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SubjectRe: [RFC PATCH v7 05/16] arm64/mm: Add support for XPFO
On Thu, Jan 10, 2019 at 02:09:37PM -0700, Khalid Aziz wrote:
> From: Juerg Haefliger <juerg.haefliger@canonical.com>
>
> Enable support for eXclusive Page Frame Ownership (XPFO) for arm64 and
> provide a hook for updating a single kernel page table entry (which is
> required by the generic XPFO code).
>
> v6: use flush_tlb_kernel_range() instead of __flush_tlb_one()
>
> CC: linux-arm-kernel@lists.infradead.org
> Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
> Signed-off-by: Tycho Andersen <tycho@docker.com>
> Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/mm/Makefile | 2 ++
> arch/arm64/mm/xpfo.c | 58 ++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 61 insertions(+)
> create mode 100644 arch/arm64/mm/xpfo.c
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index ea2ab0330e3a..f0a9c0007d23 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -171,6 +171,7 @@ config ARM64
> select SWIOTLB
> select SYSCTL_EXCEPTION_TRACE
> select THREAD_INFO_IN_TASK
> + select ARCH_SUPPORTS_XPFO
> help
> ARM 64-bit (AArch64) Linux support.
>
> diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
> index 849c1df3d214..cca3808d9776 100644
> --- a/arch/arm64/mm/Makefile
> +++ b/arch/arm64/mm/Makefile
> @@ -12,3 +12,5 @@ KASAN_SANITIZE_physaddr.o += n
>
> obj-$(CONFIG_KASAN) += kasan_init.o
> KASAN_SANITIZE_kasan_init.o := n
> +
> +obj-$(CONFIG_XPFO) += xpfo.o
> diff --git a/arch/arm64/mm/xpfo.c b/arch/arm64/mm/xpfo.c
> new file mode 100644
> index 000000000000..678e2be848eb
> --- /dev/null
> +++ b/arch/arm64/mm/xpfo.c
> @@ -0,0 +1,58 @@
> +/*
> + * Copyright (C) 2017 Hewlett Packard Enterprise Development, L.P.
> + * Copyright (C) 2016 Brown University. All rights reserved.
> + *
> + * Authors:
> + * Juerg Haefliger <juerg.haefliger@hpe.com>
> + * Vasileios P. Kemerlis <vpk@cs.brown.edu>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + */
> +
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +
> +#include <asm/tlbflush.h>
> +
> +/*
> + * Lookup the page table entry for a virtual address and return a pointer to
> + * the entry. Based on x86 tree.
> + */
> +static pte_t *lookup_address(unsigned long addr)
> +{
> + pgd_t *pgd;
> + pud_t *pud;
> + pmd_t *pmd;
> +
> + pgd = pgd_offset_k(addr);
> + if (pgd_none(*pgd))
> + return NULL;
> +
> + pud = pud_offset(pgd, addr);
> + if (pud_none(*pud))
> + return NULL;
> +
> + pmd = pmd_offset(pud, addr);
> + if (pmd_none(*pmd))
> + return NULL;
> +
> + return pte_offset_kernel(pmd, addr);
> +}
> +
> +/* Update a single kernel page table entry */
> +inline void set_kpte(void *kaddr, struct page *page, pgprot_t prot)
> +{
> + pte_t *pte = lookup_address((unsigned long)kaddr);
> +
> + set_pte(pte, pfn_pte(page_to_pfn(page), prot));

Thought on the other hand.. what if the page is PMD? Do you really want
to do this?

What if 'pte' is NULL?
> +}
> +
> +inline void xpfo_flush_kernel_tlb(struct page *page, int order)
> +{
> + unsigned long kaddr = (unsigned long)page_address(page);
> + unsigned long size = PAGE_SIZE;
> +
> + flush_tlb_kernel_range(kaddr, kaddr + (1 << order) * size);

Ditto here. You are assuming it is PTE, but it may be PMD or such.
Or worts - the lookup_address could be NULL.

> +}
> --
> 2.17.1
>

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