Bugzilla Bug 66038

dosbox-0.62 and dosbox-0.61 don't compile with gcc-3.4.2-r1 hardened. However,
compiling with gcc-3.3.4-r1 unhardened works fine. Based on the fact that gcc
is reporting an error in the PIC register, I suspect the problem is with the
hardened part rather than the gcc-3.4 part.

Reproducible: Always
Steps to Reproduce:
1. gcc-config i686-pc-linux-gnu-3.4.2
2. emerge dosbox
3. see error

Actual Results:  
For 0.62:
g++ -DHAVE_CONFIG_H -I. -I. -I../..  -I../../include -I/usr/include/SDL
-D_REENTRANT  -march=athlon-xp -O2 -pipe -frename-registers
-fomit-frame-pointer
 -c -o core_dyn_x86.o `test -f 'core_dyn_x86.cpp' || echo './'`core_dyn_x86.cpp
core_dyn_x86/risc_x86.h: In function `Bits CPU_Core_Dyn_X86_Run()':
core_dyn_x86/risc_x86.h:128: error: PIC register `%ebx' clobbered in `asm'
make[4]: *** [core_dyn_x86.o] Error 1

For 0.61:
g++ -DHAVE_CONFIG_H -I. -I. -I../..  -I../../include   -march=athlon-xp -O2
-pipe -frename-registers -fomit-frame-pointer  -I/usr/include/SDL -D_REENTRANT
-c -o core_dyn_x86.o `test -f 'core_dyn_x86.cpp' || echo './'`core_dyn_x86.cpp
In file included from core_dyn_x86.cpp:33:
../../include/paging.h:91: warning: `packed' attribute ignored
In file included from core_dyn_x86.cpp:143:
core_dyn_x86/cache.h:302:2: warning: no newline at end of file
core_dyn_x86/risc_x86.h: In function `Bits CPU_Core_Dyn_X86_Run()':
core_dyn_x86/risc_x86.h:133: error: PIC register `%ebx' clobbered in `asm'
make[4]: *** [core_dyn_x86.o] Error 1

Expected Results:  
emerged successfully

Portage 2.0.51_rc7 (default-x86-1.4, gcc-3.4.2, glibc-2.3.3.20040420-r1,
2.6.8-gentoo i686)
=================================================================
System uname: 2.6.8-gentoo i686 AMD Athlon(tm) XP 2500+
Gentoo Base System version 1.4.16
distcc 2.17 i686-pc-linux-gnu (protocols 1 and 2) (default port 3632)
[disabled]Autoconf: sys-devel/autoconf-2.59-r4
Automake: sys-devel/automake-1.8.5-r1
Binutils: sys-devel/binutils-2.14.90.0.8-r1
Headers:  sys-kernel/linux26-headers-2.6.8.1
Libtools: sys-devel/libtool-1.5.2-r5
ACCEPT_KEYWORDS="x86"
AUTOCLEAN="yes"
CFLAGS="-march=athlon-xp -O2 -pipe -frename-registers -fomit-frame-pointer "
CHOST="i686-pc-linux-gnu"
COMPILER=""
CONFIG_PROTECT="/etc /usr/X11R6/lib/X11/xkb /usr/kde/2/share/config
/usr/kde/3.3/share/config:/usr/kde/3.3/env:/usr/kde/3.3/shutdown
/usr/kde/3/share/config /usr/lib/mozilla/defaults/pref /usr/share/config
/usr/share/texmf/dvipdfm/config/ /usr/share/texmf/dvips/config/
/usr/share/texmf/tex/generic/config/ /usr/share/texmf/tex/platex/config/
/usr/share/texmf/xdvi/ /var/qmail/control"
CONFIG_PROTECT_MASK="/etc/gconf /etc/terminfo /etc/env.d"
CXXFLAGS="-march=athlon-xp -O2 -pipe -frename-registers -fomit-frame-pointer "
DISTDIR="/usr/portage/distfiles"
FEATURES="autoaddcvs ccache distlocks sandbox"
GENTOO_MIRRORS="http://gentoo.osuosl.org
http://distro.ibiblio.org/pub/Linux/distributions/gentoo"
MAKEOPTS="-j2"
PKGDIR="/usr/portage/packages"
PORTAGE_TMPDIR="/var/tmp"
PORTDIR="/usr/portage"
PORTDIR_OVERLAY="/usr/local/portage"
SYNC="rsync://rsync.namerica.gentoo.org/gentoo-portage"
USE="3dnow X aac aalib acpi aim alsa apm arts avi berkdb bitmap-fonts bonobo
cdr
cjk cmucl crypt cups curl dga dnd doc dumb-allegro dvd dvdr editor emacs encode
erandom esd ethereal evo faad fbcon ffmpeg fftw flac flash foomaticdb gdbm gif
gnome gphoto2 gpm gtk gtk2 gtkhtml guile hardened imlib jack java jce jpeg kde
ldap libg++ libwww mad mbox mikmod mmx mng motif mozdevelop mozilla
moznocompose
moznoirc moznomail mozsvg mozxmlterm mpeg mule mysql nas ncurses nls nptl oav
odbc oggvorbis opengl opie oss pam pcre pda pdflib perl pic plotutils png
postgres python qt quicktime readline samba scanner sdl slang slp spell sse ssl
svg tcltk tcpd tetex tiff truetype unicode usb wmf x86 xface xinerama xml2 xmms
xprint xv xvid zlib"

