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Re: [Gcl-devel] Re: BFD relocations
On Tue, Jun 04, 2002 at 06:06:18PM -0400, Camm Maguire wrote:
> Greetings!
>
> Daniel Jacobowitz <drow@mvista.com> writes:
>
> > On Tue, Jun 04, 2002 at 05:33:57PM -0400, Camm Maguire wrote:
> > > Greetings. and thank you again for your reply!
> > >
> > > In brief, I can relocate, but I get SIGILL on apparently correctly
> > > relocated code when trying to execute.
> > >
> > > I would be very appreciative if you might save me the pain of
> > > searching through the kernel sources and brief me on what raises
> > > SIGILL on ppc. I'm already aware of divide by zero, and of course an
> > > unknown opcode, but neither seems to be the case here. Alignment?
> >
> > Cache. Are you explicitly flushing the data and instruction caches
> > over the entire loaded range? If not, you absolutely should try that.
> >
>
> Thanks for this suggestion! I'm afraid I'm a neophyte wrt cache
> flushing. Is there a specific assembly instruction I should add, or
> do I flush via a read through the .text and .(s)data sections, or a
> copy to some distant memory?
You need to do a dcbst (and an icbi for safety) on every cache line.
That's every 32 bytes on a mainstream PPC processor (16 on the 8xx's
and 64 on the POWER4s). Like:
asm ("dcbst 0,%0\n\tsync\n\ticbi 0,%0\n\tsync\n\tisync"
: : "r" (ptr) : "memory");
That's more paranoid than you need to be, I think, but should work.
>
> Thanks again!
>
> > > Detail:
> > >
> > > gcl builds fine on ppc with bfd relocations, including gcl-tk. When
> > > building maxima-5.6 with it, which involves loading several object
> > > files, I've gotten SIGILL in the following two places when executing
> > > code from kclmac.o:
> > >
> > > objdump -d kclmac.o |head -40l
> > >
> > > kclmac.o: file format elf32-powerpc
> > >
> > > Disassembly of section .text:
> > >
> > > 00000000 <init_kclmac>:
> > > -> 0: 94 21 ff f0 stwu r1,-16(r1)
> > > 4: 7c 08 02 a6 mflr r0
> > > 8: 90 01 00 14 stw r0,20(r1)
> > > c: 3c 60 00 00 lis r3,0
> > > 10: 38 63 00 00 addi r3,r3,0
> > > 14: 4c c6 31 82 crclr 4*cr1+eq
> > > 18: 48 00 00 01 bl 18 <init_kclmac+0x18>
> > > 1c: 80 01 00 14 lwz r0,20(r1)
> > > -> 20: 7c 08 03 a6 mtlr r0
> > > 24: 38 21 00 10 addi r1,r1,16
> > > 28: 4e 80 00 20 blr
> > >
> > > 0000002c <L1>:
> > > 2c: 94 21 ff e0 stwu r1,-32(r1)
> > > 30: 7c 08 02 a6 mflr r0
> >
> > Those two spots are both apparently undistinguished, and 32 bytes
> > apart. Coincidence? I think not.
> >
> >
> > --
> > Daniel Jacobowitz Carnegie Mellon University
> > MontaVista Software Debian GNU/Linux Developer
> >
> >
>
> --
> Camm Maguire camm@enhanced.com
> ==========================================================================
> "The earth is but one country, and mankind its citizens." -- Baha'u'llah
>
--
Daniel Jacobowitz Carnegie Mellon University
MontaVista Software Debian GNU/Linux Developer