From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753994AbaIPXYu (ORCPT ); Tue, 16 Sep 2014 19:24:50 -0400 Received: from mail-oa0-f51.google.com ([209.85.219.51]:53954 "EHLO mail-oa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752512AbaIPXYt (ORCPT ); Tue, 16 Sep 2014 19:24:49 -0400 Message-ID: <5418C6BF.9090208@mvista.com> Date: Tue, 16 Sep 2014 18:24:47 -0500 From: Corey Minyard User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0 MIME-Version: 1.0 To: minyard@acm.org, Ralf Baechle , linux-mips@linux-mips.org CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH] mips: Save all registers when saving the frame References: <1410903925-10744-1-git-send-email-minyard@acm.org> In-Reply-To: <1410903925-10744-1-git-send-email-minyard@acm.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Well, there's a bug I noticed in this patch, $1 is restored from the wrong location. I'm not sure $1 ($at) needs to be restored at all, really. I guess make this a RFC. -corey On 09/16/2014 04:45 PM, minyard@acm.org wrote: > From: Corey Minyard > > The MIPS frame save code was just saving a few registers, enough to > do a backtrace if every function set up a frame. However, this is > not working if you are using DWARF unwinding, because most of the > registers are wrong. This was causing kdump backtraces to be short > or bogus. > > So save all the registers. > > Signed-off-by: Corey Minyard > --- > arch/mips/include/asm/stacktrace.h | 64 +++++++++++++++++++++++++++++--------- > 1 file changed, 50 insertions(+), 14 deletions(-) > > diff --git a/arch/mips/include/asm/stacktrace.h b/arch/mips/include/asm/stacktrace.h > index 780ee2c..05a2195 100644 > --- a/arch/mips/include/asm/stacktrace.h > +++ b/arch/mips/include/asm/stacktrace.h > @@ -2,6 +2,8 @@ > #define _ASM_STACKTRACE_H > > #include > +#include > +#include > > #ifdef CONFIG_KALLSYMS > extern int raw_show_trace; > @@ -20,6 +22,14 @@ static inline unsigned long unwind_stack(struct task_struct *task, > } > #endif > > +#define STR_PTR_LA __stringify(PTR_LA) > +#define STR_LONG_S __stringify(LONG_S) > +#define STR_LONG_L __stringify(LONG_L) > +#define STR_LONGSIZE __stringify(LONGSIZE) > + > +#define STORE_ONE_REG(r) \ > + STR_LONG_S " $" __stringify(r)",("STR_LONGSIZE"*"__stringify(r)")(%1)\n\t" > + > static __always_inline void prepare_frametrace(struct pt_regs *regs) > { > #ifndef CONFIG_KALLSYMS > @@ -32,21 +42,47 @@ static __always_inline void prepare_frametrace(struct pt_regs *regs) > __asm__ __volatile__( > ".set push\n\t" > ".set noat\n\t" > -#ifdef CONFIG_64BIT > - "1: dla $1, 1b\n\t" > - "sd $1, %0\n\t" > - "sd $29, %1\n\t" > - "sd $31, %2\n\t" > -#else > - "1: la $1, 1b\n\t" > - "sw $1, %0\n\t" > - "sw $29, %1\n\t" > - "sw $31, %2\n\t" > -#endif > + /* Store $1 so we can use it */ > + STR_LONG_S " $1,"STR_LONGSIZE"(%1)\n\t" > + /* Store the PC */ > + "1: " STR_PTR_LA " $1, 1b\n\t" > + STR_LONG_S " $1,%0\n\t" > + STORE_ONE_REG(2) > + STORE_ONE_REG(3) > + STORE_ONE_REG(4) > + STORE_ONE_REG(5) > + STORE_ONE_REG(6) > + STORE_ONE_REG(7) > + STORE_ONE_REG(8) > + STORE_ONE_REG(9) > + STORE_ONE_REG(10) > + STORE_ONE_REG(11) > + STORE_ONE_REG(12) > + STORE_ONE_REG(13) > + STORE_ONE_REG(14) > + STORE_ONE_REG(15) > + STORE_ONE_REG(16) > + STORE_ONE_REG(17) > + STORE_ONE_REG(18) > + STORE_ONE_REG(19) > + STORE_ONE_REG(20) > + STORE_ONE_REG(21) > + STORE_ONE_REG(22) > + STORE_ONE_REG(23) > + STORE_ONE_REG(24) > + STORE_ONE_REG(25) > + STORE_ONE_REG(26) > + STORE_ONE_REG(27) > + STORE_ONE_REG(28) > + STORE_ONE_REG(29) > + STORE_ONE_REG(30) > + STORE_ONE_REG(31) > + /* Restore $1 */ > + STR_LONG_L " $1,(%1)\n\t" > ".set pop\n\t" > - : "=m" (regs->cp0_epc), > - "=m" (regs->regs[29]), "=m" (regs->regs[31]) > - : : "memory"); > + : "=m" (regs->cp0_epc) > + : "r" (regs->regs) > + : "memory"); > } > > #endif /* _ASM_STACKTRACE_H */