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; flat-bin.scm - create bin files from Sassy's output
; Copyright (C) 2005 Jonathan Kraut
; This library is free software; you can redistribute it and/or
; modify it under the terms of the GNU Lesser General Public
; License as published by the Free Software Foundation; either
; version 2.1 of the License, or (at your option) any later version.
; This library is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
; Lesser General Public License for more details.
; You should have received a copy of the GNU Lesser General Public
; License along with this library; if not, write to the Free Software
; Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
; Contact:
; Jonathan Kraut
; 4130 43 ST #C2
; Sunnyside, NY 11104
; jak76@columbia.edu
; see file COPYING in the top of Sassy's distribution directory
; module flat-bin
; import api
; export all
; This is a good demonstration of how to use the output API, and we
; should probably include it in chapter 7 of the docs.
; usage:
; procedure:
; (sassy-make-bin output-file sassy-output opts ...) => unspecified
; Combines the text and data sections of sassy-output and writes a
; flat binary file to output-file. If the file already exists it is
; deleted. Any (org) directive is taken into account, and relocations
; are performed on absolute references in the data section. The data
; segment is placed (and aligned properly) immediately after the text
; segment.
; opts can be none, one or both of the following quoted symbols:
; 'boot : Make the file be an x86 boot-sector. That is, zero-fill the
; remainder of the file to 510 bytes, and add the x86 boot-sector
; signature #x55aa to bytes 511 and 512.
; 'stats : Display some stats about the output.
(define (sassy-make-bin output-file sassy-output . opts)
(define boot-sector? (memq 'boot opts))
(define stats? (memq 'stats opts))
(define data? (not (zero? (sassy-data-size sassy-output))))
; Grap some info for printout stats later.
(define text-size (sassy-text-size sassy-output))
(define data-size (sassy-data-size sassy-output))
(define text-pad 0)
(define (display-stat . itms)
(for-each display itms)
(newline))
(define (needed-reloc? x)
(and (eq? 'abs (sassy-reloc-type x))
(let ((name (sassy-reloc-name x)))
(if name
(let ((symbol (sassy-symbol-exists? sassy-output name)))
(and (eq? 'data (sassy-symbol-section symbol))
(not (eq? 'import (sassy-symbol-scope symbol)))))
(eq? 'data (sassy-reloc-section x))))))
; Align the end of the text-section to the align of the data section.
; The data section will begin at this point in the file.
; (nop) is used as the filler.
(when data?
(push-stack-align (sassy-text-stack sassy-output)
(sassy-data-align sassy-output)
#x90))
(set! text-pad (- (sassy-text-size sassy-output) text-size))
; Since the text-section is going to be loaded at whatever the given
; (org) was, all absolute relocations in the text section that refer
; to other locations in the text section already have the offset of
; (org) added to them, so we don't have to apply relocations to
; those. And we don't need to relocate relative addresses in the
; text section (and relative relocations aren't allowed in the data
; section).
; So, we only need to relocate references to symbols defined in the data
; section, or anonymous relocs in the data section
; Also, we need to grab all those references both from the
; text-section _and_ the _data_ section
(when data?
(let ((data-relocs-to-do
(filter needed-reloc? (sassy-reloc-list sassy-output))))
; Now we get ready to apply the relocations taking into account the new
; end of the text-section (or beginning of the data-section).
; For each reloc-to-do, we're going to apply it's patcher
; to the the data-offset plus the value already there
(let* ((text-offset (sassy-text-org sassy-output))
(data-offset (+ text-offset (sassy-text-size sassy-output))))
(for-each (lambda (reloc)
((sassy-reloc-patcher reloc)
(+ data-offset (sassy-reloc-value reloc))))
data-relocs-to-do))
; Now all we have to to is append the data to the text, mark it as
; a boot sectior, and spit it out.
; The fastest way to tack a data section on to a text section is
; the following
; !!!!NOTE: This actually alters the text section (append!)
(push-stack-append! (sassy-text-stack sassy-output)
(sassy-data-stack sassy-output))))
(when boot-sector?
; sanity check
(if (> (sassy-text-size sassy-output) 510)
(error "segment too big for a boot sector")
(begin
; mark it as a boot sector
(push-stack-align (sassy-text-stack sassy-output) 510 0)
(push-stack-push (sassy-text-stack sassy-output)
(list #x55 #xaa)))))
; dump to file
(when (file-exists? output-file)
(delete-file output-file))
(with-output-to-file output-file
(lambda ()
(for-each write-byte (sassy-text-list sassy-output))))
(when stats?
(display-stat "Text size: " text-size " bytes")
(display-stat "Data size: " data-size " bytes")
(display-stat "Data align: "
(sassy-data-align sassy-output)
" byte boundary")
(display-stat
"Total size: "
(+ text-size data-size text-pad)
" bytes, with " text-pad " bytes of padding in the text section.")
(when boot-sector?
(display-stat "Made a boot sector"))))
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