From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3tgG635lmhzDwBy for ; Sat, 17 Dec 2016 03:31:23 +1100 (AEDT) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uBGGNl6V095387 for ; Fri, 16 Dec 2016 11:31:20 -0500 Received: from e32.co.us.ibm.com (e32.co.us.ibm.com [32.97.110.150]) by mx0a-001b2d01.pphosted.com with ESMTP id 27cknt0mw1-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Fri, 16 Dec 2016 11:31:20 -0500 Received: from localhost by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 16 Dec 2016 09:31:18 -0700 Subject: Re: [PATCH V2 2/4] powerpc: add helper to check if offset is within rel branch range To: Masami Hiramatsu References: <1481732310-7779-1-git-send-email-anju@linux.vnet.ibm.com> <1481732310-7779-5-git-send-email-anju@linux.vnet.ibm.com> <20161216205221.b6368901a9eea6a8cb7a84ff@kernel.org> Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, ananth@in.ibm.com, naveen.n.rao@linux.vnet.ibm.com, paulus@samba.org, srikar@linux.vnet.ibm.com, benh@kernel.crashing.org, mpe@ellerman.id.au, mahesh@linux.vnet.ibm.com From: Anju T Sudhakar Date: Fri, 16 Dec 2016 22:01:03 +0530 MIME-Version: 1.0 In-Reply-To: <20161216205221.b6368901a9eea6a8cb7a84ff@kernel.org> Content-Type: text/plain; charset=windows-1252; format=flowed Message-Id: List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Masami, Thank you for reviewing the patch set. On Friday 16 December 2016 05:22 PM, Masami Hiramatsu wrote: > On Wed, 14 Dec 2016 21:48:30 +0530 > Anju T Sudhakar wrote: > >> From: "Naveen N. Rao" >> > The coding is OK to me. Please add a description for this patch > here, e.g. what is done by this patch, what kind of branch > instruction will be covered, and why thse checks are needed etc. Sure. I will give a description for this patch. Thanks and Regards, -Anju > > Thank you, > >> Signed-off-by: Naveen N. Rao >> Signed-off-by: Anju T Sudhakar >> --- >> arch/powerpc/include/asm/code-patching.h | 1 + >> arch/powerpc/lib/code-patching.c | 24 +++++++++++++++++++++++- >> 2 files changed, 24 insertions(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h >> index 2015b07..75ee4f4 100644 >> --- a/arch/powerpc/include/asm/code-patching.h >> +++ b/arch/powerpc/include/asm/code-patching.h >> @@ -22,6 +22,7 @@ >> #define BRANCH_SET_LINK 0x1 >> #define BRANCH_ABSOLUTE 0x2 >> >> +bool is_offset_in_branch_range(long offset); >> unsigned int create_branch(const unsigned int *addr, >> unsigned long target, int flags); >> unsigned int create_cond_branch(const unsigned int *addr, >> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c >> index d5edbeb..f643451 100644 >> --- a/arch/powerpc/lib/code-patching.c >> +++ b/arch/powerpc/lib/code-patching.c >> @@ -32,6 +32,28 @@ int patch_branch(unsigned int *addr, unsigned long target, int flags) >> return patch_instruction(addr, create_branch(addr, target, flags)); >> } >> >> +bool is_offset_in_branch_range(long offset) >> +{ >> + /* >> + * Powerpc branch instruction is : >> + * >> + * 0 6 30 31 >> + * +---------+----------------+---+---+ >> + * | opcode | LI |AA |LK | >> + * +---------+----------------+---+---+ >> + * Where AA = 0 and LK = 0 >> + * >> + * LI is a signed 24 bits integer. The real branch offset is computed >> + * by: imm32 = SignExtend(LI:'0b00', 32); >> + * >> + * So the maximum forward branch should be: >> + * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc >> + * The maximum backward branch should be: >> + * (0xff800000 << 2) = 0xfe000000 = -0x2000000 >> + */ >> + return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3)); >> +} >> + >> unsigned int create_branch(const unsigned int *addr, >> unsigned long target, int flags) >> { >> @@ -43,7 +65,7 @@ unsigned int create_branch(const unsigned int *addr, >> offset = offset - (unsigned long)addr; >> >> /* Check we can represent the target in the instruction format */ >> - if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3) >> + if (!is_offset_in_branch_range(offset)) >> return 0; >> >> /* Mask out the flags and target, so they don't step on each other. */ >> -- >> 2.7.4 >> >