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bianbu-linux-6.6/arch/um/include/asm/pgtable.h
Rick Edgecombe 2f0584f3f4 mm: Rename arch pte_mkwrite()'s to pte_mkwrite_novma() 
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
2023-07-11 14:10:56 -07:00

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Copyright 2003 PathScale, Inc.
* Derived from include/asm-i386/pgtable.h
*/
#ifndef __UM_PGTABLE_H
#define __UM_PGTABLE_H
#include <asm/fixmap.h>
#define _PAGE_PRESENT 0x001
#define _PAGE_NEWPAGE 0x002
#define _PAGE_NEWPROT 0x004
#define _PAGE_RW 0x020
#define _PAGE_USER 0x040
#define _PAGE_ACCESSED 0x080
#define _PAGE_DIRTY 0x100
/* If _PAGE_PRESENT is clear, we use these: */
#define _PAGE_PROTNONE 0x010 /* if the user mapped it with PROT_NONE;
pte_present gives true */
/* We borrow bit 10 to store the exclusive marker in swap PTEs. */
#define _PAGE_SWP_EXCLUSIVE 0x400
#ifdef CONFIG_3_LEVEL_PGTABLES
#include <asm/pgtable-3level.h>
#else
#include <asm/pgtable-2level.h>
#endif
extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
/* zero page used for uninitialized stuff */
extern unsigned long *empty_zero_page;
/* Just any arbitrary offset to the start of the vmalloc VM area: the
* current 8MB value just means that there will be a 8MB "hole" after the
* physical memory until the kernel virtual memory starts. That means that
* any out-of-bounds memory accesses will hopefully be caught.
* The vmalloc() routines leaves a hole of 4kB between each vmalloced
* area for the same reason. ;)
*/
extern unsigned long end_iomem;
#define VMALLOC_OFFSET (__va_space)
#define VMALLOC_START ((end_iomem + VMALLOC_OFFSET) & ~(VMALLOC_OFFSET-1))
#define PKMAP_BASE ((FIXADDR_START - LAST_PKMAP * PAGE_SIZE) & PMD_MASK)
#define VMALLOC_END (FIXADDR_START-2*PAGE_SIZE)
#define MODULES_VADDR VMALLOC_START
#define MODULES_END VMALLOC_END
#define MODULES_LEN (MODULES_VADDR - MODULES_END)
#define _PAGE_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | _PAGE_ACCESSED | _PAGE_DIRTY)
#define _KERNPG_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
#define _PAGE_CHG_MASK (PAGE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY)
#define __PAGE_KERNEL_EXEC \
(_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY | _PAGE_ACCESSED)
#define PAGE_NONE __pgprot(_PAGE_PROTNONE | _PAGE_ACCESSED)
#define PAGE_SHARED __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_USER | _PAGE_ACCESSED)
#define PAGE_COPY __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_ACCESSED)
#define PAGE_READONLY __pgprot(_PAGE_PRESENT | _PAGE_USER | _PAGE_ACCESSED)
#define PAGE_KERNEL __pgprot(_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY | _PAGE_ACCESSED)
#define PAGE_KERNEL_EXEC __pgprot(__PAGE_KERNEL_EXEC)
/*
* The i386 can't do page protection for execute, and considers that the same
* are read.
* Also, write permissions imply read permissions. This is the closest we can
* get..
*/
/*
* ZERO_PAGE is a global shared page that is always zero: used
* for zero-mapped memory areas etc..
