# SystemTap Tapset Reference Manual

## Introduction

SystemTap provides free software (GPL) infrastructure to simplify the gathering of information about the running Linux system. This assists diagnosis of a performance or functional problem. SystemTap eliminates the need for the developer to go through the tedious and disruptive instrument, recompile, install, and reboot sequence that may be otherwise required to collect data.

SystemTap provides a simple command line interface and scripting language for writing instrumentation for a live running kernel. The instrumentation makes extensive use of the probe points and functions provided in the tapset library. This document describes the various probe points and functions.

### Tapset Name Format

In this guide, tapset definitions appear in the following format:

    	name:return (parameters)
    	definition

The `return` field specifies what data type the tapset extracts and returns from the kernel during a probe (and thus, returns). Tapsets use 2 data types for `return`: `long` (tapset extracts and returns an integer) and `string` (tapset extracts and returns a string).

In some cases, tapsets do not have a `return` value. This simply means that the tapset does not extract anything from the kernel. This is common among asynchronous events such as timers, exit functions, and print functions.

## Context Functions

The context functions provide additional information about where an event occurred. These functions can provide information such as a backtrace to where the event occurred and the current register values for the processor.

!Itapset/context.stp !Itapset/linux/context.stp !Itapset/linux/context-envvar.stp !Itapset/linux/context-symbols.stp !Itapset/linux/ucontext.stp !Itapset/linux/ucontext-symbols.stp !Itapset/linux/context-unwind.stp !Itapset/linux/context-caller.stp !Itapset/linux/ucontext-unwind.stp !Itapset/linux/task.stp !Itapset/linux/task_ancestry.stp !Itapset/pn.stp !Itapset/linux/pstrace.stp !Itapset/registers.stp

## Timestamp Functions

Each timestamp function returns a value to indicate when a function is executed. These returned values can then be used to indicate when an event occurred, provide an ordering for events, or compute the amount of time elapsed between two time stamps.

!Itapset/linux/timestamp.stp !Itapset/linux/timestamp_gtod.stp !Itapset/linux/timestamp_monotonic.stp !Itapset/stopwatch.stp

## Time utility functions

Utility functions to turn seconds since the epoch (as returned by the timestamp function gettimeofday_s()) into a human readable date/time strings.

!Itapset/linux/ctime.stp !Itapset/linux/tzinfo.stp !Itapset/tzinfo.stp

## Shell command functions

Utility functions to enqueue shell commands.

!Itapset/system.stp

## Memory Tapset

This family of probe points is used to probe memory-related events or query the memory usage of the current process. It contains the following probe points:

!Itapset/linux/memory.stp !Itapset/linux/proc_mem.stp

## Task Time Tapset

This tapset defines utility functions to query time related properties of the current tasks, translate those in miliseconds and human readable strings.

!Itapset/linux/task_time.stp

## Scheduler Tapset

This family of probe points is used to probe the task scheduler activities. It contains the following probe points:

!Itapset/linux/scheduler.stp

## IO Scheduler and block IO Tapset

This family of probe points is used to probe block IO layer and IO scheduler activities. It contains the following probe points:

!Itapset/linux/ioscheduler.stp !Itapset/linux/ioblock.stp

## SCSI Tapset

This family of probe points is used to probe SCSI activities. It contains the following probe points:

!Itapset/linux/scsi.stp

## TTY Tapset

This family of probe points is used to probe TTY (Teletype) activities. It contains the following probe points:

!Itapset/linux/tty.stp

## Interrupt Request (IRQ) Tapset

This family of probe points is used to probe interrupt request (IRQ) activities. It contains the following probe points:

!Itapset/linux/irq.stp

## Networking Tapset

This family of probe points is used to probe the activities of the network device and protocol layers.

