ELF_AUX_INFO(3)

NAME
elf_aux_info - extract data from the elf auxiliary vector of the current process

LIBRARY
libc

SYNOPSIS
#include <sys/auxv.h>
int
elf_aux_info(int aux, void *buf, int buflen);

DESCRIPTION
The elf_aux_info() function retrieves the auxiliary info vector requested in aux. The information is stored into the provided buffer if it will fit. The following values, defined in <sys/elf_common.h> can be requested (corresponding buffer sizes are specified in parenthesis):

AT_CANARY
    The canary value for SSP (arbitrary sized buffer, as many bytes are returned as it fits into it, rest is zeroed).

AT_EXECPATH
    The path of executed program (MAXPATHLEN). This may not be present if the process was initialized by fexecve(2) and the namecache no longer contains the file's name.

AT_HWCAP
    CPU / hardware feature flags (sizeof(u_long)).

AT_HWCAP2
    CPU / hardware feature flags (sizeof(u_long)).

AT_NCPUS
    Number of CPUs (sizeof(int)).

AT_OSRELDATE
    The OSRELDATE of the kernel or jail the program is running on (sizeof(int)).

AT_PAGESIZES
    Vector of page sizes (arbitrary sized buffer, as many elements of the pagesizes array are returned as it fits).

AT_PAGESZ
    Page size in bytes (sizeof(int)).

AT_TIMEKEEP
    Pointer to VDSO timehands (for library internal use, sizeof(void *)).

AT_USRSTACKBASE
    Top of the user stack for main thread.

AT_USRSTACKLIM
    Limit for grow of the user stack for main thread.

RETURN VALUES
Returns zero on success, or an error number on failure.

ERRORS

[EINVAL]
    An unknown item was requested.

[EINVAL]
    The provided buffer was not the right size for the requested item.

[ENOENT]
    The requested item is not available.

HISTORY
The elf_aux_info() function appeared in FreeBSD 12.0.

BUGS
Only a small subset of available auxiliary info vector items are accessible with this function. Some items require a "right-sized" buffer while others just require a "big enough" buffer.