s390_runtime_instr(2) System Calls Manual s390_runtime_instr(2)
NAME
s390_runtime_instr - enable/disable s390 CPU run-time instrumentation
LIBRARY
Standard C library (libc, -lc)
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 in-
strumentation for the calling thread.
The command argument controls whether run-time instrumentation is
started (S390_RUNTIME_INSTR_START, 1) or stopped (S390_RUNTIME_IN-
STR_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 in-
strumentation 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 number 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.
STANDARDS
Linux on s390.
HISTORY
Linux 3.7. 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 com-
patibility 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 man-pages 6.7 2023-10-31 s390_runtime_instr(2)
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