On Oct 18, 2013, at 2:38 AM, Wolfgang Denk wrote:
> Default Debian PowerPC doesn't work on e500 because the code contains
> "lwsync" instructions, which are unsupported on this core. As a
> result, applications using this will crash with an "unhandled signal 4"
> "Illegal instruction" error.
>
> As a work around we add code to emulate this insn. This is expensive
> performance-wise, but allows to run standard user land code.
>
> Signed-off-by: Wolfgang Denk <w...@denx.de>
> Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
> Cc: Scott Wood <scottw...@freescale.com>
> ---
> I am aware that the clean solution to the problem is to build user
> space with compiler options that match the target architecture.
> However, sometimes this is just too much effort.
>
> Also, of course the performance of such an emulation sucks. But the
> the occurrence of such instructions is so rare that no significant
> slowdown can be oserved.
>
> I'm not sure if this should / could go into mainline. I'm posting it
> primarily so it can be found should anybody else need this.
> - wd
>
> arch/powerpc/kernel/traps.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index f783c93..f330374 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -986,6 +986,13 @@ static int emulate_instruction(struct pt_regs *regs)
> return 0;
> }
>
> + /* Emulating the lwsync insn as a sync insn */
> + if (instword == PPC_INST_LWSYNC) {
> + PPC_WARN_EMULATED(lwsync, regs);
> + asm volatile("sync" : : : "memory");
Do we really need the inline asm? Doesn't the fact of just taking an exception
and returning from it equate to a sync.
> + return 0;
> + }
> +
> /* Emulate the mcrxr insn. */
> if ((instword & PPC_INST_MCRXR_MASK) == PPC_INST_MCRXR) {
> int shift = (instword >> 21) & 0x1c;
> --
> 1.8.3.1
>
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