Kernel Markers Wiki

I wrote a little bit about kernel markers before, but I’ve since found a wiki with some more information: http://sourceware.org/systemtap/wiki/UsingMarkers. Besides information on adding new markers to the kernel source and building kernels that include marker support, it also has information on using markers in SystemTap.

It certainly does seem to make SystemTap scripts easier to write:

probe kernel.mark("some_marker") { printf("some_marker hit: %p, %d\n",                                                                                                             
                                                 $arg1, $arg2) }

The obvious first question from someone sitting down to write a SystemTap script that uses markers: where are the markers, what are their labels, and what are the arguments you can access using them? Perhaps the marker developers could write a tool that parses the kernel source and spits out a document that provides the names and locations of the available markers, along with the arguments that they expose.

The wiki page notes another failing with the current implementation: if a marker is a structure pointer, the struct type can’t be obtained from a SystemTap script. Consequently, the members of the struct are not easily accessible. Perhaps the documentation that results from post-processing the source could also be used to provide the type of each of the arguments. Just a suggestion.

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