Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934061AbcLNQTJ (ORCPT ); Wed, 14 Dec 2016 11:19:09 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:59530 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933894AbcLNQTG (ORCPT ); Wed, 14 Dec 2016 11:19:06 -0500 From: Anju T Sudhakar To: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Cc: 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, mhiramat@kernel.org, anju@linux.vnet.ibm.com Subject: [PATCH V2 2/4] powerpc: add helper to check if offset is within rel branch range Date: Wed, 14 Dec 2016 21:48:30 +0530 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1481732310-7779-1-git-send-email-anju@linux.vnet.ibm.com> References: <1481732310-7779-1-git-send-email-anju@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16121416-0012-0000-0000-000001F76072 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16121416-0013-0000-0000-000006A2097E Message-Id: <1481732310-7779-5-git-send-email-anju@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-12-14_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609300000 definitions=main-1612140263 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2390 Lines: 65 From: "Naveen N. Rao" 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