|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | DESCRIPTION | SYNTAX | DWARF DEBUGINFO | ON-THE-FLY ARMING | PROBE POINT FAMILIES | EXAMPLES | SEE ALSO | COLOPHON |
|
|
|
STAPPROBES(3stap) STAPPROBES(3stap)
stapprobes - systemtap probe points
The following sections enumerate the variety of probe points
supported by the systemtap translator, and some of the additional
aliases defined by standard tapset scripts. Many are individually
documented in the 3stap manual section, with the probe:: prefix.
probe PROBEPOINT [, PROBEPOINT] { [STMT ...] }
A probe declaration may list multiple comma-separated probe points
in order to attach a handler to all of the named events. Normal‐
ly, the handler statements are run whenever any of events occur.
Depending on the type of probe point, the handler statements may
refer to context variables (denoted with a dollar-sign prefix like
$foo) to read or write state. This may include function parame‐
ters for function probes, or local variables for statement probes.
The syntax of a single probe point is a general dotted-symbol se‐
quence. This allows a breakdown of the event namespace into
parts, somewhat like the Domain Name System does on the Internet.
Each component identifier may be parametrized by a string or num‐
ber literal, with a syntax like a function call. A component may
include a "*" character, to expand to a set of matching probe
points. It may also include "**" to match multiple sequential
components at once. Probe aliases likewise expand to other probe
points.
Probe aliases can be given on their own, or with a suffix. The
suffix attaches to the underlying probe point that the alias is
expanded to. For example,
syscall.read.return.maxactive(10)
expands to
kernel.function("sys_read").return.maxactive(10)
with the component maxactive(10) being recognized as a suffix.
Normally, each and every probe point resulting from wildcard- and
alias-expansion must be resolved to some low-level system instru‐
mentation facility (e.g., a kprobe address, marker, or a timer
configuration), otherwise the elaboration phase will fail.
However, a probe point may be followed by a "?" character, to in‐
dicate that it is optional, and that no error should result if it
fails to resolve. Optionalness passes down through all levels of
alias/wildcard expansion. Alternately, a probe point may be fol‐
lowed by a "!" character, to indicate that it is both optional and
sufficient. (Think vaguely of the Prolog cut operator.) If it
does resolve, then no further probe points in the same comma-sepa‐
rated list will be resolved. Therefore, the "!" sufficiency mark
only makes sense in a list of probe point alternatives.
Additionally, a probe point may be followed by a "if (expr)"
statement, in order to enable/disable the probe point on-the-fly.
With the "if" statement, if the "expr" is false when the probe
point is hit, the whole probe body including alias's body is
skipped. The condition is stacked up through all levels of
alias/wildcard expansion. So the final condition becomes the logi‐
cal-and of conditions of all expanded alias/wildcard. The expres‐
sions are necessarily restricted to global variables.
These are all syntactically valid probe points. (They are gener‐
ally semantically invalid, depending on the contents of the
tapsets, and the versions of kernel/user software installed.)
kernel.function("foo").return
process("/bin/vi").statement(0x2222)
end
syscall.*
syscall.*.return.maxactive(10)
syscall.{open,close}
sys**open
kernel.function("no_such_function") ?
module("awol").function("no_such_function") !
signal.*? if (switch)
kprobe.function("foo")
Probes may be broadly classified into "synchronous" and "asynchro‐
nous". A "synchronous" event is deemed to occur when any proces‐
sor executes an instruction matched by the specification. This
gives these probes a reference point (instruction address) from
which more contextual data may be available. Other families of
probe points refer to "asynchronous" events such as timers/coun‐
ters rolling over, where there is no fixed reference point that is
related. Each probe point specification may match multiple loca‐
tions (for example, using wildcards or aliases), and all them are
then probed. A probe declaration may also contain several comma-
separated specifications, all of which are probed.
Brace expansion is a mechanism which allows a list of probe points
to be generated. It is very similar to shell expansion. A compo‐
nent may be surrounded by a pair of curly braces to indicate that
the comma-separated sequence of one or more subcomponents will
each constitute a new probe point. The braces may be arbitrarily
nested. The ordering of expanded results is based on product or‐
der.
The question mark (?), exclamation mark (!) indicators and probe
point conditions may not be placed in any expansions that are be‐
fore the last component.
The following is an example of brace expansion.
syscall.{write,read}
# Expands to
syscall.write, syscall.read
{kernel,module("nfs")}.function("nfs*")!
# Expands to
kernel.function("nfs*")!, module("nfs").function("nfs*")!
Resolving some probe points requires DWARF debuginfo or "debug
symbols" for the specific program being instrumented. For some
others, DWARF is automatically synthesized on the fly from source
code header files. For others, it is not needed at all. Since a
systemtap script may use any mixture of probe points together, the
union of their DWARF requirements has to be met on the computer
where script compilation occurs. (See the --use-server option and
the stap-server(8) man page for information about the remote com‐
pilation facility, which allows these requirements to be met on a
different machine.)
The following point lists many of the available probe point fami‐
lies, to classify them with respect to their need for DWARF debug‐
info for the specific program for that probe point.
DWARF NON-DWARF SYMBOL-TABLE
kernel.function, .statement kernel.mark kernel.function*
module.function, .statement process.mark, process.plt module.function*
process.function, .statement begin, end, error, never process.function*
process.mark* timer
.function.callee perf
python2, python3 procfs
debuginfod kernel.statement.absolute
kernel.data
AUTO-GENERATED-DWARF kprobe.function
kernel.trace process.statement.absolute
process.begin, .end
netfilter
java
The probe types marked with * asterisks mark fallbacks, where sys‐
temtap can sometimes infer subset or substitute information. In
general, the more symbolic / debugging information available, the
higher quality probing will be available.
The following types of probe points may be armed/disarmed on-the-
fly to save overheads during uninteresting times. Arming condi‐
tions may also be added to other types of probes, but will be
treated as a wrapping conditional and won't benefit from overhead
savings.
DISARMABLE exceptions
kernel.function, kernel.statement
module.function, module.statement
process.*.function, process.*.statement
process.*.plt, process.*.mark
timer. timer.profile
java
BEGIN/END/ERROR
The probe points begin and end are defined by the translator to
refer to the time of session startup and shutdown. All "begin"
probe handlers are run, in some sequence, during the startup of
the session. All global variables will have been initialized pri‐
or to this point. All "end" probes are run, in some sequence,
during the normal shutdown of a session, such as in the aftermath
of an exit () function call, or an interruption from the user. In
the case of an error-triggered shutdown, "end" probes are not run.
