From patchwork Sat Jul 9 10:57:19 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tixy X-Patchwork-Id: 959182 Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p69B6kKe025722 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Sat, 9 Jul 2011 11:07:07 GMT Received: from canuck.infradead.org ([2001:4978:20e::1]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1QfVKf-0001cF-9E; Sat, 09 Jul 2011 11:04:22 +0000 Received: from localhost ([127.0.0.1] helo=canuck.infradead.org) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1QfVKe-00066W-Bw; Sat, 09 Jul 2011 11:04:20 +0000 Received: from casper.infradead.org ([2001:770:15f::2]) by canuck.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1QfVEY-0004Ph-9k for linux-arm-kernel@canuck.infradead.org; Sat, 09 Jul 2011 10:58:02 +0000 Received: from smarthost01.mail.zen.net.uk ([212.23.3.140]) by casper.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1QfVER-0006EY-2Q for linux-arm-kernel@lists.infradead.org; Sat, 09 Jul 2011 10:58:00 +0000 Received: from [82.69.122.217] (helo=plug1) by smarthost01.mail.zen.net.uk with esmtpsa (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.63) (envelope-from ) id 1QfVEQ-0005bd-75 for linux-arm-kernel@lists.infradead.org; Sat, 09 Jul 2011 10:57:54 +0000 Received: from [192.168.2.20] (helo=computer2) by plug1 with esmtp (Exim 4.72) (envelope-from ) id 1QfVEM-0003hY-Ka for linux-arm-kernel@lists.infradead.org; Sat, 09 Jul 2011 11:57:51 +0100 Received: from tixy by computer2 with local (Exim 4.72) (envelope-from ) id 1QfVEM-0005Ud-Dr for linux-arm-kernel@lists.infradead.org; Sat, 09 Jul 2011 11:57:50 +0100 From: Tixy To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 32/51] ARM: kprobes: Decode 16-bit Thumb branch instructions Date: Sat, 9 Jul 2011 11:57:19 +0100 Message-Id: <1310209058-20980-33-git-send-email-tixy@yxit.co.uk> X-Mailer: git-send-email 1.7.2.5 In-Reply-To: <1310209058-20980-1-git-send-email-tixy@yxit.co.uk> References: <1310209058-20980-1-git-send-email-tixy@yxit.co.uk> X-Originating-Smarthost01-IP: [82.69.122.217] X-CRM114-Version: 20090807-BlameThorstenAndJenny ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20110709_115755_889196_2C56F2C3 X-CRM114-Status: GOOD ( 17.21 ) X-Spam-Score: -1.9 (-) X-Spam-Report: SpamAssassin version 3.3.2-r929478 on casper.infradead.org summary: Content analysis details: (-1.9 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [212.23.3.140 listed in list.dnswl.org] -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter2.kernel.org [140.211.167.43]); Sat, 09 Jul 2011 11:07:07 +0000 (UTC) From: Jon Medhurst We previously changed the behaviour of probes so that conditional instructions don't fire when the condition isn't met. For ARM branches, and Thumb branches in IT blocks, this means they don't fire if the branch isn't taken. For consistency, we implement the same for Thumb conditional branch instructions. This involves setting up insn_check_cc to point to the relevant condition checking function. As the emulation routine is only called when this condition passes, it doesn't need to check again and can unconditionally update PC. Signed-off-by: Jon Medhurst --- arch/arm/kernel/kprobes-thumb.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 files changed, 38 insertions(+), 0 deletions(-) diff --git a/arch/arm/kernel/kprobes-thumb.c b/arch/arm/kernel/kprobes-thumb.c index 997fc6d..d3133fd 100644 --- a/arch/arm/kernel/kprobes-thumb.c +++ b/arch/arm/kernel/kprobes-thumb.c @@ -141,6 +141,35 @@ t16_decode_it(kprobe_opcode_t insn, struct arch_specific_insn *asi) return INSN_GOOD_NO_SLOT; } +static void __kprobes +t16_simulate_cond_branch(struct kprobe *p, struct pt_regs *regs) +{ + kprobe_opcode_t insn = p->opcode; + unsigned long pc = thumb_probe_pc(p); + long offset = insn & 0x7f; + offset -= insn & 0x80; /* Apply sign bit */ + regs->ARM_pc = pc + (offset * 2); +} + +static enum kprobe_insn __kprobes +t16_decode_cond_branch(kprobe_opcode_t insn, struct arch_specific_insn *asi) +{ + int cc = (insn >> 8) & 0xf; + asi->insn_check_cc = kprobe_condition_checks[cc]; + asi->insn_handler = t16_simulate_cond_branch; + return INSN_GOOD_NO_SLOT; +} + +static void __kprobes +t16_simulate_branch(struct kprobe *p, struct pt_regs *regs) +{ + kprobe_opcode_t insn = p->opcode; + unsigned long pc = thumb_probe_pc(p); + long offset = insn & 0x3ff; + offset -= insn & 0x400; /* Apply sign bit */ + regs->ARM_pc = pc + (offset * 2); +} + static unsigned long __kprobes t16_emulate_loregs(struct kprobe *p, struct pt_regs *regs) { @@ -472,6 +501,15 @@ const union decode_item kprobe_decode_thumb16_table[] = { /* SVC 1101 1111 xxxx xxxx */ DECODE_REJECT (0xfe00, 0xde00), + /* Conditional branch 1101 xxxx xxxx xxxx */ + DECODE_CUSTOM (0xf000, 0xd000, t16_decode_cond_branch), + + /* + * Unconditional branch + * B 1110 0xxx xxxx xxxx + */ + DECODE_SIMULATE (0xf800, 0xe000, t16_simulate_branch), + DECODE_END };