To aid users making the transition to GNU ld from the MRI linker, ld can use MRI compatible linker scripts as an alternative to the more general-purpose linker scripting language described in Command Language. MRI compatible linker scripts have a much simpler command set than the scripting language otherwise used with ld. GNU ld supports the most commonly used MRI linker commands; these commands are described in the following.
In general, MRI scripts arent of much use with the a.out object file format, since it only has three sections and MRI scripts lack some features to make use of them.
You can specify a file containing an MRI-compatible script using the -c command-line option.
Each command in an MRI-compatible script occupies its own line; each command line starts with the keyword that identifies the command (though blank lines are also allowed for punctuation). If a line of an MRI-compatible script begins with an unrecognized keyword, ld issues a warning message, but continues processing the script. Lines beginning with * are comments.
You can write these commands using all upper-case letters, or all lower case; for example, chip is the same as CHIP. The following list shows only the upper-case form of each command.
ABSOLUTE secname
ABSOLUTE secname, secname, ... secname
Normally, ld
includes in the output file all sections from all the input files. However,
in an MRI-compatible script, you can use the ABSOLUTE
command to restrict the sections that will be present in your output program.
If the ABSOLUTE
command is used at all in a script, then only the sections named explicitly
in ABSOLUTE
commands will appear in the linker output. You can still use other input
sections (whatever you select on the command line, or using LOAD)
to resolve addresses in the output file.
ALIAS out-secname, in-secname
Use this command
to place the data from input section in-secname
in a section called out-secname
in the linker output file.
in-secname
may be an integer.
ALIGN secname=expression
Align the section
called secname
to expression.
The expression
should be a power of two.
BASE expression
Use the value of expression
as the lowest address (other than absolute addresses) in the output file.
CHIP
expression
CHIP expression, expression
This command does
nothing; it is accepted only for compatibility.
END
This command does
nothing whatever; its only accepted for compatibility.
FORMAT output-format
Similar to the
OUTPUT_FORMAT
command in the more general linker language, but restricted to one of these
output formats:
LIST anything...
Print (to the
standard output file) a link map, as produced by the ld
command-line option -M.
The keyword LIST may be followed by anything on the same line, with no change in its effect.
LOAD
filename
LOAD
filename, filename,
... filename
Include one or more object file filename
in the link; this has the same effect as specifying filename
directly on the ld
command line.
NAME
output-name
output-name
is the name for the program produced by ld;
the MRI-compatible command NAME
is equivalent to the command-line option -o
or the general script language command OUTPUT.
ORDER
secname, secname,
... secname
ORDER
secname secname
secname
Normally, ld
orders the sections in its output file in the order in which they first
appear in the input files. In an MRI-compatible script, you can override
this ordering with the ORDER
command. The sections you list with ORDER
will appear first in your output file, in the order specified.
PUBLIC
name=expression
PUBLIC
name, expression
PUBLIC
name expression
Supply a value (expression)
for external symbol name used in the linker input files.
SECT
secname, expression
SECT
secname=expression
SECT
secname expression
You can use any of these three forms of the SECT
command to specify the start address (expression)
for section
sec-name.
If you have more than one SECT
statement for the same sec-name,
only the first sets the start address.