S390_RUNTIME_INSTR(2) System Calls Manual S390_RUNTIME_INSTR(2)

s390_runtime_instr - enable/disable s390 CPU run-time instrumentation

#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).

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.

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.

The value specified in command is not a valid command.
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 number will not result in an error.
Allocating memory for the run-time instrumentation control block failed.
The run-time instrumentation facility is not available.

This system call is available since Linux 3.7.

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

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.

syscall(2), signal(7)

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2021-03-22 Linux Programmer's Manual