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Gmane
From: Mathieu Desnoyers <mathieu.desnoyers <at> polymtl.ca>
Subject: [RFC patch 00/21] TIF_KERNEL_TRACE thread flags
Newsgroups: gmane.linux.kernel
Date: Sunday 15th March 2009 19:03:40 UTC (over 7 years ago)
Hello,

This is the implementatino of TIF_KERNEL_TRACE thread flags I did in the
LTTng
tree. Basically, it offers :

- Setting a per-thread flag for _all_ threads to enable system-wide syscall
  tracing.
- No performance impact when disabled, no need to stop threads upon
  activation/deactivation (does not add latency to userspace threads upon
  activation).

The most tricky bits are in the x86_64 architecture, because its entry_64.S
code does not expect the thread flags to be changed concurrently while the
thread is running. I modified entry_64.S so that the architecture does not
suffer of any performance impact when syscall audit or secure computing is
enabled, but tests for the TIF_KERNEL_TRACE flag upon return to userspace
too.

Given this looks very much like what Frederic is currently doing, I think
it's
good to post it for comments.

utrace tracehooks could potentially make this patchset obsolete, but I an
not
yet convinced that utrace offers the same low-latency guarantees as this
code.

It applies on top of kernel 2.6.29-rc7.

Mathieu

-- 
Mathieu Desnoyers
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