1 files changed, 96 insertions, 0 deletions
diff --git a/qemu/roms/seabios/scripts/vgafixup.py b/qemu/roms/seabios/scripts/vgafixup.py
new file mode 100644
index 000000000..2053cd5d7
--- /dev/null
+++ b/qemu/roms/seabios/scripts/vgafixup.py
@@ -0,0 +1,96 @@
+#!/usr/bin/env python
+# Work around x86emu bugs by replacing problematic instructions.
+#
+# Copyright (C) 2012  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+
+# The x86emu code widely used in Linux distributions when running Xorg
+# in vesamode is known to have issues with "retl", "leavel", "entryl",
+# "leal", and some variants of "calll".  This code modifies those
+# instructions that are known to be generated by gcc to avoid
+# triggering the x86emu bugs.
+
+# It is also known that the Windows vgabios emulator has issues with
+# addressing negative offsets to the %esp register.  That has been
+# worked around by not using the gcc parameter "-fomit-frame-pointer"
+# when compiling.
+
+import sys, re
+
+# leal parameter regex - example string: -3(%edx,%eax,8), %eax
+re_leal = re.compile(
+    r'^\s*(?P<offset>[^(]*?)\s*'
+    r'\(\s*(?P<base>[^,)]*?)\s*(?:,\s*(?P<index>[^,)]*?)\s*)?'
+    r'(?:,\s*(?P<scale>[^,)]*?)\s*)?\)\s*'
+    r',\s*(?P<dest>.*?)\s*$')
+
+# Find an alternate set of instructions for a given "leal" instruction
+def handle_leal(sline):
+    m = re_leal.match(sline[5:])
+    if m is None or m.group('index') == '%esp':
+        print("Unable to fixup leal instruction: %s" % (sline,))
+        sys.exit(-1)
+    offset, base, index, scale, dest = m.group(
+        'offset', 'base', 'index', 'scale', 'dest')
+    if dest == '%esp':
+        # If destination is %esp then just use 16bit leaw instead
+        return 'leaw %s\n' % (sline[5:].replace('%e', '%'),)
+    if not scale:
+        scale = '1'
+    scale = {1: 0, 2: 1, 4: 2, 8: 3}[int(scale, 0)]
+    # Try to rearrange arguments to simplify 'base' (to improve code gen)
+    if not scale and base == index:
+        base, index, scale = '', index, 1
+    elif not index or (not scale and base in (dest, '%esp') and index != dest):
+        base, index, scale = index, base, 0
+    # Produce instructions to calculate "leal"
+    insns = ['pushfw']
+    if base != dest:
+        # Calculate "leal" directly in dest register
+        if index != dest:
+            insns.insert(0, 'movl %s, %s' % (index, dest))
+        if scale:
+            insns.append('shll $%d, %s' % (scale, dest))
+        if base:
+            if base == '%esp':
+                offset += '+2'
+            insns.append('addl %s, %s' % (base, dest))
+    elif base == index:
+        # Use "imull" method
+        insns.append('imull $%d, %s' % ((1<<scale)+1, dest))
+    else:
+        # Backup/restore index register and do scaling in index register
+        insns.append('pushl %s' % (index,))
+        insns.append('shll $%d, %s' % (scale, index))
+        insns.append('addl %s, %s' % (index, dest))
+        insns.append('popl %s' % (index,))
+    if offset and offset != '0':
+        insns.append('addl $%s, %s' % (offset, dest))
+    insns.append('popfw\n')
+    return ' ; '.join(insns)
+
+def main():
+    infilename, outfilename = sys.argv[1:]
+    infile = open(infilename, 'r')
+    out = []
+    for line in infile:
+        sline = line.strip()
+        if sline == 'ret':
+            out.append('retw $2\n')
+        elif sline == 'leave':
+            out.append('movl %ebp, %esp ; popl %ebp\n')
+        elif sline.startswith('call'):
+            out.append('pushw %ax ; callw' + sline[4:] + '\n')
+        elif sline.startswith('leal'):
+            out.append(handle_leal(sline))
+            #print("-> %s\n   %s" % (sline, out[-1].strip()))
+        else:
+            out.append(line)
+    infile.close()
+    outfile = open(outfilename, 'w')
+    outfile.write(''.join(out))
+    outfile.close()
+
+if __name__ == '__main__':
+    main()