Re: [RFC] [PATCH 0/7] UBP, XOL and Uprobes [ Summary of Commentsand actions to be taken ]

[Masami Hiramatsu]

Peter Zijlstra wrote:
> On Fri, 2010-01-22 at 12:32 +0530, Srikar Dronamraju wrote:
> 
>> 2. XOL vma vs Emulation vs Single Stepping Inline vs using Protection
>> Rings.
>> 	XOL VMA is an additional process address vma.  This is
>> 	opposition to add an additional vma without user actually
>> 	requesting for the same.
>>
>> 	XOL vma and single stepping inline are the two architecture
>> 	independent implementations. While other implementations are
>> 	more architecture specific. Single stepping inline wouldnt go
>> 	well with multithreaded process.
>>
>> 	Even though XOL vma has its own issues, we will go with it since
>> 	other implementations seem to have more complications.
>>
>> 	we would look forward to implementing boosters later. 
>> 	Later on, if we come across another techniques with lesser
>> 	side-effects than the XOL vma, we would switch to using them.
> 
> How about modifying glibc to reserve like 64 bytes on the TLS structure
> it has and storing the ins and possible boost jmp there? Since each
> thread can only have a single trap at any one time that should be
> enough.

Hmm, it is a good idea. Well, we'll have a copy of original insn
in kernel, but it could be simpler than managing XOL vma. :-)

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@xxxxxxxxxx

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