diff --git a/lib/libc/sys/Makefile.inc b/lib/libc/sys/Makefile.inc --- a/lib/libc/sys/Makefile.inc +++ b/lib/libc/sys/Makefile.inc @@ -215,6 +215,7 @@ ioctl.2 \ issetugid.2 \ jail.2 \ + kcmp.2 \ kenv.2 \ kill.2 \ kldfind.2 \ diff --git a/lib/libc/sys/kcmp.2 b/lib/libc/sys/kcmp.2 new file mode 100644 --- /dev/null +++ b/lib/libc/sys/kcmp.2 @@ -0,0 +1,230 @@ +.\" SPDX-License-Identifier: BSD-2-Clause +.\" +.\" Copyright (c) 2024 The FreeBSD Foundation +.\" +.\" This documentation was written by +.\" Mark Johnston under sponsorship +.\" from the FreeBSD Foundation. +.\" +.\" 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. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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 January 23, 2024 +.Dt KCMP 2 +.Os +.Sh NAME +.Nm kcmp +.Nd compare two kernel objects +.Sh LIBRARY +.Lb libc +.Sh SYNOPSIS +.In unistd.h +.Ft int +.Fn kcmp "pid_t pid1" "pid_t pid2" "int type" "uintptr_t idx1" "uintptr_t idx2" +.Sh DESCRIPTION +The +.Nm +system call allows the caller to determine whether the two processes with +PIDs +.Fa pid1 +and +.Fa pid2 +reference the same kernel object. +The +.Fa type +parameter specifies the type of object, and +.Fa idx1 +and +.Fa idx2 +are identifiers which refer to some object in the context of process +.Fa pid1 +and +.Fa pid2 , +respectively. +.Pp +The following values for +.Fa type +may be specified: +.Bl -tag -width KCMP_FILE +.It Dv KCMP_FILE +Compare two file descriptions referred to by file descriptors +.Fa idx1 +and +.Fa idx2 . +They may be equivalent if, for example, one of the descriptors was +created by applying +.Xr dup 2 +to the other descriptor. +.It Dv KCMP_FILEOBJ +Perform a +.Dq deep comparison +of the file descriptions referred to by file descriptors +.Fa idx1 +and +.Fa idx2 . +This tests whether the underlying object referred to by the file descriptions +is the same. +For example, if the same filesystem path is opened twice, the kernel will create +two separate file descriptions to back the two file descriptors, but they will +refer to the same underlying object, a +.Xr vnode 9 . +When compared using the +.Dv KCMP_FILE +type, these descriptors will be different, but using the +.Dv KCMP_FILEOBJ +type, they will be equal (assuming that the path was not unlinked in between +the two opens). +.It Dv KCMP_FILES +Determine whether the two processes share the same file descriptor table. +This will be the case if one of the processes was created by +.Xr rfork 2 +without specifying the +.Dv RFFDG +flag. +The +.Fa idx1 +and +.Fa idx2 +parameters are ignored. +.It Dv KCMP_SIGHAND +Determine whether the two processes share the same signal handler table. +This will be the case if one of the processes was created using the +.Dv RFSIGSHARE +flag to +.Xr rfork 2 . +The +.Fa idx1 +and +.Fa idx2 +parameters are ignored. +.It Dv KCMP_VM +Determine whether the two processes share a virtual memory address space. +This may be the case if one of the processes created the other using +.Xr vfork 2 +or +.Xr rfork 2 +with the +.Dv RFMEM +flag. +The +.Fa idx1 +and +.Fa idx2 +parameters are ignored. +.El +The caller of +.Nm +must have permission to debug both processes, otherwise the system call +will fail. +.Sh RETURN VALUES +If +.Fa idx1 +and +.Fa idx2 +refer to the same object, +.Nm +returns 0. +If the object referred to by +.Fa pid1 +and +.Fa idx1 +is less or greater than the object referred to by +.Fa pid2 +and +.Fa idx2 , +.Nm +returns the values 1 and 2, respectively. +The order is defined internally by the kernel and is stable until the system +reboots. +If the two objects cannot be compared for some reason, +.Nm +returns 3. +For example, if +.Fa type +is +.Dv KCMP_FILEOBJ +and +.Fa idx1 +and +.Fa idx2 +are different descriptor types, e.g., a socket and a file, then +.Nm +will return 3. +.Pp +If an error occurs, the value -1 is returned and the global variable +.Va errno +is set to indicate the error. +.Sh ERRORS +.Nm +may fail with the following errors: +.Bl -tag -width Er +.It Bq Er ENODEV +.Dv KCMP_FILEOBJ +was specified and +.Fa idx1 +refers to a file descriptor which does not implement a comparison operator. +.It Bq Er EINVAL +The value of +.Fa type +is invalid. +.It Bq Er EBADF +One of the file descriptors referred to by +.Fa idx1 +or +.Fa idx2 +is not valid. +.It Bq Er ESRCH +One of the processes referred to by +.Fa pid1 +or +.Fa pid2 +does not exist or is not visible (e.g., due to jail restrictions). +.It Bq Er EPERM +The caller does not have permission to access one of the processes referred to +by +.Fa pid1 +or +.Fa pid2 . +.El +.Sh SEE ALSO +.Xr dup 2 , +.Xr fcntl 2 , +.Xr fork 2 , +.Xr rfork 2 , +.Xr vfork 2 +.Sh STANDARDS +The +.Nm +system call originated in Linux. +This implementation aims to be source-compatible with the Linux implementation. +.Fx +implements only a subset of the possible values for +.Fa type +supported in Linux. +More values may be added in the future. +The +.Dv KCMP_FILEOBJ +type is a FreeBSD extension. +.Sh HISTORY +The +.Nm +function was introduced in +.Fx 14.1 .