Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757123Ab0HCU7p (ORCPT ); Tue, 3 Aug 2010 16:59:45 -0400 Received: from mail3.caviumnetworks.com ([12.108.191.235]:4443 "EHLO mail3.caviumnetworks.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756404Ab0HCU7o (ORCPT ); Tue, 3 Aug 2010 16:59:44 -0400 Message-ID: <4C58833F.1080409@caviumnetworks.com> Date: Tue, 03 Aug 2010 13:59:43 -0700 From: David Daney User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-2.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: "Maciej W. Rozycki" CC: linux-mips@linux-mips.org, ralf@linux-mips.org, ananth@in.ibm.com, anil.s.keshavamurthy@intel.com, davem@davemloft.net, masami.hiramatsu.pt@hitachi.com, linux-kernel@vger.kernel.org, hschauhan@nulltrace.org Subject: Re: [PATCH 2/5] MIPS: Add instrunction format for BREAK and SYSCALL References: <1280859742-26364-1-git-send-email-ddaney@caviumnetworks.com> <1280859742-26364-3-git-send-email-ddaney@caviumnetworks.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 03 Aug 2010 20:59:43.0827 (UTC) FILETIME=[CC4D3A30:01CB334E] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1607 Lines: 54 On 08/03/2010 01:54 PM, Maciej W. Rozycki wrote: > On Tue, 3 Aug 2010, David Daney wrote: > >> diff --git a/arch/mips/include/asm/inst.h b/arch/mips/include/asm/inst.h >> index 6489f00..444ff71 100644 >> --- a/arch/mips/include/asm/inst.h >> +++ b/arch/mips/include/asm/inst.h >> @@ -247,6 +247,12 @@ struct ma_format { /* FPU multipy and add format (MIPS IV) */ >> unsigned int fmt : 2; >> }; >> >> +struct b_format { /* BREAK and SYSCALL */ >> + unsigned int opcode:6; >> + unsigned int code:20; >> + unsigned int func:6; >> +}; >> + >> #elif defined(__MIPSEL__) >> >> struct j_format { /* Jump format */ > > Please note the code field of the BREAK instruction is by toolchain > convention (bug-compatibility with the original MIPS assembler or > suchlike) treated as a pair of swapped 10-bit fields -- you may want to > double-check consistency of interpretation with usage elsewhere. > Indeed, I am familiar with that fact. From patch 3/5 we have: . . . +void __kprobes jprobe_return(void) +{ + /* Assembler quirk necessitates this '0,code' business. */ + asm volatile( + "break 0,%0\n\t" + ".globl jprobe_return_end\n" + "jprobe_return_end:\n" + : : "n" (BRK_KPROBE_BP) : "memory"); +} . . . The 'break 0,code' construct causes gas to emit values that are compatible with the other use of struct b_format in the patch set. David Daney -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/