Re: [PATCH v9 7/8] powerpc/mm: implement set_memory_attr()

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 16/03/2021 à 04:17, Jordan Niethe a écrit :
> From: Christophe Leroy <christophe.leroy@c-s.fr>

Can you please update the whole series with my new email address: christophe.leroy@csgroup.eu



> 
> In addition to the set_memory_xx() functions which allows to change
> the memory attributes of not (yet) used memory regions, implement a
> set_memory_attr() function to:
> - set the final memory protection after init on currently used
> kernel regions.
> - enable/disable kernel memory regions in the scope of DEBUG_PAGEALLOC.
> 
> Unlike the set_memory_xx() which can act in three step as the regions
> are unused, this function must modify 'on the fly' as the kernel is
> executing from them. At the moment only PPC32 will use it and changing
> page attributes on the fly is not an issue.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> Reported-by: kbuild test robot <lkp@intel.com>
> [ruscur: cast "data" to unsigned long instead of int]
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> ---
>   arch/powerpc/include/asm/set_memory.h |  2 ++
>   arch/powerpc/mm/pageattr.c            | 33 +++++++++++++++++++++++++++
>   2 files changed, 35 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/set_memory.h b/arch/powerpc/include/asm/set_memory.h
> index 64011ea444b4..b040094f7920 100644
> --- a/arch/powerpc/include/asm/set_memory.h
> +++ b/arch/powerpc/include/asm/set_memory.h
> @@ -29,4 +29,6 @@ static inline int set_memory_x(unsigned long addr, int numpages)
>   	return change_memory_attr(addr, numpages, SET_MEMORY_X);
>   }
>   
> +int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot);
> +
>   #endif
> diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
> index 2da3fbab6ff7..2fde1b195c85 100644
> --- a/arch/powerpc/mm/pageattr.c
> +++ b/arch/powerpc/mm/pageattr.c
> @@ -79,3 +79,36 @@ int change_memory_attr(unsigned long addr, int numpages, long action)
>   	return apply_to_existing_page_range(&init_mm, start, sz,
>   					    change_page_attr, (void *)action);
>   }
> +
> +/*
> + * Set the attributes of a page:
> + *
> + * This function is used by PPC32 at the end of init to set final kernel memory
> + * protection. It includes changing the maping of the page it is executing from
> + * and data pages it is using.
> + */
> +static int set_page_attr(pte_t *ptep, unsigned long addr, void *data)
> +{
> +	pgprot_t prot = __pgprot((unsigned long)data);
> +
> +	spin_lock(&init_mm.page_table_lock);
> +
> +	set_pte_at(&init_mm, addr, ptep, pte_modify(*ptep, prot));
> +	flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
> +
> +	spin_unlock(&init_mm.page_table_lock);
> +
> +	return 0;
> +}
> +
> +int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot)
> +{
> +	unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
> +	unsigned long sz = numpages * PAGE_SIZE;
> +
> +	if (numpages <= 0)
> +		return 0;
> +
> +	return apply_to_existing_page_range(&init_mm, start, sz, set_page_attr,
> +					    (void *)pgprot_val(prot));
> +}
>