From: Mark Rutland <mark.rutland@arm.com>
To: Tycho Andersen <tycho@docker.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kernel-hardening@lists.openwall.com,
Marco Benatto <marco.antonio.780@gmail.com>,
Juerg Haefliger <juerg.haefliger@canonical.com>,
linux-arm-kernel@lists.infradead.org, x86@kernel.org
Subject: Re: [kernel-hardening] [PATCH v6 10/11] mm: add a user_virt_to_phys symbol
Date: Thu, 14 Sep 2017 19:34:02 +0100 [thread overview]
Message-ID: <20170914183401.GC1711@remoulade> (raw)
In-Reply-To: <20170907173609.22696-11-tycho@docker.com>
On Thu, Sep 07, 2017 at 11:36:08AM -0600, Tycho Andersen wrote:
> We need someting like this for testing XPFO. Since it's architecture
> specific, putting it in the test code is slightly awkward, so let's make it
> an arch-specific symbol and export it for use in LKDTM.
>
> v6: * add a definition of user_virt_to_phys in the !CONFIG_XPFO case
>
> CC: linux-arm-kernel@lists.infradead.org
> CC: x86@kernel.org
> Signed-off-by: Tycho Andersen <tycho@docker.com>
> Tested-by: Marco Benatto <marco.antonio.780@gmail.com>
> ---
> arch/arm64/mm/xpfo.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++
> arch/x86/mm/xpfo.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/xpfo.h | 5 +++++
> 3 files changed, 113 insertions(+)
>
> diff --git a/arch/arm64/mm/xpfo.c b/arch/arm64/mm/xpfo.c
> index 342a9ccb93c1..94a667d94e15 100644
> --- a/arch/arm64/mm/xpfo.c
> +++ b/arch/arm64/mm/xpfo.c
> @@ -74,3 +74,54 @@ void xpfo_dma_map_unmap_area(bool map, const void *addr, size_t size,
>
> xpfo_temp_unmap(addr, size, mapping, sizeof(mapping[0]) * num_pages);
> }
> +
> +/* Convert a user space virtual address to a physical address.
> + * Shamelessly copied from slow_virt_to_phys() and lookup_address() in
> + * arch/x86/mm/pageattr.c
> + */
When can this be called? What prevents concurrent modification of the user page
tables?
i.e. must mmap_sem be held?
> +phys_addr_t user_virt_to_phys(unsigned long addr)
Does this really need to be architecture specific?
Core mm code manages to walk user page tables just fine...
> +{
> + phys_addr_t phys_addr;
> + unsigned long offset;
> + pgd_t *pgd;
> + p4d_t *p4d;
> + pud_t *pud;
> + pmd_t *pmd;
> + pte_t *pte;
> +
> + pgd = pgd_offset(current->mm, addr);
> + if (pgd_none(*pgd))
> + return 0;
Can we please separate the address and return value? e.g. pass the PA by
reference and return an error code.
AFAIK, zero is a valid PA, and even if the tables exist, they might point there
in the presence of an error.
> +
> + p4d = p4d_offset(pgd, addr);
> + if (p4d_none(*p4d))
> + return 0;
> +
> + pud = pud_offset(p4d, addr);
> + if (pud_none(*pud))
> + return 0;
> +
> + if (pud_sect(*pud) || !pud_present(*pud)) {
> + phys_addr = (unsigned long)pud_pfn(*pud) << PAGE_SHIFT;
Was there some problem with:
phys_addr = pmd_page_paddr(*pud);
... and similar for the other levels?
... I'd rather introduce new helpers than more open-coded calculations.
Thanks,
Mark.