!Itapset/linux/networking.stp !Itapset/linux/tcp.stp !Itapset/linux/udp.stp !Itapset/linux/ip.stp !Itapset/linux/inet.stp !Itapset/linux/rpc.stp !Itapset/linux/netfilter.stp

## Socket Tapset

This family of probe points is used to probe socket activities. It contains the following probe points:

!Itapset/linux/socket.stp !Itapset/linux/inet_sock.stp

## SNMP Information Tapset

This family of probe points is used to probe socket activities to provide SNMP type information. It contains the following functions and probe points:

!Itapset/linux/ipmib.stp !Itapset/linux/ipmib-filter-default.stp !Itapset/linux/tcpmib.stp !Itapset/linux/tcpmib-filter-default.stp !Itapset/linux/linuxmib.stp !Itapset/linux/linuxmib-filter-default.stp

## Kernel Process Tapset

This family of probe points is used to probe process-related activities. It contains the following probe points:

!Itapset/linux/kprocess.stp !Itapset/linux/target_set.stp !Itapset/linux/loadavg.stp

## Signal Tapset

This family of probe points is used to probe signal activities. It contains the following probe points:

!Itapset/linux/signal.stp

## Errno Tapset

This set of functions is used to handle errno number values. It contains the following functions:

!Itapset/errno.stp

## RLIMIT Tapset

This set of functions is used to handle string which defines resource limits (RLIMIT_*) and returns corresponding number of resource limit. It contains the following functions:

!Itapset/linux/rlimit.stp

## Device Tapset

This set of functions is used to handle kernel and userspace device numbers. It contains the following functions:

!Itapset/linux/dev.stp

## Directory-entry (dentry) Tapset

This family of functions is used to map kernel VFS directory entry pointers to file or full path names.

!Itapset/linux/dentry.stp

## Logging Tapset

This family of functions is used to send simple message strings to various destinations.

!Itapset/logging.stp !Itapset/linux/logging.stp

## Queue Statistics Tapset

This family of functions is used to track performance of queuing systems.

!Itapset/queue_stats.stp

## Random functions Tapset

These functions deal with random number generation.

!Itapset/random.stp

## String and data retrieving functions Tapset

Functions to retrieve strings and other primitive types from the kernel or a user space programs based on addresses. All strings are of a maximum length given by MAXSTRINGLEN.

!Itapset/linux/conversions.stp !Itapset/linux/atomic.stp !Itapset/uconversions.stp

## String and data writing functions Tapset

The SystemTap guru mode can be used to test error handling in kernel code by simulating faults. The functions in the this tapset provide standard methods of writing to primitive types in the kernel's memory. All the functions in this tapset require the use of guru mode (`-g`).

!Itapset/linux/conversions-guru.stp

## Guru tapsets

Functions to deliberately interfere with the system's behavior, in order to inject faults or improve observability. All the functions in this tapset require the use of guru mode (`-g`).

!Itapset/linux/guru-delay.stp !Itapset/linux/panic.stp !Itapset/linux/guru-signal.stp

## A collection of standard string functions

Functions to get the length, a substring, getting at individual characters, string seaching, escaping, tokenizing, and converting strings to longs.

!Itapset/string.stp !Itapset/tokenize.stp

## Utility functions for using ansi control chars in logs

Utility functions for logging using ansi control characters. This lets you manipulate the cursor position and character color output and attributes of log messages.

!Itapset/ansi.stp !Itapset/indent.stp

## SystemTap Translator Tapset

This family of user-space probe points is used to probe the operation of the SystemTap translator (`stap`) and run command (`staprun`). The tapset includes probes to watch the various phases of SystemTap and SystemTap's management of instrumentation cache. It contains the following probe points:

!Itapset/stap_staticmarkers.stp

## Network File Storage Tapsets

This family of probe points is used to probe network file storage functions and operations.

!Itapset/linux/nfs_proc.stp !Itapset/linux/nfs.stp !Itapset/linux/nfsd.stp !Itapset/linux/nfsderrno.stp

## Speculation

This family of functions provides the ability to speculative record information and then at a later point in the SystemTap script either commit the information or discard it.

!Itapset/speculative.stp