From: Ard Biesheuvel <[email protected]> The zero page should contain only zero bytes, and so mapping it read-write is unnecessary. Combine it with reserved_pg_dir, which lives in the read-only region of the kernel, and already serves a similar purpose.
Reviewed-by: Ryan Roberts <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]> --- arch/arm64/kernel/vmlinux.lds.S | 1 + arch/arm64/mm/mmu.c | 3 +-- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 2964aad0362e..2d021a576e50 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -229,6 +229,7 @@ SECTIONS #endif reserved_pg_dir = .; + empty_zero_page = .; . += PAGE_SIZE; swapper_pg_dir = .; diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index a6a00accf4f9..795743913ce5 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -66,9 +66,8 @@ long __section(".mmuoff.data.write") __early_cpu_boot_status; /* * Empty_zero_page is a special page that is used for zero-initialized data - * and COW. + * and COW. Defined in the linker script. */ -unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss; EXPORT_SYMBOL(empty_zero_page); static DEFINE_SPINLOCK(swapper_pgdir_lock); -- 2.53.0.959.g497ff81fa9-goog
