From: Catalin Marinas <catalin.marinas@arm•com>
To: Mark Brown <broonie@kernel•org>
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 16:28:58 +0000 [thread overview]
Message-ID: <20200311162858.GK3216816@arrakis.emea.arm.com> (raw)
In-Reply-To: <20200310124226.GC4106@sirena.org.uk>
On Tue, Mar 10, 2020 at 12:42:26PM +0000, Mark Brown wrote:
> On Mon, Mar 09, 2020 at 09:05:05PM +0000, Mark Brown wrote:
> > On Fri, Mar 06, 2020 at 10:27:29AM +0000, Catalin Marinas wrote:
>
> > > Does this series affect uprobes in any way? I.e. can you probe a landing
> > > pad?
>
> > You can't probe a landing pad, uprobes on landing pads will be silently
> > ignored so the program isn't disrupted, you just don't get the expected
> > trace from those uprobes. This isn't new with the BTI support since
> > the landing pads are generally pointer auth instructions, these already
> > can't be probed regardless of what's going on with this series. It's
> > already on the list to get sorted.
>
> 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.
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).
--
Catalin
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next prev parent reply other threads:[~2020-03-11 16:29 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 [this message]
2020-03-11 17:25 ` Mark Brown
2020-03-12 18:42 ` Catalin Marinas
2020-03-13 12:59 ` Mark Brown
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