+++ /dev/null
-.\" Copyright 2012 Michael Kerrisk <mtk.manpages@gmail.com>
-.\"
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-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
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-.\" Since the Linux kernel and libraries are constantly changing, this
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-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
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-.\" %%%LICENSE_END
-.\"
-.\" See also https://lwn.net/Articles/519085/
-.\"
-.\" FIXME glibc 2.18 added AT_HWCAP2, which needs to e documented
-.\"
-.TH GETAUXVAL 3 2014-08-19 "GNU" "Linux Programmer's Manual"
-.SH NAME
-getauxval \- retrieve a value from the auxiliary vector
-.SH SYNOPSIS
-.nf
-.B #include <sys/auxv.h>
-.sp
-.BI "unsigned long getauxval(unsigned long " type );
-.fi
-.SH DESCRIPTION
-The
-.BR getauxval ()
-function retrieves values from the auxiliary vector,
-a mechanism that the kernel's ELF binary loader
-uses to pass certain information to
-user space when a program is executed.
-
-Each entry in the auxiliary vector consists of a pair of values:
-a type that identifies what this entry represents,
-and a value for that type.
-Given the argument
-.IR type ,
-.BR getauxval ()
-returns the corresponding value.
-
-The value returned for each
-.I type
-is given in the following list.
-Not all
-.I type
-values are present on all architectures.
-.TP
-.BR AT_BASE
-The base address of the program interpreter (usually, the dynamic linker).
-.TP
-.BR AT_BASE_PLATFORM
-A string identifying the real platform; may differ from
-.BR AT_PLATFORM
-(PowerPC only).
-.TP
-.BR AT_CLKTCK
-The frequency with which
-.BR times (2)
-counts.
-This value can also be obtained via
-.IR sysconf(_SC_CLK_TCK) .
-.TP
-.BR AT_DCACHEBSIZE
-The data cache block size.
-.TP
-.BR AT_EGID
-The effective group ID of the thread.
-.TP
-.BR AT_ENTRY
-The entry address of the executable.
-.TP
-.BR AT_EUID
-The effective user ID of the thread.
-.TP
-.BR AT_EXECFD
-File descriptor of program.
-.TP
-.BR AT_EXECFN
-Pathname used to execute program.
-.TP
-.BR AT_FLAGS
-Flags (unused).
-.TP
-.BR AT_FPUCW
-Used FPU control word (SuperH architecture only).
-This gives some information about the FPU initialization
-performed by the kernel.
-.TP
-.BR AT_GID
-The real group ID of the thread.
-.TP
-.BR AT_HWCAP
-A pointer to a multibyte mask of bits whose settings
-indicate detailed processor capabilities.
-The contents of the bit mask are hardware dependent
-(for example, see the kernel source file
-.IR arch/x86/include/asm/cpufeature.h
-for details relating to the Intel x86 architecture).
-A human-readable version of the same information is available via
-.IR /proc/cpuinfo .
-.TP
-.BR AT_ICACHEBSIZE
-The instruction cache block size.
-.\" .TP
-.\" .BR AT_IGNORE
-.\" .TP
-.\" .BR AT_IGNOREPPC
-.\" .TP
-.\" .BR AT_NOTELF
-.TP
-.BR AT_PAGESZ
-The system page size (the same value returned by
-.IR sysconf(_SC_PAGESIZE) ).
-.TP
-.BR AT_PHDR
-The address of the program headers of the executable.
-.TP
-.BR AT_PHENT
-The size of program header entry.
-.TP
-.BR AT_PHNUM
-The number of program headers.
-.TP
-.BR AT_PLATFORM
-A pointer to a string that identifies the hardware platform
-that the program is running on.
-The dynamic linker uses this in the interpretation of
-.IR rpath
-values.
-.TP
-.BR AT_RANDOM
-The address of sixteen bytes containing a random value.
-.TP
-.BR AT_SECURE
-Has a nonzero value if this executable should be treated securely.
-Most commonly, a nonzero value indicates that the process is
-executing a set-user-ID or set-group-ID program; alternatively,
-a nonzero value may be triggered by a Linux Security Module.
-When this value is nonzero,
-the dynamic linker disables the use of certain environment variables (see
-.BR ld-linux.so (8))
-and glibc changes other aspects of its behavior.
-(See also
-.BR secure_getenv (3).)
-.TP
-.BR AT_SYSINFO
-The entry point to the system call function in the vDSO.
-Not present/needed on all architectures (e.g., absent on x86-64).
-.TP
-.BR AT_SYSINFO_EHDR
-The address of a page containing the virtual Dynamic Shared Object (vDSO)
-that the kernel creates in order to provide fast implementations of
-certain system calls.
-.TP
-.BR AT_UCACHEBSIZE
-The unified cache block size.
-.TP
-.BR AT_UID
-The real user ID of the thread.
-.SH RETURN VALUE
-On success,
-.BR getauxval ()
-returns the value corresponding to
-.IR type .
-If
-.I type
-is not found, 0 is returned.
-.SH ERRORS
-.TP
-.BR ENOENT " (since glibc 2.19)"
-.\" commit b9ab448f980e296eac21ac65f53783967cc6037b
-No entry corresponding to
-.IR type
-could be found in the auxiliary vector.
-.SH VERSIONS
-The
-.BR getauxval ()
-function was added to glibc in version 2.16.
-.SH ATTRIBUTES
-.SS Multithreading (see pthreads(7))
-The
-.BR getauxval ()
-function is thread-safe.
-.SH CONFORMING TO
-This function is a nonstandard glibc extension.
-.SH NOTES
-The primary consumer of the information in the auxiliary vector
-is the dynamic linker
-.BR ld-linux.so (8).
-The auxiliary vector is a convenient and efficient shortcut
-that allows the kernel to communicate a certain set of standard
-information that the dynamic linker usually or always needs.
-In some cases, the same information could be obtained by system calls,
-but using the auxiliary vector is cheaper.
-
-The auxiliary vector resides just above the argument list and
-environment in the process address space.
-The auxiliary vector supplied to a program can be viewed by setting the
-.B LD_SHOW_AUXV
-environment variable when running a program:
-
- $ LD_SHOW_AUXV=1 sleep 1
-
-The auxiliary vector of any process can (subject to file permissions)
-be obtained via
-.IR /proc/PID/auxv ;
-see
-.BR proc (5)
-for more information.
-.SH BUGS
-Before the addition of the
-.B ENOENT
-error in glibc 2.19,
-there was no way to unambiguously distinguish the case where
-.I type
-could not be found from the case where the value corresponding to
-.I type
-was zer0.
-.SH SEE ALSO
-.BR secure_getenv (3),
-.BR vdso (7),
-.BR ld-linux.so (8)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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