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diff --git a/lib/libsys/getrlimit.2 b/lib/libsys/getrlimit.2 new file mode 100644 index 000000000000..d54dc703ada0 --- /dev/null +++ b/lib/libsys/getrlimit.2 @@ -0,0 +1,242 @@ +.\" Copyright (c) 1980, 1991, 1993 +.\" The Regents of the University of California. All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" 3. Neither the name of the University nor the names of its contributors +.\" may be used to endorse or promote products derived from this software +.\" without specific prior written permission. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.Dd July 25, 2024 +.Dt GETRLIMIT 2 +.Os +.Sh NAME +.Nm getrlimit , +.Nm setrlimit +.Nd control maximum system resource consumption +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In sys/types.h +.In sys/time.h +.In sys/resource.h +.Ft int +.Fn getrlimit "int resource" "struct rlimit *rlp" +.Ft int +.Fn setrlimit "int resource" "const struct rlimit *rlp" +.Sh DESCRIPTION +Limits on the consumption of system resources by the current process +and each process it creates may be obtained with the +.Fn getrlimit +system call, and set with the +.Fn setrlimit +system call. +.Pp +The +.Fa resource +argument is one of the following: +.Bl -tag -width RLIMIT_FSIZEAA +.It Dv RLIMIT_AS +The maximum amount (in bytes) of virtual memory the process is +allowed to map. +.It Dv RLIMIT_CORE +The largest size (in bytes) +.Xr core 5 +file that may be created. +.It Dv RLIMIT_CPU +The maximum amount of cpu time (in seconds) to be used by +each process. +.It Dv RLIMIT_DATA +The maximum size (in bytes) of the data segment for a process; +this defines how far a program may extend its break with the +.Xr sbrk 2 +function. +.It Dv RLIMIT_FSIZE +The largest size (in bytes) file that may be created. +.It Dv RLIMIT_KQUEUES +The maximum number of kqueues this user id is allowed to create. +.It Dv RLIMIT_MEMLOCK +The maximum size (in bytes) which a process may lock into memory +using the +.Xr mlock 2 +system call. +.It Dv RLIMIT_NOFILE +The maximum number of open files for this process. +.It Dv RLIMIT_NPROC +The maximum number of simultaneous processes for this user id. +.It Dv RLIMIT_NPTS +The maximum number of pseudo-terminals this user id is allowed to create. +.It Dv RLIMIT_PIPEBUF +The maximum total size of in-kernel buffers for bi-directional pipes/fifos +that this user id is allowed to consume. +The buffers for kernel FIFOs created on the first open of a filesystem +object created by +.Pq Xr mkfifo 2 +are also charged to the user ID of the process opening it, +not the FIFO's filesystem owner. +Despite somewhat unexpected, this is in fact fair, since user of the fifo +is not necessary its creator. +.It Dv RLIMIT_RSS +When there is memory pressure and swap is available, prioritize eviction of +a process' resident pages beyond this amount (in bytes). +When memory is not under pressure, this rlimit is effectively ignored. +.Pp +Processes that exceed their set +.Dv RLIMIT_RSS +are not signalled or halted. +The limit is merely a hint to the VM daemon to prefer to deactivate pages from +processes that have exceeded their set +.Dv RLIMIT_RSS . +.It Dv RLIMIT_SBSIZE +The maximum size (in bytes) of socket buffer usage for this user. +This limits the amount of network memory, and hence the amount of +mbufs, that this user may hold at any time. +.It Dv RLIMIT_STACK +The maximum size (in bytes) of the stack segment for a process; +this defines how far a program's stack segment may be extended. +Stack extension is performed automatically by the system. +.It Dv RLIMIT_SWAP +The maximum size (in bytes) of the swap space that may be reserved or +used by all of this user id's processes. +This limit is enforced only if bit 1 of the +.Va vm.overcommit +sysctl is set. +Please see +.Xr tuning 7 +for a complete description of this sysctl. +.It Dv RLIMIT_UMTXP +The limit of the number of process-shared posix thread library objects +allocated by user id. +.It Dv RLIMIT_VMEM +An alias for +.Dv RLIMIT_AS . +.El +.Pp +A resource limit is specified as a soft limit and a hard limit. +When a soft limit is exceeded, a process might or might not receive a signal. +For example, signals are generated when the cpu time or file size is exceeded, +but not if the address space or RSS limit is exceeded. +A program that exceeds the soft limit is allowed to continue execution until it +reaches the hard limit, or modifies its own resource limit. +Even reaching the hard limit does not necessarily halt a process. +For example, if the RSS hard limit is exceeded, nothing happens. +.Pp +The +.Vt rlimit +structure is used to specify the hard and soft limits on a resource. +.Bd -literal -offset indent +struct rlimit { + rlim_t rlim_cur; /* current (soft) limit */ + rlim_t rlim_max; /* maximum value for rlim_cur */ +}; +.Ed +.Pp +Only the super-user may raise the maximum limits. +Other users +may only alter +.Fa rlim_cur +within the range from 0 to +.Fa rlim_max +or (irreversibly) lower +.Fa rlim_max . +.Pp +An +.Dq infinite +value for a limit is defined as +.Dv RLIM_INFINITY . +.Pp +Because this information is stored in the per-process information, +this system call must be executed directly by the shell if it +is to affect all future processes created by the shell; +.Ic limit +is thus a built-in command to +.Xr csh 1 . +.Pp +The system refuses to extend the data or stack space when the limits +would be exceeded in the normal way: a +.Xr brk 2 +function fails if the data space limit is reached. +When the stack limit is reached, the process receives +a segmentation fault +.Pq Dv SIGSEGV ; +if this signal is not +caught by a handler using the signal stack, this signal +will kill the process. +.Pp +A file I/O operation that would create a file larger that the process' +soft limit will cause the write to fail and a signal +.Dv SIGXFSZ +to be +generated; this normally terminates the process, but may be caught. +When +the soft cpu time limit is exceeded, a +.Dv SIGXCPU +signal is sent to the +offending process. +.Pp +When most operations would allocate more virtual memory than allowed by the +soft limit of +.Dv RLIMIT_AS , +the operation fails with +.Dv ENOMEM +and no signal is raised. +A notable exception is stack extension, described above. +If stack extension would allocate more virtual memory than allowed by the soft +limit of +.Dv RLIMIT_AS , +a +.Dv SIGSEGV +signal will be delivered. +The caller is free to raise the soft address space limit up to the hard limit +and retry the allocation. +.Sh RETURN VALUES +.Rv -std +.Sh ERRORS +The +.Fn getrlimit +and +.Fn setrlimit +system calls +will fail if: +.Bl -tag -width Er +.It Bq Er EFAULT +The address specified for +.Fa rlp +is invalid. +.It Bq Er EPERM +The limit specified to +.Fn setrlimit +would have +raised the maximum limit value, and the caller is not the super-user. +.El +.Sh SEE ALSO +.Xr csh 1 , +.Xr quota 1 , +.Xr quotactl 2 , +.Xr sigaction 2 , +.Xr sigaltstack 2 , +.Xr sysctl 3 , +.Xr ulimit 3 +.Sh HISTORY +The +.Fn getrlimit +system call appeared in +.Bx 4.2 . |