[PATCH 06/12] arm64: mm: Flip kernel VA space

Steve Capper
2017-12-04T14:10:37Z

Put the direct linear map in the top half of the VA space and then the
kernel + everything else in the bottom half.

We need to adjust:
*) KASAN shadow region placement logic,
*) KASAN_SHADOW_OFFSET computation logic,
*) virt_to_phys, phys_to_virt checks
*) page table dumper
*) KVM hyp map flip logic

These are all small changes, that need to take place atomically, so they
are bundled into this commit.

Signed-off-by: Steve Capper <steve.capper@arm.com>
---
arch/arm64/Makefile | 2 +-
arch/arm64/include/asm/memory.h | 10 +++++-----
arch/arm64/include/asm/pgtable.h | 2 +-
arch/arm64/kernel/cpufeature.c | 2 +-
arch/arm64/mm/dump.c | 8 ++++----
arch/arm64/mm/init.c | 9 +--------
arch/arm64/mm/kasan_init.c | 4 ++--
7 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index b481b4a7c011..7eaff48d2a39 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -100,7 +100,7 @@ endif
# KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - 3)) - (1 << 61)
# in 32-bit arithmetic
KASAN_SHADOW_OFFSET := $(shell printf "0x%08x00000000\n" $$(( \
- (0xffffffff & (-1 << ($(CONFIG_ARM64_VA_BITS) - 32))) \
+ (0xffffffff & (-1 << ($(CONFIG_ARM64_VA_BITS) - 1 - 32))) \
+ (1 << ($(CONFIG_ARM64_VA_BITS) - 32 - 3)) \
- (1 << (64 - 32 - 3)) )) )

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 2dedc775d151..0a912eb3d74f 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -64,15 +64,15 @@
*/
#define VA_BITS (CONFIG_ARM64_VA_BITS)
#define VA_START (UL(0xffffffffffffffff) - \
- (UL(1) << VA_BITS) + 1)
-#define PAGE_OFFSET (UL(0xffffffffffffffff) - \
(UL(1) << (VA_BITS - 1)) + 1)
-#define PAGE_OFFSET_END (~0UL)
+#define PAGE_OFFSET (UL(0xffffffffffffffff) - \
+ (UL(1) << VA_BITS) + 1)
+#define PAGE_OFFSET_END (VA_START)
#define KIMAGE_VADDR (MODULES_END)
#define MODULES_END (MODULES_VADDR + MODULES_VSIZE)
#define MODULES_VADDR (VA_START + KASAN_SHADOW_SIZE)
#define MODULES_VSIZE (SZ_128M)
-#define VMEMMAP_START (PAGE_OFFSET - VMEMMAP_SIZE)
+#define VMEMMAP_START (-VMEMMAP_SIZE)
#define PCI_IO_END (VMEMMAP_START - SZ_2M)
#define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE)
#define FIXADDR_TOP (PCI_IO_START - SZ_2M)
@@ -223,7 +223,7 @@ static inline unsigned long kaslr_offset(void)
* space. Testing the top bit for the start of the region is a
* sufficient check.
*/
-#define __is_lm_address(addr) (!!((addr) & BIT(VA_BITS - 1)))
+#define __is_lm_address(addr) (!((addr) & BIT(VA_BITS - 1)))

#define __lm_to_phys(addr) (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET)
#define __kimg_to_phys(addr) ((addr) - kimage_voffset)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 72cde7268cad..054b37143a50 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -31,7 +31,7 @@
* and fixed mappings
*/
#define VMALLOC_START (MODULES_END)
-#define VMALLOC_END (PAGE_OFFSET - PUD_SIZE - VMEMMAP_SIZE - SZ_64K)
+#define VMALLOC_END (- PUD_SIZE - VMEMMAP_SIZE - SZ_64K)

#define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 5a6e1f3611eb..99b1d1ebe551 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -834,7 +834,7 @@ static bool hyp_flip_space(const struct arm64_cpu_capabilities *entry,
* - the idmap doesn't clash with it,
* - the kernel is not running at EL2.
*/
- return idmap_addr > GENMASK(VA_BITS - 2, 0) && !is_kernel_in_hyp_mode();
+ return idmap_addr <= GENMASK(VA_BITS - 2, 0) && !is_kernel_in_hyp_mode();
}

static bool has_no_fpsimd(const struct arm64_cpu_capabilities *entry, int __unused)
diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index ca74a2aace42..b7b09c0fc50d 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -30,6 +30,8 @@
#include <asm/ptdump.h>

static const struct addr_marker address_markers[] = {
+ { PAGE_OFFSET, "Linear Mapping start" },
+ { VA_START, "Linear Mapping end" },
#ifdef CONFIG_KASAN
{ KASAN_SHADOW_START, "Kasan shadow start" },
{ KASAN_SHADOW_END, "Kasan shadow end" },
@@ -43,10 +45,8 @@ static const struct addr_marker address_markers[] = {
{ PCI_IO_START, "PCI I/O start" },
{ PCI_IO_END, "PCI I/O end" },
#ifdef CONFIG_SPARSEMEM_VMEMMAP
- { VMEMMAP_START, "vmemmap start" },
- { VMEMMAP_START + VMEMMAP_SIZE, "vmemmap end" },
+ { VMEMMAP_START, "vmemmap" },
#endif
- { PAGE_OFFSET, "Linear Mapping" },
{ -1, NULL },
};

@@ -375,7 +375,7 @@ static void ptdump_initialize(void)
static struct ptdump_info kernel_ptdump_info = {
.mm = &init_mm,
.markers = address_markers,
- .base_addr = VA_START,
+ .base_addr = PAGE_OFFSET,
};

void ptdump_check_wx(void)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 00e7b900ca41..230d78b75831 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -361,19 +361,12 @@ static void __init fdt_enforce_memory_region(void)

void __init arm64_memblock_init(void)
{
- const s64 linear_region_size = -(s64)PAGE_OFFSET;
+ const s64 linear_region_size = BIT(VA_BITS - 1);

/* Handle linux,usable-memory-range property */
fdt_enforce_memory_region();

/*
- * Ensure that the linear region takes up exactly half of the kernel
- * virtual address space. This way, we can distinguish a linear address
- * from a kernel/module/vmalloc address by testing a single bit.
- */
- BUILD_BUG_ON(linear_region_size != BIT(VA_BITS - 1));
-
- /*
* Select a suitable value for the base of physical memory.
*/
memstart_addr = round_down(memblock_start_of_DRAM(),
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index acba49fb5aac..5aef679e61c6 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -205,10 +205,10 @@ void __init kasan_init(void)
kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
pfn_to_nid(virt_to_pfn(lm_alias(_text))));

- kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
+ kasan_populate_zero_shadow(kasan_mem_to_shadow((void *) VA_START),
(void *)mod_shadow_start);
kasan_populate_zero_shadow((void *)kimg_shadow_end,
- kasan_mem_to_shadow((void *)PAGE_OFFSET));
+ (void *)KASAN_SHADOW_END);

if (kimg_shadow_start > mod_shadow_end)
kasan_populate_zero_shadow((void *)mod_shadow_end,
--
2.11.0