Subject: Re: [PATCH 1/3] powerpc: Enable emulate_step In Little Endian Mode

From: Benjamin Herrenschmidt <[email-masked]>
Date: Wed, 30 Oct 2013 11:13:43 +1100

On Fri, 2013-10-18 at 14:40 -0500, Tom Musta wrote:
> This patch modifies the endian chicken switch in the single step
> emulation code (emulate_step()).  The old (big endian) code bailed
> early if a load or store instruction was to be emulated in little
> endian mode.
> 
> The new code modifies the check and only bails in a cross-endian
> situation (LE mode in a kernel compiled for BE and vice verse).

I get a malformed patch error, looks like it got wrapped.

Cheers,
Ben.

> Signed-off-by: Tom Musta <[email-masked]>
> ---
>  arch/powerpc/lib/sstep.c |   12 +++++++++---
>  1 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index b1faa15..5e0d0e9 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -1222,12 +1222,18 @@ int __kprobes emulate_step(struct pt_regs *regs,
> unsigned int instr)
>  	}
>  
>  	/*
> -	 * Following cases are for loads and stores, so bail out
> -	 * if we're in little-endian mode.
> +	 * Following cases are for loads and stores and this
> +	 * implementation does not support cross-endian.  So
> +	 * bail out if this is the case.
>  	 */
> +#ifdef __BIG_ENDIAN__
>  	if (regs->msr & MSR_LE)
>  		return 0;
> -
> +#endif
> +#ifdef __LITTLE_ENDIAN__
> +	if (!regs->msr & MSR_LE)
> +		return 0;
> +#endif
>  	/*
>  	 * Save register RA in case it's an update form load or store
>  	 * and the access faults.