626e5dce00
If the kernel is built CONFIG_CFI_CLANG=y, reading smaps may cause a panic. This is due to a failed CFI check; which is triggered becuase the signature of the function pointer for printing smaps padding VMAs does not match exactly with that for show_smap(). Fix this by casting the function pointer to the expected type based on whether printing maps or smaps padding. Bug: 330117029 Bug: 327600007 Bug: 330767927 Bug: 328266487 Bug: 329803029 Change-Id: I65564a547dacbc4131f8557344c8c96e51f90cd5 Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
134 lines
3.9 KiB
C
134 lines
3.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_PAGE_SIZE_MIGRATION_H
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#define _LINUX_PAGE_SIZE_MIGRATION_H
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/*
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* Page Size Migration
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*
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* Copyright (c) 2024, Google LLC.
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* Author: Kalesh Singh <kaleshsingh@goole.com>
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*
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* This file contains the APIs for mitigations to ensure
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* app compatibility during the transition from 4kB to 16kB
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* page size in Android.
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*/
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#include <linux/mm.h>
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#include <linux/seq_file.h>
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#include <linux/sizes.h>
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/*
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* vm_flags representation of VMA padding pages.
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*
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* This allows the kernel to identify the portion of an ELF LOAD segment VMA
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* that is padding.
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*
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* 4 high bits of vm_flags [63,60] are used to represent ELF segment padding
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* up to 60kB, which is sufficient for ELFs of both 16kB and 64kB segment
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* alignment (p_align).
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*
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* The representation is illustrated below.
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*
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* 63 62 61 60
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* _________ _________ _________ _________
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* | Bit 3 | Bit 2 | Bit 1 | Bit 0 |
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* | of 4kB | of 4kB | of 4kB | of 4kB |
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* | chunks | chunks | chunks | chunks |
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* |_________|_________|_________|_________|
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*/
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#define VM_PAD_WIDTH 4
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#define VM_PAD_SHIFT (BITS_PER_LONG - VM_PAD_WIDTH)
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#define VM_TOTAL_PAD_PAGES ((1ULL << VM_PAD_WIDTH) - 1)
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#define VM_PAD_MASK (VM_TOTAL_PAD_PAGES << VM_PAD_SHIFT)
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#define VMA_PAD_START(vma) (vma->vm_end - (vma_pad_pages(vma) << PAGE_SHIFT))
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#if PAGE_SIZE == SZ_4K && defined(CONFIG_64BIT)
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extern void vma_set_pad_pages(struct vm_area_struct *vma,
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unsigned long nr_pages);
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extern unsigned long vma_pad_pages(struct vm_area_struct *vma);
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extern void madvise_vma_pad_pages(struct vm_area_struct *vma,
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unsigned long start, unsigned long end);
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extern struct vm_area_struct *get_pad_vma(struct vm_area_struct *vma);
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extern struct vm_area_struct *get_data_vma(struct vm_area_struct *vma);
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extern void show_map_pad_vma(struct vm_area_struct *vma,
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struct vm_area_struct *pad,
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struct seq_file *m, void *func, bool smaps);
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extern void split_pad_vma(struct vm_area_struct *vma, struct vm_area_struct *new,
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unsigned long addr, int new_below);
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#else /* PAGE_SIZE != SZ_4K || !defined(CONFIG_64BIT) */
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static inline void vma_set_pad_pages(struct vm_area_struct *vma,
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unsigned long nr_pages)
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{
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}
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static inline unsigned long vma_pad_pages(struct vm_area_struct *vma)
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{
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return 0;
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}
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static inline void madvise_vma_pad_pages(struct vm_area_struct *vma,
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unsigned long start, unsigned long end)
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{
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}
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static inline struct vm_area_struct *get_pad_vma(struct vm_area_struct *vma)
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{
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return NULL;
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}
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static inline struct vm_area_struct *get_data_vma(struct vm_area_struct *vma)
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{
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return vma;
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}
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static inline void show_map_pad_vma(struct vm_area_struct *vma,
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struct vm_area_struct *pad,
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struct seq_file *m, void *func, bool smaps)
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{
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}
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static inline void split_pad_vma(struct vm_area_struct *vma, struct vm_area_struct *new,
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unsigned long addr, int new_below)
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{
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}
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#endif /* PAGE_SIZE == SZ_4K && defined(CONFIG_64BIT) */
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static inline unsigned long vma_data_pages(struct vm_area_struct *vma)
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{
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return vma_pages(vma) - vma_pad_pages(vma);
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}
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/*
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* Sets the correct padding bits / flags for a VMA split.
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*/
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static inline unsigned long vma_pad_fixup_flags(struct vm_area_struct *vma,
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unsigned long newflags)
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{
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if (newflags & VM_PAD_MASK)
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return (newflags & ~VM_PAD_MASK) | (vma->vm_flags & VM_PAD_MASK);
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else
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return newflags;
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}
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/*
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* Merging of padding VMAs is uncommon, as padding is only allowed
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* from the linker context.
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*
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* To simplify the semantics, adjacent VMAs with padding are not
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* allowed to merge.
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*/
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static inline bool is_mergable_pad_vma(struct vm_area_struct *vma,
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unsigned long vm_flags)
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{
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/* Padding VMAs cannot be merged with other padding or real VMAs */
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return !((vma->vm_flags | vm_flags) & VM_PAD_MASK);
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}
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#endif /* _LINUX_PAGE_SIZE_MIGRATION_H */
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