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https://gitee.com/bianbu-linux/linux-6.6
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The x86 Shadow stack feature includes a new type of memory called shadow stack. This shadow stack memory has some unusual properties, which requires some core mm changes to function properly. One of these unusual properties is that shadow stack memory is writable, but only in limited ways. These limits are applied via a specific PTE bit combination. Nevertheless, the memory is writable, and core mm code will need to apply the writable permissions in the typical paths that call pte_mkwrite(). The goal is to make pte_mkwrite() take a VMA, so that the x86 implementation of it can know whether to create regular writable or shadow stack mappings. But there are a couple of challenges to this. Modifying the signatures of each arch pte_mkwrite() implementation would be error prone because some are generated with macros and would need to be re-implemented. Also, some pte_mkwrite() callers operate on kernel memory without a VMA. So this can be done in a three step process. First pte_mkwrite() can be renamed to pte_mkwrite_novma() in each arch, with a generic pte_mkwrite() added that just calls pte_mkwrite_novma(). Next callers without a VMA can be moved to pte_mkwrite_novma(). And lastly, pte_mkwrite() and all callers can be changed to take/pass a VMA. Start the process by renaming pte_mkwrite() to pte_mkwrite_novma() and adding the pte_mkwrite() wrapper in linux/pgtable.h. Apply the same pattern for pmd_mkwrite(). Since not all archs have a pmd_mkwrite_novma(), create a new arch config HAS_HUGE_PAGE that can be used to tell if pmd_mkwrite() should be defined. Otherwise in the !HAS_HUGE_PAGE cases the compiler would not be able to find pmd_mkwrite_novma(). No functional change. Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/lkml/CAHk-=wiZjSu7c9sFYZb3q04108stgHff2wfbokGCCgW7riz+8Q@mail.gmail.com/ Link: https://lore.kernel.org/all/20230613001108.3040476-2-rick.p.edgecombe%40intel.com
149 lines
4.8 KiB
C
149 lines
4.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*/
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/*
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* page table flags for software walked/managed MMUv3 (ARC700) and MMUv4 (HS)
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* There correspond to the corresponding bits in the TLB
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*/
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#ifndef _ASM_ARC_PGTABLE_BITS_ARCV2_H
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#define _ASM_ARC_PGTABLE_BITS_ARCV2_H
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#ifdef CONFIG_ARC_CACHE_PAGES
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#define _PAGE_CACHEABLE (1 << 0) /* Cached (H) */
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#else
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#define _PAGE_CACHEABLE 0
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#endif
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#define _PAGE_EXECUTE (1 << 1) /* User Execute (H) */
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#define _PAGE_WRITE (1 << 2) /* User Write (H) */
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#define _PAGE_READ (1 << 3) /* User Read (H) */
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#define _PAGE_ACCESSED (1 << 4) /* Accessed (s) */
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#define _PAGE_DIRTY (1 << 5) /* Modified (s) */
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#define _PAGE_SPECIAL (1 << 6)
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#define _PAGE_GLOBAL (1 << 8) /* ASID agnostic (H) */
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#define _PAGE_PRESENT (1 << 9) /* PTE/TLB Valid (H) */
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/* We borrow bit 5 to store the exclusive marker in swap PTEs. */
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#define _PAGE_SWP_EXCLUSIVE _PAGE_DIRTY
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#ifdef CONFIG_ARC_MMU_V4
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#define _PAGE_HW_SZ (1 << 10) /* Normal/super (H) */
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#else
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#define _PAGE_HW_SZ 0
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#endif
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/* Defaults for every user page */
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#define ___DEF (_PAGE_PRESENT | _PAGE_CACHEABLE)
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/* Set of bits not changed in pte_modify */
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#define _PAGE_CHG_MASK (PAGE_MASK_PHYS | _PAGE_ACCESSED | _PAGE_DIRTY | \
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_PAGE_SPECIAL)
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/* More Abbrevaited helpers */
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#define PAGE_U_NONE __pgprot(___DEF)
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#define PAGE_U_R __pgprot(___DEF | _PAGE_READ)
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#define PAGE_U_W_R __pgprot(___DEF | _PAGE_READ | _PAGE_WRITE)
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#define PAGE_U_X_R __pgprot(___DEF | _PAGE_READ | _PAGE_EXECUTE)
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#define PAGE_U_X_W_R __pgprot(___DEF \
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| _PAGE_READ | _PAGE_WRITE | _PAGE_EXECUTE)
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#define PAGE_KERNEL __pgprot(___DEF | _PAGE_GLOBAL \
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| _PAGE_READ | _PAGE_WRITE | _PAGE_EXECUTE)
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#define PAGE_SHARED PAGE_U_W_R
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#define pgprot_noncached(prot) (__pgprot(pgprot_val(prot) & ~_PAGE_CACHEABLE))
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/*
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* Mapping of vm_flags (Generic VM) to PTE flags (arch specific)
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*
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* Certain cases have 1:1 mapping
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* e.g. __P101 means VM_READ, VM_EXEC and !VM_SHARED
