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Re: [RFC][Revised Patch 4/5] New Probe family : probe kprobe.function()
- From: Prerna Saxena <prerna at linux dot vnet dot ibm dot com>
- To: systemtap at sourceware dot org
- Cc: "Frank Ch. Eigler" <fche at redhat dot com>
- Date: Sun, 19 Apr 2009 23:41:31 +0530
- Subject: Re: [RFC][Revised Patch 4/5] New Probe family : probe kprobe.function()
- References: <49EB61E1.6060302@linux.vnet.ibm.com>
Documentation updates
--
Prerna Saxena
Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India
Index: git-19-apr/stapprobes.3stap.in
===================================================================
--- git-19-apr.orig/stapprobes.3stap.in
+++ git-19-apr/stapprobes.3stap.in
@@ -64,6 +64,7 @@ syscall.*
kernel.function("no_such_function") ?
module("awol").function("no_such_function") !
signal.*? if (switch)
+kprobe.function("foo")
.ESAMPLE
@@ -378,6 +379,40 @@ Other local variables are not generally
a ".return" probe hits, the probed function will have already returned.
+.SS DWARFLESS
+In absence of debugging information, entry & exit points of kernel & module
+functions can be probed using the "kprobe" family of probes.
+However, these do not permit looking up the arguments / local variables
+of the function.
+Following constructs are supported :
+.SAMPLE
+kprobe.function(FUNCTION)
+kprobe.function(FUNCTION).return
+kprobe.module(NAME).function(FUNCTION)
+kprobe.module(NAME).function(FUNCTION).return
+kprobe.statement.(ADDRESS).absolute
+.ESAMPLE
+.PP
+Probes of type
+.B function
+are recommended for kernel functions, whereas probes of type
+.B module
+are recommended for probing functions of the specified module.
+In case the absolute address of a kernel or module function is known,
+.B statement
+probes can be utilized.
+.PP
+Note that
+.I FUNCTION
+and
+.I MODULE
+names
+.B must not
+contain wildcards, or the probe will not be registered.
+Also, statement probes must be run under guru-mode only.
+
+
+
.SS USER-SPACE
Early prototype support for user-space probing is available in the
form of a non-symbolic probe point: