Re: [RFC PATCH v2 5/8] arm64: Detect an FTRACE frame and mark a stack trace unreliable
From: Mark Rutland <mark.rutland@arm.com>
Date: 2021-03-23 16:48:46
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On Tue, Mar 23, 2021 at 10:26:50AM -0500, Madhavan T. Venkataraman wrote:
On 3/23/21 9:57 AM, Mark Rutland wrote: Thanks for explaining the nesting. It is now clear to me.
No problem!
So, my next question is - can we define a practical limit for the nesting so that any nesting beyond that is fatal? The reason I ask is - if there is a max, then we can allocate an array of stack frames out of band for the special frames so they are not part of the stack and will not likely get corrupted.
I suspect we can't define such a fatal limit without introducing a local DoS vector on some otherwise legitimate workload, and I fear this will further complicate the entry/exit logic, so I'd prefer to avoid introducing a new limit. What exactly do you mean by a "special frame", and why do those need additional protection over regular frame records?
Also, we don't have to do any special detection. If the number of out of band frames used is one or more then we have exceptions and the stack trace is unreliable.
What is expected to protect against? Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel