#define VMALLOC_START (VA_START)
-#else
-#include <asm/kasan.h>
-#define VMALLOC_START (KASAN_SHADOW_END + SZ_64K)
-#endif
-
#define VMALLOC_END (PAGE_OFFSET - PUD_SIZE - VMEMMAP_SIZE - SZ_64K)

#define vmemmap ((struct page *)(VMALLOC_END + SZ_64K))
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index cfed56f0ad26..c67ba4453ec6 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -53,6 +53,7 @@
#include <asm/cpufeature.h>
#include <asm/cpu_ops.h>
#include <asm/kasan.h>
+#include <asm/kernel-pgtable.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/smp_plat.h>
@@ -291,6 +292,17 @@ u64 __cpu_logical_map[NR_CPUS] = { [0 ... NR_CPUS-1] = INVALID_HWID };

void __init setup_arch(char **cmdline_p)
{
+ static struct vm_struct vmlinux_vm;
+
+ vmlinux_vm.addr = (void *)KIMAGE_VADDR;
+ vmlinux_vm.size = round_up((u64)_end - KIMAGE_VADDR,
+ SWAPPER_BLOCK_SIZE);
+ vmlinux_vm.phys_addr = __pa(KIMAGE_VADDR);
+ vmlinux_vm.flags = VM_MAP;
+ vmlinux_vm.caller = setup_arch;
+
+ vm_area_add_early(&vmlinux_vm);
+
pr_info("Boot CPU: AArch64 Processor [%08x]\n", read_cpuid_id());

sprintf(init_utsname()->machine, ELF_PLATFORM);
diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index 5a22a119a74c..e83ffb00560c 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -35,7 +35,9 @@ struct addr_marker {
};

enum address_markers_idx {
- VMALLOC_START_NR = 0,
+ MODULES_START_NR = 0,
+ MODULES_END_NR,
+ VMALLOC_START_NR,
VMALLOC_END_NR,
#ifdef CONFIG_SPARSEMEM_VMEMMAP
VMEMMAP_START_NR,
@@ -45,12 +47,12 @@ enum address_markers_idx {
FIXADDR_END_NR,
PCI_START_NR,
PCI_END_NR,
- MODULES_START_NR,
- MODUELS_END_NR,
KERNEL_SPACE_NR,
};

static struct addr_marker address_markers[] = {
+ { MODULES_VADDR, "Modules start" },
+ { MODULES_END, "Modules end" },
{ VMALLOC_START, "vmalloc() Area" },
{ VMALLOC_END, "vmalloc() End" },
#ifdef CONFIG_SPARSEMEM_VMEMMAP
@@ -61,9 +63,7 @@ static struct addr_marker address_markers[] = {
{ FIXADDR_TOP, "Fixmap end" },
{ PCI_IO_START, "PCI I/O start" },
{ PCI_IO_END, "PCI I/O end" },
- { MODULES_VADDR, "Modules start" },
- { MODULES_END, "Modules end" },
- { PAGE_OFFSET, "Kernel Mapping" },
+ { PAGE_OFFSET, "Linear Mapping" },
{ -1, NULL },
};

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index f3b061e67bfe..baa923bda651 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -302,22 +302,26 @@ void __init mem_init(void)
#ifdef CONFIG_KASAN
" kasan : 0x%16lx - 0x%16lx (%6ld GB)\n"
#endif
+ " modules : 0x%16lx - 0x%16lx (%6ld MB)\n"
" vmalloc : 0x%16lx - 0x%16lx (%6ld GB)\n"
+ " .init : 0x%p" " - 0x%p" " (%6ld KB)\n"
+ " .text : 0x%p" " - 0x%p" " (%6ld KB)\n"
+ " .data : 0x%p" " - 0x%p" " (%6ld KB)\n"
#ifdef CONFIG_SPARSEMEM_VMEMMAP
" vmemmap : 0x%16lx - 0x%16lx (%6ld GB maximum)\n"
" 0x%16lx - 0x%16lx (%6ld MB actual)\n"
#endif
" fixed : 0x%16lx - 0x%16lx (%6ld KB)\n"
" PCI I/O : 0x%16lx - 0x%16lx (%6ld MB)\n"
- " modules : 0x%16lx - 0x%16lx (%6ld MB)\n"
- " memory : 0x%16lx - 0x%16lx (%6ld MB)\n"
- " .init : 0x%p" " - 0x%p" " (%6ld KB)\n"
- " .text : 0x%p" " - 0x%p" " (%6ld KB)\n"
- " .data : 0x%p" " - 0x%p" " (%6ld KB)\n",
+ " memory : 0x%16lx - 0x%16lx (%6ld MB)\n",
#ifdef CONFIG_KASAN
MLG(KASAN_SHADOW_START, KASAN_SHADOW_END),
#endif
+ MLM(MODULES_VADDR, MODULES_END),
MLG(VMALLOC_START, VMALLOC_END),
+ MLK_ROUNDUP(__init_begin, __init_end),
+ MLK_ROUNDUP(_text, _etext),
+ MLK_ROUNDUP(_sdata, _edata),
#ifdef CONFIG_SPARSEMEM_VMEMMAP
MLG((unsigned long)vmemmap,
(unsigned long)vmemmap + VMEMMAP_SIZE),
@@ -326,11 +330,7 @@ void __init mem_init(void)
#endif
MLK(FIXADDR_START, FIXADDR_TOP),
MLM(PCI_IO_START, PCI_IO_END),
- MLM(MODULES_VADDR, MODULES_END),
- MLM(PAGE_OFFSET, (unsigned long)high_memory),
- MLK_ROUNDUP(__init_begin, __init_end),
- MLK_ROUNDUP(_text, _etext),
- MLK_ROUNDUP(_sdata, _edata));
+ MLM(PAGE_OFFSET, (unsigned long)high_memory));

