Manual Pages  — ELF_AUX_INFO

elf_aux_info – extract data from the elf auxiliary vector of the current process

LIBRARY SYNOPSIS DESCRIPTION RETURN VALUES ERRORS HISTORY BUGS

Standard C Library (libc, -lc)

#include <sys/auxv.h>

int
elf_aux_info(int aux, void *buf, int buflen);

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.

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

[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.

The elf_aux_info() function appeared in FreeBSD 12.0 .

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.