Bug 892 - Kprobes: Multiple probes
Summary: Kprobes: Multiple probes
Alias: None
Product: systemtap
Classification: Unclassified
Component: kprobes (show other bugs)
Version: unspecified
: P2 normal
Target Milestone: ---
Assignee: Ananth Mavinakayanahalli
Depends on:
Blocks: 912
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Reported: 2005-04-29 18:42 UTC by E. Zannoni
Modified: 2005-07-12 14:47 UTC (History)
1 user (show)

See Also:
Last reconfirmed:


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Description E. Zannoni 2005-04-29 18:42:40 UTC
Prototype posted to lkml. Going with one interface.
Comment 1 Ananth N Mavinakayanahalli 2005-05-03 17:40:53 UTC
Patch now in Andrew Morton's -mm tree. Should be part of 2.6.12-rc3-mm3
Comment 2 Ananth N Mavinakayanahalli 2005-05-05 18:42:09 UTC
This bug relates to the enhancement work that is required to enable multiple
kprobes to be registered at a given address. This feature is required since
different users may want different data to be extracted at a given location.

The patch that is currently upstream (2.6.12-rc3-mm3) provides an architecture
agnostic implementation for supporting the registration of multiple kprobes at
the address. It provides for a "manager" kprobe that will have custom
(pre-post-fault) handlers that have in them the logic of walking a list of
kprobes and invoking the individual handlers (execpt in the case of a fault
handler, where only the fault handler corresponding to the kprobe that generated
the fault is invoked).

Note that a jprobe can't coexist with a kprobe (yet).
Comment 3 Ananth N Mavinakayanahalli 2005-06-14 15:41:20 UTC
Status as of 14 June:

- The multiple kprobes support patch is now in the mainline
- Patch to allow a jprobe to coexist with kprobes is in -mm (2.6.12-rc6-mm1)

Note: Due to the new no-exec feature that has been added upstream for ppc64,
multiple probes is currently broken on POWER4 and above. Working with arch
maintainer to resolve the issue.
Comment 4 Ananth N Mavinakayanahalli 2005-06-24 13:08:19 UTC
This isn't an issue as far as RHEL4-U2 is concerned as linux-2.6.9 (off which
RHEL4 kernels are based) doesn't have no-execute support for ppc64.

Also submitted a patch on 17 June to use existing x86_64 code to allocate
executable scratch pages for out of line singlestepping. This patch will show up
in the next -mm.
Comment 5 Ananth N Mavinakayanahalli 2005-07-12 14:47:52 UTC
All patches to provide this feature are upstream - Andrew pushed the single-step
out of line patch to Linus on 23 June.

Closing this bug.