From: Kees Cook <keescook@chromium.org>
To: Luke Cheeseman <Luke.Cheeseman2@arm.com>
Cc: Mark Rutland <Mark.Rutland@arm.com>,
Diogo Sampaio <Diogo.Sampaio@arm.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Catalin Marinas <Catalin.Marinas@arm.com>,
Luke Cheeseman <luke.cheeseman@arm.com>,
Will Deacon <Will.Deacon@arm.com>,
Kristina Martsenko <Kristina.Martsenko@arm.com>,
Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
Amit Kachhap <Amit.Kachhap@arm.com>,
Kristof Beyls <Kristof.Beyls@arm.com>,
Christof Douma <Christof.Douma@arm.com>,
Suzuki Poulose <Suzuki.Poulose@arm.com>,
Dave P Martin <Dave.Martin@arm.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC v2 0/7] arm64: return address signing
Date: Thu, 30 May 2019 11:05:15 -0700 [thread overview]
Message-ID: <201905301058.CA55245A0@keescook> (raw)
In-Reply-To: <DB7PR08MB3865A83066179CE419D171EDBF180@DB7PR08MB3865.eurprd08.prod.outlook.com>
On Thu, May 30, 2019 at 04:55:08PM +0000, Luke Cheeseman wrote:
> The semantics of this attribute are straightforward enough but it
> raises some questions. One question being why would I want to turn off
> BTI (also controlled by this option) for one function in a file? Which
> gets a bit odd.
It's about leaving very early CPU startup functions in the kernel from
getting marked up (since they are running before or during the PAC setup).
> I don't know if the alternatives have been suggested but it's
> possible to achieve the result you seem to be after (a function without
> return address signing) in a couple of ways. First and foremost,
> separating the function out into it's own file and compiling with
> -mbranch-protection=none. Alternatively, writing the function in assembly
> or perhaps even a naked function with inline assembly.
Fair enough. :) Thanks for the clarification. Yeah, split on compilation
unit could work. (In the future, though, having the attribute flexibility
would be nice.)
Kristina, would it be feasible to split these functions into a separate
source file? (There doesn't seem to be a need to inline them, given
they're not performance sensitive and only used once, etc?)
--
Kees Cook
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next prev parent reply other threads:[~2019-05-30 18:05 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-29 19:03 [RFC v2 0/7] arm64: return address signing Kristina Martsenko
2019-05-29 19:03 ` [RFC v2 1/7] arm64: cpufeature: add pointer auth meta-capabilities Kristina Martsenko
2019-05-30 1:58 ` Kees Cook
2019-05-30 10:50 ` Suzuki K Poulose
2019-06-13 16:13 ` Suzuki K Poulose
2019-05-29 19:03 ` [RFC v2 2/7] arm64: install user ptrauth keys at kernel exit time Kristina Martsenko
2019-05-30 2:04 ` Kees Cook
2019-06-06 16:26 ` Catalin Marinas
2019-05-29 19:03 ` [RFC v2 3/7] arm64: cpufeature: handle conflicts based on capability Kristina Martsenko
2019-05-30 2:49 ` Kees Cook
2019-05-30 14:16 ` Suzuki K Poulose
2019-05-31 14:00 ` Kristina Martsenko
2019-05-31 15:08 ` Suzuki K Poulose
2019-05-29 19:03 ` [RFC v2 4/7] arm64: enable ptrauth earlier Kristina Martsenko
2019-05-30 3:11 ` Kees Cook
2019-06-13 15:41 ` Suzuki K Poulose
2019-05-29 19:03 ` [RFC v2 5/7] arm64: initialize and switch ptrauth kernel keys Kristina Martsenko
2019-05-30 3:34 ` Kees Cook
2019-05-30 16:26 ` Kristina Martsenko
2019-06-04 10:03 ` Dave Martin
2019-06-06 16:44 ` Catalin Marinas
2019-06-12 16:21 ` Kristina Martsenko
2019-06-13 10:44 ` Catalin Marinas
2019-05-29 19:03 ` [RFC v2 6/7] arm64: unwind: strip PAC from kernel addresses Kristina Martsenko
2019-05-30 3:36 ` Kees Cook
2019-05-29 19:03 ` [RFC v2 7/7] arm64: compile the kernel with ptrauth return address signing Kristina Martsenko
2019-05-30 3:45 ` Kees Cook
2019-05-30 3:09 ` [RFC v2 0/7] arm64: " Kees Cook
2019-05-30 7:25 ` Will Deacon
2019-05-30 8:39 ` Ard Biesheuvel
2019-05-30 9:11 ` Ramana Radhakrishnan
2019-05-30 9:12 ` Ramana Radhakrishnan
2019-06-06 17:44 ` Kristina Martsenko
2019-06-08 4:09 ` Kees Cook
[not found] ` <DB7PR08MB3865C4AA36C9C465B2A687DABF180@DB7PR08MB3865.eurprd08.prod.outlook.com>
2019-05-30 15:57 ` Kees Cook
[not found] ` <DB7PR08MB3865A83066179CE419D171EDBF180@DB7PR08MB3865.eurprd08.prod.outlook.com>
2019-05-30 18:05 ` Kees Cook [this message]
2019-05-31 9:22 ` Will Deacon
2019-06-02 15:43 ` Kees Cook
2019-06-03 10:40 ` Will Deacon
2019-06-04 13:52 ` Luke Cheeseman
2019-06-06 17:43 ` Kristina Martsenko
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