| /* SPDX-License-Identifier: GPL-2.0 */ |
| #ifndef _LINUX_PAGE_SIZE_MIGRATION_INLINE_H |
| #define _LINUX_PAGE_SIZE_MIGRATION_INLINE_H |
| |
| /* |
| * Page Size Migration |
| * |
| * Copyright (c) 2024, Google LLC. |
| * Author: Kalesh Singh <[email protected]> |
| * |
| * This file contains inline APIs for mitigations to ensure |
| * app compatibility during the transition from 4kB to 16kB |
| * page size in Android. |
| */ |
| |
| #include <linux/mm_types.h> |
| #include <linux/sizes.h> |
| |
| #include <asm/page.h> |
| |
| /* |
| * vm_flags representation of VMA padding pages. |
| * |
| * This allows the kernel to identify the portion of an ELF LOAD segment VMA |
| * that is padding. |
| * |
| * 4 high bits of vm_flags [62,59] are used to represent ELF segment padding |
| * up to 60kB, which is sufficient for ELFs of both 16kB and 64kB segment |
| * alignment (p_align). |
| * |
| * The representation is illustrated below. |
| * |
| * 62 61 60 59 |
| * _________ _________ _________ _________ |
| * | Bit 3 | Bit 2 | Bit 1 | Bit 0 | |
| * | of 4kB | of 4kB | of 4kB | of 4kB | |
| * | chunks | chunks | chunks | chunks | |
| * |_________|_________|_________|_________| |
| * |
| * NOTE: Bit 63 is already used by mseal() |
| */ |
| |
| #define VM_PAD_WIDTH 4 |
| #define VM_PAD_SHIFT (BITS_PER_LONG - VM_PAD_WIDTH - 1) |
| #define VM_TOTAL_PAD_PAGES ((1ULL << VM_PAD_WIDTH) - 1) |
| #define VM_PAD_MASK (VM_TOTAL_PAD_PAGES << VM_PAD_SHIFT) |
| #define VMA_PAD_START(vma) (vma->vm_end - (vma_pad_pages(vma) << PAGE_SHIFT)) |
| |
| #if PAGE_SIZE == SZ_4K && defined(CONFIG_64BIT) |
| /* |
| * Sets the correct padding bits / flags for a VMA split. |
| */ |
| static inline unsigned long vma_pad_fixup_flags(struct vm_area_struct *vma, |
| unsigned long newflags) |
| { |
| if (newflags & VM_PAD_MASK) |
| return (newflags & ~VM_PAD_MASK) | (vma->vm_flags & VM_PAD_MASK); |
| else |
| return newflags; |
| } |
| #else /* PAGE_SIZE != SZ_4K || !defined(CONFIG_64BIT) */ |
| static inline unsigned long vma_pad_fixup_flags(struct vm_area_struct *vma, |
| unsigned long newflags) |
| { |
| return newflags; |
| } |
| #endif /* PAGE_SIZE == SZ_4K && defined(CONFIG_64BIT) */ |
| |
| #endif /* _LINUX_PAGE_SIZE_MIGRATION_INLINE_H */ |
