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

.SH NAME
gelf_getnote \- Get class\-independent note information at the supplied offset

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

.BI "size_t gelf_getnote (Elf_Data *" data ", size_t " offset ", GElf_Nhdr *" result ", size_t *" name_offset ", size_t *" desc_offset ");"

.SH DESCRIPTION
Retrieve the ELF note header from
.I data
at offset
.I offset
and store it in a class\-independent representation pointed to by
.IR result .
The note name and note descriptor offsets relative to the start of
.I data
are stored in
.I *name_offset
and
.IR *desc_offset ,
respectively.
.B GElf_Nhdr
fields
.IR n_namesz ,
.IR n_descsz ,
and
.I n_type
describe the note's name length, descriptor length and type, respectively.
Alignment and padding of the note data entry are handled automatically
by this function.
See
.BR elf (5)
for more information regarding ELF notes.

.SH PARAMETERS
.TP
.I data
Pointer to an
.B Elf_Data
associated with a
.B SHT_NOTE
section or a
.B PT_NOTE
segment.
.I data->d_type
should be
.B ELF_T_NHDR
or
.BR ELF_T_NHDR8 .

.TP
.I offset
Offset of a note header within
.IR data .

.TP
.I result
Pointer to a caller\-provided
.B GElf_Nhdr
structure for storing the requested note header.
.I result
must not be NULL.

.TP
.I name_offset
Pointer to a caller\-provided
.B size_t
for storing the name offset of the requested note.  This offset is relative to
.IR data->d_buf .
.I name_offset
must not be NULL.

.TP
.I desc_offset
Pointer to a caller\-provided
.B size_t
for storing the descriptor offset of the requested note. This offset is
relative to
.IR data->d_buf .
.I desc_offset
must not be NULL.

.SH RETURN VALUE
On success, this function updates
.IR *result ,
.IR *name_offset ,
and
.I *desc_offset
and returns the offset of the next note.  If there are no notes remaining
then the return value will be greater than or equal to the
.B d_size
of
.IR data .
On failure, this function returns zero and sets elf_errno.  If
.I data
is NULL then zero is returned without setting elf_errno.

.SH EXAMPLE
.nf
  size_t offset = 0;
  GElf_Nhdr nhdr;
  size_t name_offset;
  size_t desc_offset;
  while (offset < data->d_size
         && (offset = gelf_getnote (data, offset,
                                    &nhdr, &name_offset, &desc_offset)) > 0)
    {
      const char *name = nhdr.n_namesz == 0 ? "" : data->d_buf + name_offset;
      const char *desc = nhdr.n_descsz == 0 ? "" : data->d_buf + desc_offset;

      /* Process note here.  name and desc are not guaranteed to be
         zero-terminated.  The presence of null characters should be
         verified using n_namesz and n_descsz.  */
      [...]
    }
.fi

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

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

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

.SH HISTORY
.B gelf_getnote
first appeared in elfutils 0.130.  This function is an elfutils libelf extension and
may not be available in other libelf implementations.