There are no target variables available in either context.
If the order of execution among "begin" or "end" probes is signif‐
icant, then an optional sequence number may be provided:
begin(N)
end(N)
The number N may be positive or negative. The probe handlers are
run in increasing order, and the order between handlers with the
same sequence number is unspecified. When "begin" or "end" are
given without a sequence, they are effectively sequence zero.
The error probe point is similar to the end probe, except that
each such probe handler run when the session ends after errors
have occurred. In such cases, "end" probes are skipped, but each
"error" probe is still attempted. This kind of probe can be used
to clean up or emit a "final gasp". It may also be numerically
parametrized to set a sequence.
NEVER
The probe point never is specially defined by the translator to
mean "never". Its probe handler is never run, though its state‐
ments are analyzed for symbol / type correctness as usual. This
probe point may be useful in conjunction with optional probes.
SYSCALL and ND_SYSCALL
The syscall.* and nd_syscall.* aliases define several hundred
probes, too many to detail here. They are of the general form:
syscall.NAME
nd_syscall.NAME
syscall.NAME.return
nd_syscall.NAME.return
Generally, a pair of probes are defined for each normal system
call as listed in the syscalls(2) manual page, one for entry and
one for return. Those system calls that never return do not have
a corresponding .return probe. The nd_* family of probes are
about the same, except it uses non-DWARF based searching mecha‐
nisms, which may result in a lower quality of symbolic context da‐
ta (parameters), and may miss some system calls. You may want to
try them first, in case kernel debugging information is not imme‐
diately available.
Each probe alias provides a variety of variables. Looking at the
tapset source code is the most reliable way. Generally, each
variable listed in the standard manual page is made available as a
script-level variable, so syscall.open exposes filename, flags,
and mode. In addition, a standard suite of variables is available
at most aliases:
argstr A pretty-printed form of the entire argument list, without
parentheses.
name The name of the system call.
retval For return probes, the raw numeric system-call result.
retstr For return probes, a pretty-printed string form of the sys‐
tem-call result.
As usual for probe aliases, these variables are all initialized
once from the underlying $context variables, so that later changes
to $context variables are not automatically reflected. Not all
probe aliases obey all of these general guidelines. Please report
any bothersome ones you encounter as a bug. Note that on some
kernel/userspace architecture combinations (e.g., 32-bit userspace
on 64-bit kernel), the underlying $context variables may need ex‐
plicit sign extension / masking. When this is an issue, consider
using the tapset-provided variables instead of raw $context vari‐
ables.
If debuginfo availability is a problem, you may try using the non-
DWARF syscall probe aliases instead. Use the nd_syscall. prefix
instead of syscall. The same context variables are available, as
far as possible.
nd_syscall probes on kernels that use syscall wrappers to pass ar‐
guments via pt_regs (currently 4.17+ on x86_64 and 4.19+ on
aarch64) support syscall argument writing when guru mode is en‐
abled. If a probe syscall parameter is modified in the probe body
then immediately before the probe exits the parameter's current
value will be written to pt_regs. This overwrites the previous
value. nd_syscall probes also include two parameters for each of
the syscall's string parameters. One holds a quoted version of
the string passed to the syscall. The other holds an unquoted ver‐
sion of the string intended to be used when modifying the parame‐
ter. If the probe modifies the unquoted string variable then as
the probe is about to exit the contents of this variable will be
written to the user space buffer passed to the syscall. It is the
user's responsibility to ensure that this buffer is large enough
to hold the modified string and that it is located in a writable
memory segment.
TIMERS
There are two main types of timer probes: "jiffies" timer probes
and time interval timer probes.
Intervals defined by the standard kernel "jiffies" timer may be
used to trigger probe handlers asynchronously. Two probe point
variants are supported by the translator:
timer.jiffies(N)
timer.jiffies(N).randomize(M)
The probe handler is run every N jiffies (a kernel-defined unit of
time, typically between 1 and 60 ms). If the "randomize" compo‐
nent is given, a linearly distributed random value in the range
[-M..+M] is added to N every time the handler is run. N is re‐
stricted to a reasonable range (1 to around a million), and M is
restricted to be smaller than N. There are no target variables
provided in either context. It is possible for such probes to be
run concurrently on a multi-processor computer.
Alternatively, intervals may be specified in units of time. There
are two probe point variants similar to the jiffies timer:
timer.ms(N)
timer.ms(N).randomize(M)
Here, N and M are specified in milliseconds, but the full options
for units are seconds (s/sec), milliseconds (ms/msec), microsec‐
onds (us/usec), nanoseconds (ns/nsec), and hertz (hz). Randomiza‐
tion is not supported for hertz timers.
The actual resolution of the timers depends on the target kernel.
For kernels prior to 2.6.17, timers are limited to jiffies resolu‐
tion, so intervals are rounded up to the nearest jiffies interval.
After 2.6.17, the implementation uses hrtimers for tighter preci‐
sion, though the actual resolution will be arch-dependent. In ei‐
ther case, if the "randomize" component is given, then the random
value will be added to the interval before any rounding occurs.
Profiling timers are also available to provide probes that execute
on all CPUs at the rate of the system tick (CONFIG_HZ) or at a
given frequency (hz). On some kernels, this is a one-concurrent-
user-only or disabled facility, resulting in error -16 (EBUSY)
during probe registration.
timer.profile.tick
timer.profile.freq.hz(N)
Full context information of the interrupted process is available,
making this probe suitable for a time-based sampling profiler.
It is recommended to use the tapset probe timer.profile rather
than timer.profile.tick. This probe point behaves identically to
timer.profile.tick when the underlying functionality is available,
and falls back to using perf.sw.cpu_clock on some recent kernels
which lack the corresponding profile timer facility.
Profiling timers with specified frequencies are only accurate up
to around 100 hz. You may need to provide a larger value to
achieve the desired rate.
Note that if a timer probe is set to fire at a very high rate and
if the probe body is complex, succeeding timer probes can get
skipped, since the time for them to run has already passed. Nor‐
mally systemtap reports missed probes, but it will not report
these skipped probes.
DWARF
This family of probe points uses symbolic debugging information
for the target kernel/module/program, as may be found in un‐
stripped executables, or the separate debuginfo packages. They
allow placement of probes logically into the execution path of the
target program, by specifying a set of points in the source or ob‐
ject code. When a matching statement executes on any processor,
the probe handler is run in that context.
Probe points in the DWARF family can be identified by the target
kernel module (or user process), source file, line number, func‐
tion name, or some combination of these.
