From: will.deacon@arm•com (Will Deacon)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] Fix for the arm64 kern_addr_valid() function
Date: Wed, 16 Apr 2014 08:51:44 +0100 [thread overview]
Message-ID: <20140416075144.GA29754@arm.com> (raw)
In-Reply-To: <1397584404-28762-1-git-send-email-anderson@redhat.com>
Hi Dave,
On Tue, Apr 15, 2014 at 06:53:24PM +0100, Dave Anderson wrote:
> Fix for the arm64 kern_addr_valid() function to recognize
> virtual addresses in the kernel logical memory map. The
> function fails as written because it does not check whether
> the addresses in that region are mapped at the pmd level to
> 2MB or 512MB pages, continues the page table walk to the
> pte level, and issues a garbage value to pfn_valid().
>
> Tested on 4K-page and 64K-page kernels.
>
> Signed-off-by: Dave Anderson <anderson@redhat•com>
> ---
> arch/arm64/mm/mmu.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 6b7e895..0a472c4 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -374,6 +374,9 @@ int kern_addr_valid(unsigned long addr)
> if (pmd_none(*pmd))
> return 0;
>
> + if (pmd_sect(*pmd))
> + return pfn_valid(pmd_pfn(*pmd));
> +
> pte = pte_offset_kernel(pmd, addr);
> if (pte_none(*pte))
> return 0;
Whilst this patch looks fine to me, I wonder whether walking the page tables
is really necessary for this function? The only user is fs/proc/kcore.c,
which basically wants to know if a lowmem address is actually backed by
physical memory. Our current implementation of kern_addr_valid will return
true even for MMIO mappings, whilst I think we could actually just do
something like:
if ((((long)addr) >> VA_BITS) != -1UL)
return 0;
return pfn_valid(__pa(addr) >> PAGE_SHIFT);
Am I missing something here?
Will
next prev parent reply other threads:[~2014-04-16 7:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-15 17:53 [PATCH] Fix for the arm64 kern_addr_valid() function Dave Anderson
2014-04-16 7:51 ` Will Deacon [this message]
2014-04-16 13:35 ` Dave Anderson
2014-04-29 14:25 ` Catalin Marinas
2014-04-29 14:34 ` Don Dutile
2014-04-29 15:00 ` Will Deacon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140416075144.GA29754@arm.com \
--to=will.deacon@arm$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox