From: Will Deacon <will@kernel.org>
To: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
Dave Martin <Dave.Martin@arm.com>,
linux-arm-kernel@lists.infradead.org,
Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH v2 02/10] arm64: asm: Override SYM_FUNC_START when building the kernel with BTI
Date: Wed, 6 May 2020 16:48:00 +0100 [thread overview]
Message-ID: <20200506154759.GC12919@willie-the-truck> (raw)
In-Reply-To: <20200506152552.GE5299@sirena.org.uk>
On Wed, May 06, 2020 at 04:25:52PM +0100, Mark Brown wrote:
> On Wed, May 06, 2020 at 03:45:44PM +0100, Will Deacon wrote:
> > On Wed, May 06, 2020 at 02:40:21PM +0100, Dave Martin wrote:
>
> > > I really don't think we should fudge this: if the linker doesn't think
> > > the inputs are BTI-enabled then the compiler or linker is broken, or
> > > there's a bug in the kernel source tree.
>
> > > The checking done by the toolchain is important -- if we want to
> > > suppress it, we should have an override option than depends on BROKEN
> > > (because yes, you're explicitly risking a broken kernel if you do this).
>
> > > The fact that all gcc and clang both screwed this up in various ways at
> > > some point is not our fault, or our problem, providing that fixes are
> > > available...
>
> > > Am I being too paranoid?
>
> That's my position too, we want the warning - I think if we're going to
> do any handling it should either be to prevent use of kernel BTI
> entirely or to do what Will was originally suggesting and print some
> explanatory text somewhere. My inclination is that the former is safer
> and fits more with the general architecture approach to this sort of
> thing.
>
> > I don't think so, but I'm just looking for an answer to "What do we do if
> > people start running into this warning?". As it stands, it sounds like it's
> > unlikely that they will, but if they do then we're going to have to hack
> > something to make it go away.
>
> It's possible that this e-mail thread showing up in searches might well
> answer people's questions anyway (it is going to be one of the few hits
> for the warning ATM). How about we deal with this when we get to it, or
> at least as a followup?
Yes, I don't think it's worth writing patches for this now, just wanted
to get a vague idea of our options if people start complaining.
Cheers,
Will
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-05-06 15:48 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 21:16 [PATCH v2 00/10] arm64: BTI kernel and vDSO support Mark Brown
2020-04-29 21:16 ` [PATCH v2 01/10] arm64: bti: Support building kernel C code using BTI Mark Brown
2020-05-05 16:50 ` Dave Martin
2020-05-05 17:31 ` Mark Brown
2020-05-06 12:24 ` Amit Kachhap
2020-04-29 21:16 ` [PATCH v2 02/10] arm64: asm: Override SYM_FUNC_START when building the kernel with BTI Mark Brown
2020-05-05 14:56 ` Will Deacon
2020-05-05 15:18 ` Mark Brown
2020-05-05 16:08 ` Will Deacon
2020-05-05 17:21 ` Mark Brown
2020-05-06 7:10 ` Will Deacon
2020-05-06 10:41 ` Mark Brown
2020-05-06 10:50 ` Will Deacon
2020-05-06 11:43 ` Mark Brown
2020-05-06 12:27 ` Will Deacon
2020-05-06 13:03 ` Mark Brown
2020-05-06 13:40 ` Dave Martin
2020-05-06 14:45 ` Will Deacon
2020-05-06 15:25 ` Mark Brown
2020-05-06 15:48 ` Will Deacon [this message]
2020-05-06 15:33 ` Dave Martin
2020-04-29 21:16 ` [PATCH v2 03/10] arm64: Set GP bit in kernel page tables to enable BTI for the kernel Mark Brown
2020-04-29 21:16 ` [PATCH v2 04/10] arm64: bpf: Annotate JITed code for BTI Mark Brown
2020-04-29 21:16 ` [PATCH v2 05/10] arm64: mm: Mark executable text as guarded pages Mark Brown
2020-04-29 21:16 ` [PATCH v2 06/10] arm64: bti: Provide Kconfig for kernel mode BTI Mark Brown
2020-04-29 21:16 ` [PATCH v2 07/10] arm64: asm: Provide a mechanism for generating ELF note for BTI Mark Brown
2020-05-05 14:58 ` Will Deacon
2020-05-05 16:51 ` Dave Martin
2020-05-05 17:06 ` Mark Brown
2020-05-06 11:26 ` Will Deacon
2020-05-06 12:38 ` Mark Brown
2020-05-06 13:44 ` Will Deacon
2020-05-06 15:39 ` Mark Brown
2020-04-29 21:16 ` [PATCH v2 08/10] arm64: vdso: Annotate " Mark Brown
2020-04-29 21:16 ` [PATCH v2 09/10] arm64: vdso: Force the vDSO to be linked as BTI when built " Mark Brown
2020-04-29 21:16 ` [PATCH v2 10/10] arm64: vdso: Map the vDSO text with guarded pages " Mark Brown
2020-04-30 17:18 ` [PATCH v2 00/10] arm64: BTI kernel and vDSO support Catalin Marinas
2020-04-30 17:23 ` 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=20200506154759.GC12919@willie-the-truck \
--to=will@kernel.org \
--cc=Dave.Martin@arm.com \
--cc=Vincenzo.Frascino@arm.com \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=keescook@chromium.org \
--cc=linux-arm-kernel@lists.infradead.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