Message ID | 20140206040442.GA5486@morn.localdomain |
---|---|
State | New |
Headers | show |
[Changing subject to reflect reality] I don't really understand what it is all about, as I initially said. But I've been told on freebsd IRC channels to post the issue to freebsd-emulation list, which I'm Cc'ing now, and if noone there answers, also to John Baldwin <jhb@FreeBSD>. To bring some context back, here are a few pointers: http://bugs.debian.org/737142 -- talking about pc-bsd, but it appears that the prob affects other BSD kernels too http://thread.gmane.org/gmane.comp.emulators.qemu/254074 -- this thread http://lists.gnu.org/archive/html/qemu-stable/2013-03/msg00037.html - a weird issue with freebsd reported last december If it's a bug in *BSD kernels, maybe someone there will be glad to fix it. And maybe together we can come out with a more elegant solution to this issue, or maybe to confirm (or deny) that the proposed patch is a right thing to do. Thanks, /mjt 06.02.2014 08:04, Kevin O'Connor wrote: > On Wed, Feb 05, 2014 at 12:44:06PM -0500, Kevin O'Connor wrote: >> On Tue, Feb 04, 2014 at 04:33:19PM +0400, Michael Tokarev wrote: >>> We have a bugreport in debian, http://bugs.debian.org/737142, >>> stating that PC-BSD does not work with seabios-1.7.4 anymore. >>> >>> I digged in, and found out that it fails only with -vga std >>> (cirrus works fine). So I bisected the issue - only changing >>> vgabios-stdvga.bin, and found this: > [...] >> This seems to be similar to the freebsd problem reported last year - >> see: >> http://lists.gnu.org/archive/html/qemu-stable/2013-03/msg00037.html > [...] >> (*) The best I can think of is to try and construct some hand crafted >> assembler that can catch buggy x86emu emulators and force a failure.. > > I have put together some assember to try and run-time test for known > broken versions of x86emu. This patch to SeaVGABIOS does seem to > catch the freebsd issue and in my tests it convinces freebsd to take a > different approach. The patch is a bit ugly though. > > Comments welcome. > -Kevin > > > commit e3caa553e940efb6184b30a5637134c4aa9f8b65 > Author: Kevin O'Connor <kevin@koconnor.net> > Date: Wed Feb 5 22:47:29 2014 -0500 > > vgabios: Attempt to detect old x86emu and force a fault. > > Check for cases where the leal instruction does not work. This > instruction is known to not be emulated properly on old versions of > x86emu. If a broken version of x86emu is found, force a fault that > x86emu will easily detect. This should help prevent soft failures > when running old software. > > Signed-off-by: Kevin O'Connor <kevin@koconnor.net> > > diff --git a/vgasrc/vgaentry.S b/vgasrc/vgaentry.S > index 9854448..e246e7c 100644 > --- a/vgasrc/vgaentry.S > +++ b/vgasrc/vgaentry.S > @@ -45,9 +45,27 @@ _rom_header_signature: > * Entry points > ****************************************************************/ > > - // This macro is the same as ENTRY_ARG except the "calll" > - // instruction is avoided to work around known issues in the > - // emulation of some versions of x86emu. > + // Force a fault if found to be running on broken x86emu versions. > + DECLFUNC x86emu_fault > +x86emu_fault: > + int $0x03 > +1: hlt > + jmp 1b > + > + // This macro implements a call while avoiding instructions > + // that old versions of x86emu have problems with. > + .macro VGA_CALLL cfunc > + // Make sure leal instruction works. > + movl $0x8000, %ecx > + leal (%ecx, %ecx, 