stap
STAP(1) STAP(1)
NAME
stap - systemtap script translator/driver
SYNOPSIS
stap [ OPTIONS ] FILENAME [ ARGUMENTS ]
stap [ OPTIONS ] - [ ARGUMENTS ]
stap [ OPTIONS ] -e SCRIPT [ ARGUMENTS ]
DESCRIPTION
The stap program is the front-end to the Systemtap tool. It accepts
probing instructions (written in a simple scripting language), trans-
lates those instructions into C code, compiles this C code, and loads
the resulting kernel module into a running Linux kernel to perform the
requested system trace/probe functions. You can supply the script in
a named file, from standard input, or from the command line. The pro-
gram runs until it is interrupted by the user, or if the script volun-
tarily invokes the exit() function, or by sufficient number of soft
errors.
The language, which is described in a later section, is strictly
typed, declaration free, procedural, and inspired by awk. It allows
source code points or events in the kernel to be associated with han-
dlers, which are subroutines that are executed synchronously. It is
somewhat similar conceptually to "breakpoint command lists" in the gdb
debugger.
This manual corresponds to version 0.6.2.
OPTIONS
The systemtap translator supports the following options. Any other
option prints a list of supported options.
-v Increase verbosity. Produce a larger volume of informative (?)
output each time option repeated.
-h Show help message.
-V Show version message.
-k Keep the temporary directory after all processing. This may be
useful in order to examine the generated C code, or to reuse
the compiled kernel object.
-g Guru mode. Enable parsing of unsafe expert-level constructs
like embedded C.
-P Prologue-searching mode. Activate heuristics to work around
incorrect debbugging information for $target variables.
-u Unoptimized mode. Disable unused code elision during elabora-
tion.
-w Suppressed warnings mode. Disable warning messages for elided
code in user script.
-b Use bulk mode (percpu files) for kernel-to-user data transfer.
-t Collect timing information on the number of times probe exe-
cutes and average amount of time spent in each probe.
-sNUM Use NUM megabyte buffers for kernel-to-user data transfer. On
a multiprocessor in bulk mode, this is a per-processor amount.
-p NUM Stop after pass NUM. The passes are numbered 1-5: parse, elab-
orate, translate, compile, run. See the PROCESSING section for
details.
-I DIR Add the given directory to the tapset search directory. See
the description of pass 2 for details.
-D NAME=VALUE
Add the given C preprocessor directive to the module Makefile.
These can be used to override limit parameters described below.
-R DIR Look for the systemtap runtime sources in the given directory.
-r RELEASE
Build for given kernel release instead of currently running
one.
-m MODULE
Use the given name for the generated kernel object module,
instead of a unique randomized name. The generated kernel
object module is copied to the current directory.
-o FILE
Send standard output to named file. In bulk mode, percpu files
will start with FILE_ followed by the cpu number.
-c CMD Start the probes, run CMD, and exit when CMD finishes.
-x PID Sets target() to PID. This allows scripts to be written that
filter on a specific process.
ARGUMENTS
Any additional arguments on the command line are passed to the script
parser for substitution. See below.
SCRIPT LANGUAGE
The systemtap script language resembles awk. There are two main out-
ermost constructs: probes and functions. Within these, statements and
expressions use C-like operator syntax and precedence.
GENERAL SYNTAX
Whitespace is ignored. Three forms of comments are supported:
# ... shell style, to the end of line, except for $# and @#
// ... C++ style, to the end of line
/* ... C style ... */
Literals are either strings enclosed in double-quotes (passing through
the usual C escape codes with backslashes), or integers (in decimal,
hexadecimal, or octal, using the same notation as in C). All strings
are limited in length to some reasonable value (a few hundred bytes).
Integers are 64-bit signed quantities, although the parser also
accepts (and wraps around) values above positive 2**63.
In addition, script arguments given at the end of the command line may
be inserted. Use $1 ... $<NN> for insertion unquoted, @1 ... @<NN>
for insertion as a string literal. The number of arguments may be
accessed through $# (as an unquoted number) or through @# (as a quoted
number). These may be used at any place a token may begin, including
within the preprocessing stage. Reference to an argument number
beyond what was actually given is an error.
PREPROCESSING
A simple conditional preprocessing stage is run as a part of parsing.
The general form is similar to the cond ? exp1 : exp2 ternary opera-
tor:
%( CONDITION %? TRUE-TOKENS %)
%( CONDITION %? TRUE-TOKENS %: FALSE-TOKENS %)
The CONDITION is either an expression whose format is determined by
its first keyword, or a string literals comparison or a numeric liter-
als comparison.
