From: James Morse <james.morse@arm.com>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Pratyush Anand <panand@redhat.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
"David A . Long" <dave.long@linaro.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/3] arm64: kprobes: Move extable address check into arch_prepare_kprobe()
Date: Fri, 11 Jan 2019 18:22:38 +0000 [thread overview]
Message-ID: <92c160a8-7627-0c64-ed73-df616e9c057d@arm.com> (raw)
In-Reply-To: <20190109110500.b4b5049f4c67dfc85b9ced4e@kernel.org>
Hi,
On 09/01/2019 02:05, Masami Hiramatsu wrote:
> On Tue, 8 Jan 2019 17:13:36 +0000
> James Morse <james.morse@arm.com> wrote:
>> On 08/01/2019 02:39, Masami Hiramatsu wrote:
>>> On Thu, 3 Jan 2019 17:05:18 +0000
>>> James Morse <james.morse@arm.com> wrote:
>>>> On 17/12/2018 06:40, Masami Hiramatsu wrote:
>>>>> Move extable address check into arch_prepare_kprobe() from
>>>>> arch_within_kprobe_blacklist().
>>>>
>>>> I'm trying to work out the pattern for what should go in the blacklist, and what
>>>> should be rejected by the arch code.
>>>>
>>>> It seems address-ranges should be blacklisted as the contents don't matter.
>>>> easy-example: the idmap text.
>>>
>>> Yes, more precisely, the code smaller than a function (symbol), it must be
>>> rejected by arch_prepare_kprobe(), since blacklist is poplated based on
>>> kallsyms.
>>
>> Ah, okay, so the pattern is the blacklist should only be for whole symbols,
>> (which explains why its usually based on sections).
>
> Correct. Actually, the blacklist is generated based on the symbol info
> from symbol address.
>
>> I see kprobe_add_ksym_blacklist() would go wrong if you give it something like:
>> platform_drv_probe+0x50/0xb0, as it will log platform_drv_probe+0x50 as the
>> start_addr and platform_drv_probe+0x50+0xb0 as the end.
>
> Yes, it expects given address is the entry of a symbol.
>> But how does anything from the arch code's blacklist get into the
>> kprobe_blacklist list?
>
> It should be done via arch_populate_kprobe_blacklist().
>> We don't have an arch_populate_kprobe_blacklist(), so rely on
>> within_kprobe_blacklist() calling arch_within_kprobe_blacklist() with the
>> address, as well as walking kprobe_blacklist.
>>
>> Is this cleanup ahead of a series that does away with
>> arch_within_kprobe_blacklist() so that debugfs list is always complete?
>
> Right, after this cleanup, I will send arch_populate_kprobe_blacklist()
> patch for arm64 and others. My plan is to move all arch_within_kprobe_blacklist()
> to arch_populate_kprobe_blacklist() so that user can get more precise blacklist
> via debugfs.
Thanks, now it all makes sense!
Reviewed-by: James Morse <james.morse@arm.com>
Could you include a paragraph like that in the cover-letter or commit-message?
The 'fix' in the cover-letter subject had me looking for the bug!
Thanks,
James
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next prev parent reply other threads:[~2019-01-11 18:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-17 6:40 [PATCH 0/3] arm64: kprobes: Fix blacklist checking on arm64 Masami Hiramatsu
2018-12-17 6:40 ` [PATCH 1/3] arm64: kprobes: Move extable address check into arch_prepare_kprobe() Masami Hiramatsu
2019-01-03 17:05 ` James Morse
2019-01-08 2:39 ` Masami Hiramatsu
2019-01-08 17:13 ` James Morse
2019-01-09 2:05 ` Masami Hiramatsu
2019-01-11 18:22 ` James Morse [this message]
2019-01-15 5:49 ` Masami Hiramatsu
2018-12-17 6:41 ` [PATCH 2/3] arm64: kprobes: Remove unneeded RODATA check Masami Hiramatsu
2019-01-03 17:07 ` James Morse
2018-12-17 6:41 ` [PATCH 3/3] arm64: kprobes: Move exception_text check in blacklist Masami Hiramatsu
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