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>,
Kees Cook <keescook@chromium.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 02/10] arm64: asm: Override SYM_FUNC_START when building the kernel with BTI
Date: Wed, 6 May 2020 08:10:26 +0100 [thread overview]
Message-ID: <20200506071025.GA7021@willie-the-truck> (raw)
In-Reply-To: <20200505172100.GI5377@sirena.org.uk>
On Tue, May 05, 2020 at 06:21:00PM +0100, Mark Brown wrote:
> On Tue, May 05, 2020 at 05:08:53PM +0100, Will Deacon wrote:
> > On Tue, May 05, 2020 at 04:18:06PM +0100, Mark Brown wrote:
>
> > > > I also see a scary linker warning about the native VDSO:
>
> > > > aarch64-none-linux-gnu-ld: arch/arm64/kernel/vdso/vgettimeofday.o: warning: BTI turned on by -z force-bti when all inputs do not have BTI in NOTE section.
>
> > > I can't reproduce this, I am using clang-10 as well... can you share
> > > your exact command line and config? I'm using
>
> > Just been debugging this, and it seems that not all clangs are created
> > equal. Updating mine from 10.0.2 to 11.0.1 means I now get the
> > '.note.gnu.property' sections emitted for C files compiled using
> > '-mbranch-protection=pac-ret+leaf+bti', whereas I didn't before.
>
> Oh, that's irritating. I'm using clang from the llvm.org packages,
> currently that's:
>
> 10.0.0-++20200115115127+cbe681bd833-1~exp1~20200115105727.528
>
> so if this is a clang issue it looks like they fixed it in the clang-10
> branch. I'm not sure it's worth trying to detect and handle this or
> not, I don't know how widely deployed toolchains that don't emit the
> property are and there's a fairly clear solution. What do you think?
The linker fixes this up when it warns, right? If so, I think the current
behaviour is fine *but* we might want to improve the diagnostic a bit not
to worry/confuse people. e.g. something like:
"Your compiler is not emitting '.note.gnu.property' sections: forcing
support for BTI in the linker, but consider upgrading your toolchain."
Will
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next prev parent reply other threads:[~2020-05-06 7:10 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 [this message]
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
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
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