Commit 14c127c9 authored by Steve Capper's avatar Steve Capper Committed by Will Deacon
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arm64: mm: Flip kernel VA space 



In order to allow for a KASAN shadow that changes size at boot time, one
must fix the KASAN_SHADOW_END for both 48 & 52-bit VAs and "grow" the
start address. Also, it is highly desirable to maintain the same
function addresses in the kernel .text between VA sizes. Both of these
requirements necessitate us to flip the kernel address space halves s.t.
the direct linear map occupies the lower addresses.

This patch puts the direct linear map in the lower addresses of the
kernel VA range and everything else in the higher ranges.

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

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

As part of the re-arrangement, a guard region of 2MB (to preserve
alignment for fixed map) is added after the vmemmap. Otherwise the
vmemmap could intersect with IS_ERR pointers.

Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarSteve Capper <steve.capper@arm.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 9cb1c5dd

arch/arm64/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -130,7 +130,7 @@ KBUILD_AFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT) 
#				 - (1 << (64 - KASAN_SHADOW_SCALE_SHIFT))

# 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 - $(KASAN_SHADOW_SCALE_SHIFT))) \

	- (1 << (64 - 32 - $(KASAN_SHADOW_SCALE_SHIFT))) )) )

arch/arm64/include/asm/memory.h

+4 −4
Original line number Diff line number Diff line
@@ -38,9 +38,9 @@ 
 */

#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		(UL(0xffffffffffffffff) - \

	(UL(1) << VA_BITS) + 1)

#define KIMAGE_VADDR		(MODULES_END)

#define BPF_JIT_REGION_START	(VA_START + KASAN_SHADOW_SIZE)

#define BPF_JIT_REGION_SIZE	(SZ_128M)
@@ -48,7 +48,7 @@ 
#define MODULES_END		(MODULES_VADDR + MODULES_VSIZE)

#define MODULES_VADDR		(BPF_JIT_REGION_END)

#define MODULES_VSIZE		(SZ_128M)

#define VMEMMAP_START		(PAGE_OFFSET - VMEMMAP_SIZE)

#define VMEMMAP_START		(-VMEMMAP_SIZE - SZ_2M)

#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)
@@ -231,7 +231,7 @@ static inline const void *__tag_set(const void *addr, u8 tag) 
 * 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)

arch/arm64/include/asm/pgtable.h

+1 −1
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ 
 *	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))

arch/arm64/kernel/hibernate.c

+1 −1
Original line number Diff line number Diff line
@@ -496,7 +496,7 @@ int swsusp_arch_resume(void) 
		rc = -ENOMEM;

		goto out;

	}

	rc = copy_page_tables(tmp_pg_dir, PAGE_OFFSET, 0);

	rc = copy_page_tables(tmp_pg_dir, PAGE_OFFSET, VA_START);

	if (rc)

		goto out;

arch/arm64/mm/dump.c

+3 −2
Original line number Diff line number Diff line
@@ -26,6 +26,8 @@ 
#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" },
@@ -42,7 +44,6 @@ static const struct addr_marker address_markers[] = { 
	{ VMEMMAP_START,		"vmemmap start" },

	{ VMEMMAP_START + VMEMMAP_SIZE,	"vmemmap end" },

#endif

	{ PAGE_OFFSET,			"Linear mapping" },

	{ -1,				NULL },

};
@@ -376,7 +377,7 @@ 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)

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