*/
#define ZERO_PAGE(vaddr) virt_to_page(empty_zero_page)
#define pte_clear(mm,addr,xp) pte_set_val(*(xp), (phys_t) 0, __pgprot(_PAGE_NEWPAGE))
#define pmd_none(x) (!((unsigned long)pmd_val(x) & ~_PAGE_NEWPAGE))
#define pmd_bad(x) ((pmd_val(x) & (~PAGE_MASK & ~_PAGE_USER)) != _KERNPG_TABLE)
#define pmd_present(x) (pmd_val(x) & _PAGE_PRESENT)
#define pmd_clear(xp) do { pmd_val(*(xp)) = _PAGE_NEWPAGE; } while (0)
#define pmd_newpage(x) (pmd_val(x) & _PAGE_NEWPAGE)
#define pmd_mkuptodate(x) (pmd_val(x) &= ~_PAGE_NEWPAGE)
#define pud_newpage(x) (pud_val(x) & _PAGE_NEWPAGE)
#define pud_mkuptodate(x) (pud_val(x) &= ~_PAGE_NEWPAGE)
#define p4d_newpage(x) (p4d_val(x) & _PAGE_NEWPAGE)
#define p4d_mkuptodate(x) (p4d_val(x) &= ~_PAGE_NEWPAGE)
#define pmd_pfn(pmd) (pmd_val(pmd) >> PAGE_SHIFT)
#define pmd_page(pmd) phys_to_page(pmd_val(pmd) & PAGE_MASK)
#define pte_page(x) pfn_to_page(pte_pfn(x))
#define pte_present(x) pte_get_bits(x, (_PAGE_PRESENT | _PAGE_PROTNONE))
/*
* =================================
* Flags checking section.
* =================================
*/
static inline int pte_none(pte_t pte)
{
return pte_is_zero(pte);
}
/*
* The following only work if pte_present() is true.
* Undefined behaviour if not..
*/
static inline int pte_read(pte_t pte)
{
return((pte_get_bits(pte, _PAGE_USER)) &&
!(pte_get_bits(pte, _PAGE_PROTNONE)));
}
static inline int pte_exec(pte_t pte){
return((pte_get_bits(pte, _PAGE_USER)) &&
!(pte_get_bits(pte, _PAGE_PROTNONE)));
}
static inline int pte_write(pte_t pte)
{
return((pte_get_bits(pte, _PAGE_RW)) &&
!(pte_get_bits(pte, _PAGE_PROTNONE)));
}
static inline int pte_dirty(pte_t pte)
{
return pte_get_bits(pte, _PAGE_DIRTY);
}
static inline int pte_young(pte_t pte)
{
return pte_get_bits(pte, _PAGE_ACCESSED);
}
static inline int pte_newpage(pte_t pte)
{
return pte_get_bits(pte, _PAGE_NEWPAGE);
}
static inline int pte_newprot(pte_t pte)
{
return(pte_present(pte) && (pte_get_bits(pte, _PAGE_NEWPROT)));
}
/*
* =================================
* Flags setting section.
* =================================
*/
static inline pte_t pte_mknewprot(pte_t pte)
{
pte_set_bits(pte, _PAGE_NEWPROT);
return(pte);
}
static inline pte_t pte_mkclean(pte_t pte)
{
pte_clear_bits(pte, _PAGE_DIRTY);
return(pte);
}
static inline pte_t pte_mkold(pte_t pte)
{
pte_clear_bits(pte, _PAGE_ACCESSED);
return(pte);
}
static inline pte_t pte_wrprotect(pte_t pte)
{
if (likely(pte_get_bits(pte, _PAGE_RW)))
pte_clear_bits(pte, _PAGE_RW);
else
return pte;
return(pte_mknewprot(pte));
}
static inline pte_t pte_mkread(pte_t pte)
{
if (unlikely(pte_get_bits(pte, _PAGE_USER)))
return pte;
pte_set_bits(pte, _PAGE_USER);
return(pte_mknewprot(pte));
}
static inline pte_t pte_mkdirty(pte_t pte)
{
pte_set_bits(pte, _PAGE_DIRTY);
return(pte);
}
static inline pte_t pte_mkyoung(pte_t pte)
{
pte_set_bits(pte, _PAGE_ACCESSED);
return(pte);
}
static inline pte_t pte_mkwrite_novma(pte_t pte)
{
if (unlikely(pte_get_bits(pte, _PAGE_RW)))
return pte;
pte_set_bits(pte, _PAGE_RW);
return(pte_mknewprot(pte));
}
static inline pte_t pte_mkuptodate(pte_t pte)
{
pte_clear_bits(pte, _PAGE_NEWPAGE);
if(pte_present(pte))
pte_clear_bits(pte, _PAGE_NEWPROT);
return(pte);
}
static inline pte_t pte_mknewpage(pte_t pte)
{
pte_set_bits(pte, _PAGE_NEWPAGE);
return(pte);
}
static inline void set_pte(pte_t *pteptr, pte_t pteval)
{
pte_copy(*pteptr, pteval);
/* If it's a swap entry, it needs to be marked _PAGE_NEWPAGE so
* fix_range knows to unmap it. _PAGE_NEWPROT is specific to
* mapped pages.
