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RE: Patch [1/3] Userspace probes new interfaces
- From: "Zhang, Yanmin" <yanmin dot zhang at intel dot com>
- To: <prasanna at in dot ibm dot com>
- Cc: <systemtap at sources dot redhat dot com>, "Keshavamurthy, Anil S" <anil dot s dot keshavamurthy at intel dot com>, "Mao, Bibo" <bibo dot mao at intel dot com>
- Date: Thu, 2 Feb 2006 15:31:05 +0800
- Subject: RE: Patch [1/3] Userspace probes new interfaces
>>-----Original Message-----
>>From: Prasanna S Panchamukhi [mailto:prasanna@in.ibm.com]
>>Sent: 2006年1月27日 20:59
>>To: Zhang, Yanmin
>>Cc: systemtap@sources.redhat.com; Keshavamurthy, Anil S; Mao, Bibo
>>Subject: Re: Patch [1/3] Userspace probes new interfaces
>>
>>Yanmin,
>>
>>> >>
>>> >>Please check get_kprobe_user(), p.kp.addr it is used to distinguish
>>> >>between kernel and user space probes.
>>> I know get_kprobe_user uses it, but should the uprobe implementation assign an appropriate value to p.kp.addr? It's not good to ask
>>the caller of register_uprobe to do so because the page might be not in memory or not been mapped into the address space of the process.
>>
>>Another aspect of assigning p.kp.addr, is that even the offset can be
>>derieved from using the address. The user-space tool can read the
>>application's elf section and symbol table to calculate the offset
>>using the address as suggested by Roland.
[YM] Your case is not good at a dynamic libs because they are position independent and can't be expected at a fixed address before being mapped into process address space.