Initial commit

tools/ld.py

@@ -0,0 +1,100 @@
+import argparse
+import struct
+import sys
+
+import obj_pb2
+
+CRT0_FILE = '/home/paulmathieu/vhdl/bin/crt0.o'
+
+
+def parse_objs(objs):
+    sections = []
+    relocs = []
+
+    for obj in objs:
+        of = obj_pb2.ObjFile()
+        of.ParseFromString(obj.read())
+        sections += of.sections
+        relocs += of.relocs
+
+    return sections, relocs
+
+
+def map_sections(sections):
+    secmap = []
+
+    addr = 0
+
+    # _start goes first
+    for sec in sections:
+        if sec.name == '_start':
+            secmap.append((addr, sec))
+            addr += len(sec.text)
+            sections.remove(sec)
+            break
+    assert secmap, "could not find symbol _start :/"
+
+    for sec in sections:
+        secmap.append((addr, sec))
+        addr += len(sec.text)
+
+    return secmap
+
+
+def do_relocs(secmap, relocs):
+    namemap = {s[1].name: s for s in secmap}
+    for reloc in relocs:
+        assert reloc.section in namemap
+        assert reloc.target in namemap
+        _, sec = namemap[reloc.section]
+        # the reloc hex should look like /e.ff0000/
+        buff = bytearray(sec.text)
+        target_addr = namemap[reloc.target][0]
+        reg = buff[reloc.offset] & 0xf
+        buff[reloc.offset+0:reloc.offset+4] = [
+                0xf0 | reg, (target_addr >> 0) & 0xff,
+                0x90 | reg, (target_addr >> 8) & 0xff,
+                ]
+        sec.text = bytes(buff)
+
+
+def dump(secmap):
+    out = bytearray()
+    for _, sec in secmap:
+        out += sec.text
+    return out
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(description='Assemble.')
+    parser.add_argument('--debug', action='store_true',
+                        help='print debug info')
+    parser.add_argument('objfiles', metavar='O', nargs='+',
+                        type=argparse.FileType('rb'),
+                        help='input file (default: stdin)')
+    parser.add_argument('--output', '-o', type=argparse.FileType('wb'),
+                        default=sys.stdout.buffer, help='output file')
+    parser.add_argument('--vhdl', action='store_true',
+                        help='vhdl output')
+    return parser.parse_args()
+
+
+def main():
+    args = parse_args()
+
+    with open(CRT0_FILE, 'rb') as crt0:
+        sections, relocs = parse_objs(args.objfiles + [crt0])
+
+    sectionmap = map_sections(sections)
+    do_relocs(sectionmap, relocs)
+    text = dump(sectionmap)
+
+    if args.vhdl:
+        args.output.write(',\n'.join(f'x"{x:04x}"' for x in
+                          struct.unpack(f'>{len(text) // 2}H', text)).encode())
+    else:
+        args.output.write(text)
+
+
+if __name__ == "__main__":
+    main()