If the first part is the identifier kernel_vr or kernel_v to refer to
the kernel version number, with ("2.6.13-1.322FC3smp") or without
("2.6.13") the release code suffix, then the second part is one of the
six standard numeric comparison operators <, <=, ==, !=, >, and >=,
and the third part is a string literal that contains an RPM-style ver-
sion-release value. The condition is deemed satisfied if the version
of the target kernel (as optionally overridden by the -r option) com-
pares to the given version string. The comparison is performed by the
glibc function strverscmp. As a special case, if the operator is for
simple equality (==), or inequality (!=), and the third part contains
any wildcard characters (* or ? or [), then the expression is treated
as a wildcard (mis)match as evaluated by fnmatch.
If, on the other hand, the first part is the identifier arch to refer
to the processor architecture, then the second part then the second
part is one of the two string comparison operators == or !=, and the
third part is a string literal for matching it. This comparison is a
wildcard (mis)match.
Otherwise, the CONDITION is expected to be a comparison between two
string literals or two numeric literals. In this case, the arguments
are the only variables usable.
The TRUE-TOKENS and FALSE-TOKENS are zero or more general parser to-
kens (possibly including nested preprocessor conditionals), and are
pasted into the input stream if the condition is true or false. For
example, the following code induces a parse error unless the target
kernel version is newer than 2.6.5:
%( kernel_v <= "2.6.5" %? **ERROR** %) # invalid token sequence
The following code might adapt to hypothetical kernel version drift:
probe kernel.function (
%( kernel_v <= "2.6.12" %? "__mm_do_fault" %:
%( kernel_vr == "2.6.13*smp" %? "do_page_fault" %:
UNSUPPORTED %) %)
) { /* ... */ }
%( arch == "ia64" %?
probe syscall.vliw = kernel.function("vliw_widget") {}
%)
VARIABLES
Identifiers for variables and functions are an alphanumeric sequence,
and may include "_" and "$" characters. They may not start with a
plain digit, as in C. Each variable is by default local to the probe
or function statement block within which it is mentioned, and there-
fore its scope and lifetime is limited to a particular probe or func-
tion invocation.
Scalar variables are implicitly typed as either string or integer.
Associative arrays also have a string or integer value, and a a tuple
of strings and/or integers serving as a key. Here are a few basic ex-
pressions.
var1 = 5
var2 = "bar"
array1 [pid()] = "name" # single numeric key
array2 ["foo",4,i++] += 5 # vector of string/num/num keys
if (["hello",5,4] in array2) println ("yes") # membership test
The translator performs type inference on all identifiers, including
array indexes and function parameters. Inconsistent type-related use
of identifiers signals an error.
Variables may be declared global, so that they are shared amongst all
probes and live as long as the entire systemtap session. There is one
namespace for all global variables, regardless of which script file
they are found within. A global declaration may be written at the
outermost level anywhere, not within a block of code. The following
declaration marks a few variables as global. The translator will in-
fer for each its value type, and if it is used as an array, its key
types. Optionally, scalar globals may be initialized with a string or
number literal.
global var1, var2, var3=4
Arrays are limited in size by the MAXMAPENTRIES variable -- see the
SAFETY AND SECURITY section for details. Optionally, global arrays
may be declared with a maximum size in brackets, overriding MAXMAPEN-
TRIES for that array only. Note that this doesn’t indicate the type
of keys for the array, just the size.
global tiny_array[10], normal_array, big_array[50000]
STATEMENTS
Statements enable procedural control flow. They may occur within
functions and probe handlers. The total number of statements executed
in response to any single probe event is limited to some number de-
fined by a macro in the translated C code, and is in the neighbourhood
of 1000.
EXP Execute the string- or integer-valued expression and throw away
the value.
{ STMT1 STMT2 ... }
Execute each statement in sequence in this block. Note that
separators or terminators are generally not necessary between
statements.
