From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3wp9Gx5GKnzDqL0 for ; Thu, 15 Jun 2017 14:18:33 +1000 (AEST) Date: Wed, 14 Jun 2017 23:18:05 -0500 From: Segher Boessenkool To: Anton Blanchard Cc: benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, ravi.bangoria@linux.vnet.ibm.com, npiggin@gmail.com, naveen.n.rao@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH 1/2] powerpc: Fix emulation of mcrf in emulate_step() Message-ID: <20170615041805.GB16550@gate.crashing.org> References: <20170614234639.11997-1-anton@ozlabs.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170614234639.11997-1-anton@ozlabs.org> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Anton, On Thu, Jun 15, 2017 at 09:46:38AM +1000, Anton Blanchard wrote: > The mcrf emulation code was looking at the CR fields in the reverse > order. It also relied on reserved fields being zero which is somewhat > fragile, so fix that too. It masked out the reserved bits. I find the new code to be less readable (but also more correct ;-) ). Maybe there should be (inline) helper function to insert/extract CR fields? Segher > --- a/arch/powerpc/lib/sstep.c > +++ b/arch/powerpc/lib/sstep.c > @@ -683,8 +683,10 @@ int analyse_instr(struct instruction_op *op, struct pt_regs *regs, > case 19: > switch ((instr >> 1) & 0x3ff) { > case 0: /* mcrf */ > - rd = (instr >> 21) & 0x1c; > - ra = (instr >> 16) & 0x1c; > + rd = 7 - ((instr >> 23) & 0x7); > + ra = 7 - ((instr >> 18) & 0x7); > + rd *= 4; > + ra *= 4; > val = (regs->ccr >> ra) & 0xf; > regs->ccr = (regs->ccr & ~(0xfUL << rd)) | (val << rd); > goto instr_done;