utrace-based uprobes

[Jim Keniston]

Enclosed are updated versions of the uprobes patches that have been
sitting on the shelf for 1.5 months.  (It's a long story.)  These should
apply cleanly against any -mm kernel that includes utrace.

As noted my email to Roland of several minutes ago, we hope to soon
publish an update that completely reworks single-stepping out of line.

I also anticipate that we'll store the uretprobe trampoline in the same
vm area that holds the instruction slots, so if you review this stuff,
don't spend a lot of time worrying over init_uretprobes(),
do_init_uretprobes(), and uretprobe_set_trampoline().  The user won't
have to specify a trampoline address.

Jim Keniston

-------- Forwarded Message --------
From: Jim Keniston <jkenisto@us.ibm.com>
To: RedHat_perftools <external-perftools-list@redhat.com>
Subject: utrace-based uprobes
Date: 26 Jan 2007 18:34:03 -0800

As promised yesterday, here, in patch form, is our utrace-based
implementation of user-space probes.

Patch #1 implements the basic uprobes feature set for i386, and provides
Documentation/uprobes.txt, a user's guide.

Patch #2 adds user-space return probes.

Patch #3 adds the ability to register or unregister probes from probe
handlers.

The only existing kernel files tweaked by these patches are a couple of
Makefiles and arch/i386/Kconfig, so these patches should work for any
kernel that includes utrace.

In systemtap cvs,
- private/uprobes/patches contains these patches;
- private/uprobes/src contains the source files (which are currently in
sync with the patches); and
- private/uprobes/test and private/wilder/uprobes/test contain tests.

Comments welcome.

Jim Keniston
IBM LTC-RAS
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