Here is a list of DWARF probe points currently supported:
kernel.function(PATTERN)
kernel.function(PATTERN).call
kernel.function(PATTERN).callee(PATTERN)
kernel.function(PATTERN).callee(PATTERN).return
kernel.function(PATTERN).callee(PATTERN).call
kernel.function(PATTERN).callees(DEPTH)
kernel.function(PATTERN).return
kernel.function(PATTERN).inline
kernel.function(PATTERN).label(LPATTERN)
module(MPATTERN).function(PATTERN)
module(MPATTERN).function(PATTERN).call
module(MPATTERN).function(PATTERN).callee(PATTERN)
module(MPATTERN).function(PATTERN).callee(PATTERN).return
module(MPATTERN).function(PATTERN).callee(PATTERN).call
module(MPATTERN).function(PATTERN).callees(DEPTH)
module(MPATTERN).function(PATTERN).return
module(MPATTERN).function(PATTERN).inline
module(MPATTERN).function(PATTERN).label(LPATTERN)
kernel.statement(PATTERN)
kernel.statement(PATTERN).nearest
kernel.statement(ADDRESS).absolute
module(MPATTERN).statement(PATTERN)
process("PATH").function("NAME")
process("PATH").statement("*@FILE.c:123")
process("PATH").library("PATH").function("NAME")
process("PATH").library("PATH").statement("*@FILE.c:123")
process("PATH").library("PATH").statement("*@FILE.c:123").nearest
process("PATH").function("*").return
process("PATH").function("myfun").label("foo")
process("PATH").function("foo").callee("bar")
process("PATH").function("foo").callee("bar").return
process("PATH").function("foo").callee("bar").call
process("PATH").function("foo").callees(DEPTH)
process(PID).function("NAME")
process(PID).function("myfun").label("foo")
process(PID).plt("NAME")
process(PID).plt("NAME").return
process(PID).statement("*@FILE.c:123")
process(PID).statement("*@FILE.c:123").nearest
process(PID).statement(ADDRESS).absolute
debuginfod.process("PATH").**
(See the USER-SPACE section below for more information on the
process probes.)
The list above includes multiple variants and modifiers which pro‐
vide additional functionality or filters. They are:
.function
Places a probe near the beginning of the named func‐
tion, so that parameters are available as context
variables.
.return
Places a probe at the moment after the return from
the named function, so the return value is available
as the "$return" context variable.
.inline
Filters the results to include only instances of in‐
lined functions. Note that inlined functions do not
have an identifiable return point, so .return is not
supported on .inline probes.
.call Filters the results to include only non-inlined
functions (the opposite set of .inline)
.exported
Filters the results to include only exported func‐
tions.
.statement
Places a probe at the exact spot, exposing those lo‐
cal variables that are visible there.
.statement.nearest
Places a probe at the nearest available line number
for each line number given in the statement.
.callee
Places a probe on the callee function given in the
.callee modifier, where the callee must be a func‐
tion called by the target function given in .func‐
tion. The advantage of doing this over directly
probing the callee function is that this probe point
is run only when the callee is called from the tar‐
get function (add the -DSTAP_CALLEE_MATCHALL direc‐
tive to override this when calling stap(1)).
Note that only callees that can be statically deter‐
mined are available. For example, calls through
function pointers are not available. Additionally,
calls to functions located in other objects (e.g.
libraries) are not available (instead use another
probe point). This feature will only work for code
compiled with GCC 4.7+.
.callees
Shortcut for .callee("*"), which places a probe on
all callees of the function.
.callees(DEPTH)
Recursively places probes on callees. For example,
.callees(2) will probe both callees of the target
function, as well as callees of those callees. And
.callees(3) goes one level deeper, etc... A callee
probe at depth N is only triggered when the N
callers in the callstack match those that were stat‐
ically determined during analysis (this also may be
overridden using -DSTAP_CALLEE_MATCHALL).
In the above list of probe points, MPATTERN stands for a string
literal that aims to identify the loaded kernel module of inter‐
est. For in-tree kernel modules, the name suffices (e.g. "btrfs").
The name may also include the "*", "[]", and "?" wildcards to
match multiple in-tree modules. Out-of-tree modules are also sup‐
ported by specifying the full path to the ko file. Wildcards are
not supported. The file must follow the convention of being named
<module_name>.ko (characters ',' and '-' are replaced by '_').
LPATTERN stands for a source program label. It may also contain
"*", "[]", and "?" wildcards. PATTERN stands for a string literal
that aims to identify a point in the program. It is made up of
three parts:
• The first part is the name of a function, as would appear in
the nm program's output. This part may use the "*" and "?"
wildcarding operators to match multiple names.
• The second part is optional and begins with the "@" character.
It is followed by the path to the source file containing the
function, which may include a wildcard pattern, such as
mm/slab*. If it does not match as is, an implicit "*/" is op‐
tionally added before the pattern, so that a script need only
name the last few components of a possibly long source direc‐
tory path.
• Finally, the third part is optional if the file name part was
given, and identifies the line number in the source file pre‐
ceded by a ":" or a "+". The line number is assumed to be an
absolute line number if preceded by a ":", or relative to the
declaration line of the function if preceded by a "+". All
the lines in the function can be matched with ":*". A range
of lines x through y can be matched with ":x-y". Ranges and
specific lines can be mixed using commas, e.g. ":x,y-z".
As an alternative, PATTERN may be a numeric constant, indicating
an address. Such an address may be found from symbol tables of
the appropriate kernel / module object file. It is verified
against known statement code boundaries, and will be relocated for
use at run time.
In guru mode only, absolute kernel-space addresses may be speci‐
fied with the ".absolute" suffix. Such an address is considered
already relocated, as if it came from /proc/kallsyms, so it cannot
be checked against statement/instruction boundaries.
CONTEXT VARIABLES
Many of the source-level context variables, such as function para‐
meters, locals, globals visible in the compilation unit, may be
visible to probe handlers. They may refer to these variables by
prefixing their name with "$" within the scripts. In addition, a
special syntax allows limited traversal of structures, pointers,
and arrays. More syntax allows pretty-printing of individual
variables or their groups. See also @cast. Note that variables
may be inaccessible due to them being paged out, or for a few oth‐
er reasons. See also man error::fault(7stap).
Functions called from DWARF class probe points and from
process.mark probes may also refer to context variables.
$var refers to an in-scope variable or thread local storage
variable "var". If it's an integer-like type, it will be
cast to a 64-bit int for systemtap script use. String-like
pointers (char *) may be copied to systemtap string values
using the kernel_string or user_string functions.
