From: Mark Brown <broonie@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: "Szabolcs Nagy" <szabolcs.nagy@arm.com>,
"Will Deacon" <will@kernel.org>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Paul Elliott" <paul.elliott@arm.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Yu-cheng Yu" <yu-cheng.yu@intel.com>,
"Amit Kachhap" <amit.kachhap@arm.com>,
"Vincenzo Frascino" <vincenzo.frascino@arm.com>,
"Marc Zyngier" <maz@kernel.org>,
"Eugene Syromiatnikov" <esyr@redhat.com>,
"H . J . Lu " <hjl.tools@gmail.com>,
"Andrew Jones" <drjones@redhat.com>,
"Kees Cook" <keescook@chromium.org>,
"Arnd Bergmann" <arnd@arndb.de>, "Jann Horn" <jannh@google.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Kristina Martšenko" <kristina.martsenko@arm.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Florian Weimer" <fweimer@redhat.com>,
"Sudakshina Das" <sudi.das@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linux-fsdevel@vger.kernel.org, nd@arm.com
Subject: Re: [PATCH v10 00/13] arm64: Branch Target Identification support
Date: Mon, 23 Mar 2020 13:24:12 +0000 [thread overview]
Message-ID: <20200323132412.GD4948@sirena.org.uk> (raw)
In-Reply-To: <20200323122143.GB4892@mbp>
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On Mon, Mar 23, 2020 at 12:21:44PM +0000, Catalin Marinas wrote:
> On Fri, Mar 20, 2020 at 05:39:46PM +0000, Szabolcs Nagy wrote:
> +int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state,
> + bool has_interp, bool is_interp)
> +{
> + if (is_interp != has_interp)
> + return prot;
> +
> + if (!(state->flags & ARM64_ELF_BTI))
> + return prot;
> +
> + if (prot & PROT_EXEC)
> + prot |= PROT_BTI;
> +
> + return prot;
> +}
> At a quick look, for dynamic binaries we have has_interp == true and
> is_interp == false. I don't know why but, either way, the above code
> needs a comment with some justification.
I don't really know for certain either, I inherited this code as is with
the understanding that this was all agreed with the toolchain and libc
people - the actual discussion that lead to the decisions being made
happened before I was involved. My understanding is that the idea was
that the dynamic linker would be responsible for mapping everything in
dynamic applications other than itself but other than consistency I
don't know why. I guess it defers more decision making to userspace but
I'm having a hard time thinking of sensible cases where one might wish
to make a decision other than enabling PROT_BTI.
I'd be perfectly happy to drop the check if that makes more sense to
people, otherwise I can send a patch adding a comment explaining the
situation.
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next prev parent reply other threads:[~2020-03-23 13:24 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-16 16:50 [PATCH v10 00/13] arm64: Branch Target Identification support Mark Brown
2020-03-16 16:50 ` [PATCH v10 01/13] ELF: UAPI and Kconfig additions for ELF program properties Mark Brown
2020-03-16 16:50 ` [PATCH v10 02/13] ELF: Add ELF program property parsing support Mark Brown
2020-03-16 16:50 ` [PATCH v10 03/13] arm64: Basic Branch Target Identification support Mark Brown
2020-03-16 16:50 ` [PATCH v10 04/13] elf: Allow arch to tweak initial mmap prot flags Mark Brown
2020-03-16 16:50 ` [PATCH v10 05/13] arm64: elf: Enable BTI at exec based on ELF program properties Mark Brown
2020-03-16 16:50 ` [PATCH v10 06/13] arm64: BTI: Decode BYTPE bits when printing PSTATE Mark Brown
2020-03-16 16:50 ` [PATCH v10 07/13] arm64: unify native/compat instruction skipping Mark Brown
2020-03-16 16:50 ` [PATCH v10 08/13] arm64: traps: Shuffle code to eliminate forward declarations Mark Brown
2020-03-16 16:50 ` [PATCH v10 09/13] arm64: BTI: Reset BTYPE when skipping emulated instructions Mark Brown
2020-03-16 16:50 ` [PATCH v10 10/13] KVM: " Mark Brown
2020-03-16 16:50 ` [PATCH v10 11/13] arm64: mm: Display guarded pages in ptdump Mark Brown
2020-03-16 16:50 ` [PATCH v10 12/13] mm: smaps: Report arm64 guarded pages in smaps Mark Brown
2020-03-16 16:50 ` [PATCH v10 13/13] arm64: BTI: Add Kconfig entry for userspace BTI Mark Brown
2020-03-17 18:49 ` [PATCH v10 00/13] arm64: Branch Target Identification support Catalin Marinas
2020-03-20 17:39 ` Szabolcs Nagy
2020-03-23 12:21 ` Catalin Marinas
2020-03-23 13:24 ` Mark Brown [this message]
2020-03-23 13:57 ` Mark Rutland
2020-03-23 14:39 ` Catalin Marinas
2020-03-23 14:55 ` Mark Rutland
2020-03-23 15:32 ` Mark Brown
2020-03-24 15:43 ` Szabolcs Nagy
2020-03-23 15:02 ` Mark Rutland
2020-04-22 15:44 ` Mark Brown
2020-04-22 16:29 ` Catalin Marinas
2020-04-28 13:28 ` Will Deacon
2020-04-28 15:12 ` Mark Brown
2020-04-28 15:18 ` Will Deacon
2020-04-28 15:58 ` Mark Brown
2020-04-28 16:01 ` Will Deacon
2020-04-30 21:26 ` Will Deacon
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