; Null statement, do nothing. It is useful as an optional sepa-
rator between statements to improve syntax-error detection and
to handle certain grammar ambiguities.
if (EXP) STMT1 [ else STMT2 ]
Compare integer-valued EXP to zero. Execute the first (non-ze-
ro) or second STMT (zero).
while (EXP) STMT
While integer-valued EXP evaluates to non-zero, execute STMT.
for (EXP1; EXP2; EXP3) STMT
Execute EXP1 as initialization. While EXP2 is non-zero, exe-
cute STMT, then the iteration expression EXP3.
foreach (VAR in ARRAY [ limit EXP ]) STMT
Loop over each element of the named global array, assigning
current key to VAR. The array may not be modified within the
statement. By adding a single + or - operator after the VAR or
the ARRAY identifier, the iteration will proceed in a sorted
order, by ascending or descending index or value. Using the
optional limit keyword limits the number of loop iterations to
EXP times. EXP is evaluted once at the beginning of the loop.
foreach ([VAR1, VAR2, ...] in ARRAY [ limit EXP ]) STMT
Same as above, used when the array is indexed with a tuple of
keys. A sorting suffix may be used on at most one VAR or ARRAY
identifier.
break, continue
Exit or iterate the innermost nesting loop (while or for or
foreach) statement.
return EXP
Return EXP value from enclosing function. If the function’s
value is not taken anywhere, then a return statement is not
needed, and the function will have a special "unknown" type
with no return value.
next Return now from enclosing probe handler.
delete ARRAY[INDEX1, INDEX2, ...]
Remove from ARRAY the element specified by the index tuple.
The value will no longer be available, and subsequent itera-
tions will not report the element. It is not an error to
delete an element that does not exist.
delete ARRAY
Remove all elements from ARRAY.
delete SCALAR
Removes the value of SCALAR. Integers and strings are cleared
to 0 and "" respectively, while statistics are reset to the
initial empty state.
EXPRESSIONS
Systemtap supports a number of operators that have the same general
syntax, semantics, and precedence as in C and awk. Arithmetic is per-
formed as per typical C rules for signed integers. Division by zero
or overflow is detected and results in an error.
binary numeric operators
* / % + - >> << & ^ | && ||
binary string operators
. (string concatenation)
numeric assignment operators
= *= /= %= += -= >>= <<= &= ^= |=
string assignment operators
= .=
unary numeric operators
+ - ! ~ ++ --
binary numeric or string comparison operators
< > <= >= == !=
ternary operator
cond ? exp1 : exp2
grouping operator
( exp )
function call
fn ([ arg1, arg2, ... ])
array membership check
exp in array
[exp1, exp2, ...] in array
PROBES
The main construct in the scripting language identifies probes.
Probes associate abstract events with a statement block ("probe han-
dler") that is to be executed when any of those events occur. The
general syntax is as follows:
probe PROBEPOINT [, PROBEPOINT] { [STMT ...] }
Events are specified in a special syntax called "probe points". There
are several varieties of probe points defined by the translator, and
tapset scripts may define further ones using aliases. These are list-
ed in the stapprobes(5) manual pages.
The probe handler is interpreted relative to the context of each
event. For events associated with kernel code, this context may in-
clude variables defined in the source code at that spot. These "tar-
get variables" are presented to the script as variables whose names
are prefixed with "$". They may be accessed only if the kernel’s com-
piler preserved them despite optimization. This is the same con-
straint that a debugger user faces when working with optimized code.
Some other events have very little context.
New probe points may be defined using "aliases". Probe point aliases
look similar to probe definitions, but instead of activating a probe
at the given point, it just defines a new probe point name as an alias
to an existing one. There are two types of alias, i.e. the prologue
style and the epilogue style which are identified by "=" and "+=" re-
spectively.
For prologue style alias, the statement block that follows an alias
definition is implicitly added as a prologue to any probe that refers
to the alias. While for the epilogue style alias, the statement block
that follows an alias definition is implicitly added as an epilogue to
any probe that refers to the alias. For example:
probe syscall.read = kernel.function("sys_read") {
fildes = $fd
}
defines a new probe point syscall.read, which expands to
kernel.function("sys_read"), with the given statement as a prologue.
And
probe syscall.read += kernel.function("sys_read") {
fildes = $fd
}
defines a new probe point with the given statement as an epilogue.
Another probe definition may use the alias like this:
probe syscall.read {
printf("reading fd=%d0, fildes)
}
FUNCTIONS
Systemtap scripts may define subroutines to factor out common work.