@var("varname")
an alternative syntax for $varname
@var("varname","module")
The global variable or global thread local storage variable
in scope of the given module already loaded into the cur‐
rent probed process. Useful to get an exported variable in
a shared library loaded into the process being probed, or a
global variable in a process while a shared library probe
is being executed. For user-space modules only. For exam‐
ple: @var("_r_debug","/lib/ld-linux.so.2")
@var("varname@src/file.c")
refers to the global (either file local or external) vari‐
able varname defined when the file src/file.c was compiled.
The CU in which the variable is resolved is the first CU in
the module of the probe point which matches the given file
name at the end and has the shortest file name path (e.g.
given @var("foo@bar/baz.c") and CUs with file name paths
src/sub/module/bar/baz.c and src/bar/baz.c the second CU
will be chosen to resolve the (file) global variable foo
@var("varname@src/file.c","module")
The global variable in scope of the given CU, defined in
the given module, even if the variable is static (so the
name is not unique without the CU name).
$var->field traversal via a structure's or a pointer's field.
This
generalized indirection operator may be repeated to follow
more levels. Note that the . operator is not used for
plain structure members, only -> for both purposes. (This
is because "." is reserved for string concatenation.) Also
note that for direct dereferencing of $var pointer {ker‐
nel,user}_{char,int,...}($var) should be used. (Refer to
stapfuncs(5) for more details.)
$return
is available in return probes only for functions that are
declared with a return value, which can be determined using
@defined($return).
$var[N]
indexes into an array. The index given with a literal num‐
ber or even an arbitrary numeric expression.
A number of operators exist for such basic context variable ex‐
pressions:
$$vars expands to a character string that is equivalent to
sprintf("parm1=%x ... parmN=%x var1=%x ... varN=%x",
parm1, ..., parmN, var1, ..., varN)
for each variable in scope at the probe point. Some values
may be printed as =? if their run-time location cannot be
found.
$$locals
expands to a subset of $$vars for only local variables.
$$parms
expands to a subset of $$vars for only function parameters.
$$return
is available in return probes only. It expands to a string
that is equivalent to sprintf("return=%x", $return) if the
probed function has a return value, or else an empty
string.
& $EXPR
expands to the address of the given context variable ex‐
pression, if it is addressable.
@defined($EXPR)
expands to 1 or 0 iff the given context variable expression
is resolvable, for use in conditionals such as
@defined($foo->bar) ? $foo->bar : 0
Use full $context variables or @cast() expressions in @de‐
fine parameters for unambiguous processing. The TYPECAST
script-level variable facility is incompletely supported.
Simplify the parameters by reducing nesting or indirection,
if encountering "Collapsing unresolved @define to ..."
warnings.
@probewrite($VAR)
see the PROBES section of stap(1).
$EXPR$ expands to a string with all of $EXPR's members, equivalent
to
sprintf("{.a=%i, .b=%u, .c={...}, .d=[...]}",
$EXPR->a, $EXPR->b)
$EXPR$$
expands to a string with all of $var's members and submem‐
bers, equivalent to
sprintf("{.a=%i, .b=%u, .c={.x=%p, .y=%c}, .d=[%i, ...]}",
$EXPR->a, $EXPR->b, $EXPR->c->x, $EXPR->c->y, $EXPR->d[0])
@errno expands to the last value the C library global variable er‐
rno was set to.
MORE ON RETURN PROBES
For the kernel ".return" probes, only a certain fixed number of
returns may be outstanding. The default is a relatively small
number, on the order of a few times the number of physical CPUs.
If many different threads concurrently call the same blocking
function, such as futex(2) or read(2), this limit could be exceed‐
ed, and skipped "kretprobes" would be reported by "stap -t". To
work around this, specify a
probe FOO.return.maxactive(NNN)
suffix, with a large enough NNN to cover all expected concurrently
blocked threads. Alternately, use the
stap -DKRETACTIVE=NNNN
stap command line macro setting to override the default for all
".return" probes.
For ".return" probes, context variables other than the "$return"
may be accessible, as a convenience for a script programmer wish‐
ing to access function parameters. These values are snapshots
taken at the time of function entry. (Local variables within the
function are not generally accessible, since those variables did
not exist in allocated/initialized form at the snapshot moment.)
These entry-snapshot variables should be accessed via @en‐
try($var).
In addition, arbitrary entry-time expressions can also be saved
for ".return" probes using the @entry(expr) operator. For exam‐
ple, one can compute the elapsed time of a function:
probe kernel.function("do_filp_open").return {
println( get_timeofday_us() - @entry(get_timeofday_us()) )
}
The following table summarizes how values related to a function
parameter context variable, a pointer named addr, may be accessed
from a .return probe.
at-entry value past-exit value
$addr not available
$addr->x->y @cast(@entry($addr),"struct zz")->x->y
$addr[0] {kernel,user}_{char,int,...}(& $addr[0])
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 sup‐
ported :
kprobe.function(FUNCTION)
kprobe.function(FUNCTION).call
kprobe.function(FUNCTION).return
kprobe.module(NAME).function(FUNCTION)
kprobe.module(NAME).function(FUNCTION).call
kprobe.module(NAME).function(FUNCTION).return
kprobe.statement(ADDRESS).absolute
Probes of type function are recommended for kernel functions,
whereas probes of type module are recommended for probing func‐
tions of the specified module. In case the absolute address of a
kernel or module function is known, statement probes can be uti‐
lized.
Note that FUNCTION and MODULE names must not contain wildcards, or
the probe will not be registered. Also, statement probes must be
run under guru-mode only.
USER-SPACE
Support for user-space probing is available for kernels that are
configured with the utrace extensions, or have the uprobes facili‐
ty in linux 3.5. (Various kernel build configuration options need
to be enabled; systemtap will advise if these are missing.)
There are several forms. First, a non-symbolic probe point:
process(PID).statement(ADDRESS).absolute
is analogous to kernel.statement(ADDRESS).absolute in that both
use raw (unverified) virtual addresses and provide no $variables.
The target PID parameter must identify a running process, and AD‐
DRESS should identify a valid instruction address. All threads of
that process will be probed.