Re: 
"I suspect the problem is with the hardened part rather than the gcc-3.4 part."

Actually the problem here is that dosbox-0.62 and most any program in the tree that starts with dos* is simply not pic aware. 
Considering that it's in games-emulation chances are the hardened team is not going to devote resources into making it pic/pie aware. 

Try CFLAGS="-nopie" emerge dosbox --nodeps

You are right. CFLAGS="-nopie" still doesn't work, but CXXFLAGS="-nopie"
compiles and works properly.

What's the hardened team's recommendation in this case?

It's not setXid so the risk factor is pretty low.
-rwxr-x---  1 root games 993444 Sep 30 22:42 /usr/games/bin/dosbox
The offending block of code is some inline asm which would also be riddled with text relocations. Basically it's not worth our time. If we had to recommend anything it would be.
1) don't use dosbox.
2) edit the ebuild to allow this to compile for other people. The logic would be something like so.

inherit flag-o-matic

src_unpack() {
  filter-flags -fPIC
}
If that does not work then try append-flags -fno-pic
or use hardened && append-flags -nopie
Lots of ways to work around this. 
But sorry no inline __asm__ love for you.
Alternatively the user could/should also get in contact with the upstream maintainer/author of dosbox and explain the problem at hand and work with them 
on a proper long term solution.

#if defined(__PIC__) || defined(__pic__)
 // New block of ams that's pic aware here. Or raw c
#else
 // Orig inline asm that's not pic aware here.
#endif

Alex - Can you try adding flag-o-matic to the inherit line and filter-flags
-fPIC to the src_unpack function please?

If that works, I'll add it to the ebuild in portage.

The dosbox guys suggested that passing --disable-dynamic-x86 might make it
work.  Can you give that a try and report please?

Adding --disable-dynamic-x86 to ./configure in the ebuild works for me,
dosbox-0.62 emerges without problems then. 
But please note, that I just checked, if it compiles, not if dosbox behaves
correctly after emerging it. ;-)

Have you had a chance to try running anything under dosbox with
--disable-dynamic-x86 passed to configure?  I'll go ahead and pass that in the
case of USE="hardened" if it seems to work ok.

I am using dosbox only occasionally and right now I have no spare time for
these old DOS games. ;-) But I will try to test a little bit when I return home
this evening. 
Mhmm, I just remembered, that my machine at home still uses gcc-3.3.4 and that
I can't test with gcc-3.4.2 at the moment. But the error described in this bug
occurs with gcc-3.3.4 too, therefore I would expect that --disable-dynamic-x86
will also work for gcc-3.4.2 if it works for gcc-3.3.4.

Ok. I added a patch to the ebuild.  If that doesn't make things happy, I can
try other things.

Sorry for the delay... :-( OK, I reemerged dosbox-0.62 and it compiled and
worked. I could start some of my old DOS games. I am not sure, if there was any
performance impact as that is a highly subjective matter without proper
measurements...
At the moment I would conclude, that everything is OK. Of course, it would be
desirable that the dosbox developers fix this dynamic x86 core in the near
future. ;-)

yeah....that's probably not going to happen.  If it works at all with hardened,
that's probably the best we can hope for.  Thanks for testing.