From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (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 3tf1wp3zWPzDw1T for ; Thu, 15 Dec 2016 03:19:06 +1100 (AEDT) Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uBEGEEeY009858 for ; Wed, 14 Dec 2016 11:19:04 -0500 Received: from e23smtp01.au.ibm.com (e23smtp01.au.ibm.com [202.81.31.143]) by mx0b-001b2d01.pphosted.com with ESMTP id 27b5w17nhn-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Wed, 14 Dec 2016 11:19:03 -0500 Received: from localhost by e23smtp01.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 15 Dec 2016 02:19:00 +1000 Received: from d23relay06.au.ibm.com (d23relay06.au.ibm.com [9.185.63.219]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id 13A832BB0059 for ; Thu, 15 Dec 2016 03:18:59 +1100 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay06.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id uBEGIwAF52232270 for ; Thu, 15 Dec 2016 03:18:58 +1100 Received: from d23av04.au.ibm.com (localhost [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id uBEGIw1x031467 for ; Thu, 15 Dec 2016 03:18:58 +1100 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 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> Message-Id: <1481732310-7779-5-git-send-email-anju@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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