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

From: Masami Hiramatsu
Date: Fri Jan 22 2010 - 13:37:54 EST

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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