Subject: Re: [PATCH 0/6] PowerPc 8xx TLB/MMU fixes

From: Benjamin Herrenschmidt <[email-masked]>
Date: Tue, 06 Oct 2009 12:52:15 +1100

\
> So how does this look? Does it change anything?
> It should as the previous way was way off :(
> 
> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> index c33c6de..08a392f 100644
> --- a/arch/powerpc/mm/fault.c
> +++ b/arch/powerpc/mm/fault.c
> @@ -153,7 +153,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
>  #ifdef DEBUG_DCBX
>  		const char *istr = NULL;
> 
> -		insn = *((unsigned long *)regs->nip);
> +		__get_user(insn, (unsigned long __user *)regs->nip);

No, use get_user() not __get_user() or if you use the later, also use
access_ok(), and test the result in case it errors (if it does, you
probably want to just goto bad access and SEGV).

Cheers,
Ben.

>  		if (((insn >> (31-5)) & 0x3f) == 31) {
>  			if (((insn >> 1) & 0x3ff) == 1014) /* dcbz ? 0x3f6 */
>  				istr = "dcbz";
> @@ -178,11 +178,12 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
>  					       ra, rb, dar);
>  					is_write = 0;
>  				}
> -
> +#if 0
>  				if (trap == 0x300 && address != dar) {
>  					__asm__ ("mtdar %0" : : "r" (dar));
>  					return 0;
>  				}
> +#endif
>  			}
>  		}
>  #endif
> @@ -191,7 +192,7 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
> 
>  			/* This is from a dcbX or icbi insn gone bad, these
>  			 * insn do not set DAR so we have to do it here instead */
> -			insn = *((unsigned long *)regs->nip);
> +			__get_user(insn, (unsigned long __user *)regs->nip);
> 
>  			ra = (insn >> (31-15)) & 0x1f; /* Reg RA */
>  			rb = (insn >> (31-20)) & 0x1f; /* Reg RB */
> 
>