Re: [PATCH 1/2] arm64: Fix STRICT_MM_TYPECHECKS errors from pgprot

[Ard Biesheuvel]

Hi Laura,

On 11 November 2015 at 03:03, Laura Abbott <labbott@xxxxxxxxxxxxxxxxx> wrote:
>
> Several accesses of pgprot values are incorrect when compiled with
> STRICT_MM_TYPECHECKS. Use the appropriate pgprot_val/__pgprot wrappers
> to access the structures appropriately.
>

I spotted 2 out of these, and Catalin has already queued fixes for
them (see below)

> Signed-off-by: Laura Abbott <labbott@xxxxxxxxxxxxxxxxx>
> ---
> Found while working on the set_memory_* work
> ---
>  arch/arm64/mm/mmu.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index c2fa6b5..83a1162 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -146,7 +146,7 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
>                 if (((addr | next | phys) & ~CONT_MASK) == 0) {
>                         /* a block of CONT_PTES  */
>                         __populate_init_pte(pte, addr, next, phys,
> -                                           prot | __pgprot(PTE_CONT));
> +                                        __pgprot(pgprot_val(prot) | PTE_CONT));

Got this one

>                 } else {
>                         /*
>                          * If the range being split is already inside of a
> @@ -475,7 +475,7 @@ void mark_rodata_ro(void)
>  {
>         create_mapping_late(__pa(_stext), (unsigned long)_stext,
>                                 (unsigned long)_etext - (unsigned long)_stext,
> -                               PAGE_KERNEL_EXEC | PTE_RDONLY);
> +                               __pgprot(pgprot_val(PAGE_KERNEL_EXEC) | PTE_RDONLY));
>

This needs PAGE_KERNEL_RO (which was just introduced). The reason is
that PAGE_KERNEL_EXEC has PTE_WRITE set as well, making the range
writeable under the ARMv8.1 DBM feature, that manages the dirty bit in
hardware (writing to a page with the PTE_RDONLY and PTE_WRITE bits
both set will clear the PTE_RDONLY bit in that case)

>  }
>  #endif
> @@ -691,7 +691,7 @@ void __set_fixmap(enum fixed_addresses idx,
>  void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
>  {
>         const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
> -       pgprot_t prot = PAGE_KERNEL | PTE_RDONLY;
> +       pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | PTE_RDONLY);

Got this one as well (using PAGE_KERNEL_RO)

>         int size, offset;
>         void *dt_virt;
>
> --
> 2.5.0
>
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