STAPFUNCS(3stap)                                                                                                STAPFUNCS(3stap)



NAME
       stapfuncs - systemtap functions


DESCRIPTION
       The  following sections enumerate a few of public functions provided by standard tapsets installed, show in the stappaths
       (7) manual page.   Most are individually documented in the 3stap manual section, with the function:: prefix.

       Each function is described with a signature, and its behavior/restrictions.  The signature line includes the name of  the
       function,  the  type  of its return value (if any), and the names and types of all parameters.  The syntax is the same as
       printed with the stap option -p2.  Examples:


       example1:long (v:string, k:long)
              In function "example1", do something with the given string and integer.  Return some integer.


       example2:unknown ()
              In function "example2", do something.  There is no explicit return value and take no parameters.



   TARGET_SET
       target_set_pid:long (tid:long)
              Return whether the given process-id is within the "target set", that is whether it is a  descendent  of  the  top-
              level target() process.

       target_set_report:unknown ()
              Print a report about the target set, and their ancestry.


   ERRNO
       errno_str:string (e:long)
              Return  the  symbolic string associated with the given error code, like "ENOENT" for the number 2, or "E#3333" for
              an out-of-range value like 3333.


   REGISTERS
       register:long (name:string)
              Return the value of the named CPU register, as it was saved when the current probe point was hit.  If the register
              is 32 bits, it is sign-extended to 64 bits.

              For  the  i386  architecture, the following names are recognized.  (name1/name2 indicates that name1 and name2 are
              alternative names for the same register.)  eax/ax, ebp/bp, ebx/bx, ecx/cx, edi/di, edx/dx,  eflags/flags,  eip/ip,
              esi/si, esp/sp, orig_eax/orig_ax, xcs/cs, xds/ds, xes/es, xfs/fs, xss/ss.

              For  the  x86_64  architecture,  the following names are recognized: 64-bit registers: r8, r9, r10, r11, r12, r13,
              r14, r15, rax/ax, rbp/bp, rbx/bx, rcx/cx, rdi/di, rdx/dx, rip/ip, rsi/si, rsp/sp; 32-bit registers: eax, ebp, ebx,
              ecx, edx, edi, edx, eip, esi, esp, flags/eflags, orig_eax; segment registers: xcs/cs, xss/ss.

              For powerpc, the following names are recognized: r0, r1, ... r31, nip, msr, orig_gpr3, ctr, link, xer, ccr, softe,
              trap, dar, dsisr, result.

              For s390x, the following names are recognized: r0, r1, ... r15, args, psw.mask, psw.addr, orig_gpr2, ilc, trap.


       u_register:long (name:string)
              Same as register(name), except that if the register is 32 bits, it is zero-extended to 64 bits.


   NUMBERED FUNCTION ARGUMENTS
       The functions in this section provide the values of a probed function's arguments.  They can be called when you have  hit
       a  probe  point  at  the  entry  to a function.  Arguments are referred to by number, starting at 1.  Ordinarily, you can
       access arguments by name as well, but you may find these functions useful if the code you are probing was  built  without
       debugging information.

       On 32-bit architectures -- and when probing 32-bit applications on 64-bit architectures -- a 64-bit argument occupies two
       "arg slots."  For example, if you are probing the following function

          void f(int a, long long b, char *c)

       you would refer to a, b, and c as int_arg(1), longlong_arg(2), and pointer_arg(3), respectively, on  a  64-bit  architec-
       ture; but on a 32-bit architecture, you would refer to c as pointer_arg(4) (since b occupies slots 2 and 3).

       If  the  function you are probing doesn't follow the default rules for argument passing, you need to call one of the fol-
       lowing functions (which see) in your handler before calling any *_arg function: asmlinkage(), fastcall(),  or  regparm().
       (This isn't necessary when referring to arguments only by name.)

       int_arg:long (n:long)
              Return the value of argument n as a signed int (i.e., a 32-bit integer sign-extended to 64 bits).

       uint_arg:long (n:long)
              Return the value of argument n as an unsigned int (i.e., a 32-bit integer zero-extended to 64 bits).

       long_arg:long (n:long)
              Return  the  value  of  argument n as a signed long.  On architectures where a long is 32 bits, the value is sign-
              extended to 64 bits.

       ulong_arg:long (n:long)
              Return the value of argument n as an unsigned long.  On architectures where a long is 32 bits, the value is  zero-
              extended to 64 bits.

       longlong_arg:long (n:long)
              Return the value of argument n as a 64-bit value.

       ulonglong_arg:long (n:long)
              Same as longlong_arg(n).

       pointer_arg:long (n:long)
              Same as ulong_arg(n).  Use with any type of pointer.

       s32_arg:long (n:long)
              Same as int_arg(n).

       u32_arg:long (n:long)
              Same as uint_arg(n).

       s64_arg:long (n:long)
              Same as longlong_arg(n).

       u64_arg:long (n:long)
              Same as [u]longlong_arg(n).

       asmlinkage:unknown ()
              The probed kernel function is declared asmlinkage in the source.

       fastcall:unknown ()
              The probed kernel function is declared fastcall in the source.

       regparm:unknown (n:long)
              The  probed  function  was  built with the gcc -mregparm=n option.  (The i386 kernel is built with -mregparm=3, so
              systemtap considers regparm(3) the default for kernel functions on that architecture.)

