From: Kees Cook <keescook@chromium.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <Mark.Rutland@arm.com>,
Luke Cheeseman <Luke.Cheeseman2@arm.com>,
Diogo Sampaio <Diogo.Sampaio@arm.com>,
Luke Cheeseman <luke.cheeseman@arm.com>,
Catalin Marinas <Catalin.Marinas@arm.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
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: Sun, 2 Jun 2019 08:43:55 -0700 [thread overview]
Message-ID: <201906020843.140EC55FB@keescook> (raw)
In-Reply-To: <20190531092202.GA19208@fuggles.cambridge.arm.com>
On Fri, May 31, 2019 at 10:22:02AM +0100, Will Deacon wrote:
> On Thu, May 30, 2019 at 11:05:15AM -0700, Kees Cook wrote:
> > 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?)
>
> Right, and we could call it kernel.c
>
> Sarcasm aside, please fix this in the toolchain. Moving logically unrelated
> functions into one file just because the toolchain doesn't yet support this
> feature just messes up the codebase and removes the incentive to get this
> implemented properly. After all, you need something to do now that asm goto
> is out of the way, right? ;)
LLVM tracking bug created...
https://bugs.llvm.org/show_bug.cgi?id=42095
--
Kees Cook
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next prev parent reply other threads:[~2019-06-02 15:44 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
2019-05-31 9:22 ` Will Deacon
2019-06-02 15:43 ` Kees Cook [this message]
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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