Re: [PATCH v11 8/9] arm64: Add kernel return probes support (kretprobes)

From	David Long <dave.long@linaro.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v11 8/9] arm64: Add kernel return probes support (kretprobes)
Date	2016-03-21 14:40 +0100
Message-ID	<rf8dP-6jL-3@gated-at.bofh.it> (permalink)
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On 03/17/2016 08:58 AM, 平松雅巳 / HIRAMATU，MASAMI wrote:
>> From: 平松雅巳 / HIRAMATU，MASAMI [mailto:masami.hiramatsu.pt@hitachi.com]
>>
>> Hi,
>>
>>> From: Sandeepa Prabhu <sandeepa.s.prabhu@gmail.com>
>>>
>>> The pre-handler of this special 'trampoline' kprobe executes the return
>>> probe handler functions and restores original return address in ELR_EL1.
>>> This way the saved pt_regs still hold the original register context to be
>>> carried back to the probed kernel function.
>>
>> This patch seems not well separated.
>>
>>> diff --git a/arch/arm64/kernel/kprobes.c b/arch/arm64/kernel/kprobes.c
>>> index bd3f233..13d3333 100644
>>> --- a/arch/arm64/kernel/kprobes.c
>>> +++ b/arch/arm64/kernel/kprobes.c
>>
>> [snip]
>>
>>> +void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
>>> +				      struct pt_regs *regs)
>>> +{
>>> +	ri->ret_addr = (kprobe_opcode_t *)regs->regs[30];
>>> +
>>> +	/* replace return addr (x30) with trampoline */
>>> +	regs->regs[30] = (long)&kretprobe_trampoline;
>>
>> So, where is the kretprobe_trampoline? It seems that function is
>> defined in other patch.
>>
>>> +}
>>> +
>>> +int __kprobes arch_trampoline_kprobe(struct kprobe *p)
>>> +{
>>> +	return 0;
>>> }
>>
>> And what this function is for??
>
> Ah, sorry, this was my fault. Yes, this function is required.
> But this implementation also means there is an asm-based trampoline
> function which should be included in this patch.
>
> David, could you tell me the repository which I can get the latest
> version of this series? I'd like to see the whole code of kprobes/arm64.
>
> Thank you,
>

It can be found in:

http://git.linaro.org/people/dave.long/linux.git

...in the kprobes64-v11 branch.

Thanks,
-dl

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Re: [PATCH v11 8/9] arm64: Add kernel return probes support  (kretprobes) David Long <dave.long@linaro.org> - 2016-03-21 14:40 +0100

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