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Diffstat (limited to 'Documentation/kprobes.txt')
| -rw-r--r-- | Documentation/kprobes.txt | 34 |
1 files changed, 31 insertions, 3 deletions
diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt index d71fafffce9..da5404ab756 100644 --- a/Documentation/kprobes.txt +++ b/Documentation/kprobes.txt @@ -14,6 +14,7 @@ CONTENTS 8. Kprobes Example 9. Jprobes Example 10. Kretprobes Example +Appendix A: The kprobes debugfs interface 1. Concepts: Kprobes, Jprobes, Return Probes @@ -349,9 +350,12 @@ for instrumentation and error reporting.) If the number of times a function is called does not match the number of times it returns, registering a return probe on that function may -produce undesirable results. We have the do_exit() case covered. -do_execve() and do_fork() are not an issue. We're unaware of other -specific cases where this could be a problem. +produce undesirable results. In such a case, a line: +kretprobe BUG!: Processing kretprobe d000000000041aa8 @ c00000000004f48c +gets printed. With this information, one will be able to correlate the +exact instance of the kretprobe that caused the problem. We have the +do_exit() case covered. do_execve() and do_fork() are not an issue. +We're unaware of other specific cases where this could be a problem. If, upon entry to or exit from a function, the CPU is running on a 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 http://www.redhat.com/magazine/005mar05/features/kprobes/ http://www-users.cs.umn.edu/~boutcher/kprobes/ http://www.linuxsymposium.org/2006/linuxsymposium_procv2.pdf (pages 101-115) + + +Appendix A: The kprobes debugfs interface + +With recent kernels (> 2.6.20) the list of registered kprobes is visible +under the /debug/kprobes/ directory (assuming debugfs is mounted at /debug). + +/debug/kprobes/list: Lists all registered probes on the system + +c015d71a k vfs_read+0x0 +c011a316 j do_fork+0x0 +c03dedc5 r tcp_v4_rcv+0x0 + +The first column provides the kernel address where the probe is inserted. +The second column identifies the type of probe (k - kprobe, r - kretprobe +and j - jprobe), while the third column specifies the symbol+offset of +the probe. If the probed function belongs to a module, the module name +is also specified. + +/debug/kprobes/enabled: Turn kprobes ON/OFF + +Provides a knob to globally turn registered kprobes ON or OFF. By default, +all kprobes are enabled. By echoing "0" to this file, all registered probes +will be disarmed, till such time a "1" is echoed to this file. |