From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
broonie@kernel.org, jthierry@redhat.com, catalin.marinas@arm.com,
will@kernel.org, linux-arm-kernel@lists.infradead.org,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC PATCH v2 0/4] arm64: Implement stack trace reliability checks
Date: Sun, 11 Apr 2021 12:54:15 -0500 [thread overview]
Message-ID: <1be20ada-6b52-c6e8-508c-7572c438d2b7@linux.microsoft.com> (raw)
In-Reply-To: <20210409225321.2czbawz6p2aquf5m@treble>
On 4/9/21 5:53 PM, Josh Poimboeuf wrote:
> On Fri, Apr 09, 2021 at 05:32:27PM -0500, Josh Poimboeuf wrote:
>> On Fri, Apr 09, 2021 at 05:05:58PM -0500, Madhavan T. Venkataraman wrote:
>>>> FWIW, over the years we've had zero issues with encoding the frame
>>>> pointer on x86. After you save pt_regs, you encode the frame pointer to
>>>> point to it. Ideally in the same macro so it's hard to overlook.
>>>>
>>>
>>> I had the same opinion. In fact, in my encoding scheme, I have additional
>>> checks to make absolutely sure that it is a true encoding and not stack
>>> corruption. The chances of all of those values accidentally matching are,
>>> well, null.
>>
>> Right, stack corruption -- which is already exceedingly rare -- would
>> have to be combined with a miracle or two in order to come out of the
>> whole thing marked as 'reliable' :-)
>>
>> And really, we already take a similar risk today by "trusting" the frame
>> pointer value on the stack to a certain extent.
>
> Oh yeah, I forgot to mention some more benefits of encoding the frame
> pointer (or marking pt_regs in some other way):
>
> a) Stack addresses can be printed properly: '%pS' for printing regs->pc
> and '%pB' for printing call returns.
>
> Using '%pS' for call returns (as arm64 seems to do today) will result
> in printing the wrong function when you have tail calls to noreturn
> functions on the stack (which is actually quite common for calls to
> panic(), die(), etc).
>
> More details:
>
> https://lkml.kernel.org/r/20210403155948.ubbgtwmlsdyar7yp@treble
>
> b) Stack dumps to the console can dump the exception registers they find
> along the way. This is actually quite nice for debugging.
>
>
Great.
I am preparing version 3 taking into account comments from yourself,
Mark Rutland and Mark Brown.
Stay tuned.
Madhavan
next prev parent reply other threads:[~2021-04-11 17:54 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <705993ccb34a611c75cdae0a8cb1b40f9b218ebd>
2021-04-05 20:43 ` [RFC PATCH v2 0/4] arm64: Implement stack trace reliability checks madvenka
2021-04-05 20:43 ` [RFC PATCH v2 1/4] arm64: Implement infrastructure for " madvenka
2021-04-08 15:15 ` Mark Brown
2021-04-08 17:17 ` Mark Brown
2021-04-08 19:30 ` Madhavan T. Venkataraman
2021-04-08 23:30 ` Madhavan T. Venkataraman
2021-04-09 11:57 ` Mark Brown
2021-04-05 20:43 ` [RFC PATCH v2 2/4] arm64: Mark a stack trace unreliable if an EL1 exception frame is detected madvenka
2021-04-05 20:43 ` [RFC PATCH v2 3/4] arm64: Detect FTRACE cases that make the stack trace unreliable madvenka
2021-04-08 16:58 ` Mark Brown
2021-04-08 19:23 ` Madhavan T. Venkataraman
2021-04-09 11:31 ` Mark Brown
2021-04-09 14:02 ` Madhavan T. Venkataraman
2021-04-09 12:27 ` Mark Rutland
2021-04-09 17:23 ` Madhavan T. Venkataraman
2021-04-05 20:43 ` [RFC PATCH v2 4/4] arm64: Mark stack trace as unreliable if kretprobed functions are present madvenka
2021-04-09 12:09 ` [RFC PATCH v2 0/4] arm64: Implement stack trace reliability checks Mark Rutland
2021-04-09 17:16 ` Madhavan T. Venkataraman
2021-04-09 21:37 ` Josh Poimboeuf
2021-04-09 22:05 ` Madhavan T. Venkataraman
2021-04-09 22:32 ` Josh Poimboeuf
2021-04-09 22:53 ` Josh Poimboeuf
2021-04-11 17:54 ` Madhavan T. Venkataraman [this message]
2021-04-12 16:59 ` Mark Brown
2021-04-13 22:53 ` Josh Poimboeuf
2021-04-14 12:24 ` Mark Brown
2021-04-12 17:36 ` Mark Brown
2021-04-12 19:55 ` Madhavan T. Venkataraman
2021-04-13 11:02 ` Mark Brown
2021-04-14 10:23 ` Madhavan T. Venkataraman
2021-04-14 12:35 ` Mark Brown
2021-04-16 14:43 ` Madhavan T. Venkataraman
2021-04-16 15:36 ` Mark Brown
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=1be20ada-6b52-c6e8-508c-7572c438d2b7@linux.microsoft.com \
--to=madvenka@linux.microsoft.com \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=jpoimboe@redhat.com \
--cc=jthierry@redhat.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=live-patching@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=peterz@infradead.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
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;
as well as URLs for NNTP newsgroup(s).