From: James Morse <james.morse@arm.com>
To: Pratyush Anand <panand@redhat.com>
Cc: "David Long" <dave.long@linaro.org>,
"Will Deacon" <will.deacon@arm.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Sandeepa Prabhu" <sandeepa.s.prabhu@gmail.com>,
"William Cohen" <wcohen@redhat.com>,
"Steve Capper" <steve.capper@linaro.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
"Marc Zyngier" <marc.zyngier@arm.com>,
"Dave P Martin" <Dave.Martin@arm.com>,
"Mark Rutland" <mark.rutland@arm.com>,
"Robin Murphy" <Robin.Murphy@arm.com>,
"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
"Jens Wiklander" <jens.wiklander@linaro.org>,
"Christoffer Dall" <christoffer.dall@linaro.org>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Yang Shi" <yang.shi@linaro.org>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Viresh Kumar" <viresh.kumar@linaro.org>,
"Suzuki K. Poulose" <suzuki.poulose@arm.com>,
"Kees Cook" <keescook@chromium.org>,
"Zi Shen Lim" <zlim.lnx@gmail.com>,
"John Blackwood" <john.blackwood@ccur.com>,
"Feng Kan" <fkan@apm.com>,
"Balamurugan Shanmugam" <bshanmugam@apm.com>,
"Vladimir Murzin" <Vladimir.Murzin@arm.com>,
"Mark Salyzyn" <salyzyn@android.com>,
"Petr Mladek" <pmladek@suse.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Mark Brown" <broonie@kernel.org>
Subject: Re: [PATCH v11 3/9] arm64: add copy_to/from_user to kprobes blacklist
Date: Fri, 18 Mar 2016 18:12:20 +0000 [thread overview]
Message-ID: <56EC4504.6060702@arm.com> (raw)
In-Reply-To: <20160318144325.GB29225@dhcppc6.redhat.com>
Hi Pratyush,
On 18/03/16 14:43, Pratyush Anand wrote:
> On 18/03/2016:02:02:49 PM, James Morse wrote:
>> In kernel/entry.S when entered from EL0 we test for TIF_SINGLESTEP in the
>> thread_info flags, and use disable_step_tsk/enable_step_tsk to save/restore the
>> single-step state.
>>
>> Could we do this regardless of which EL we came from?
>
> Thanks for another idea. I think, we can not do this as it is, because
> TIF_SINGLESTEP will not be set for kprobe events.
Hmmm, I see kernel_enable_single_step() doesn't set it, but setup_singlestep()
in patch 5 could...
There is probably a good reason its never set for a kernel thread, I will have a
look at where else it is used.
> But, we can introduce a
> variant disable_step_kernel and enable_step_kernel, which can be called in
> el1_da.
What about sp/pc misalignment, or undefined instructions?
Or worse... an irq occurs during your el1_da call (el1_da may re-enable irqs).
el1_irq doesn't know you were careful not to unmask debug exceptions, it blindly
turns them back on.
The problem is the 'single step me' bit is still set, save/restoring it will
save us having to consider every interaction, (and then missing some!).
It would also mean you don't have to disable interrupts while single stepping in
patch 5 (comment above kprobes_save_local_irqflag()).
Thanks,
James
next prev parent reply other threads:[~2016-03-18 18:13 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-09 5:32 [PATCH v11 0/9] arm64: Add kernel probes (kprobes) support David Long
2016-03-09 5:32 ` [PATCH v11 1/9] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature David Long
2016-03-11 18:07 ` James Morse
2016-03-18 13:06 ` David Long
2016-03-15 11:04 ` Marc Zyngier
2016-03-21 7:08 ` David Long
2016-03-09 5:32 ` [PATCH v11 2/9] arm64: Add more test functions to insn.c David Long
2016-03-09 5:32 ` [PATCH v11 3/9] arm64: add copy_to/from_user to kprobes blacklist David Long
2016-03-15 18:47 ` James Morse
2016-03-16 5:43 ` Pratyush Anand
2016-03-16 10:27 ` James Morse
2016-03-17 7:57 ` Pratyush Anand
2016-03-18 13:29 ` Pratyush Anand
2016-03-18 14:02 ` James Morse
2016-03-18 14:43 ` Pratyush Anand
2016-03-18 18:12 ` James Morse [this message]
2016-03-21 5:17 ` Pratyush Anand
2016-03-21 14:52 ` Will Deacon
2016-03-22 16:51 ` Pratyush Anand
2016-03-17 12:04 ` 平松雅巳 / HIRAMATU，MASAMI
2016-03-09 5:32 ` [PATCH v11 4/9] arm64: add conditional instruction simulation support David Long
2016-03-13 12:09 ` Marc Zyngier
2016-03-14 4:04 ` Pratyush Anand
2016-03-14 7:38 ` Marc Zyngier
2016-03-21 8:35 ` David Long
2016-03-09 5:32 ` [PATCH v11 5/9] arm64: Kprobes with single stepping support David Long
2016-04-20 1:29 ` Li Bin
2016-03-09 5:32 ` [PATCH v11 6/9] arm64: kprobes instruction simulation support David Long
2016-03-12 3:56 ` Marc Zyngier
2016-03-21 9:39 ` David Long
2016-03-09 5:32 ` [PATCH v11 7/9] arm64: Add trampoline code for kretprobes David Long
2016-03-13 13:52 ` Marc Zyngier
2016-03-21 13:30 ` David Long
2016-03-09 5:32 ` [PATCH v11 8/9] arm64: Add kernel return probes support (kretprobes) David Long
2016-03-17 12:22 ` 平松雅巳 / HIRAMATU，MASAMI
2016-03-17 12:58 ` 平松雅巳 / HIRAMATU，MASAMI
2016-03-21 13:33 ` David Long
2016-03-09 5:32 ` [PATCH v11 9/9] kprobes: Add arm64 case in kprobe example module David Long
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