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authorAnanth N Mavinakayanahalli <ananth@in.ibm.com>2007-05-08 03:34:16 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-08 14:15:19 -0400
commitbf8f6e5b3e51ee0c64c2d1350c70198ddc8ad3f7 (patch)
treec48ebb92f836cfac58465eacc9658fbc2bac4783 /Documentation/kprobes.txt
parent4c4308cb93450989846ac49faeb6dab943e7657e (diff)
Kprobes: The ON/OFF knob thru debugfs
This patch provides a debugfs knob to turn kprobes on/off o A new file /debug/kprobes/enabled indicates if kprobes is enabled or not (default enabled) o Echoing 0 to this file will disarm all installed probes o Any new probe registration when disabled will register the probe but not arm it. A message will be printed out in such a case. o When a value 1 is echoed to the file, all probes (including ones registered in the intervening period) will be enabled o Unregistration will happen irrespective of whether probes are globally enabled or not. o Update Documentation/kprobes.txt to reflect these changes. While there also update the doc to make it current. We are also looking at providing sysrq key support to tie to the disabling feature provided by this patch. [akpm@linux-foundation.org: Use bool like a bool!] [akpm@linux-foundation.org: add printk facility levels] [cornelia.huck@de.ibm.com: Add the missing arch_trampoline_kprobe() for s390] Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/kprobes.txt')
-rw-r--r--Documentation/kprobes.txt34
1 files changed, 31 insertions, 3 deletions
diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
index d71fafffce90..da5404ab7569 100644
--- a/Documentation/kprobes.txt
+++ b/Documentation/kprobes.txt
@@ -14,6 +14,7 @@ CONTENTS
148. Kprobes Example 148. Kprobes Example
159. Jprobes Example 159. Jprobes Example
1610. Kretprobes Example 1610. Kretprobes Example
17Appendix A: The kprobes debugfs interface
17 18
181. Concepts: Kprobes, Jprobes, Return Probes 191. Concepts: Kprobes, Jprobes, Return Probes
19 20
@@ -349,9 +350,12 @@ for instrumentation and error reporting.)
349 350
350If the number of times a function is called does not match the number 351If the number of times a function is called does not match the number
351of times it returns, registering a return probe on that function may 352of times it returns, registering a return probe on that function may
352produce undesirable results. We have the do_exit() case covered. 353produce undesirable results. In such a case, a line:
353do_execve() and do_fork() are not an issue. We're unaware of other 354kretprobe BUG!: Processing kretprobe d000000000041aa8 @ c00000000004f48c
354specific cases where this could be a problem. 355gets printed. With this information, one will be able to correlate the
356exact instance of the kretprobe that caused the problem. We have the
357do_exit() case covered. do_execve() and do_fork() are not an issue.
358We're unaware of other specific cases where this could be a problem.
355 359
356If, upon entry to or exit from a function, the CPU is running on 360If, upon entry to or exit from a function, the CPU is running on
357a stack other than that of the current task, registering a return 361a stack other than that of the current task, registering a return
@@ -614,3 +618,27 @@ http://www-106.ibm.com/developerworks/library/l-kprobes.html?ca=dgr-lnxw42Kprobe
614http://www.redhat.com/magazine/005mar05/features/kprobes/ 618http://www.redhat.com/magazine/005mar05/features/kprobes/
615http://www-users.cs.umn.edu/~boutcher/kprobes/ 619http://www-users.cs.umn.edu/~boutcher/kprobes/
616http://www.linuxsymposium.org/2006/linuxsymposium_procv2.pdf (pages 101-115) 620http://www.linuxsymposium.org/2006/linuxsymposium_procv2.pdf (pages 101-115)
621
622
623Appendix A: The kprobes debugfs interface
624
625With recent kernels (> 2.6.20) the list of registered kprobes is visible
626under the /debug/kprobes/ directory (assuming debugfs is mounted at /debug).
627
628/debug/kprobes/list: Lists all registered probes on the system
629
630c015d71a k vfs_read+0x0
631c011a316 j do_fork+0x0
632c03dedc5 r tcp_v4_rcv+0x0
633
634The first column provides the kernel address where the probe is inserted.
635The second column identifies the type of probe (k - kprobe, r - kretprobe
636and j - jprobe), while the third column specifies the symbol+offset of
637the probe. If the probed function belongs to a module, the module name
638is also specified.
639
640/debug/kprobes/enabled: Turn kprobes ON/OFF
641
642Provides a knob to globally turn registered kprobes ON or OFF. By default,
643all kprobes are enabled. By echoing "0" to this file, all registered probes
644will be disarmed, till such time a "1" is echoed to this file.