Second, non-symbolic user-kernel interface events handled by
utrace may be probed:
process(PID).begin
process("FULLPATH").begin
process.begin
process(PID).thread.begin
process("FULLPATH").thread.begin
process.thread.begin
process(PID).end
process("FULLPATH").end
process.end
process(PID).thread.end
process("FULLPATH").thread.end
process.thread.end
process(PID).syscall
process("FULLPATH").syscall
process.syscall
process(PID).syscall.return
process("FULLPATH").syscall.return
process.syscall.return
A process.begin probe gets called when new process described by
PID or FULLPATH gets created. In addition, it is called once from
the context of each preexisting process, at systemtap script
startup. This is useful to track live processes. A
process.thread.begin probe gets called when a new thread described
by PID or FULLPATH gets created. A process.end probe gets called
when process described by PID or FULLPATH dies. A
process.thread.end probe gets called when a thread described by
PID or FULLPATH dies. A process.syscall probe gets called when a
thread described by PID or FULLPATH makes a system call. The sys‐
tem call number is available in the $syscall context variable, and
the first 6 arguments of the system call are available in the
$argN (ex. $arg1, $arg2, ...) context variable. A
process.syscall.return probe gets called when a thread described
by PID or FULLPATH returns from a system call. The system call
number is available in the $syscall context variable, and the re‐
turn value of the system call is available in the $return context
variable. A
If a process probe is specified without a PID or FULLPATH, all
user threads will be probed. However, if systemtap was invoked
with the -c or -x options, then process probes are restricted to
the process hierarchy associated with the target process. If a
process probe is unspecified (i.e. without a PID or FULLPATH), but
with the -c option, the PATH of the -c cmd will be heuristically
filled into the process PATH. In that case, only command parame‐
ters are allowed in the -c command (i.e. no command substitution
allowed and no occurrences of any of these characters:
'|&;<>(){}').
Third, symbolic static instrumentation compiled into programs and
shared libraries may be probed:
process("PATH").mark("LABEL")
process("PATH").provider("PROVIDER").mark("LABEL")
process(PID).mark("LABEL")
process(PID).provider("PROVIDER").mark("LABEL")
A .mark probe gets called via a static probe which is defined in
the application by STAP_PROBE1(PROVIDER,LABEL,arg1), which are
macros defined in sys/sdt.h. The PROVIDER is an arbitrary appli‐
cation identifier, LABEL is the marker site identifier, and arg1
is the integer-typed argument. STAP_PROBE1 is used for probes
with 1 argument, STAP_PROBE2 is used for probes with 2 arguments,
and so on. The arguments of the probe are available in the con‐
text variables $arg1, $arg2, ... An alternative to using the
STAP_PROBE macros is to use the dtrace script to create custom
macros. Additionally, the variables $$name and $$provider are
available as parts of the probe point name. The sys/sdt.h macro
names DTRACE_PROBE* are available as aliases for STAP_PROBE*.
Finally, full symbolic source-level probes in user-space programs
and shared libraries are supported. These are exactly analogous
to the symbolic DWARF-based kernel/module probes described above.
They expose the same sorts of context $variables for function pa‐
rameters, local variables, and so on.
process("PATH").function("NAME")
process("PATH").statement("*@FILE.c:123")
process("PATH").plt("NAME")
process("PATH").library("PATH").plt("NAME")
process("PATH").library("PATH").function("NAME")
process("PATH").library("PATH").statement("*@FILE.c:123")
process("PATH").function("*").return
process("PATH").function("myfun").label("foo")
process("PATH").function("foo").callee("bar")
process("PATH").plt("NAME").return
debuginfod.process("PATH").**
process(PID).function("NAME")
process(PID).statement("*@FILE.c:123")
process(PID).plt("NAME")
Note that for all process probes, PATH names refer to executables
that are searched the same way shells do: relative to the working
directory if they contain a "/" character, otherwise in $PATH. If
PATH names refer to scripts, the actual interpreters (specified in
the script in the first line after the #! characters) are probed.
In the debuginfod probe family PATH names likewise refer to exe‐
cutables, but are searched for in the currently defined $DEBUGIN‐
FOD_URLS.
Tapset process probes placed in the special directory $pre‐
fix/share/systemtap/tapset/PATH/ with relative paths will have
their process parameter prefixed with the location of the tapset.
For example,
process("foo").function("NAME")
expands to
process("/usr/bin/foo").function("NAME")
when placed in $prefix/share/systemtap/tapset/PATH/usr/bin/
If PATH is a process component parameter referring to shared li‐
braries then all processes that map it at runtime would be select‐
ed for probing. If PATH is a library component parameter refer‐
ring to shared libraries then the process specified by the process
component would be selected. Note that the PATH pattern in a li‐
brary component will always apply to libraries statically deter‐
mined to be in use by the process. However, you may also specify
the full path to any library file even if not statically needed by
the process.
A .plt probe will probe functions in the program linkage table
corresponding to the rest of the probe point. .plt can be speci‐
fied as a shorthand for .plt("*"). The symbol name is available
as a $$name context variable; function arguments are not avail‐
able, since PLTs are processed without debuginfo. A .plt.return
probe places a probe at the moment after the return from the named
function.
If the PATH string contains wildcards as in the MPATTERN case,
then standard globbing is performed to find all matching paths.
In this case, the $PATH environment variable is not used.
If systemtap was invoked with the -c or -x options, then process
probes are restricted to the process hierarchy associated with the
target process.
DEBUGINFOD
These probes take the form
debuginfod.process("PATH").**
They are very similar to the process("PATH").** probe family. The
key difference is that the process probes search for PATH in the
host filesystem, while debuginfod probes search the current feder‐
ation of debuginfod servers, using the currently defined $DEBUGIN‐
FOD_URLS (see debuginfod(8) ).
In order to probe the contents of one or more elf/archive files
and/or elf/archive containing directories, the below will create a
debuginfod server which will scan and process the elf files within
and prepare them for systemtap.
$ debuginfod [options] [-F -R -Z etc.] /path1 /path2
$ env DEBUGINFOD_URLS=http://localhost:8002/ stap ...
JAVA
Support for probing Java methods is available using Byteman as a
backend. Byteman is an instrumentation tool from the JBoss project
which systemtap can use to monitor invocations for a specific
method or line in a Java program.
Systemtap does so by generating a Byteman script listing the
probes to instrument and then invoking the Byteman bminstall util‐
ity.
This Java instrumentation support is currently a prototype feature
with major limitations. Moreover, Java probing currently does not
work across users; the stap script must run (with appropriate per‐
missions) under the same user that the Java process being probed.
(Thus a stap script under root currently cannot probe Java methods
in a non-root-user Java process.)
The first probe type refers to Java processes by the name of the
Java process:
java("PNAME").class("CLASSNAME").method("PATTERN")
java("PNAME").class("CLASSNAME").method("PATTERN").return
The PNAME argument must be a pre-existing jvm pid, and be identi‐
fiable via a jps listing.
