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Message-ID: <fd6c7bf8-9783-48da-b9f2-e0973d636f21@gmail.com>
Date: Fri, 14 Nov 2025 12:34:33 -0500
From: Demi Marie Obenour <demiobenour@...il.com>
To: musl@...ts.openwall.com, Rich Felker <dalias@...c.org>,
Da Xie <xxie_xd@....com>
Subject: Re: Future plans for RISC-V Zicfiss/Zicfilp support?
On 11/13/25 08:36, Rich Felker wrote:
> On Thu, Nov 13, 2025 at 05:19:08PM +0800, Da Xie wrote:
>> Hi everyone,
>>
>> I'm new to the musl community and was exploring its support for RISC-V.
>>
>> I was wondering if there are any plans to support the Zicfiss (shadow
>> stack) and/or Zicfilp (landing pads) extensions in the future. I
>> understand these are relatively new extensions aimed at improving
>> security (similar in spirit to Arm's GCS).
>
> Plans, no, and probably not. We have not supported similar things for
> other architectures because they break existing API contracts about
> how the stack can be used and make it impossible to free resources or
> make promises not to enter unrecoverable late-failure situations, and
> because the idea of playing whack-a-mole with gadgets when you have
> functions like system() present as valid call targets anyway seems
> like very misplaced hardening effort in terms of cost vs benefits.
>
> If there's some way it can work in a non-contract-breaking way,
> supporting it could be on the table eventually, but it's up to folks
> who want it to explain convincingly how that could work.
>
> Rich
If you are okay with sharing, do you have an explanation for why
shadow stacks cause resource problems? Stacks used to be executable,
so making them non-executable was already a compatibility break in
the past.
--
Sincerely,
Demi Marie Obenour (she/her/hers)
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