mirror of https://github.com/mkerrisk/man-pages
122 lines
3.8 KiB
Groff
122 lines
3.8 KiB
Groff
.\" Copyright (c) IBM Corp. 2012
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.\" Author: Jan Glauber <jang@linux.vnet.ibm.com>
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.TH S390_RUNTIME_INSTR 2 2021-03-22 "Linux Programmer's Manual"
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.SH NAME
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s390_runtime_instr \- enable/disable s390 CPU run-time instrumentation
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.SH SYNOPSIS
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.nf
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.BR "#include <asm/runtime_instr.h>" " /* Definition of " S390_* " constants */"
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.BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */"
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.B #include <unistd.h>
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.PP
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.BI "int syscall(SYS_s390_runtime_instr, int " command ", int " signum );
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.fi
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.PP
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.IR Note :
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glibc provides no wrapper for
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.BR s390_runtime_instr (),
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necessitating the use of
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.BR syscall (2).
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.SH DESCRIPTION
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The
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.BR s390_runtime_instr ()
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system call starts or stops CPU run-time instrumentation for the
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calling thread.
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.PP
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The
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.IR command
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argument controls whether run-time instrumentation is started
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.RB ( S390_RUNTIME_INSTR_START ,
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1) or stopped
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.RB ( S390_RUNTIME_INSTR_STOP ,
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2) for the calling thread.
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.PP
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The
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.IR signum
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argument specifies the number of a real-time signal.
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This argument was used to specify a signal number that should be delivered
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to the thread if the run-time instrumentation buffer was full or if
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the run-time-instrumentation-halted interrupt had occurred.
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This feature was never used,
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and in Linux 4.4 support for this feature was removed;
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.\" commit b38feccd663b55ab07116208b68e1ffc7c3c7e78
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thus, in current kernels, this argument is ignored.
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.SH RETURN VALUE
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On success,
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.BR s390_runtime_instr ()
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returns 0 and enables the thread for
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run-time instrumentation by assigning the thread a default run-time
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instrumentation control block.
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The caller can then read and modify the control block and start the run-time
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instrumentation.
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On error, \-1 is returned and
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.IR errno
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is set to indicate the error.
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.SH ERRORS
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.TP
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.B EINVAL
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The value specified in
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.IR command
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is not a valid command.
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.TP
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.B EINVAL
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The value specified in
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.IR signum
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is not a real-time signal number.
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From Linux 4.4 onwards, the
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.IR signum
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argument has no effect,
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so that an invalid signal number will not result in an error.
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.TP
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.B ENOMEM
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Allocating memory for the run-time instrumentation control block failed.
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.TP
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.B EOPNOTSUPP
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The run-time instrumentation facility is not available.
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.SH VERSIONS
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This system call is available since Linux 3.7.
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.SH CONFORMING TO
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This Linux-specific system call is available only on the s390 architecture.
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The run-time instrumentation facility is available
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beginning with System z EC12.
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.SH NOTES
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The
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.I asm/runtime_instr.h
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header file is available
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.\" commit df2f815a7df7edb5335a3bdeee6a8f9f6f9c35c4
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since Linux 4.16.
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.PP
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Starting with Linux 4.4,
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support for signalling was removed, as was the check whether
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.IR signum
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is a valid real-time signal.
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For backwards compatibility with older kernels, it is recommended to pass
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a valid real-time signal number in
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.I signum
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and install a handler for that signal.
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.SH SEE ALSO
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.BR syscall (2),
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.BR signal (7)
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