The PATTERN parameter specifies the signature of the Java method
to probe. The signature must consist of the exact name of the
method, followed by a bracketed list of the types of the argu‐
ments, for instance "myMethod(int,double,Foo)". Wildcards are not
supported.
The probe can be set to trigger at a specific line within the
method by appending a line number with colon, just as in other
types of probes: "myMethod(int,double,Foo):245".
The CLASSNAME parameter identifies the Java class the method be‐
longs to, either with or without the package qualification. By de‐
fault, the probe only triggers on descendants of the class that do
not override the method definition of the original class. However,
CLASSNAME can take an optional caret prefix, as in ^org.my.My‐
Class, which specifies that the probe should also trigger on all
descendants of MyClass that override the original method. For in‐
stance, every method with signature foo(int) in program
org.my.MyApp can be probed at once using
java("org.my.MyApp").class("^java.lang.Object").method("foo(int)")
The second probe type works analogously, but refers to Java
processes by PID:
java(PID).class("CLASSNAME").method("PATTERN")
java(PID).class("CLASSNAME").method("PATTERN").return
(PIDs for an already running process can be obtained using the
jps(1) utility.)
Context variables defined within java probes include $arg1 through
$arg10 (for up to the first 10 arguments of a method), represented
as character-pointers for the toString() form of each actual argu‐
ment. The arg1 through arg10 script variables provide access to
these as ordinary strings, fetched via user_string_warn().
Prior to systemtap version 3.1, $arg1 through $arg10 could contain
either integers or character pointers, depending on the types of
the objects being passed to each particular java method. This
previous behaviour may be invoked with the stap --compatible=3.0
flag.
PROCFS
These probe points allow procfs "files" in /proc/systemtap/MODNAME
to be created, read and written using a permission that may be
modified using the proper umask value. Default permissions are
0400 for read probes, and 0200 for write probes. If both a read
and write probe are being used on the same file, a default permis‐
sion of 0600 will be used. Using procfs.umask(0040).read would
result in a 0404 permission set for the file. (MODNAME is the
name of the systemtap module). The proc filesystem is a pseudo-
filesystem which is used as an interface to kernel data struc‐
tures. There are several probe point variants supported by the
translator:
procfs("PATH").read
procfs("PATH").umask(UMASK).read
procfs("PATH").read.maxsize(MAXSIZE)
procfs("PATH").umask(UMASK).maxsize(MAXSIZE)
procfs("PATH").write
procfs("PATH").umask(UMASK).write
procfs.read
procfs.umask(UMASK).read
procfs.read.maxsize(MAXSIZE)
procfs.umask(UMASK).read.maxsize(MAXSIZE)
procfs.write
procfs.umask(UMASK).write
Note that there are a few differences when procfs probes are used
in the stapbpf runtime. FIFO special files are used instead of
proc filesystem files. These files are created in /var/tmp/sys‐
temtap-USER/MODNAME. (USER is the name of the user). Additional‐
ly, users cannot create both read and write probes on the same
file.
PATH is the file name (relative to /proc/systemtap/MODNAME or
/var/tmp/systemtap-USER/MODNAME) to be created. If no PATH is
specified (as in the last two variants above), PATH defaults to
"command". The file name "__stdin" is used internally by systemtap
for input probes and should not be used as a PATH for procfs
probes; see the input probe section below.
When a user reads /proc/systemtap/MODNAME/PATH (normal runtime) or
/var/tmp/systemtap-USER/MODNAME (stapbpf runtime), the correspond‐
ing procfs read probe is triggered. The string data to be read
should be assigned to a variable named $value, like this:
procfs("PATH").read { $value = "100\n" }
When a user writes into /proc/systemtap/MODNAME/PATH (normal run‐
time) or /var/tmp/systemtap-USER/MODNAME (stapbpf runtime), the
corresponding procfs write probe is triggered. The data the user
wrote is available in the string variable named $value, like this:
procfs("PATH").write { printf("user wrote: %s", $value) }
MAXSIZE is the size of the procfs read buffer. Specifying MAXSIZE
allows larger procfs output. If no MAXSIZE is specified, the
procfs read buffer defaults to STP_PROCFS_BUFSIZE (which defaults
to MAXSTRINGLEN, the maximum length of a string). If setting the
procfs read buffers for more than one file is needed, it may be
easiest to override the STP_PROCFS_BUFSIZE definition. Here's an
example of using MAXSIZE:
procfs.read.maxsize(1024) {
$value = "long string..."
$value .= "another long string..."
$value .= "another long string..."
$value .= "another long string..."
}
INPUT
These probe points make input from stdin available to the script
during runtime. The translator currently supports two variants of
this family:
input.char
input.line
input.char is triggered each time a character is read from stdin.
The current character is available in the string variable named
char. There is no newline buffering; the next character is read
from stdin as soon as it becomes available.
input.line causes all characters read from stdin to be buffered
until a newline is read, at which point the probe will be trig‐
gered. The current line of characters (including the newline) is
made available in a string variable named line. Note that no more
than MAXSTRINGLEN characters will be buffered. Any additional
characters will not be included in line.
Input probes are aliases for procfs("__stdin").write. Systemtap
reconfigures stdin if the presence of this procfs probe is detect‐
ed, therefore "__stdin" should not be used as a path argument for
procfs probes. Additionally, input probes will not work with the
-F and --remote options.
NETFILTER HOOKS
These probe points allow observation of network packets using the
netfilter mechanism. A netfilter probe in systemtap corresponds to
a netfilter hook function in the original netfilter probes API. It
is probably more convenient to use tapset::netfilter(3stap), which
wraps the primitive netfilter hooks and does the work of extract‐
ing useful information from the context variables.
There are several probe point variants supported by the transla‐
tor:
netfilter.hook("HOOKNAME").pf("PROTOCOL_F")
netfilter.pf("PROTOCOL_F").hook("HOOKNAME")
netfilter.hook("HOOKNAME").pf("PROTOCOL_F").priority("PRIORITY")
netfilter.pf("PROTOCOL_F").hook("HOOKNAME").priority("PRIORITY")
PROTOCOL_F is the protocol family to listen for, currently one of
NFPROTO_IPV4, NFPROTO_IPV6, NFPROTO_ARP, or NFPROTO_BRIDGE.
HOOKNAME is the point, or 'hook', in the protocol stack at which
to intercept the packet. The available hook names for each proto‐
col family are taken from the kernel header files <linux/netfil‐
ter_ipv4.h>, <linux/netfilter_ipv6.h>, <linux/netfilter_arp.h> and
<linux/netfilter_bridge.h>. For instance, allowable hook names for
NFPROTO_IPV4 are NF_INET_PRE_ROUTING, NF_INET_LOCAL_IN, NF_IN‐
ET_FORWARD, NF_INET_LOCAL_OUT, and NF_INET_POST_ROUTING.
