From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zen.linaro.local ([81.128.185.34]) by smtp.gmail.com with ESMTPSA id h3sm8081600wrb.31.2017.01.27.05.58.01 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 27 Jan 2017 05:58:01 -0800 (PST) Received: from zen (localhost [127.0.0.1]) by zen.linaro.local (Postfix) with ESMTPS id 8CA173E0342; Fri, 27 Jan 2017 13:58:01 +0000 (GMT) References: <1485285380-10565-1-git-send-email-peter.maydell@linaro.org> <1485285380-10565-11-git-send-email-peter.maydell@linaro.org> User-agent: mu4e 0.9.19; emacs 25.1.91.4 From: Alex =?utf-8?Q?Benn=C3=A9e?= To: Peter Maydell Cc: qemu-arm@nongnu.org, qemu-devel@nongnu.org, patches@linaro.org, Liviu Ionescu Subject: Re: [PATCH 10/10] armv7m: R14 should reset to 0xffffffff In-reply-to: <1485285380-10565-11-git-send-email-peter.maydell@linaro.org> Date: Fri, 27 Jan 2017 13:58:01 +0000 Message-ID: <87ziic8v12.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-TUID: SaCW1RuF3E3Q Peter Maydell writes: > For M profile (unlike A profile) the reset value of R14 is specified > as 0xffffffff. (The rationale is that this is an illegal exception > return value, so if guest code tries to return to it it will result > in a helpful exception.) > > Registers r0 to r12 and the flags are architecturally UNKNOWN on > reset, so we leave those at zero. > > Signed-off-by: Peter Maydell Reviewed-by: Alex Bennée > --- > target/arm/cpu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/target/arm/cpu.c b/target/arm/cpu.c > index 0814f73..e9f10f7 100644 > --- a/target/arm/cpu.c > +++ b/target/arm/cpu.c > @@ -196,6 +196,9 @@ static void arm_cpu_reset(CPUState *s) > */ > env->v7m.ccr = R_V7M_CCR_STKALIGN_MASK; > > + /* Unlike A/R profile, M profile defines the reset LR value */ > + env->regs[14] = 0xffffffff; > + > /* Load the initial SP and PC from the vector table at address 0 */ > rom = rom_ptr(0); > if (rom) { -- Alex Bennée From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35721) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cX72X-0008QH-JN for qemu-devel@nongnu.org; Fri, 27 Jan 2017 08:58:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cX72S-0001To-NJ for qemu-devel@nongnu.org; Fri, 27 Jan 2017 08:58:09 -0500 Received: from mail-wm0-x234.google.com ([2a00:1450:400c:c09::234]:36416) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cX72S-0001T9-H1 for qemu-devel@nongnu.org; Fri, 27 Jan 2017 08:58:04 -0500 Received: by mail-wm0-x234.google.com with SMTP id c85so117933726wmi.1 for ; Fri, 27 Jan 2017 05:58:04 -0800 (PST) References: <1485285380-10565-1-git-send-email-peter.maydell@linaro.org> <1485285380-10565-11-git-send-email-peter.maydell@linaro.org> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <1485285380-10565-11-git-send-email-peter.maydell@linaro.org> Date: Fri, 27 Jan 2017 13:58:01 +0000 Message-ID: <87ziic8v12.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH 10/10] armv7m: R14 should reset to 0xffffffff List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: qemu-arm@nongnu.org, qemu-devel@nongnu.org, patches@linaro.org, Liviu Ionescu Peter Maydell writes: > For M profile (unlike A profile) the reset value of R14 is specified > as 0xffffffff. (The rationale is that this is an illegal exception > return value, so if guest code tries to return to it it will result > in a helpful exception.) > > Registers r0 to r12 and the flags are architecturally UNKNOWN on > reset, so we leave those at zero. > > Signed-off-by: Peter Maydell Reviewed-by: Alex Bennée > --- > target/arm/cpu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/target/arm/cpu.c b/target/arm/cpu.c > index 0814f73..e9f10f7 100644 > --- a/target/arm/cpu.c > +++ b/target/arm/cpu.c > @@ -196,6 +196,9 @@ static void arm_cpu_reset(CPUState *s) > */ > env->v7m.ccr = R_V7M_CCR_STKALIGN_MASK; > > + /* Unlike A/R profile, M profile defines the reset LR value */ > + env->regs[14] = 0xffffffff; > + > /* Load the initial SP and PC from the vector table at address 0 */ > rom = rom_ptr(0); > if (rom) { -- Alex Bennée