From patchwork Mon Oct 15 05:24:59 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Paul Walmsley X-Patchwork-Id: 1592161 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by patchwork2.kernel.org (Postfix) with ESMTP id 69D7DDFB34 for ; Mon, 15 Oct 2012 05:27:00 +0000 (UTC) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1TNdAn-0002yL-8o; Mon, 15 Oct 2012 05:25:05 +0000 Received: from utopia.booyaka.com ([74.50.51.50]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1TNdAj-0002xj-Au for linux-arm-kernel@lists.infradead.org; Mon, 15 Oct 2012 05:25:02 +0000 Received: (qmail 16302 invoked by uid 1019); 15 Oct 2012 05:24:59 -0000 Date: Mon, 15 Oct 2012 05:24:59 +0000 (UTC) From: Paul Walmsley To: Mans Rullgard Subject: [PATCH v3] ARM: vfp: fix save and restore when running on pre-VFPv3 and CONFIG_VFPv3 set In-Reply-To: Message-ID: References: <20121013090255.GT28061@n2100.arm.linux.org.uk> <20121013133654.GU28061@n2100.arm.linux.org.uk> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 X-Spam-Note: CRM114 invocation failed X-Spam-Score: -1.9 (-) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-1.9 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 SPF_HELO_PASS SPF: HELO matches SPF record -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: Dave Martin , Russell King - ARM Linux , Tony Lindgren , Catalin Marinas , linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org After commit 846a136881b8f73c1f74250bf6acfaa309cab1f2 ("ARM: vfp: fix saving d16-d31 vfp registers on v6+ kernels"), the OMAP 2430SDP board started crashing during boot with omap2plus_defconfig: [ 3.875122] mmcblk0: mmc0:e624 SD04G 3.69 GiB [ 3.915954] mmcblk0: p1 [ 4.086639] Internal error: Oops - undefined instruction: 0 [#1] SMP ARM [ 4.093719] Modules linked in: [ 4.096954] CPU: 0 Not tainted (3.6.0-02232-g759e00b #570) [ 4.103149] PC is at vfp_reload_hw+0x1c/0x44 [ 4.107666] LR is at __und_usr_fault_32+0x0/0x8 It turns out that the context save/restore fix unmasked a latent bug in commit 5aaf254409f8d58229107b59507a8235b715a960 ("ARM: 6203/1: Make VFPv3 usable on ARMv6"). When CONFIG_VFPv3 is set, but the kernel is booted on a pre-VFPv3 core, the code attempts to save and restore the d16-d31 VFP registers. These are only present on non-D16 VFPv3+, so this results in an undefined instruction exception. The code didn't crash before commit 846a136 because the save and restore code was only touching d0-d15, present on all VFP. Fix by implementing a request from Russell King to add a new HWCAP flag that affirmatively indicates the presence of the d16-d31 registers: http://marc.info/?l=linux-arm-kernel&m=135013547905283&w=2 and some feedback from Måns to clarify the name of the HWCAP flag. Signed-off-by: Paul Walmsley Cc: Tony Lindgren Cc: Russell King Cc: Catalin Marinas Cc: Dave Martin Cc: Måns Rullgård Tested-by: Tony Lindgren Tested-by: Jon Hunter --- Thanks for the suggestion, Måns; certainly a readability improvement. arch/arm/include/asm/vfpmacros.h | 12 ++++++------ arch/arm/include/uapi/asm/hwcap.h | 3 ++- arch/arm/vfp/vfpmodule.c | 9 ++++++--- 3 files changed, 14 insertions(+), 10 deletions(-) diff --git a/arch/arm/include/asm/vfpmacros.h b/arch/arm/include/asm/vfpmacros.h index 6a6f1e4..301c1db 100644 --- a/arch/arm/include/asm/vfpmacros.h +++ b/arch/arm/include/asm/vfpmacros.h @@ -27,9 +27,9 @@ #if __LINUX_ARM_ARCH__ <= 6 ldr \tmp, =elf_hwcap @ may not have MVFR regs ldr \tmp, [\tmp, #0] - tst \tmp, #HWCAP_VFPv3D16 - ldceql p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d16-d31} - addne \base, \base, #32*4 @ step over unused register space + tst \tmp, #HWCAP_VFPD32 + ldcnel p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d16-d31} + addeq \base, \base, #32*4 @ step over unused register space #else VFPFMRX \tmp, MVFR0 @ Media and VFP Feature Register 0 and \tmp, \tmp, #MVFR0_A_SIMD_MASK @ A_SIMD field @@ -51,9 +51,9 @@ #if __LINUX_ARM_ARCH__ <= 6 ldr \tmp, =elf_hwcap @ may not have MVFR regs ldr \tmp, [\tmp, #0] - tst \tmp, #HWCAP_VFPv3D16 - stceql p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d16-d31} - addne \base, \base, #32*4 @ step over unused register space + tst \tmp, #HWCAP_VFPD32 + stcnel p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d16-d31} + addeq \base, \base, #32*4 @ step over unused register space #else VFPFMRX \tmp, MVFR0 @ Media and VFP Feature Register 0 and \tmp, \tmp, #MVFR0_A_SIMD_MASK @ A_SIMD field diff --git a/arch/arm/include/uapi/asm/hwcap.h b/arch/arm/include/uapi/asm/hwcap.h index f254f65..3688fd1 100644 --- a/arch/arm/include/uapi/asm/hwcap.h +++ b/arch/arm/include/uapi/asm/hwcap.h @@ -18,11 +18,12 @@ #define HWCAP_THUMBEE (1 << 11) #define HWCAP_NEON (1 << 12) #define HWCAP_VFPv3 (1 << 13) -#define HWCAP_VFPv3D16 (1 << 14) +#define HWCAP_VFPv3D16 (1 << 14) /* also set for VFPv4-D16 */ #define HWCAP_TLS (1 << 15) #define HWCAP_VFPv4 (1 << 16) #define HWCAP_IDIVA (1 << 17) #define HWCAP_IDIVT (1 << 18) +#define HWCAP_VFPD32 (1 << 19) /* set if VFP has 32 regs (not 16) */ #define HWCAP_IDIV (HWCAP_IDIVA | HWCAP_IDIVT) diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c index c834b32..3b44e0d 100644 --- a/arch/arm/vfp/vfpmodule.c +++ b/arch/arm/vfp/vfpmodule.c @@ -701,11 +701,14 @@ static int __init vfp_init(void) elf_hwcap |= HWCAP_VFPv3; /* - * Check for VFPv3 D16. CPUs in this configuration - * only have 16 x 64bit registers. + * Check for VFPv3 D16 and VFPv4 D16. CPUs in + * this configuration only have 16 x 64bit + * registers. */ if (((fmrx(MVFR0) & MVFR0_A_SIMD_MASK)) == 1) - elf_hwcap |= HWCAP_VFPv3D16; + elf_hwcap |= HWCAP_VFPv3D16; /* also v4-D16 */ + else + elf_hwcap |= HWCAP_VFPD32; } #endif /*