PRIORITY is an integer priority giving the order in which the
probe point should be triggered relative to any other netfilter
hook functions which trigger on the same packet. Hook functions
execute on each packet in order from smallest priority number to
largest priority number. If no PRIORITY is specified (as in the
first two probe point variants above), PRIORITY defaults to "0".
There are a number of predefined priority names of the form
NF_IP_PRI_* and NF_IP6_PRI_* which are defined in the kernel head‐
er files <linux/netfilter_ipv4.h> and <linux/netfilter_ipv6.h> re‐
spectively. The script is permitted to use these instead of speci‐
fying an integer priority. (The probe points for NFPROTO_ARP and
NFPROTO_BRIDGE currently do not expose any named hook priorities
to the script writer.) Thus, allowable ways to specify the prior‐
ity include:
priority("255")
priority("NF_IP_PRI_SELINUX_LAST")
A script using guru mode is permitted to specify any identifier or
number as the parameter for hook, pf, and priority. This feature
should be used with caution, as the parameter is inserted verbatim
into the C code generated by systemtap.
The netfilter probe points define the following context variables:
$hooknum
The hook number.
$skb The address of the sk_buff struct representing the packet.
See <linux/skbuff.h> for details on how to use this struct,
or alternatively use the tapset tapset::netfilter(3stap)
for easy access to key information.
$in The address of the net_device struct representing the net‐
work device on which the packet was received (if any). May
be 0 if the device is unknown or undefined at that stage in
the protocol stack.
$out The address of the net_device struct representing the net‐
work device on which the packet will be sent (if any). May
be 0 if the device is unknown or undefined at that stage in
the protocol stack.
$verdict
(Guru mode only.) Assigning one of the verdict values de‐
fined in <linux/netfilter.h> to this variable alters the
further progress of the packet through the protocol stack.
For instance, the following guru mode script forces all
ipv6 network packets to be dropped:
probe netfilter.pf("NFPROTO_IPV6").hook("NF_IP6_PRE_ROUTING") {
$verdict = 0 /* nf_drop */
}
For convenience, unlike the primitive probe points dis‐
cussed here, the probes defined in tapset::netfilter(3stap)
export the lowercase names of the verdict constants (e.g.
NF_DROP becomes nf_drop) as local variables.
KERNEL TRACEPOINTS
This family of probe points hooks up to static probing tracepoints
inserted into the kernel or modules. As with markers, these tra‐
cepoints are special macro calls inserted by kernel developers to
make probing faster and more reliable than with DWARF-based
probes, and DWARF debugging information is not required to probe
tracepoints. Tracepoints have an extra advantage of more strong‐
ly-typed parameters than markers.
Tracepoint probes look like: kernel.trace("name"). The tracepoint
name string, which may contain the usual wildcard characters, is
matched against the names defined by the kernel developers in the
tracepoint header files. To restrict the search to specific sub‐
systems (e.g. sched, ext3, etc...), the following syntax can be
used: kernel.trace("system:name"). The tracepoint system string
may also contain the usual wildcard characters.
The handler associated with a tracepoint-based probe may read the
optional parameters specified at the macro call site. These are
named according to the declaration by the tracepoint author. For
example, the tracepoint probe kernel.trace("sched:sched_switch")
provides the parameters $prev and $next. If the parameter is a
complex type, as in a struct pointer, then a script can access
fields with the same syntax as DWARF $target variables. Also,
tracepoint parameters cannot be modified, but in guru-mode a
script may modify fields of parameters.
The subsystem and name of the tracepoint are available in $$system
and $$name and a string of name=value pairs for all parameters of
the tracepoint is available in $$vars or $$parms.
KERNEL MARKERS (OBSOLETE)
This family of probe points hooks up to an older style of static
probing markers inserted into older kernels or modules. These
markers are special STAP_MARK macro calls inserted by kernel de‐
velopers to make probing faster and more reliable than with DWARF-
based probes. Further, DWARF debugging information is not re‐
quired to probe markers.
Marker probe points begin with kernel. The next part names the
marker itself: mark("name"). The marker name string, which may
contain the usual wildcard characters, is matched against the
names given to the marker macros when the kernel and/or module was
compiled. Optionally, you can specify format("format"). Speci‐
fying the marker format string allows differentiation between two
markers with the same name but different marker format strings.
The handler associated with a marker-based probe may read the op‐
tional parameters specified at the macro call site. These are
named $arg1 through $argNN, where NN is the number of parameters
supplied by the macro. Number and string parameters are passed in
a type-safe manner.
The marker format string associated with a marker is available in
$format. And also the marker name string is available in $name.
KERNEL HARDWARE BREAKPOINTS
This family of probes is used to set hardware watchpoints for a
given
(global) kernel symbol. The probes take three components as in‐
puts :
1. The virtual address / name of the kernel symbol to be traced is
supplied as argument to this class of probes. ( Probes for only
data segment variables are supported. Probing local variables of a
function cannot be done.)
2. Nature of access to be probed : a. .write probe gets triggered
when a write happens at the specified address/symbol name. b. rw
probe is triggered when either a read or write happens.
3. .length (optional) Users have the option of specifying the ad‐
dress interval to be probed using "length" constructs. The user-
specified length gets approximated to the closest possible address
length that the architecture can support. If the specified length
exceeds the limits imposed by architecture, an error message is
flagged and probe registration fails. Wherever 'length' is not
specified, the translator requests a hardware breakpoint probe of
length 1. It should be noted that the "length" construct is not
valid with symbol names.
Following constructs are supported :
probe kernel.data(ADDRESS).write
probe kernel.data(ADDRESS).rw
probe kernel.data(ADDRESS).length(LEN).write
probe kernel.data(ADDRESS).length(LEN).rw
probe kernel.data("SYMBOL_NAME").write
probe kernel.data("SYMBOL_NAME").rw
This set of probes make use of the debug registers of the proces‐
sor, which is a scarce resource. (4 on x86 , 1 on powerpc ) The
script translation flags a warning if a user requests more hard‐
ware breakpoint probes than the limits set by architecture. For
example,a pass-2 warning is flashed when an input script requests
5 hardware breakpoint probes on an x86 system while x86 architec‐
ture supports a maximum of 4 breakpoints. Users are cautioned to
set probes judiciously.