#undef MLK
#undef MLM
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index 0ca411fc5ea3..acdd1ac166ec 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);
@@ -126,8 +128,14 @@ static void __init clear_pgds(unsigned long start,

void __init kasan_init(void)
{
+ u64 kimg_shadow_start, kimg_shadow_end;
struct memblock_region *reg;

+ kimg_shadow_start = round_down((u64)kasan_mem_to_shadow(_text),
+ SWAPPER_BLOCK_SIZE);
+ kimg_shadow_end = round_up((u64)kasan_mem_to_shadow(_end),
+ SWAPPER_BLOCK_SIZE);
+
/*
* We are going to perform proper setup of shadow memory.
* At first we should unmap early shadow (clear_pgds() call bellow).
@@ -141,8 +149,13 @@ void __init kasan_init(void)

clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);

+ vmemmap_populate(kimg_shadow_start, kimg_shadow_end,
+ pfn_to_nid(virt_to_pfn(kimg_shadow_start)));
+
kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
- kasan_mem_to_shadow((void *)MODULES_VADDR));
+ (void *)kimg_shadow_start);
+ 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);
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 75b5f0dc3bdc..0b28f1469f9b 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -53,6 +53,10 @@ u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
EXPORT_SYMBOL(empty_zero_page);

+static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
+static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss;
+static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss;
+
pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
unsigned long size, pgprot_t vma_prot)
{
@@ -349,14 +353,14 @@ static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end
{

unsigned long kernel_start = __pa(_stext);
- unsigned long kernel_end = __pa(_end);
+ unsigned long kernel_end = __pa(_etext);

/*
- * The kernel itself is mapped at page granularity. Map all other
- * memory, making sure we don't overwrite the existing kernel mappings.
+ * Take care not to create a writable alias for the
+ * read-only text and rodata sections of the kernel image.
*/

- /* No overlap with the kernel. */
+ /* No overlap with the kernel text */
if (end < kernel_start || start >= kernel_end) {
__create_pgd_mapping(pgd, start, __phys_to_virt(start),
end - start, PAGE_KERNEL,
@@ -365,7 +369,7 @@ static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end
}

/*
- * This block overlaps the kernel mapping. Map the portion(s) which
+ * This block overlaps the kernel text mapping. Map the portion(s) which
* don't overlap.
*/
if (start < kernel_start)
@@ -438,12 +442,29 @@ static void __init map_kernel(pgd_t *pgd)
map_kernel_chunk(pgd, __init_begin, __init_end, PAGE_KERNEL_EXEC);
map_kernel_chunk(pgd, _data, _end, PAGE_KERNEL);

- /*
- * The fixmap falls in a separate pgd to the kernel, and doesn't live
- * in the carveout for the swapper_pg_dir. We can simply re-use the
- * existing dir for the fixmap.
- */
- set_pgd(pgd_offset_raw(pgd, FIXADDR_START), *pgd_offset_k(FIXADDR_START));
+ if (pgd_index(FIXADDR_START) != pgd_index((u64)_end)) {
+ /*
+ * The fixmap falls in a separate pgd to the kernel, and doesn't
+ * live in the carveout for the swapper_pg_dir. We can simply
+ * re-use the existing dir for the fixmap.
+ */
+ set_pgd(pgd_offset_raw(pgd, FIXADDR_START),
+ *pgd_offset_k(FIXADDR_START));
+ } else if (CONFIG_PGTABLE_LEVELS > 3) {
+ /*
+ * The fixmap shares its top level pgd entry with the kernel
+ * mapping. This can really only occur when we are running
+ * with 16k/4 levels, so we can simply reuse the pud level
+ * entry instead.
+ */
+ BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
+
+ set_pud(pud_set_fixmap_offset(pgd, FIXADDR_START),
+ __pud(__pa(bm_pmd) | PUD_TYPE_TABLE));
+ pud_clear_fixmap();
+ } else {
+ BUG();
+ }

kasan_copy_shadow(pgd);
}
@@ -569,10 +590,6 @@ void vmemmap_free(unsigned long start, unsigned long end)
}
#endif /* CONFIG_SPARSEMEM_VMEMMAP */

-static pte_t bm_pte[PTRS_PER_PTE] __page_aligned_bss;
-static pmd_t bm_pmd[PTRS_PER_PMD] __page_aligned_bss;
-static pud_t bm_pud[PTRS_PER_PUD] __page_aligned_bss;
-
static inline pud_t * fixmap_pud(unsigned long addr)
{
return (CONFIG_PGTABLE_LEVELS > 3) ? &bm_pud[pud_index(addr)]
@@ -598,8 +615,19 @@ void __init early_fixmap_init(void)
unsigned long addr = FIXADDR_START;

pgd = pgd_offset_k(addr);
- pgd_populate(&init_mm, pgd, bm_pud);
- pud = fixmap_pud(addr);
+ if (CONFIG_PGTABLE_LEVELS > 3 && !pgd_none(*pgd)) {
+ /*
+ * We only end up here if the kernel mapping and the fixmap
+ * share the top level pgd entry, which should only happen on
+ * 16k/4 levels configurations.
+ */
+ BUG_ON(!IS_ENABLED(CONFIG_ARM64_16K_PAGES));
+ pud = pud_offset_kimg(pgd, addr);
+ memblock_free(__pa(bm_pud), sizeof(bm_pud));
+ } else {
+ pgd_populate(&init_mm, pgd, bm_pud);
+ pud = fixmap_pud(addr);
+ }
pud_populate(&init_mm, pud, bm_pmd);
pmd = fixmap_pmd(addr);
pmd_populate_kernel(&init_mm, pmd, bm_pte);
--
2.5.0