From: Michael Ellerman <patch-notifications@ellerman•id.au>
To: Paul Mackerras <paulus@ozlabs•org>, linuxppc-dev@lists•ozlabs.org
Subject: Re: [2/3] powerpc/mm: Preserve CFAR value on SLB miss caused by access to bogus address
Date: Tue, 13 Sep 2016 22:16:29 +1000 (AEST) [thread overview]
Message-ID: <3sYNvL0LZCz9sdm@ozlabs.org> (raw)
In-Reply-To: <20160902114921.GB12433@fergus.ozlabs.ibm.com>
On Fri, 2016-02-09 at 11:49:21 UTC, Paul Mackerras wrote:
> Currently, if userspace or the kernel accesses a completely bogus address,
> for example with any of bits 46-59 set, we first take an SLB miss interrupt,
> install a corresponding SLB entry with VSID 0, retry the instruction, then
> take a DSI/ISI interrupt because there is no HPT entry mapping the address.
> However, by the time of the second interrupt, the Come-From Address Register
> (CFAR) has been overwritten by the rfid instruction at the end of the SLB
> miss interrupt handler. Since bogus accesses can often be caused by a
> function return after the stack has been overwritten, the CFAR value would
> be very useful as it could indicate which function it was whose return had
> led to the bogus address.
>
> This patch adds code to create a full exception frame in the SLB miss handler
> in the case of a bogus address, rather than inserting an SLB entry with a
> zero VSID field. Then we call a new slb_miss_bad_addr() function in C code,
> which delivers a signal for a user access or creates an oops for a kernel
> access. In the latter case the oops message will show the CFAR value at the
> time of the access.
>
> In the case of the radix MMU, a segment miss interrupt indicates an access
> outside the ranges mapped by the page tables. Previously this was handled
> by the code for an unrecoverable SLB miss (one with MSR[RI] = 0), which is
> not really correct. With this patch, we now handle these interrupts with
> slb_miss_bad_addr(), which is much more consistent.
>
> Signed-off-by: Paul Mackerras <paulus@ozlabs•org>
> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux•vnet.ibm.com>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/f0f558b131db0e793fd90aac5d
cheers
next prev parent reply other threads:[~2016-09-13 12:16 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-02 11:47 [PATCH 1/3] powerpc/mm: Don't alias user region to other regions below PAGE_OFFSET Paul Mackerras
2016-09-02 11:49 ` [PATCH 2/3] powerpc/mm: Preserve CFAR value on SLB miss caused by access to bogus address Paul Mackerras
2016-09-04 11:30 ` Aneesh Kumar K.V
2016-09-07 5:52 ` Paul Mackerras
2016-09-13 12:16 ` Michael Ellerman [this message]
2016-09-02 11:50 ` [PATCH 3/3] powerpc/mm: Speed up computation of base and actual page size for a HPTE Paul Mackerras
2016-09-04 11:16 ` Aneesh Kumar K.V
2016-09-05 5:04 ` Aneesh Kumar K.V
2016-09-07 5:07 ` Paul Mackerras
2016-09-07 6:17 ` [PATCH v2 " Paul Mackerras
2016-09-08 10:08 ` Paul Mackerras
2016-09-08 10:16 ` Paolo Bonzini
2016-09-12 0:58 ` Paul Mackerras
2016-09-12 3:03 ` Michael Ellerman
2016-09-12 9:45 ` Paolo Bonzini
2016-09-02 12:22 ` [PATCH 1/3] powerpc/mm: Don't alias user region to other regions below PAGE_OFFSET Aneesh Kumar K.V
2016-09-03 9:54 ` Paul Mackerras
2016-09-04 11:31 ` Aneesh Kumar K.V
2016-09-08 9:47 ` [1/3] " Michael Ellerman
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=3sYNvL0LZCz9sdm@ozlabs.org \
--to=patch-notifications@ellerman$(echo .)id.au \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
--cc=paulus@ozlabs$(echo .)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