Re: [RFC] Unable to use qemu-ppc to run 32-bit powerpc executables generated on gcc110 machine

[Thomas Huth]

On 12/08/2022 09.03, Pierre Muller wrote:
> Le 12/08/2022 à 06:16, Thomas Huth a écrit :
> > On 11/08/2022 23.38, Pierre Muller wrote:
> > >     I am using qemu to check code generated by Free Pascal compiler
> > > for various CPUs.
> > >
> > >     Recently, this allowed me to find out that Free Pascal was generating
> > > wrong instructions, leading to SIGBUS errors using qemu-mips.
> > >     The same binaries worked without troubles on mips test machines,
> > > probably because SIGBUS is handled directly inside the kernel.
> > >
> > >     Here I would like to report the problem I get when trying to run
> > > powerpc executables using shared libs generated on gcc110 machine.
> > >
> > >     I copied over the needed libraries into a sys-root directory.
> > >
> > >     The problem is that the code crashes with a Illegal Instruction
> > > after only a very few instructions:
> > >
> > > muller@gcc186:~/pas/check$ ~/sys-root/bin/qemu-ppc -cpu g2 -d in_asm -L
> > > ~/sys-root/powerpc-linux ./twide1
> > [...]
> > > 0x3ffc1d60:  f00004d7  xxlxor   v0, v0, v0
> > >
> > > qemu: uncaught target signal 4 (Illegal instruction) - core dumped
> > >
> > > The problem is the the 'xxlxor' instruction is a VSX extension instruction.
> > >
> > >    There is apparently no cpu in the powerpc cpu list that enabled this
> > > extension.
> > > The output of cat /proc/cpuinfo on gcc110 gives that:
> > > .....
> > > processor       : 63
> > > cpu             : POWER7 (architected), altivec supported
> > > clock           : 3550.000000MHz
> > > revision        : 2.1 (pvr 003f 0201)
> > >
> > > timebase        : 512000000
> > > platform        : pSeries
> > > model           : IBM,8231-E2B
> > > machine         : CHRP IBM,8231-E2B
> > >
> > >     Is there a way to enable cpu features separately for ppc like is done 
> > > for
> > > x86_64?
> > > Or would it be possible to define a new cpu inside qemu source that would 
> > > match
> > > the description above?
> >
> > So you are building on a POWER7 host and try to run the binaries on an
> > emulated G2? That sounds weird. Why don't you use
>
>    The g2 was just an example, I used a script to iterate
> over all possible cpus (as listed by --cpu help),
> but I always get a Illegal instruction on xllxor,
> because none of the cpu in the least seems to enable VSX
> extension.

Ok, I see, so the question is wether it is somehow possible to enable the 
vector extensions on a 32-bit CPU by default somehow...
CC:-ing Laurent, maybe he knows...

 Thomas