From: Mark Brown <broonie@kernel.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: "Paul Elliott" <paul.elliott@arm.com>,
"Peter Zijlstra" <peterz@infradead.org>,
"Andrew Jones" <drjones@redhat.com>,
"Amit Kachhap" <amit.kachhap@arm.com>,
"Vincenzo Frascino" <vincenzo.frascino@arm.com>,
"Will Deacon" <will@kernel.org>,
linux-arch@vger.kernel.org, "Marc Zyngier" <maz@kernel.org>,
"Eugene Syromiatnikov" <esyr@redhat.com>,
"Szabolcs Nagy" <szabolcs.nagy@arm.com>,
"H . J . Lu " <hjl.tools@gmail.com>,
"Yu-cheng Yu" <yu-cheng.yu@intel.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>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Thomas Gleixner" <tglx@linutronix.de>,
linux-arm-kernel@lists.infradead.org,
"Florian Weimer" <fweimer@redhat.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
"Sudakshina Das" <sudi.das@arm.com>
Subject: Re: [PATCH v8 00/11] arm64: Branch Target Identification support
Date: Wed, 11 Mar 2020 17:25:56 +0000 [thread overview]
Message-ID: <20200311172556.GJ5411@sirena.org.uk> (raw)
In-Reply-To: <20200311162858.GK3216816@arrakis.emea.arm.com>
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On Wed, Mar 11, 2020 at 04:28:58PM +0000, Catalin Marinas wrote:
> On Tue, Mar 10, 2020 at 12:42:26PM +0000, Mark Brown wrote:
> > Sorry, I realized thanks to Amit's off-list prompting that I was testing
> > that I was verifying with the wrong kernel binary here (user error since
> > it took me a while to sort out uprobes) so this isn't quite right - you
> > can probe the landing pads with or without this series.
> Can we not change aarch64_insn_is_nop() to actually return true only for
> NOP and ignore everything else in the hint space? We tend to re-use the
> hint instructions for new things in the architecture, so I'd rather
> white-list what we know we can safely probe than black-listing only some
> of the hint instructions.
That's literally the patch I am sitting on which made the difference
with the testing on the wrong binary.
> I haven't assessed the effort of doing the above (probably not a lot)
> but as a short-term workaround we could add the BTI and PAC hint
> instructions to the aarch64_insn_is_nop() (though my preferred option is
> the white-list one).
The only thing I've seen in testing with just NOPs whitelisted is an
inability to probe the PAC instructions which isn't the best user
experience, especially since the effect is that the probes get silently
ignored. This isn't extensive userspace testing though. Adding
whitelisting of the BTI and PAC hints would definitely be a safer as a
first step though. I can post either version?
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next prev parent reply other threads:[~2020-03-11 17:26 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-27 17:44 [PATCH v8 00/11] arm64: Branch Target Identification support Mark Brown
2020-02-27 17:44 ` [PATCH v8 01/11] ELF: UAPI and Kconfig additions for ELF program properties Mark Brown
2020-02-27 17:44 ` [PATCH v8 02/11] ELF: Add ELF program property parsing support Mark Brown
2020-02-27 17:44 ` [PATCH v8 03/11] arm64: Basic Branch Target Identification support Mark Brown
2020-03-11 16:31 ` Catalin Marinas
2020-02-27 17:44 ` [PATCH v8 04/11] elf: Allow arch to tweak initial mmap prot flags Mark Brown
2020-02-27 17:44 ` [PATCH v8 05/11] arm64: elf: Enable BTI at exec based on ELF program properties Mark Brown
2020-02-27 17:44 ` [PATCH v8 06/11] arm64: BTI: Decode BYTPE bits when printing PSTATE Mark Brown
2020-02-27 17:44 ` [PATCH v8 07/11] arm64: unify native/compat instruction skipping Mark Brown
2020-02-27 17:44 ` [PATCH v8 08/11] arm64: traps: Shuffle code to eliminate forward declarations Mark Brown
2020-02-27 17:44 ` [PATCH v8 09/11] arm64: BTI: Reset BTYPE when skipping emulated instructions Mark Brown
2020-02-27 17:44 ` [PATCH v8 10/11] KVM: " Mark Brown
2020-02-27 17:44 ` [PATCH v8 11/11] arm64: mm: Display guarded pages in ptdump Mark Brown
2020-02-28 1:35 ` [PATCH v8 00/11] arm64: Branch Target Identification support Richard Henderson
2020-03-11 19:15 ` Mark Brown
2020-03-06 10:21 ` Catalin Marinas
2020-03-06 10:27 ` Catalin Marinas
2020-03-09 21:05 ` Mark Brown
2020-03-10 12:42 ` Mark Brown
2020-03-11 16:28 ` Catalin Marinas
2020-03-11 17:25 ` Mark Brown [this message]
2020-03-12 18:42 ` Catalin Marinas
2020-03-13 12:59 ` Mark Brown
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