S390_RUNTIME_INSTR(2)                                                      System Calls Manual                                                     S390_RUNTIME_INSTR(2)

NAME
       s390_runtime_instr - enable/disable s390 CPU run-time instrumentation

SYNOPSIS
       #include <asm/runtime_instr.h> /* Definition of S390_* constants */
       #include <sys/syscall.h>       /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_s390_runtime_instr, int command, int signum);

       Note: glibc provides no wrapper for s390_runtime_instr(), necessitating the use of syscall(2).

DESCRIPTION
       The s390_runtime_instr() system call starts or stops CPU run-time instrumentation for the calling thread.

       The  command  argument controls whether run-time instrumentation is started (S390_RUNTIME_INSTR_START, 1) or stopped (S390_RUNTIME_INSTR_STOP, 2) for the calling
       thread.

       The signum argument specifies the number of a real-time signal.  This argument was used to specify a signal number that should be delivered to the thread if  the
       run-time instrumentation buffer was full or if the run-time-instrumentation-halted interrupt had occurred.  This feature was never used, and in Linux 4.4 support
       for this feature was removed; thus, in current kernels, this argument is ignored.

RETURN VALUE
       On success, s390_runtime_instr() returns 0 and enables the thread for run-time instrumentation by assigning the thread a default run-time instrumentation control
       block.   The caller can then read and modify the control block and start the run-time instrumentation.  On error, -1 is returned and errno is set to indicate the
       error.

ERRORS
       EINVAL The value specified in command is not a valid command.

       EINVAL The value specified in signum is not a real-time signal number.  From Linux 4.4 onwards, the signum argument has no effect, so that an invalid signal num‐
              ber will not result in an error.

       ENOMEM Allocating memory for the run-time instrumentation control block failed.

       EOPNOTSUPP
              The run-time instrumentation facility is not available.

VERSIONS
       This system call is available since Linux 3.7.

CONFORMING TO
       This Linux-specific system call is available only on the s390 architecture.  The run-time instrumentation facility is available beginning with System z EC12.

NOTES
       The asm/runtime_instr.h header file is available since Linux 4.16.

       Starting with Linux 4.4, support for signalling was removed, as was the check whether signum is a valid real-time signal.  For backwards compatibility with older
       kernels, it is recommended to pass a valid real-time signal number in signum and install a handler for that signal.

SEE ALSO
       syscall(2), signal(7)

Linux Programmer's Manual                                                      2021-03-22                                                          S390_RUNTIME_INSTR(2)