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bianbu-linux-6.6/arch/m68k/include/asm/mcf_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 */
#ifndef _MCF_PGTABLE_H
#define _MCF_PGTABLE_H
#include <asm/mcfmmu.h>
#include <asm/page.h>
/*
* MMUDR bits, in proper place. We write these directly into the MMUDR
* after masking from the pte.
*/
#define CF_PAGE_LOCKED MMUDR_LK /* 0x00000002 */
#define CF_PAGE_EXEC MMUDR_X /* 0x00000004 */
#define CF_PAGE_WRITABLE MMUDR_W /* 0x00000008 */
#define CF_PAGE_READABLE MMUDR_R /* 0x00000010 */
#define CF_PAGE_SYSTEM MMUDR_SP /* 0x00000020 */
#define CF_PAGE_COPYBACK MMUDR_CM_CCB /* 0x00000040 */
#define CF_PAGE_NOCACHE MMUDR_CM_NCP /* 0x00000080 */
#define CF_CACHEMASK (~MMUDR_CM_CCB)
#define CF_PAGE_MMUDR_MASK 0x000000fe
#define _PAGE_NOCACHE030 CF_PAGE_NOCACHE
/*
* MMUTR bits, need shifting down.
*/
#define CF_PAGE_MMUTR_MASK 0x00000c00
#define CF_PAGE_MMUTR_SHIFT 10
#define CF_PAGE_VALID (MMUTR_V << CF_PAGE_MMUTR_SHIFT)
#define CF_PAGE_SHARED (MMUTR_SG << CF_PAGE_MMUTR_SHIFT)
/*
* Fake bits, not implemented in CF, will get masked out before
* hitting hardware.
*/
#define CF_PAGE_DIRTY 0x00000001
#define CF_PAGE_ACCESSED 0x00001000
#define _PAGE_CACHE040 0x020 /* 68040 cache mode, cachable, copyback */
#define _PAGE_NOCACHE_S 0x040 /* 68040 no-cache mode, serialized */
#define _PAGE_NOCACHE 0x060 /* 68040 cache mode, non-serialized */
#define _PAGE_CACHE040W 0x000 /* 68040 cache mode, cachable, write-through */
#define _DESCTYPE_MASK 0x003
#define _CACHEMASK040 (~0x060)
#define _PAGE_GLOBAL040 0x400 /* 68040 global bit, used for kva descs */
/* We borrow bit 7 to store the exclusive marker in swap PTEs. */
#define _PAGE_SWP_EXCLUSIVE CF_PAGE_NOCACHE
/*
* Externally used page protection values.
*/
#define _PAGE_PRESENT (CF_PAGE_VALID)
#define _PAGE_ACCESSED (CF_PAGE_ACCESSED)
#define _PAGE_DIRTY (CF_PAGE_DIRTY)
#define _PAGE_READWRITE (CF_PAGE_READABLE \
| CF_PAGE_WRITABLE \
| CF_PAGE_SYSTEM \
| CF_PAGE_SHARED)
/*
* Compound page protection values.
*/
#define PAGE_NONE __pgprot(CF_PAGE_VALID \
| CF_PAGE_ACCESSED)
#define PAGE_SHARED __pgprot(CF_PAGE_VALID \
| CF_PAGE_ACCESSED \
| CF_PAGE_SHARED)
#define PAGE_INIT __pgprot(CF_PAGE_VALID \
| CF_PAGE_READABLE \
| CF_PAGE_WRITABLE \
| CF_PAGE_EXEC \
| CF_PAGE_SYSTEM)
#define PAGE_KERNEL __pgprot(CF_PAGE_VALID \
| CF_PAGE_ACCESSED \
| CF_PAGE_READABLE \
| CF_PAGE_WRITABLE \
| CF_PAGE_EXEC \
| CF_PAGE_SYSTEM \
| CF_PAGE_SHARED)
#define PAGE_COPY __pgprot(CF_PAGE_VALID \
| CF_PAGE_ACCESSED \
| CF_PAGE_READABLE \
| CF_PAGE_DIRTY)
#define PTE_MASK PAGE_MASK
#define CF_PAGE_CHG_MASK (PTE_MASK | CF_PAGE_ACCESSED | CF_PAGE_DIRTY)
#ifndef __ASSEMBLY__
#define pmd_pgtable(pmd) pfn_to_virt(pmd_val(pmd) >> PAGE_SHIFT)
/*
* 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 mk_pte(page, pgprot) pfn_pte(page_to_pfn(page), (pgprot))
static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
{
pte_val(pte) = (pte_val(pte) & CF_PAGE_CHG_MASK) | pgprot_val(newprot);
return pte;
}
#define pmd_set(pmdp, ptep) do {} while (0)
static inline void pgd_set(pgd_t *pgdp, pmd_t *pmdp)
{
pgd_val(*pgdp) = virt_to_phys(pmdp);
}
#define __pte_page(pte) ((void *) (pte_val(pte) & PAGE_MASK))
#define pmd_page_vaddr(pmd) ((unsigned long) (pmd_val(pmd)))
static inline int pte_none(pte_t pte)
{
return !pte_val(pte);
}
static inline int pte_present(pte_t pte)
{
return pte_val(pte) & CF_PAGE_VALID;
}
static inline void pte_clear(struct mm_struct *mm, unsigned long addr,
pte_t *ptep)
{
pte_val(*ptep) = 0;
}
#define pte_page(pte) virt_to_page(__pte_page(pte))
static inline int pmd_none2(pmd_t *pmd) { return !pmd_val(*pmd); }
#define pmd_none(pmd) pmd_none2(&(pmd))
static inline int pmd_bad2(pmd_t *pmd) { return 0; }
#define pmd_bad(pmd) pmd_bad2(&(pmd))
#define pmd_present(pmd) (!pmd_none2(&(pmd)))
static inline void pmd_clear(pmd_t *pmdp) { pmd_val(*pmdp) = 0; }
#define pte_ERROR(e) \
printk(KERN_ERR "%s:%d: bad pte %08lx.\n", \
__FILE__, __LINE__, pte_val(e))
#define pgd_ERROR(e) \
printk(KERN_ERR "%s:%d: bad pgd %08lx.\n", \
__FILE__, __LINE__, pgd_val(e))
/*
* The following only work if pte_present() is true.