1), %ecx > + cmpl $0x10000, %ecx > + jne x86emu_fault > + // Use callw instead of calll > + push %ax > + callw \cfunc > + .endm > + > + // This macro is the same as ENTRY_ARG except VGA_CALLL is used. > .macro ENTRY_ARG_VGA cfunc > cli > cld > @@ -57,7 +75,7 @@ _rom_header_signature: > movl %esp, %ebx // Backup %esp, then zero high bits > movzwl %sp, %esp > movl %esp, %eax // First arg is pointer to struct bregs > - pushw %ax ; callw \cfunc > + VGA_CALLL \cfunc > movl %ebx, %esp // Restore %esp (including high bits) > POPBREGS > .endm > @@ -103,7 +121,7 @@ entry_10_extrastack: > movw %ds, %dx // Setup %ss/%esp and call function > movw %dx, %ss > movl %eax, %esp > - pushw %ax ; callw handle_10 > + VGA_CALLL handle_10 > > movl %esp, %eax // Restore registers and return > movw BREGS_size+4(%eax), %ss >
On Wed, Feb 05, 2014 at 11:04:42PM -0500, Kevin O'Connor wrote: > On Wed, Feb 05, 2014 at 12:44:06PM -0500, Kevin O'Connor wrote: > > On Tue, Feb 04, 2014 at 04:33:19PM +0400, Michael Tokarev wrote: > > > We have a bugreport in debian, http://bugs.debian.org/737142, > > > stating that PC-BSD does not work with seabios-1.7.4 anymore. > > > > > > I digged in, and found out that it fails only with -vga std > > > (cirrus works fine). So I bisected the issue - only changing > > > vgabios-stdvga.bin, and found this: > [...] > > This seems to be similar to the freebsd problem reported last year - > > see: > > http://lists.gnu.org/archive/html/qemu-stable/2013-03/msg00037.html > [...] > > (*) The best I can think of is to try and construct some hand crafted > > assembler that can catch buggy x86emu emulators and force a failure.. > > I have put together some assember to try and run-time test for known > broken versions of x86emu. This patch to SeaVGABIOS does seem to > catch the freebsd issue and in my tests it convinces freebsd to take a > different approach. The patch is a bit ugly though. There hasn't been much comment, but I have pushed this patch to the main seabios repo for now. -Kevin
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On 2/6/14, 4:44 AM, Michael Tokarev wrote: > [Changing subject to reflect reality] > > I don't really understand what it is all about, as I initially > said. But I've been told on freebsd IRC channels to post the issue > to freebsd-emulation list, which I'm Cc'ing now, and if noone > there answers, also to John Baldwin <jhb@FreeBSD>. > > To bring some context back, here are a few pointers: > > http://bugs.debian.org/737142 -- talking about pc-bsd, but it > appears that the prob affects other BSD kernels too > http://thread.gmane.org/gmane.comp.emulators.qemu/254074 -- this > thread > http://lists.gnu.org/archive/html/qemu-stable/2013-03/msg00037.html > - a weird issue with freebsd reported last december > > If it's a bug in *BSD kernels, maybe someone there will be glad to > fix it. And maybe together we can come out with a more elegant > solution to this issue, or maybe to confirm (or deny) that the > proposed patch is a right thing to do. Yes it does look like a bug in FreeBSD kernel. Is there a PR already or should I create one and assign to myself? I will try to fix this when I have some free cycles. I assume this also happens when running FreeBSD under qemu on FreeBSD, right? Cheers, > Thanks, > > /mjt > > 06.02.2014 08:04, Kevin O'Connor wrote: >> On Wed, Feb 05, 2014 at 12:44:06PM -0500, Kevin O'Connor wrote: >>> On Tue, Feb 04, 2014 at 04:33:19PM +0400, Michael