It is possible to specify userspace virtual memory addresses in
this family of probes and the handlers would trigger upon the cor‐
responding memory read/write events in those processes. But one
cannot easily control which processes are monitored. Using `if
(pid() == target())` is a workaround but it is inefficient. Better
use the userland hardware breakpoint probes below instead.
USERLAND HARDWARE BREAKPOINTS
This family of probes is very similar to its kernel-space counter‐
part but it targets the userland processes only.
The following constructs are currently supported:
probe process.data(ADDRESS).write
probe process.data(ADDRESS).rw
probe process.data(ADDRESS).length(LEN).write
probe process.data(ADDRESS).length(LEN).rw
Currently, only the target process specified by -x PID or -c CMD
has the watchpoints registered. The ADDRESS must be a valid virtu‐
al memory address in that process's address space.
PERF
This family of probe points interfaces to the kernel "perf event"
infrastructure for controlling hardware performance counters. The
events being attached to are described by the "type", "config"
fields of the perf_event_attr structure, and are sampled at an in‐
terval governed by the "sample_period" and "sample_freq" fields.
These fields are made available to systemtap scripts using the
following syntax:
probe perf.type(NN).config(MM).sample(XX)
probe perf.type(NN).config(MM).hz(XX)
probe perf.type(NN).config(MM)
probe perf.type(NN).config(MM).process("PROC")
probe perf.type(NN).config(MM).counter("COUNTER")
probe perf.type(NN).config(MM).process("PROC").counter("NAME")
The systemtap probe handler is called once per XX increments of
the underlying performance counter when using the .sample field or
at a frequency in hertz when using the .hz field. When not speci‐
fied, the default behavior is to sample at a count of 1000000.
The range of valid type/config is described by the
perf_event_open(2) system call, and/or the linux/perf_event.h
file. Invalid combinations or exhausted hardware counter re‐
sources result in errors during systemtap script startup. System‐
tap does not sanity-check the values: it merely passes them
through to the kernel for error- and safety-checking. By default
the perf event probe is systemwide unless .process is specified,
which will bind the probe to a specific task. If the name is
omitted then it is inferred from the stap -c argument. A perf
event can be read on demand using .counter. The body of the perf
probe handler will not be invoked for a .counter probe; instead,
the counter is read in a user space probe via:
process("PROC").statement("func@file") {stat <<< @perf("NAME")}
PYTHON
Support for probing python 2 and python 3 function is available
with the help of an extra python support module. Note that the de‐
buginfo for the version of python being probed is required. To run
a python script with the extra python support module you'd add the
'-m HelperSDT' option to your python command, like this:
stap foo.stp -c "python -m HelperSDT foo.py"
Python probes look like the following:
python2.module("MPATTERN").function("PATTERN")
python2.module("MPATTERN").function("PATTERN").call
python2.module("MPATTERN").function("PATTERN").return
python3.module("MPATTERN").function("PATTERN")
python3.module("MPATTERN").function("PATTERN").call
python3.module("MPATTERN").function("PATTERN").return
The list above includes multiple variants and modifiers which pro‐
vide additional functionality or filters. They are:
.function
Places a probe at the beginning of the named func‐
tion by default, unless modified by PATTERN. Parame‐
ters are available as context variables.
.call Places a probe at the beginning of the named func‐
tion. Parameters are available as context variables.
.return
Places a probe at the moment before the return from
the named function. Parameters and local/global
python variables are available as context variables.
PATTERN stands for a string literal that aims to identify a point
in the python program. It is made up of three parts:
• The first part is the name of a function (e.g. "foo") or class
method (e.g. "bar.baz"). This part may use the "*" and "?"
wildcarding operators to match multiple names.
• The second part is optional and begins with the "@" character.
It is followed by the path to the source file containing the
function, which may include a wildcard pattern. The python
path is searched for a matching filename.
• Finally, the third part is optional if the file name part was
given, and identifies the line number in the source file pre‐
ceded by a ":" or a "+". The line number is assumed to be an
absolute line number if preceded by a ":", or relative to the
declaration line of the function if preceded by a "+". All
the lines in the function can be matched with ":*". A range
of lines x through y can be matched with ":x-y". Ranges and
specific lines can be mixed using commas, e.g. ":x,y-z".
In the above list of probe points, MPATTERN stands for a python
module or script name that names the python module of interest.
This part may use the "*" and "?" wildcarding operators to match
multiple names. The python path is searched for a matching file‐
name.
Here are some example probe points, defining the associated
events.
begin, end, end
refers to the startup and normal shutdown of the session.
In this case, the handler would run once during startup and
twice during shutdown.
timer.jiffies(1000).randomize(200)
refers to a periodic interrupt, every 1000 +/- 200 jiffies.
kernel.function("*init*"), kernel.function("*exit*")
refers to all kernel functions with "init" or "exit" in the
name.
kernel.function("*@kernel/time.c:240")
refers to any functions within the "kernel/time.c" file
that span line 240. Note that this is not a probe at the
statement at that line number. Use the kernel.statement
probe instead.
kernel.trace("sched_*")
refers to all scheduler-related (really, prefixed) trace‐
points in the kernel.
kernel.mark("getuid")
refers to an obsolete STAP_MARK(getuid, ...) macro call in
the kernel.
module("usb*").function("*sync*").return
refers to the moment of return from all functions with
"sync" in the name in any of the USB drivers.
kernel.statement(0xc0044852)
refers to the first byte of the statement whose compiled
instructions include the given address in the kernel.
kernel.statement("*@kernel/time.c:296")
refers to the statement of line 296 within "kernel/time.c".
kernel.statement("bio_init@fs/bio.c+3")
refers to the statement at line bio_init+3 within
"fs/bio.c".
kernel.data("pid_max").write
refers to a hardware breakpoint of type "write" set on
pid_max
syscall.*.return
refers to the group of probe aliases with any name in the
third position
stap(1),
probe::*(3stap),
tapset::*(3stap)
This page is part of the systemtap (a tracing and live-system
analysis tool) project. Information about the project can be
found at ⟨https://sourceware.org/systemtap/⟩. If you have a bug
report for this manual page, send it to systemtap@sourceware.org.
This page was obtained from the project's upstream Git repository
⟨git://sourceware.org/git/systemtap.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-07-24.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
STAPPROBES(3stap)
Pages that refer to this page: stap(1), stap-merge(1), stapex(3stap), syscalls(3stap), tapset::syscalls(3stap), error::pass2(7stap), error::pass3(7stap), error::sdt(7stap), stappaths(7), warning::buildid(7stap), stapbpf(8), stapdyn(8), stap-exporter(8), staprun(8), stap-server(8)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|