xref: /freebsd/contrib/elftoolchain/libdwarf/dwarf_get_section_bytes.3 (revision ae500c1ff8974130f7f2692772cf288b90349e0d)

.\" Copyright (c) 2011 Kai Wang
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.\" $Id: dwarf_get_section_bytes.3 3644 2018-10-15 19:55:01Z jkoshy $
.\"
.Dd August 26, 2011
.Dt DWARF_GET_SECTION_BYTES 3
.Os
.Sh NAME
.Nm dwarf_get_section_bytes
.Nd retrieve ELF section byte streams
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft Dwarf_Ptr
.Fo dwarf_get_section_bytes
.Fa "Dwarf_P_Debug dbg"
.Fa "Dwarf_Signed dwarf_section"
.Fa "Dwarf_Signed *elf_section_index"
.Fa "Dwarf_Unsigned *length"
.Fa "Dwarf_Error *err"
.Fc
.Sh DESCRIPTION
Function
.Fn dwarf_get_section_bytes
returns the ELF section byte streams generated by a prior call
to function
.Xr dwarf_transform_to_disk_form 3 .
.Pp
Each call to function
.Fn dwarf_get_section_bytes
will return the byte stream for one ELF section.
The first call to this function will always return the first ELF
section, and the subsequent calls will return the rest of sections
in the order when they were generated, until the last one.
The total number of sections generated is returned by the function
.Xr dwarf_transform_to_disk_form 3 .
.Pp
Argument
.Ar dbg
should reference a DWARF producer instance allocated using the
functions
.Xr dwarf_producer_init 3
or
.Xr dwarf_producer_init_b 3 .
.Pp
Argument
.Ar dwarf_section
is currently ignored.
.Pp
Argument
.Ar elf_section_index
should point to a location which will be set to the section index value
of the returned ELF section.
.Pp
Argument
.Ar length
should point to a location which will hold the length in bytes of the
returned ELF section.
.Pp
If argument
.Ar err
is not NULL, it will be used to store error information in case of an
error.
.Ss Memory Management
The memory areas used for the returned ELF section byte streams should
be freed using the function
.Fn dwarf_producer_finish .
.Sh RETURN VALUES
On success, function
.Fn dwarf_get_section_bytes
returns a pointer to a ELF section byte stream.
In case of an error, function
.Fn dwarf_get_section_bytes
will return NULL and set the argument
.Ar err .
.Sh EXAMPLES
To generate and retrieve ELF section byte streams, use:
.Bd -literal -offset indent
Dwarf_P_Debug dbg;
Dwarf_Signed count, i, sec_index;
Dwarf_Unsigned len;
Dwarf_Ptr bytes;
Dwarf_Error de;

/* ... Assume that `dbg' refers to a DWARF producer instance,
 * and that application code has added DWARF debugging
 * information to the producer instance. ...
 */
if ((count = dwarf_transform_to_disk_form(dbg, &de)) ==
    DW_DLV_NOCOUNT) {
	warnx("dwarf_transform_to_disk_form failed: %s",
	    dwarf_errmsg(-1));
	return;
}

/* Retrieve section data. */
for (i = 0; i < count; i++) {
	bytes = dwarf_get_section_bytes(dbg, i, &sec_index, &len,
	    &de);
	if (bytes == NULL) {
		warnx("dwarf_get_section_bytes failed: %s",
		    dwarf_errmsg(-1));
		continue;
	}
	/* ... use the returned byte stream ... */
}

/* Release resources. */
dwarf_producer_finish(dbg, &de);
.Ed
.Sh ERRORS
Function
.Fn dwarf_get_section_bytes
can fail with:
.Bl -tag -width ".Bq Er DW_DLE_NO_ENTRY"
.It Bq Er DW_DLE_ARGUMENT
One of the arguments
.Ar dbg ,
.Ar elf_section_index ,
or
.Ar length
was NULL.
.It Bq Er DW_DLE_NO_ENTRY
There were no more ELF sections to retrieve, or the function was
called before a call to
.Xr dwarf_transform_to_disk_form 3 .
.El
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_producer_finish 3 ,
.Xr dwarf_producer_init 3 ,
.Xr dwarf_producer_init_b 3 ,
.Xr dwarf_reset_section_bytes 3 ,
.Xr dwarf_transform_to_disk_form 3