From: David Long <dave.long@linaro.org>
To: "Jon Medhurst (Tixy)" <tixy@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org,
Russell King <linux@arm.linux.org.uk>,
Sandeepa Prabhu <sandeepa.prabhu@linaro.org>,
William Cohen <wcohen@redhat.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
davem@davemloft.net, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/5] arm64: Kprobes with single stepping support
Date: Thu, 20 Nov 2014 23:28:32 -0500 [thread overview]
Message-ID: <546EBF70.9020706@linaro.org> (raw)
In-Reply-To: <1416317295.1735.9.camel@linaro.org>
On 11/18/14 08:28, Jon Medhurst (Tixy) wrote:
> On Tue, 2014-11-18 at 01:32 -0500, David Long wrote:
>> From: Sandeepa Prabhu <sandeepa.prabhu@linaro.org>
>>
>> Add support for basic kernel probes(kprobes) and jump probes
>> (jprobes) for ARM64.
>>
>> Kprobes will utilize software breakpoint and single step debug
>> exceptions supported on ARM v8.
>>
>> software breakpoint is placed at the probe address to trap the
>> kernel execution into kprobe handler.
>>
>> ARM v8 support single stepping to be enabled while exception return
>> (ERET) with next PC in exception return address (ELR_EL1).
>> kprobe handler prepares a executable memory slot for out-of-line
>> execution with the copy of the original instruction under probe, and
>> enable single stepping from the instruction slot. With this scheme,
>> the instruction is executed with the exact same register context
>> 'except PC' that points to instruction slot.
>>
>> Debug mask(PSTATE.D) is enabled only when single stepping a recursive
>> kprobes i.e. during kprobes reenter so that probes instruction can be
>> single stepped within the kprobe handler -exception- context.
>
> Does this mean that at the point the probed instruction is
> single-stepped there is nothing extra that has been pushed on on the
> kernel stack by any kprobes handling code? I just want to check that you
> aren't going to hit the problems that the 32-bit kprobes code is
> currently being fixed for [1].
>
> The simulated instructions in patch 2 don't access the stack, so they
> are safe from the problem.
>
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-November/303525.html
>
Took me a while to read through the background on this. I believe it is
true nothing extra is put on the stack in the single-step case.
-dl
next prev parent reply other threads:[~2014-11-21 4:28 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-18 6:32 [PATCH v3 0/5] ARM64: Add kernel probes(Kprobes) support David Long
2014-11-18 6:32 ` [PATCH v3 1/5] arm64: Kprobes with single stepping support David Long
2014-11-18 13:28 ` Jon Medhurst (Tixy)
2014-11-21 4:28 ` David Long [this message]
2014-11-18 14:38 ` William Cohen
2014-11-18 14:39 ` William Cohen
2014-11-18 14:56 ` Will Deacon
2014-11-19 11:21 ` Sandeepa Prabhu
2014-11-19 11:25 ` Will Deacon
2014-11-19 14:55 ` David Long
2014-11-20 5:10 ` Sandeepa Prabhu
2014-11-26 6:46 ` David Long
2014-11-26 10:09 ` Will Deacon
2014-12-22 10:10 ` Pratyush Anand
2014-11-18 6:32 ` [PATCH v3 2/5] arm64: Kprobes instruction simulation support David Long
2014-11-18 14:43 ` William Cohen
2014-11-18 6:32 ` [PATCH v3 3/5] arm64: Add kernel return probes support(kretprobes) David Long
2014-11-18 14:50 ` William Cohen
2014-11-18 6:32 ` [PATCH v3 4/5] kprobes: Add arm64 case in kprobe example module David Long
2014-11-18 6:32 ` [PATCH v3 5/5] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature David Long
2014-11-18 14:52 ` Will Deacon
2014-11-20 7:20 ` Masami Hiramatsu
2014-11-21 6:16 ` David Long
2014-11-20 15:02 ` [PATCH v3 0/5] ARM64: Add kernel probes(Kprobes) support Steve Capper
2014-11-26 8:33 ` Masami Hiramatsu
2014-11-26 10:03 ` Steve Capper
2014-11-26 17:46 ` David Long
2014-11-26 18:59 ` Steve Capper
2014-11-27 6:07 ` Masami Hiramatsu
2014-11-28 16:01 ` Steve Capper
2014-12-01 9:37 ` Masami Hiramatsu
2014-12-02 19:27 ` William Cohen
2014-12-02 20:00 ` William Cohen
2014-12-03 3:36 ` Masami Hiramatsu
2014-12-03 14:54 ` William Cohen
2014-12-03 22:54 ` David Long
2014-12-04 0:02 ` David Long
2014-12-04 1:16 ` William Cohen
2014-12-04 2:48 ` David Long
2014-12-04 10:21 ` Steve Capper
2014-12-04 10:43 ` Masami Hiramatsu
2014-12-04 11:29 ` Steve Capper
2014-12-04 11:53 ` Masami Hiramatsu
2014-12-09 13:33 ` Steve Capper
2014-12-09 14:27 ` David Long
2014-12-10 16:38 ` Steve Capper
2014-12-12 22:42 ` David Long
2014-12-12 23:10 ` Steve Capper
2014-12-15 5:58 ` Masami Hiramatsu
2014-12-15 6:29 ` David Long
2014-12-05 5:08 ` William Cohen
2014-11-27 5:13 ` Masami Hiramatsu
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