Functions take any number of scalar (integer or string) arguments, and
must return a single scalar (integer or string). An example function
declaration looks like this:
function thisfn (arg1, arg2) {
return arg1 + arg2
}
Note the general absence of type declarations, which are instead in-
ferred by the translator. However, if desired, a function definition
may include explicit type declarations for its return value and/or its
arguments. This is especially helpful for embedded-C functions. In
the following example, the type inference engine need only infer type
type of arg2 (a string).
function thatfn:string (arg1:long, arg2) {
return sprint(arg1) . arg2
}
Functions may call others or themselves recursively, up to a fixed
nesting limit. This limit is defined by a macro in the translated C
code and is in the neighbourhood of 10.
PRINTING
There are a set of function names that are specially treated by the
translator. They format values for printing to the standard systemtap
output stream in a more convenient way. The sprint* variants return
the formatted string instead of printing it.
print, sprint
Print one or more values of any type, concatenated directly to-
gether.
println, sprintln
Print values like print and sprint, but also append a newline.
printd, sprintd
Take a string delimiter and two or more values of any type, and
print the values with the delimiter interposed. The delimiter
must be a literal string constant.
printdln, sprintdln
Print values with a delimiter like printd and sprintd, but also
append a newline.
printf, sprintf
Take a formatting string and a number of values of correspond-
ing types, and print them all. The format must be a literal
string constant.
The printf formatting directives similar to those of C, except that
they are fully type-checked by the translator.
x = sprintf("take %d steps forward, %d steps back\n", 3, 2)
printf("take %d steps forward, %d steps back\n", 3+1, 2*2)
bob = "bob"
alice = "alice"
print(bob)
print("hello")
print(10)
printf("%s phoned %s %.4x times\n", bob, alice . bob, 3456)
printf("%s except after %s\n",
sprintf("%s before %s",
sprint(1), sprint(3)),
sprint("C"))
id[bob] = 1234
id[alice] = 5678
foreach (name in id)
printdln("|", strlen(name), name, id[name])
STATISTICS
It is often desirable to collect statistics in a way that avoids the
penalties of repeatedly exclusive locking the global variables those
numbers are being put into. Systemtap provides a solution using a
special operator to accumulate values, and several pseudo-functions to
extract the statistical aggregates.
The aggregation operator is <<<, and resembles an assignment, or a C++
output-streaming operation. The left operand specifies a scalar or
array-index lvalue, which must be declared global. The right operand
is a numeric expression. The meaning is intuitive: add the given num-
ber to the pile of numbers to compute statistics of. (The specific
list of statistics to gather is given separately, by the extraction
functions.)
foo <<< 1
stats[pid()] <<< memsize
The extraction functions are also special. For each appearance of a
distinct extraction function operating on a given identifier, the
translator arranges to compute a set of statistics that satisfy it.
The statistics system is thereby "on-demand". Each execution of an
extraction function causes the aggregation to be computed for that mo-
ment across all processors.
Here is the set of extractor functions. The first argument of each is
the same style of lvalue used on the left hand side of the accumulate
operation. The @count(v), @sum(v), @min(v), @max(v), @avg(v) extrac-
tor functions compute the number/total/minimum/maximum/average of all
accumulated values. The resulting values are all simple integers.
Histograms are also available, but are more complicated because they
have a vector rather than scalar value. @hist_linear(v,start,stop,in-
terval) represents a linear histogram from "start" to "stop" by incre-
ments of "interval". The interval must be positive. Similarly,
@hist_log(v) represents a base-2 logarithmic histogram. Printing a
histogram with the print family of functions renders a histogram ob-
ject as a tabular "ASCII art" bar chart.
probe foo {
x <<< $value
}
probe end {
printf ("avg %d = sum %d / count %d\n",
@avg(x), @sum(x), @count(x))
print (@hist_log(v))
}
EMBEDDED C
When in guru mode, the translator accepts embedded code in the script.
Such code is enclosed between %{ and %} markers, and is transcribed
verbatim, without analysis, in some sequence, into the generated C
code. At the outermost level, this may be useful to add #include in-
structions, and any auxiliary definitions for use by other embedded
code.
The other place where embedded code is permitted is as a function
body. In this case, the script language body is replaced entirely by
a piece of C code enclosed again between %{ and %} markers. This C
code may do anything reasonable and safe. There are a number of un-
documented but complex safety constraints on atomicity, concurrency,
resource consumption, and run time limits, so this is an advanced
technique.
The memory locations set aside for input and output values are made
available to it using a macro THIS. Here are some examples:
function add_one (val) %{
THIS->__retvalue = THIS->val + 1;
%}
function add_one_str (val) %{
strlcpy (THIS->__retvalue, THIS->val, MAXSTRINGLEN);
strlcat (THIS->__retvalue, "one", MAXSTRINGLEN);
%}
The function argument and return value types have to be inferred by
the translator from the call sites in order for this to work. The us-
er should examine C code generated for ordinary script-language func-
tions in order to write compatible embedded-C ones.