* Undefined behaviour if not...
* [we have the full set here even if they don't change from m68k]
*/
static inline int pte_read(pte_t pte)
{
return pte_val(pte) & CF_PAGE_READABLE;
}
static inline int pte_write(pte_t pte)
{
return pte_val(pte) & CF_PAGE_WRITABLE;
}
static inline int pte_exec(pte_t pte)
{
return pte_val(pte) & CF_PAGE_EXEC;
}
static inline int pte_dirty(pte_t pte)
{
return pte_val(pte) & CF_PAGE_DIRTY;
}
static inline int pte_young(pte_t pte)
{
return pte_val(pte) & CF_PAGE_ACCESSED;
}
static inline pte_t pte_wrprotect(pte_t pte)
{
pte_val(pte) &= ~CF_PAGE_WRITABLE;
return pte;
}
static inline pte_t pte_rdprotect(pte_t pte)
{
pte_val(pte) &= ~CF_PAGE_READABLE;
return pte;
}
static inline pte_t pte_exprotect(pte_t pte)
{
pte_val(pte) &= ~CF_PAGE_EXEC;
return pte;
}
static inline pte_t pte_mkclean(pte_t pte)
{
pte_val(pte) &= ~CF_PAGE_DIRTY;
return pte;
}
static inline pte_t pte_mkold(pte_t pte)
{
pte_val(pte) &= ~CF_PAGE_ACCESSED;
return pte;
}
static inline pte_t pte_mkwrite_novma(pte_t pte)
{
pte_val(pte) |= CF_PAGE_WRITABLE;
return pte;
}
static inline pte_t pte_mkread(pte_t pte)
{
pte_val(pte) |= CF_PAGE_READABLE;
return pte;
}
static inline pte_t pte_mkexec(pte_t pte)
{
pte_val(pte) |= CF_PAGE_EXEC;
return pte;
}
static inline pte_t pte_mkdirty(pte_t pte)
{
pte_val(pte) |= CF_PAGE_DIRTY;
return pte;
}
static inline pte_t pte_mkyoung(pte_t pte)
{
pte_val(pte) |= CF_PAGE_ACCESSED;
return pte;
}
static inline pte_t pte_mknocache(pte_t pte)
{
pte_val(pte) |= 0x80 | (pte_val(pte) & ~0x40);
return pte;
}
static inline pte_t pte_mkcache(pte_t pte)
{
pte_val(pte) &= ~CF_PAGE_NOCACHE;
return pte;
}
#define swapper_pg_dir kernel_pg_dir
extern pgd_t kernel_pg_dir[PTRS_PER_PGD];
/*
* 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 -------------> 0 0 0 E <-- type --->
*
* E is the exclusive marker that is not stored in swap entries.
*/
#define __swp_type(x) ((x).val & 0x7f)
#define __swp_offset(x) ((x).val >> 11)
#define __swp_entry(typ, off) ((swp_entry_t) { ((typ) & 0x7f) | \
(off << 11) })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x) (__pte((x).val))
static inline int pte_swp_exclusive(pte_t pte)
{
return pte_val(pte) & _PAGE_SWP_EXCLUSIVE;
}
static inline pte_t pte_swp_mkexclusive(pte_t pte)
{
pte_val(pte) |= _PAGE_SWP_EXCLUSIVE;
return pte;
}
static inline pte_t pte_swp_clear_exclusive(pte_t pte)
{
pte_val(pte) &= ~_PAGE_SWP_EXCLUSIVE;
return pte;
}
#define pmd_pfn(pmd) (pmd_val(pmd) >> PAGE_SHIFT)
#define pmd_page(pmd) (pfn_to_page(pmd_val(pmd) >> PAGE_SHIFT))
#define pfn_pte(pfn, prot) __pte(((pfn) << PAGE_SHIFT) | pgprot_val(prot))
#define pte_pfn(pte) (pte_val(pte) >> PAGE_SHIFT)
#endif /* !__ASSEMBLY__ */
#endif /* _MCF_PGTABLE_H */
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