Tokarev >>> wrote: >>>> We have a bugreport in debian, >>>> http://bugs.debian.org/737142, stating that PC-BSD does not >>>> work with seabios-1.7.4 anymore. >>>> >>>> I digged in, and found out that it fails only with -vga std >>>> (cirrus works fine). So I bisected the issue - only >>>> changing vgabios-stdvga.bin, and found this: >> [...] >>> This seems to be similar to the freebsd problem reported last >>> year - see: >>> http://lists.gnu.org/archive/html/qemu-stable/2013-03/msg00037.html >> >>> [...] >>> (*) The best I can think of is to try and construct some hand >>> crafted assembler that can catch buggy x86emu emulators and >>> force a failure.. >> >> I have put together some assember to try and run-time test for >> known broken versions of x86emu. This patch to SeaVGABIOS does >> seem to catch the freebsd issue and in my tests it convinces >> freebsd to take a different approach. The patch is a bit ugly >> though. >> >> Comments welcome. -Kevin >> >> >> commit e3caa553e940efb6184b30a5637134c4aa9f8b65 Author: Kevin >> O'Connor <kevin@koconnor.net> Date: Wed Feb 5 22:47:29 2014 >> -0500 >> >> vgabios: Attempt to detect old x86emu and force a fault. >> >> Check for cases where the leal instruction does not work. This >> instruction is known to not be emulated properly on old versions >> of x86emu. If a broken version of x86emu is found, force a fault >> that x86emu will easily detect. This should help prevent soft >> failures when running old software. >> >> Signed-off-by: Kevin O'Connor <kevin@koconnor.net> >> >> diff --git a/vgasrc/vgaentry.S b/vgasrc/vgaentry.S index >> 9854448..e246e7c 100644 --- a/vgasrc/vgaentry.S +++ >> b/vgasrc/vgaentry.S @@ -45,9 +45,27 @@ _rom_header_signature: * >> Entry points >> ****************************************************************/ >> >> - // This macro is the same as ENTRY_ARG except the >> "calll" - // instruction is avoided to work around known >> issues in the - // emulation of some versions of x86emu. + >> // Force a fault if found to be running on broken x86emu >> versions. + DECLFUNC x86emu_fault +x86emu_fault: + >> int $0x03 +1: hlt + jmp 1b + + // This macro >> implements a call while avoiding instructions + // that >> old versions of x86emu have problems with. + .macro >> VGA_CALLL cfunc + // Make sure leal instruction works. + >> movl $0x8000, %ecx + leal (%ecx, %ecx, 1), %ecx + >> cmpl $0x10000, %ecx + jne x86emu_fault + // Use >> callw instead of calll + push %ax + callw \cfunc + >> .endm + + // This macro is the same as ENTRY_ARG except >> VGA_CALLL is used. .macro ENTRY_ARG_VGA cfunc cli cld @@ -57,7 >> +75,7 @@ _rom_header_signature: movl %esp, %ebx // Backup >> %esp, then zero high bits movzwl %sp, %esp movl %esp, %eax >> // First arg is pointer to struct bregs - pushw %ax ; >> callw \cfunc + VGA_CALLL \cfunc movl %ebx, %esp // >> Restore %esp (including high bits) POPBREGS .endm @@ -103,7 >> +121,7 @@ entry_10_extrastack: movw %ds, %dx // Setup >> %ss/%esp and call function movw %dx, %ss movl %eax, %esp - >> pushw %ax ; callw handle_10 + VGA_CALLL handle_10 >> >> movl %esp, %eax // Restore registers and return movw >> BREGS_size+4(%eax), %ss >> > > _______________________________________________ > freebsd-emulation@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-emulation To > unsubscribe, send any mail to > "freebsd-emulation-unsubscribe@freebsd.org" > -----BEGIN PGP SIGNATURE----- iQIcBAEBCgAGBQJS+qWRAAoJEJW2GBstM+nsz3sP/AsGiEPWzHAbQP5nYR9alDiL