Subject: Re: [PATCH v1 1/3] arch/powerpc/set_memory: Implement set_memory_xx routines

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 02 Aug 2017 15:39:47 +0530

Balbir Singh <[email-masked]> writes:

> Add support for set_memory_xx routines. With the STRICT_KERNEL_RWX
> feature support we got support for changing the page permissions
> for pte ranges. This patch adds support for both radix and hash
> so that we can change their permissions via set/clear masks.
>
> A new helper is required for hash (hash__change_memory_range()
> is changed to hash__change_boot_memory_range() as it deals with
> bolted PTE's).
>
> hash__change_memory_range() works with vmalloc'ed PAGE_SIZE requests
> for permission changes. hash__change_memory_range() does not invoke
> updatepp, instead it changes the software PTE and invalidates the PTE.
>
> For radix, radix__change_memory_range() is setup to do the right
> thing for vmalloc'd addresses. It takes a new parameter to decide
> what attributes to set.
>
....

> +int hash__change_memory_range(unsigned long start, unsigned long end,
> +				unsigned long set, unsigned long clear)
> +{
> +	unsigned long idx;
> +	pgd_t *pgdp;
> +	pud_t *pudp;
> +	pmd_t *pmdp;
> +	pte_t *ptep;
> +
> +	start = ALIGN_DOWN(start, PAGE_SIZE);
> +	end = PAGE_ALIGN(end); // aligns up
> +
> +	/*
> +	 * Update the software PTE and flush the entry.
> +	 * This should cause a new fault with the right
> +	 * things setup in the hash page table
> +	 */
> +	pr_debug("Changing flags on range %lx-%lx setting 0x%lx removing 0x%lx\n",
> +		 start, end, set, clear);
> +
> +	for (idx = start; idx < end; idx += PAGE_SIZE) {

> +		pgdp = pgd_offset_k(idx);
> +		pudp = pud_alloc(&init_mm, pgdp, idx);
> +		if (!pudp)
> +			return -1;
> +		pmdp = pmd_alloc(&init_mm, pudp, idx);
> +		if (!pmdp)
> +			return -1;
> +		ptep = pte_alloc_kernel(pmdp, idx);
> +		if (!ptep)
> +			return -1;
> +		hash__pte_update(&init_mm, idx, ptep, clear, set, 0);
> +		hash__flush_tlb_kernel_range(idx, idx + PAGE_SIZE);
> +	}

You can use find_linux_pte_or_hugepte. with my recent patch series
find_init_mm_pte() ?

-aneesh