1.\" 2.\" Copyright (c) 2019 Ian Lepore <ian@freebsd.org> 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24.\" 25.Dd June 24, 2025 26.Dt ELF_AUX_INFO 3 27.Os 28.Sh NAME 29.Nm elf_aux_info 30.Nd extract data from the elf auxiliary vector of the current process 31.Sh LIBRARY 32.Lb libc 33.Sh SYNOPSIS 34.In sys/auxv.h 35.Ft int 36.Fn elf_aux_info "int aux" "void *buf" "int buflen" 37.Sh DESCRIPTION 38The 39.Fn elf_aux_info 40function retrieves the auxiliary info vector requested in 41.Va aux . 42The information is stored into the provided buffer if it will fit. 43The following values, defined in 44.In sys/elf_common.h 45can be requested (corresponding buffer sizes are specified in parenthesis): 46.Bl -tag -width AT_OSRELDATE 47.It AT_CANARY 48The canary value for SSP (arbitrary sized buffer, as many bytes are 49returned as it fits into it, rest is zeroed). 50.It AT_EXECPATH 51The path of executed program 52.Dv (MAXPATHLEN). 53This may not be present if the process was initialized by 54.Xr fexecve 2 55and the namecache no longer contains the file's name. 56.It AT_HWCAP 57CPU / hardware feature flags 58.Dv (sizeof(u_long)). 59.It AT_HWCAP2 60CPU / hardware feature flags 61.Dv (sizeof(u_long)). 62.It AT_HWCAP3 63CPU / hardware feature flags 64.Dv (sizeof(u_long)). 65.It AT_HWCAP4 66CPU / hardware feature flags 67.Dv (sizeof(u_long)). 68.It AT_NCPUS 69Number of CPUs 70.Dv (sizeof(int)). 71.It AT_OSRELDATE 72The 73.Dv OSRELDATE 74of the kernel or jail the program is running on 75.Dv (sizeof(int)). 76.It AT_PAGESIZES 77Vector of page sizes (arbitrary sized buffer, as many elements of the 78.Dv pagesizes 79array are returned as it fits). 80.It AT_PAGESZ 81Page size in bytes 82.Dv (sizeof(int)). 83.It AT_TIMEKEEP 84Pointer to VDSO timehands (for library internal use, 85.Dv sizeof(void *)). 86.It AT_USRSTACKBASE 87Top of the user stack for main thread. 88.It AT_USRSTACKLIM 89Limit for grow of the user stack for main thread. 90.El 91.Sh RETURN VALUES 92Returns zero on success, or an error number on failure. 93.Sh ERRORS 94.Bl -tag -width Er 95.It Bq Er EINVAL 96An unknown item was requested. 97.It Bq Er EINVAL 98The provided buffer was not the right size for the requested item. 99.It Bq Er ENOENT 100The requested item is not available. 101.El 102.Sh HISTORY 103The 104.Fn elf_aux_info 105function appeared in 106.Fx 12.0 . 107.Sh BUGS 108Only a small subset of available auxiliary info vector items are 109accessible with this function. 110Some items require a "right-sized" buffer while others just require a 111"big enough" buffer. 112