dmMd8RB4yVYLmJJXCxLldMjNw3kuHRcZ8IrvCaxsFvUHnzdQudmqCc6uxgcWdC3Y gqSYP2/dnG5OXsUqmRHW0yKpfrBlbOA/utRDZz9MzTx4m7sudY8y8ZEUmb2OyJOZ CjQrW5OyHIXUxzdKMlcpiAy5+edQVWk5TBdyz6h0WVrk4A9uuAjOw/DYse05lGVF l1d/Eto+Wui38fMTjfdVJqVcPrfy859aODf/vRkmznujd0Zumr/8OMXmEsF+Q+iv ktRNWab39DXIArMsYbCGr7Xg7Q0ZjZB0eAjB8zxW1a0p/7V4Spf9QQu9wNHVi4sf DOwiaU2K+2/zz/BYIyicyZN+glQMLcq+t3u8uagm6GOcHMx1ZsyFeyIhj8Gbtjfl VUPOVZfu25dogr5GY2U68tPHoiQStsSvdSg4+jaDYK5AZcs1BGZ5i5ncArjATV1Z KIe3ISOzu20BMhjAXHALnTNMFuBWD6+Va6ExVHWkWuz445aQ0REx3hJDqWbm7iVd DTD2N6Bs/uL7P3aVODgz8EqQ6EMhswFYgqSirMb9w38FCLnJ56aAA31kFU00U28p OG8kzgc3dY0II1vVfNLhrJ5kGNDOKxZ62KsXbLHPdBl3cgKweqghd53WTjU/dSo6 0NVfAqheJ3ifZ0I0yB3d =jTIz -----END PGP SIGNATURE-----
10.02.2014 19:41, Kevin O'Connor wrote: [] > There hasn't been much comment, but I have pushed this patch to the > main seabios repo for now. Xin Li (Cc'ed) replied to this email. Meanwhile I tried your patch, and it indeed fixes the reported issues with FreeBSD and PCBSD. Even if FreeBSD fixes this bug, we still have to support runnin old, unfixed, systems in qemu/kvm, so seabios-side change is needed anyway. Oh well. Thanks, /mjt
On Mon, Feb 17, 2014 at 09:35:30PM +0400, Michael Tokarev wrote: > 10.02.2014 19:41, Kevin O'Connor wrote: > [] > > There hasn't been much comment, but I have pushed this patch to the > > main seabios repo for now. > > Xin Li (Cc'ed) replied to this email. Yes. Thanks. It would be good for FreeBSD to also fix the underlying issue. > Meanwhile I tried your patch, and it indeed fixes the reported issues > with FreeBSD and PCBSD. > > Even if FreeBSD fixes this bug, we still have to support runnin old, > unfixed, systems in qemu/kvm, so seabios-side change is needed anyway. Yeah. That's why I went ahead and committed the SeaVGABIOS workaround. The workaround also makes early versions of X11 behave better (they fail outright now instead of hanging). -Kevin
diff --git a/vgasrc/vgaentry.S b/vgasrc/vgaentry.S index 9854448..e246e7c 100644 --- a/vgasrc/vgaentry.S +++ b/vgasrc/vgaentry.S @@ -45,9 +45,27 @@ _rom_header_signature: * Entry points ****************************************************************/ - // This macro is the same as ENTRY_ARG except the "calll" - // instruction is avoided to work around known issues in the - // emulation of some versions of x86emu. + // Force a fault if found to be running on broken x86emu versions. + DECLFUNC x86emu_fault +x86emu_fault: + int $0x03 +1: hlt + jmp 1b + + // This macro implements a call while avoiding instructions + // that old versions of x86emu have problems with. + .macro VGA_CALLL cfunc + // Make sure leal instruction works. + movl $0x8000, %ecx + leal (%ecx, %ecx, 1), %ecx + cmpl $0x10000, %ecx + jne x86emu_fault + // Use callw instead of calll + push %ax + callw \cfunc + .endm + + // This macro is the same as ENTRY_ARG except VGA_CALLL is used. .macro ENTRY_ARG_VGA cfunc cli cld @@ -57,7 +75,7 @@ _rom_header_signature: movl %esp, %ebx // Backup %esp, then zero high bits movzwl %sp, %esp movl %esp, %eax // First arg is pointer to struct bregs - pushw %ax ; callw \cfunc + VGA_CALLL \cfunc movl %ebx, %esp // Restore %esp (including high bits) POPBREGS .endm @@ -103,7 +121,7 @@ entry_10_extrastack: movw %ds, %dx // Setup %ss/%esp and call function movw %dx, %ss movl %eax, %esp - pushw %ax ; callw handle_10 + VGA_CALLL handle_10 movl %esp, %eax // Restore registers and return movw BREGS_size+4(%eax), %ss