From: Ard Biesheuvel ardb@kernel.org

commit 7bc1a0f9e1765830e945669c99c59c35cf9bca82 upstream.

On arm64, the global variable memstart_addr represents the physical address of PAGE_OFFSET, and so physical to virtual translations or vice versa used to come down to simple additions or subtractions involving the values of PAGE_OFFSET and memstart_addr.

When support for 52-bit virtual addressing was introduced, we had to deal with PAGE_OFFSET potentially being outside of the region that can be covered by the virtual range (as the 52-bit VA capable build needs to be able to run on systems that are only 48-bit VA capable), and for this reason, another translation was introduced, and recorded in the global variable physvirt_offset.

However, if we go back to the original definition of memstart_addr, i.e., the physical address of PAGE_OFFSET, it turns out that there is no need for two separate translations: instead, we can simply subtract the size of the unaddressable VA space from memstart_addr to make the available physical memory appear in the 48-bit addressable VA region.

This simplifies things, but also fixes a bug on KASLR builds, which may update memstart_addr later on in arm64_memblock_init(), but fails to update vmemmap and physvirt_offset accordingly.

Fixes: 5383cc6efed1 ("arm64: mm: Introduce vabits_actual") Signed-off-by: Ard Biesheuvel ardb@kernel.org Reviewed-by: Steve Capper steve.capper@arm.com Link: https://lore.kernel.org/r/20201008153602.9467-2-ardb@kernel.org Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Vincenzo Frascino vincenzo.frascino@arm.com --- arch/arm64/include/asm/memory.h | 5 ++--- arch/arm64/include/asm/pgtable.h | 4 ++-- arch/arm64/mm/init.c | 30 ++++++++++-------------------- 3 files changed, 14 insertions(+), 25 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index 08df42e4db96..51d867cf146c 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -178,7 +178,6 @@ extern u64 vabits_actual; #include <linux/bitops.h> #include <linux/mmdebug.h>

-extern s64 physvirt_offset; extern s64 memstart_addr; /* PHYS_OFFSET - the physical address of the start of memory. */ #define PHYS_OFFSET ({ VM_BUG_ON(memstart_addr & 1); memstart_addr; }) @@ -254,7 +253,7 @@ static inline const void *__tag_set(const void *addr, u8 tag) */ #define __is_lm_address(addr) (!(((u64)addr) & BIT(vabits_actual - 1)))

-#define __lm_to_phys(addr) (((addr) + physvirt_offset)) +#define __lm_to_phys(addr) (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET) #define __kimg_to_phys(addr) ((addr) - kimage_voffset)

#define __virt_to_phys_nodebug(x) ({ \ @@ -272,7 +271,7 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x); #define __phys_addr_symbol(x) __pa_symbol_nodebug(x) #endif /* CONFIG_DEBUG_VIRTUAL */

-#define __phys_to_virt(x) ((unsigned long)((x) - physvirt_offset)) +#define __phys_to_virt(x) ((unsigned long)((x) - PHYS_OFFSET) | PAGE_OFFSET) #define __phys_to_kimg(x) ((unsigned long)((x) + kimage_voffset))

/* diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 69dfc340e71b..8c420f916fe2 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -23,6 +23,8 @@ #define VMALLOC_START (MODULES_END) #define VMALLOC_END (- PUD_SIZE - VMEMMAP_SIZE - SZ_64K)

+#define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT)) + #define FIRST_USER_ADDRESS 0UL

#ifndef __ASSEMBLY__ @@ -33,8 +35,6 @@ #include <linux/mm_types.h> #include <linux/sched.h>

-extern struct page *vmemmap; - extern void __pte_error(const char *file, int line, unsigned long val); extern void __pmd_error(const char *file, int line, unsigned long val); extern void __pud_error(const char *file, int line, unsigned long val); diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 45c00a54909c..602bd19630ff 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -50,12 +50,6 @@ s64 memstart_addr __ro_after_init = -1; EXPORT_SYMBOL(memstart_addr);

-s64 physvirt_offset __ro_after_init; -EXPORT_SYMBOL(physvirt_offset); - -struct page *vmemmap __ro_after_init; -EXPORT_SYMBOL(vmemmap); - phys_addr_t arm64_dma_phys_limit __ro_after_init;

#ifdef CONFIG_KEXEC_CORE @@ -321,20 +315,6 @@ void __init arm64_memblock_init(void) memstart_addr = round_down(memblock_start_of_DRAM(), ARM64_MEMSTART_ALIGN);

- physvirt_offset = PHYS_OFFSET - PAGE_OFFSET; - - vmemmap = ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT)); - - /* - * If we are running with a 52-bit kernel VA config on a system that - * does not support it, we have to offset our vmemmap and physvirt_offset - * s.t. we avoid the 52-bit portion of the direct linear map - */ - if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52)) { - vmemmap += (_PAGE_OFFSET(48) - _PAGE_OFFSET(52)) >> PAGE_SHIFT; - physvirt_offset = PHYS_OFFSET - _PAGE_OFFSET(48); - } - /* * Remove the memory that we will not be able to cover with the * linear mapping. Take care not to clip the kernel which may be @@ -349,6 +329,16 @@ void __init arm64_memblock_init(void) memblock_remove(0, memstart_addr); }

+ /* + * If we are running with a 52-bit kernel VA config on a system that + * does not support it, we have to place the available physical + * memory in the 48-bit addressable part of the linear region, i.e., + * we have to move it upward. Since memstart_addr represents the + * physical address of PAGE_OFFSET, we have to *subtract* from it. + */ + if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52) && (vabits_actual != 52)) + memstart_addr -= _PAGE_OFFSET(48) - _PAGE_OFFSET(52); + /* * Apply the memory limit if it was set. Since the kernel may be loaded * high up in memory, add back the kernel region that must be accessible