[PATCH v2 3/3] powerpc: mm: support page table check

[Christophe Leroy]

Le 23/09/2022 à 08:08, Rohan McLure a écrit :
> On creation and clearing of a page table mapping, instrument such calls
> by invoking page_table_check_pte_set and page_table_check_pte_clear
> respectively. These calls serve as a sanity check against illegal
> mappings.
> 
> Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK for all ppc64, and 32-bit
> platforms implementing Book3S.
> 
> Change pud_pfn to be a runtime bug rather than a build bug as it is
> consumed by page_table_check_pud_{clear,set} which are not called.
> 
> See also:
> 
> riscv support in commit 3fee229a8eb9 ("riscv/mm: enable
> ARCH_SUPPORTS_PAGE_TABLE_CHECK")
> arm64 in commit 42b2547137f5 ("arm64/mm: enable
> ARCH_SUPPORTS_PAGE_TABLE_CHECK")
> x86_64 in commit d283d422c6c4 ("x86: mm: add x86_64 support for page table
> check")
> 
> Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>
> ---
> V2: Update spacing and types assigned to pte_update calls > ---

> diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
> index 9091e4904a6b..45ba36d968aa 100644
> --- a/arch/powerpc/include/asm/nohash/32/pgtable.h
> +++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
> @@ -166,6 +166,7 @@ void unmap_kernel_page(unsigned long va);
>   #define _PAGE_CHG_MASK	(PTE_RPN_MASK | _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_SPECIAL)
>   
>   #ifndef __ASSEMBLY__
> +#include <linux/page_table_check.h>
>   
>   #define pte_clear(mm, addr, ptep) \
>   	do { pte_update(mm, addr, ptep, ~0, 0, 0); } while (0)
> @@ -305,7 +306,11 @@ static inline int __ptep_test_and_clear_young(struct mm_struct *mm,
>   static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
>   				       pte_t *ptep)
>   {
> -	return __pte(pte_update(mm, addr, ptep, ~0, 0, 0));
> +	unsigned long old = pte_update(mm, addr, ptep, ~0, 0, 0);

You missed that one, should be pte_t to avoid twice __pte(old)

> +
> +	page_table_check_pte_clear(mm, addr, __pte(old));
> +
> +	return __pte(old);
>   }
>   
>   #define __HAVE_ARCH_PTEP_SET_WRPROTECT