              For some architectures, the *_arg functions may reject unusually high values of n.


   QUEUE_STATS
       The queue_stats tapset provides functions that, given notifications of  elementary  queuing  events  (wait,  run,  done),
       tracks  averages  such  as  queue  length,  service and wait times, utilization.  The following three functions should be
       called from appropriate probes, in sequence.

       qs_wait:unknown (qname:string)
              Record that a new request was enqueued for the given queue name.

       qs_run:unknown (qname:string)
              Record that a previously enqueued request was removed from the given wait queue and is now being serviced.

       qs_done:unknown (qname:string)
              Record that a request originally from the given queue has completed being serviced.

       Functions with the prefix qsq_ are for querying the  statistics  averaged  since  the  first  queue  operation  (or  when
       qsq_start was called). Since statistics are often fractional, a scale parameter is multiplies the result to a more useful
       scale.  For some fractions, a scale of 100 will usefully return percentage numbers.

       qsq_start:unknown (qname:string)
              Reset the statistics counters for the given queue, and start tracking anew from this moment.

       qsq_print:unknown (qname:string)
              Print a line containing a selection of the given queue's statistics.

       qsq_utilization:long (qname:string, scale:long)
              Return the fraction of elapsed time when the resource was utilized.

       qsq_blocked:long (qname:string, scale:long)
              Return the fraction of elapsed time when the wait queue was used.

       qsq_wait_queue_length:long (qname:string, scale:long)
              Return the average length of the wait queue.

       qsq_service_time:long (qname:string, scale:long)
              Return the average time required to service a request.

       qsq_wait_time:long (qname:string, scale:long)
              Return the average time a request took from being enqueued to completed.

       qsq_throughput:long (qname:string, scale:long)
              Return the average rate of requests per scale units of time.


   INDENT
       The indent tapset provides functions to generate indented lines for nested kinds of trace messages.  Each line contains a
       relative timestamp, and the process name / pid.

       thread_indent:string (delta:long)
              Return  a string with an appropriate indentation for this thread.  Call it with a small positive or matching nega-
              tive delta.  If this is the outermost, initial level of indentation, reset the relative timestamp base to zero.

       thread_timestamp:long ()
              Return an absolute timestamp value for use by the indentation function.  The default function uses gettimeofday_us


   SYSTEM
       system (cmd:string)
              Runs a command on the system. The command will run in the background when the current probe completes.



   INET
       These functions convert between network (big-endian) and host byte order, like their namesake C functions.

       ntohll:long (x:long)
              Convert from network to host byte order, 64-bit.

       ntohl:long (x:long)
              Convert from network to host byte order, 32-bit.

       ntohs:long (x:long)
              Convert from network to host byte order, 16-bit.

       htonll:long (x:long)
              Convert from host to network byte order, 64-bit.

       htonl:long (x:long)
              Convert from host to network byte order, 32-bit.

       htons:long (x:long)
              Convert from host to network byte order, 16-bit.


   SIGNAL
       get_sa_flags:long (act:long)
              Returns the numeric value of sa_flags.

       get_sa_handler:long (act:long)
              Returns the numeric value of sa_handler.

       sigset_mask_str:string (mask:long)
              Returns the string representation of the sigset sa_mask.

       is_sig_blocked:long (task:long, sig:long)
              Returns 1 if the signal is currently blocked, or 0 if it is not.

       sa_flags_str:string (sa_flags:long)
              Returns the string representation of sa_flags.

       sa_handler_str(handler)
              Returns the string representation of sa_handler. If it is not SIG_DFL, SIG_IGN or  SIG_ERR,  it  will  return  the
              address of the handler.

       signal_str(num)
              Returns the string representation of the given signal number.


   DEVICE
       MAJOR:long(dev:long)
              Extracts the major device number from a kernel device number (kdev_t).

       MINOR:long(dev:long)
              Extracts the minor device number from a kernel device number (kdev_t).

       MKDEV:long(major:long, minor:long)
              Creates a value that can be compared to a kernel device number (kdev_t).

       usrdev2kerndev:long(dev:long)
              Converts a user-space device number into the format used in the kernel.


FILES
       More files and their corresponding paths can be found in the stappaths (7) manual page.


SEE ALSO
       stap(1), function::*(3stap), tapset::*(3stap), stappaths(7)



                                                                                                                STAPFUNCS(3stap)