.TH GELF_UPDATE_AUXV 3 2025-12-31 "Libelf" "Libelf Programmer's Manual"

.SH NAME
gelf_update_auxv \- Update information in the auxiliary vector at the given index

.SH SYNOPSIS
.nf
.B #include <gelf.h>

.BI "int gelf_update_auxv (Elf_Data *" data ", int " ndx ", GElf_auxv_t *" src ");"

.SH DESCRIPTION
Copy a class\-independent auxiliary vector entry from
.I src
into the
.B NT_AUXV
note associated with
.I data
at index
.IR ndx .
See
.BR getauxval (3)
for more information regarding the auxiliary vector.

.SH PARAMETERS
.TP
.I data
Pointer to an
.B Elf_Data
associated with an
.B NT_AUXV
ELF note.
.I data->d_type
should be
.BR ELF_T_AUXV .
.B NT_AUXV
notes are normally found in core files.  The auxiliary vector can also be
read directly from /proc/PID/auxv of a live process, in which case this
function does not write back to
.I data
itself.

.TP
.I ndx
Zero\-based index of the auxiliary vector entry to be updated within
.IR data .

.TP
.I src
Pointer to a caller\-provided auxiliary vector entry.  For
.B ELFCLASS32
binaries,
.B a_type
and
.B a_val
must fit within unsigned 32-bit values.
.I src
must not be NULL.

.SH RETURN VALUE
On success, this function returns a non-zero value, updates the
auxiliary vector entry at index
.I ndx
in
.IR data ,
and marks the section or segment associated with
.I data
with
.BR ELF_F_DIRTY .
On failure, zero is returned and elf_errno is set.  If
.I data
is NULL, then zero is returned without setting elf_errno.

.SH SEE ALSO
.BR gelf_getauxv (3),
.BR getauxval (3),
.BR libelf (3),
.BR elf (5)

.SH ATTRIBUTES
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR gelf_update_auxv ()
T}	Thread safety	MT-Safe
.TE

.SH REPORTING BUGS
Report bugs to <elfutils-devel@sourceware.org> or https://sourceware.org/bugzilla/.

.SH HISTORY