From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e32.co.us.ibm.com", Issuer "Equifax" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 4F2D9B70BA for ; Thu, 3 Mar 2011 02:44:32 +1100 (EST) Received: from d03relay03.boulder.ibm.com (d03relay03.boulder.ibm.com [9.17.195.228]) by e32.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p22FXm8g008293 for ; Wed, 2 Mar 2011 08:33:48 -0700 Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d03relay03.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p22FiGRK109536 for ; Wed, 2 Mar 2011 08:44:18 -0700 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p22FiFY0017321 for ; Wed, 2 Mar 2011 08:44:16 -0700 Subject: Re: [PATCH] powerpc/ptrace: remove BUG_ON when full register set not available From: Michael Wolf To: Benjamin Herrenschmidt In-Reply-To: <1299035316.8833.806.camel@pasglop> References: <1299011204.28753.8.camel@w500> <1299035316.8833.806.camel@pasglop> Content-Type: text/plain; charset="UTF-8" Date: Wed, 02 Mar 2011 09:44:09 -0600 Message-ID: <1299080649.3087.6.camel@w500> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, mikey@neuling.org, anton@samba.org Reply-To: mjw@us.ibm.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2011-03-02 at 14:08 +1100, Benjamin Herrenschmidt wrote: > > --- ptracev2.orig/include/linux/regset.h 2011-02-20 12:15:57.000000000 -0600 > > +++ ptracev2/include/linux/regset.h 2011-02-28 13:33:36.685302349 -0600 > > @@ -240,6 +240,34 @@ static inline int user_regset_copyout(un > > } > > return 0; > > } > > +/* want the count to be the registers 14-31 inclusive */ > > +#define POISON_REG_CNT (PT_R31-PT_R14+1) > > +static inline int user_regset_copyout_poison(unsigned int *pos, > > + unsigned int *count, > > + void **kbuf, void __user **ubuf, > > + const int start_pos, > > + const int end_pos) > > +{ > > I wouldn't put that in a generic location... especially something > like POISON_REG_CNT is very specific to powerpc and our ABI. Yeah I put it there thinking about readability but only use it in the one place. If we go forward with this current strategy I will remove the #define and just comment more. > > .../... > > > static inline int user_regset_copyin(unsigned int *pos, unsigned int *count, > > const void **kbuf, > > --- ptracev2.orig/arch/powerpc/kernel/ptrace.c 2011-02-20 12:15:57.000000000 -0600 > > +++ ptracev2/arch/powerpc/kernel/ptrace.c 2011-03-01 13:49:12.686354353 -0600 > > @@ -234,11 +234,29 @@ static int gpr_get(struct task_struct *t > > if (target->thread.regs == NULL) > > return -EIO; > > > > - CHECK_FULL_REGS(target->thread.regs); > > Wouldn't it be a simpler/cleaner approach to use a single function call > here that checks if the reg set is full and if not, put poison values > in the thread.regs structure itself ? > > The resulting code would be more palatable... That was actually the way I had done the first patch while debugging the problem but Paul Mackerras didn't like that I changed the thread struct. It is not clear to me which is better. Reporting a poison value that isn't actually there or to change the data. Hopefully a consensus can be reached and then I can submit a new patch based on that. > > Cheers, > Ben. > > > - ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, > > - target->thread.regs, > > - 0, offsetof(struct pt_regs, msr)); > > + if (!FULL_REGS(target->thread.regs)) { > > + /* Don't have the full register set. Copy out register r0-r13 */ > > + ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, > > + target->thread.regs, > > + 0, sizeof(long)*PT_R14); > > + > > + /* Dont want to change the actual register values so rather than read the */ > > + /* actual register copy a poison value into the buffer instead */ > > + if (!ret) > > + ret = user_regset_copyout_poison(&pos, &count, &kbuf, &ubuf, > > + sizeof(long)*PT_R14, offsetof(struct pt_regs, nip)); > > + > > + /* Copy out the rest of the registers as usual */ > > + if (!ret) > > + ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, > > + target->thread.regs, > > + offsetof(struct pt_regs, nip), offsetof(struct pt_regs, msr)); > > + > > + } else > > + ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, > > + target->thread.regs, > > + 0, offsetof(struct pt_regs, msr)); > > if (!ret) { > > unsigned long msr = get_user_msr(target); > > ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &msr, > > @@ -645,11 +663,29 @@ static int gpr32_get(struct task_struct > > if (target->thread.regs == NULL) > > return -EIO; > > > > - CHECK_FULL_REGS(target->thread.regs); > > - > > pos /= sizeof(reg); > > count /= sizeof(reg); > > > > + if(!FULL_REGS(target->thread.regs)) { > > + if (kbuf) { > > + /* Don't have the full register set. Copy out register r0-r13 */ > > + for (; count > 0 && pos < PT_R14; --count) > > + *k++ = regs[pos++]; > > + > > + /* Dont want to change the actual register values so rather than read the */ > > + /* actual register copy a poison value into the buffer instead */ > > + for (; count > 0 && pos <= PT_R31; --count,pos++) > > + *k++ = 0xdeadbeef; > > + > > + } else { > > + for (; count > 0 && pos < PT_R14; --count) > > + if (__put_user((compat_ulong_t) regs[pos++], u++)) > > + return -EFAULT; > > + for (; count > 0 && pos <= PT_R31; --count,pos++) > > + if (__put_user((compat_ulong_t) 0xdeadbeef, u++)) > > + return -EFAULT; > > + } > > + } > > if (kbuf) > > for (; count > 0 && pos < PT_MSR; --count) > > *k++ = regs[pos++]; > > > > > > _______________________________________________ > > Linuxppc-dev mailing list > > Linuxppc-dev@lists.ozlabs.org > > https://lists.ozlabs.org/listinfo/linuxppc-dev > >