*/
*pteptr = pte_mknewpage(*pteptr);
if(pte_present(*pteptr)) *pteptr = pte_mknewprot(*pteptr);
}
static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *pteptr, pte_t pteval)
{
set_pte(pteptr, pteval);
}
#define __HAVE_ARCH_PTE_SAME
static inline int pte_same(pte_t pte_a, pte_t pte_b)
{
return !((pte_val(pte_a) ^ pte_val(pte_b)) & ~_PAGE_NEWPAGE);
}
/*
* Conversion functions: convert a page and protection to a page entry,
* and a page entry and page directory to the page they refer to.
*/
#define phys_to_page(phys) pfn_to_page(phys_to_pfn(phys))
#define __virt_to_page(virt) phys_to_page(__pa(virt))
#define page_to_phys(page) pfn_to_phys(page_to_pfn(page))
#define virt_to_page(addr) __virt_to_page((const unsigned long) addr)
#define mk_pte(page, pgprot) \
({ pte_t pte; \
\
pte_set_val(pte, page_to_phys(page), (pgprot)); \
if (pte_present(pte)) \
pte_mknewprot(pte_mknewpage(pte)); \
pte;})
static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
{
pte_set_val(pte, (pte_val(pte) & _PAGE_CHG_MASK), newprot);
return pte;
}
/*
* the pmd page can be thought of an array like this: pmd_t[PTRS_PER_PMD]
*
* this macro returns the index of the entry in the pmd page which would
* control the given virtual address
*/
#define pmd_page_vaddr(pmd) ((unsigned long) __va(pmd_val(pmd) & PAGE_MASK))
struct mm_struct;
extern pte_t *virt_to_pte(struct mm_struct *mm, unsigned long addr);
#define update_mmu_cache(vma,address,ptep) do {} while (0)
/*
* Encode/decode swap entries and swap PTEs. Swap PTEs are all PTEs that
* are !pte_none() && !pte_present().
*
* Format of swap PTEs:
*
* 3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1
* 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
* <--------------- offset ----------------> E < type -> 0 0 0 1 0
*
* E is the exclusive marker that is not stored in swap entries.
* _PAGE_NEWPAGE (bit 1) is always set to 1 in set_pte().
*/
#define __swp_type(x) (((x).val >> 5) & 0x1f)
#define __swp_offset(x) ((x).val >> 11)
#define __swp_entry(type, offset) \
((swp_entry_t) { (((type) & 0x1f) << 5) | ((offset) << 11) })
#define __pte_to_swp_entry(pte) \
((swp_entry_t) { pte_val(pte_mkuptodate(pte)) })
#define __swp_entry_to_pte(x) ((pte_t) { (x).val })
static inline int pte_swp_exclusive(pte_t pte)
{
return pte_get_bits(pte, _PAGE_SWP_EXCLUSIVE);
}
static inline pte_t pte_swp_mkexclusive(pte_t pte)
{
pte_set_bits(pte, _PAGE_SWP_EXCLUSIVE);
return pte;
}
static inline pte_t pte_swp_clear_exclusive(pte_t pte)
{
pte_clear_bits(pte, _PAGE_SWP_EXCLUSIVE);
return pte;
}
/* Clear a kernel PTE and flush it from the TLB */
#define kpte_clear_flush(ptep, vaddr) \
do { \
pte_clear(&init_mm, (vaddr), (ptep)); \
__flush_tlb_one((vaddr)); \
} while (0)
#endif
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