next prev parent reply other threads:[~2017-09-14 18:34 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-07 17:35 [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Tycho Andersen
2017-09-07 17:35 ` [PATCH v6 01/11] mm: add MAP_HUGETLB support to vm_mmap Tycho Andersen
2017-09-08 7:42 ` Christoph Hellwig
2017-09-07 17:36 ` [PATCH v6 02/11] x86: always set IF before oopsing from page fault Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 03/11] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO) Tycho Andersen
2017-09-07 18:33 ` Ralph Campbell
2017-09-07 18:50 ` Tycho Andersen
2017-09-08 7:51 ` Christoph Hellwig
2017-09-08 14:58 ` Tycho Andersen
2017-09-09 15:35 ` Laura Abbott
2017-09-11 15:03 ` Tycho Andersen
2017-09-11 7:24 ` Yisheng Xie
2017-09-11 14:50 ` Tycho Andersen
2017-09-11 16:03 ` Juerg Haefliger
2017-09-11 16:59 ` Tycho Andersen
2017-09-12 8:05 ` Yisheng Xie
2017-09-12 14:36 ` Tycho Andersen
2017-09-12 18:13 ` Tycho Andersen
2017-09-14 6:15 ` Yisheng Xie
2017-09-20 23:46 ` Dave Hansen
2017-09-21 0:02 ` Tycho Andersen
2017-09-21 0:04 ` Dave Hansen
2017-09-11 18:32 ` Tycho Andersen
2017-09-11 21:54 ` Marco Benatto
2017-09-20 15:48 ` Dave Hansen
2017-09-20 22:34 ` Tycho Andersen
2017-09-20 23:21 ` Dave Hansen
2017-09-21 0:09 ` Tycho Andersen
2017-09-21 0:27 ` Dave Hansen
2017-09-21 1:37 ` Tycho Andersen
2017-11-10 1:09 ` Tycho Andersen
2017-11-13 22:20 ` Dave Hansen
2017-11-13 22:46 ` Dave Hansen
2017-11-15 0:33 ` [kernel-hardening] " Tycho Andersen
2017-11-15 0:37 ` Dave Hansen
2017-11-15 0:42 ` Tycho Andersen
2017-11-15 3:44 ` Matthew Wilcox
2017-11-15 7:00 ` Dave Hansen
2017-11-15 14:58 ` Matthew Wilcox
2017-11-15 16:20 ` [kernel-hardening] " Tycho Andersen
2017-11-15 21:34 ` Matthew Wilcox
2017-09-21 0:03 ` Dave Hansen
2017-09-21 0:28 ` Dave Hansen
2017-09-21 1:04 ` Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 04/11] swiotlb: Map the buffer if it was unmapped by XPFO Tycho Andersen
2017-09-07 18:10 ` Christoph Hellwig
2017-09-07 18:44 ` Tycho Andersen
2017-09-08 7:13 ` Christoph Hellwig
2017-09-07 17:36 ` [PATCH v6 05/11] arm64/mm: Add support for XPFO Tycho Andersen
2017-09-08 7:53 ` Christoph Hellwig
2017-09-08 17:24 ` Tycho Andersen
2017-09-14 10:41 ` Julien Grall
2017-09-14 11:29 ` Juergen Gross
2017-09-14 18:22 ` [kernel-hardening] " Mark Rutland
2017-09-18 21:27 ` Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 06/11] xpfo: add primitives for mapping underlying memory Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 07/11] arm64/mm, xpfo: temporarily map dcache regions Tycho Andersen
2017-09-14 18:25 ` Mark Rutland
2017-09-18 21:29 ` Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 08/11] arm64/mm: Add support for XPFO to swiotlb Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 09/11] arm64/mm: disable section/contiguous mappings if XPFO is enabled Tycho Andersen
2017-09-09 15:38 ` Laura Abbott
2017-09-07 17:36 ` [PATCH v6 10/11] mm: add a user_virt_to_phys symbol Tycho Andersen
2017-09-08 7:55 ` Christoph Hellwig
2017-09-08 15:44 ` Kees Cook
2017-09-11 7:36 ` Christoph Hellwig
2017-09-14 18:34 ` Mark Rutland [this message]
2017-09-18 20:56 ` [kernel-hardening] " Tycho Andersen
2017-09-07 17:36 ` [PATCH v6 11/11] lkdtm: Add test for XPFO Tycho Andersen
2017-09-07 19:08 ` Kees Cook
2017-09-10 0:57 ` kbuild test robot
2017-09-11 10:34 ` [PATCH v6 00/11] Add support for eXclusive Page Frame Ownership Yisheng Xie
2017-09-11 15:02 ` Tycho Andersen
2017-09-12 7:07 ` Yisheng Xie
2017-09-12 7:40 ` Juerg Haefliger
2017-09-12 8:11 ` Yisheng Xie
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