BUILT-INS
A set of builtin functions and probe point aliases are provided by the
scripts installed under the /usr/share/systemtap/tapset directory.
These are described in the stapfuncs(5) and stapprobes(5) manual
pages.
PROCESSING
The translator begins pass 1 by parsing the given input script, and
all scripts (files named *.stp) found in a tapset directory. The di-
rectories listed with -I are processed in sequence, each processed in
"guru mode". For each directory, a number of subdirectories are also
searched. These subdirectories are derived from the selected kernel
version (the -R option), in order to allow more kernel-version-specif-
ic scripts to override less specific ones. For example, for a kernel
version 2.6.12-23.FC3 the following patterns would be searched, in se-
quence: 2.6.12-23.FC3/*.stp, 2.6.12/*.stp, 2.6/*.stp, and finally
*.stp Stopping the translator after pass 1 causes it to print the
parse trees.
In pass 2, the translator analyzes the input script to resolve symbols
and types. References to variables, functions, and probe aliases that
are unresolved internally are satisfied by searching through the
parsed tapset scripts. If any tapset script is selected because it
defines an unresolved symbol, then the entirety of that script is
added to the translator’s resolution queue. This process iterates un-
til all symbols are resolved and a subset of tapset scripts is select-
ed.
Next, all probe point descriptions are validated against the wide va-
riety supported by the translator. Probe points that refer to code
locations ("synchronous probe points") require the appropriate kernel
debugging information to be installed. In the associated probe han-
dlers, target-side variables (whose names begin with "$") are found
and have their run-time locations decoded.
Next, all probes and functions are analyzed for optimization opportu-
nities, in order to remove variables, expressions, and functions that
have no useful value and no side-effect. Embedded-C functions are as-
sumed to have side-effects unless they include the magic string
/* pure */. Since this optimization can hide latent code errors such
as type mismatches or invalid $target variables, it sometimes may be
useful to disable the optimizations with the -u option.
Finally, all variable, function, parameter, array, and index types are
inferred from context (literals and operators). Stopping the transla-
tor after pass 2 causes it to list all the probes, functions, and
variables, along with all inferred types. Any inconsistent or unre-
solved types cause an error.
In pass 3, the translator writes C code that represents the actions of
all selected script files, and creates a Makefile to build that into a
kernel object. These files are placed into a temporary directory.
Stopping the translator at this point causes it to print the contents
of the C file.
In pass 4, the translator invokes the Linux kernel build system to
create the actual kernel object file. This involves running make in
the temporary directory, and requires a kernel module build system
(headers, config and Makefiles) to be installed in the usual spot
/lib/modules/VERSION/build. Stopping the translator after pass 4 is
the last chance before running the kernel object. This may be useful
if you want to archive the file.
In pass 5, the translator invokes the systemtap auxiliary program
staprun program for the given kernel object. This program arranges to
load the module then communicates with it, copying trace data from the
kernel into temporary files, until the user sends an interrupt signal.
Any run-time error encountered by the probe handlers, such as running
out of memory, division by zero, exceeding nesting or runtime limits,
results in a soft error indication. Soft errors in excess of MAXER-
RORS block of all subsequent probes, and terminate the session. Fi-
nally, staprun unloads the module, and cleans up.
EXAMPLES
See the stapex(5) manual page for a collection of samples.
CACHING
The systemtap translator caches the pass 3 output (the generated C
code) and the pass 4 output (the compiled kernel module) if pass 4
completes successfully. This cached output is reused if the same
script is translated again assuming the same conditions exist (same
kernel version, same systemtap version, etc.). Cached files are
stored in the $SYSTEMTAP_DIR/cache directory, which may be periodical-
ly cleaned/erased by the user.
SAFETY AND SECURITY
Systemtap is an administrative tool. It exposes kernel internal data
structures and potentially private user information. It acquires ei-
ther root privileges
To actually run the kernel objects it builds, a user must be one of
the following:
· the root user;
· a member of the stapdev group; or
· a member of the stapusr group. Members of the stapusr group can
only use modules located in the /lib/modules/VERSION/systemtap di-
rectory. This directory must be owned by root and not be world
writable.