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* which directly corresponds to PAGE_U_X_R
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*
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* Other rules which cause the divergence from 1:1 mapping
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*
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* 1. Although ARC700 can do exclusive execute/write protection (meaning R
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* can be tracked independet of X/W unlike some other CPUs), still to
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* keep things consistent with other archs:
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* -Write implies Read: W => R
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* -Execute implies Read: X => R
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*
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* 2. Pvt Writable doesn't have Write Enabled initially: Pvt-W => !W
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* This is to enable COW mechanism
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*/
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/* xwr */
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#ifndef __ASSEMBLY__
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#define pte_write(pte) (pte_val(pte) & _PAGE_WRITE)
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#define pte_dirty(pte) (pte_val(pte) & _PAGE_DIRTY)
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#define pte_young(pte) (pte_val(pte) & _PAGE_ACCESSED)
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#define pte_special(pte) (pte_val(pte) & _PAGE_SPECIAL)
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#define PTE_BIT_FUNC(fn, op) \
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static inline pte_t pte_##fn(pte_t pte) { pte_val(pte) op; return pte; }
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PTE_BIT_FUNC(mknotpresent, &= ~(_PAGE_PRESENT));
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PTE_BIT_FUNC(wrprotect, &= ~(_PAGE_WRITE));
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PTE_BIT_FUNC(mkwrite_novma, |= (_PAGE_WRITE));
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PTE_BIT_FUNC(mkclean, &= ~(_PAGE_DIRTY));
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PTE_BIT_FUNC(mkdirty, |= (_PAGE_DIRTY));
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PTE_BIT_FUNC(mkold, &= ~(_PAGE_ACCESSED));
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PTE_BIT_FUNC(mkyoung, |= (_PAGE_ACCESSED));
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PTE_BIT_FUNC(mkspecial, |= (_PAGE_SPECIAL));
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PTE_BIT_FUNC(mkhuge, |= (_PAGE_HW_SZ));
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static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
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{
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return __pte((pte_val(pte) & _PAGE_CHG_MASK) | pgprot_val(newprot));
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}
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static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
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pte_t *ptep, pte_t pteval)
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{
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set_pte(ptep, pteval);
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}
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void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
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pte_t *ptep);
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/*
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* Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
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* are !pte_none() && !pte_present().
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*
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* Format of swap PTEs:
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*
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* 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
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* 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
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* <-------------- offset -------------> <--- zero --> E < type ->
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*
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* E is the exclusive marker that is not stored in swap entries.
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* The zero'ed bits include _PAGE_PRESENT.
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*/
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#define __swp_entry(type, off) ((swp_entry_t) \
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{ ((type) & 0x1f) | ((off) << 13) })
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/* Decode a PTE containing swap "identifier "into constituents */
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#define __swp_type(pte_lookalike) (((pte_lookalike).val) & 0x1f)
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#define __swp_offset(pte_lookalike) ((pte_lookalike).val >> 13)
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#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
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#define __swp_entry_to_pte(x) ((pte_t) { (x).val })
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static inline int pte_swp_exclusive(pte_t pte)
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{
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return pte_val(pte) & _PAGE_SWP_EXCLUSIVE;
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}
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PTE_BIT_FUNC(swp_mkexclusive, |= (_PAGE_SWP_EXCLUSIVE));
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PTE_BIT_FUNC(swp_clear_exclusive, &= ~(_PAGE_SWP_EXCLUSIVE));
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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#include <asm/hugepage.h>
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#endif
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#endif /* __ASSEMBLY__ */
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#endif
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