The kernel modules generated by stap program are run by the staprun
program. The latter is a part of the Systemtap package, dedicated to
module loading and unloading (but only in the white zone), and kernel-
to-user data transfer. Since staprun does not perform any additional
security checks on the kernel objects it is given, it would be unwise
for a system administrator to add untrusted users to the stapdev or
stapusr groups.
The translator asserts certain safety constraints. It aims to ensure
that no handler routine can run for very long, allocate memory, per-
form unsafe operations, or in unintentionally interfere with the ker-
nel. Use of script global variables is suitably locked to protect
against manipulation by concurrent probe handlers. Use of guru mode
constructs such as embedded C can violate these constraints, leading
to kernel crash or data corruption.
The resource use limits are set by macros in the generated C code.
These may be overridden with the -D flag. A selection of these is as
follows:
MAXNESTING
Maximum number of recursive function call levels, default 10.
MAXSTRINGLEN
Maximum length of strings, default 128.
MAXTRYLOCK
Maximum number of iterations to wait for locks on global vari-
ables before declaring possible deadlock and skipping the
probe, default 1000.
MAXACTION
Maximum number of statements to execute during any single probe
hit (with interrupts disabled), default 1000.
MAXACTION_INTERRUPTIBLE
Maximum number of statements to execute during any single probe
hit which is executed with interrupts enabled (such as be-
gin/end probes), default (MAXACTION * 10).
MAXMAPENTRIES
Maximum number of rows in any single global array, default
2048.
MAXERRORS
Maximum number of soft errors before an exit is triggered, de-
fault 0, which means that the first error will exit the script.
MAXSKIPPED
Maximum number of skipped reentrant probes before an exit is
triggered, default 100.
MINSTACKSPACE
Minimum number of free kernel stack bytes required in order to
run a probe handler, default 1024. This number should be large
enough for the probe handler’s own needs, plus a safety margin.
Multipule scripts can write data into a relay buffer concurrently. A
host script provides an interface for accessing its relay buffer to
guest scripts. Then, the output of the guests are merged into the
output of the host. To run a script as a host, execute stap with
-DRELAYHOST[=name] option. The name identifies your host script among
several hosts. While running the host, execute stap with
-DRELAYGUEST[=name] to add a guest script to the host. Note that you
must unload guests before unloading a host. If there are some guests
connected to the host, unloading the host will be failed.
In case something goes wrong with stap or staprun after a probe has
already started running, one may safely kill both user processes, and
remove the active probe kernel module with rmmod. Any pending trace
messages may be lost.
In addition to the methods outlined above, the generated kernel module
also uses overload processing to make sure that probes can’t run for
too long. If more than STP_OVERLOAD_THRESHOLD cycles (default
500000000) have been spent in all the probes on a single cpu during
the last STP_OVERLOAD_INTERVAL cycles (default 1000000000), the probes
have overloaded the system and an exit is triggered.
By default, overload processing is turned on for all modules. If you
would like to disable overload processing, define STP_NO_OVERLOAD.
FILES
~/.systemtap
Systemtap data directory for cached systemtap files, unless
overridden by the SYSTEMTAP_DIR environment variable.
/tmp/stapXXXXXX
Temporary directory for systemtap files, including translated C
code and kernel object.
/usr/share/systemtap/tapset
The automatic tapset search directory, unless overridden by the
SYSTEMTAP_TAPSET environment variable.
/usr/share/systemtap/runtime
The runtime sources, unless overridden by the SYSTEMTAP_RUNTIME
environment variable.
/lib/modules/VERSION/build
The location of kernel module building infrastructure.
/usr/lib/debug/lib/modules/VERSION
The location of kernel debugging information when packaged into
the kernel-debuginfo RPM, unless overridden by the SYSTEM-
TAP_DEBUGINFO_PATH environment variable. The default value for
this variable is -:.debug:/usr/lib/debug. This path is inter-
preted by elfutils as a list of base directories of which vari-
ous subdirectories will be searched. The - at the front means
to skip CRC matching for separated debug objects and is a small
performance win if no possible corruption is suspected.
/usr/bin/staprun
The auxiliary program supervising module loading, interaction,
and unloading.
SEE ALSO
stapprobes(5), stapfuncs(5), stapex(5), awk(1), gdb(1)
BUGS
Use the Bugzilla link off of the project web page or our mailing list.
http://sources.redhat.com/systemtap/,<systemtap@sources.redhat.com>.
Red Hat 2009-04-20 STAP(1)
