From patchwork Sat Feb 27 16:59:07 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Chang S. Bae" X-Patchwork-Id: 42155 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 621113894416; Sat, 27 Feb 2021 17:04:06 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 621113894416 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1614445446; bh=vDoY8RhaYf9m72dgXs7VuwmYuj0SLsR+DgG35pIH44Y=; h=To:Subject:Date:In-Reply-To:References:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=tNlVqf06y5401NFRWF0YpTiEFXt6gmfFMSZI0yRAPdVVCbnFcHGm8egkuJjaZQwUQ lfPZZyd2Cyp4Ooyd9rFEzn/D1ZrBbFbIDHUHRqkLo1eTZoSfvfPLaYpX3cAdJXNCfU ofYaNnRWZC0gr/HuO5o99fdhTjFtCCE0mMKlRFw8= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by sourceware.org (Postfix) with ESMTPS id 49EF73893679 for ; Sat, 27 Feb 2021 17:04:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 49EF73893679 IronPort-SDR: +C3rxzAVusL2vMhTMhIwG1IZubHpAsaq5uQLOvDVw/lATrmlX2rZnhZ7ZOmEB8J9+NzOGVmpyh feXc4TO+NkQg== X-IronPort-AV: E=McAfee;i="6000,8403,9908"; a="183680704" X-IronPort-AV: E=Sophos;i="5.81,211,1610438400"; d="scan'208";a="183680704" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Feb 2021 09:03:58 -0800 IronPort-SDR: 2tIpCS+LSZvEB+r9FQeTXmXhXl5DS6oqV07bz4gf5D/ug3rRmMX1RUWH4eoPi/sC5tYcZh9y5D Sm7Say/fAXqg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,211,1610438400"; d="scan'208";a="503906845" Received: from chang-linux-3.sc.intel.com ([172.25.66.175]) by fmsmga001.fm.intel.com with ESMTP; 27 Feb 2021 09:03:58 -0800 To: bp@suse.de, tglx@linutronix.de, mingo@kernel.org, luto@kernel.org, x86@kernel.org Subject: [PATCH v6 2/6] x86/signal: Introduce helpers to get the maximum signal frame size Date: Sat, 27 Feb 2021 08:59:07 -0800 Message-Id: <20210227165911.32757-3-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210227165911.32757-1-chang.seok.bae@intel.com> References: <20210227165911.32757-1-chang.seok.bae@intel.com> X-Spam-Status: No, score=-10.5 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_ASCII_DIVIDERS, KAM_DMARC_STATUS, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: "Chang S. Bae via Libc-alpha" From: "Chang S. Bae" Reply-To: "Chang S. Bae" Cc: linux-arch@vger.kernel.org, len.brown@intel.com, tony.luck@intel.com, libc-alpha@sourceware.org, ravi.v.shankar@intel.com, chang.seok.bae@intel.com, jannh@google.com, linux-kernel@vger.kernel.org, dave.hansen@intel.com, linux-api@vger.kernel.org, Dave.Martin@arm.com Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" Signal frames do not have a fixed format and can vary in size when a number of things change: support XSAVE features, 32 vs. 64-bit apps. Add the code to support a runtime method for userspace to dynamically discover how large a signal stack needs to be. Introduce a new variable, max_frame_size, and helper functions for the calculation to be used in a new user interface. Set max_frame_size to a system-wide worst-case value, instead of storing multiple app-specific values. Signed-off-by: Chang S. Bae Reviewed-by: Len Brown Acked-by: H.J. Lu Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v2: * Renamed the fpstate size helper with cleanup (Borislav Petkov) * Moved the sigframe struct size defines to where used (Borislav Petkov) * Removed unneeded sentence in the changelog (Borislav Petkov) Change from v1: * Took stack alignment into account for sigframe size (Dave Martin) --- arch/x86/include/asm/fpu/signal.h | 2 ++ arch/x86/include/asm/sigframe.h | 2 ++ arch/x86/kernel/cpu/common.c | 3 ++ arch/x86/kernel/fpu/signal.c | 19 +++++++++++ arch/x86/kernel/signal.c | 57 +++++++++++++++++++++++++++++-- 5 files changed, 81 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/fpu/signal.h b/arch/x86/include/asm/fpu/signal.h index 7fb516b6893a..8b6631dffefd 100644 --- a/arch/x86/include/asm/fpu/signal.h +++ b/arch/x86/include/asm/fpu/signal.h @@ -29,6 +29,8 @@ unsigned long fpu__alloc_mathframe(unsigned long sp, int ia32_frame, unsigned long *buf_fx, unsigned long *size); +unsigned long fpu__get_fpstate_size(void); + extern void fpu__init_prepare_fx_sw_frame(void); #endif /* _ASM_X86_FPU_SIGNAL_H */ diff --git a/arch/x86/include/asm/sigframe.h b/arch/x86/include/asm/sigframe.h index 84eab2724875..5b1ed650b124 100644 --- a/arch/x86/include/asm/sigframe.h +++ b/arch/x86/include/asm/sigframe.h @@ -85,4 +85,6 @@ struct rt_sigframe_x32 { #endif /* CONFIG_X86_64 */ +void __init init_sigframe_size(void); + #endif /* _ASM_X86_SIGFRAME_H */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 35ad8480c464..6954932272d5 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -58,6 +58,7 @@ #include #include #include +#include #include "cpu.h" @@ -1331,6 +1332,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) fpu__init_system(c); + init_sigframe_size(); + #ifdef CONFIG_X86_32 /* * Regardless of whether PCID is enumerated, the SDM says diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index a4ec65317a7f..dbb304e48f16 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -507,6 +507,25 @@ fpu__alloc_mathframe(unsigned long sp, int ia32_frame, return sp; } + +unsigned long fpu__get_fpstate_size(void) +{ + unsigned long ret = xstate_sigframe_size(); + + /* + * This space is needed on (most) 32-bit kernels, or when a 32-bit + * app is running on a 64-bit kernel. To keep things simple, just + * assume the worst case and always include space for 'freg_state', + * even for 64-bit apps on 64-bit kernels. This wastes a bit of + * space, but keeps the code simple. + */ + if ((IS_ENABLED(CONFIG_IA32_EMULATION) || + IS_ENABLED(CONFIG_X86_32)) && use_fxsr()) + ret += sizeof(struct fregs_state); + + return ret; +} + /* * Prepare the SW reserved portion of the fxsave memory layout, indicating * the presence of the extended state information in the memory layout diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c index ea794a083c44..800243afd1ef 100644 --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -212,6 +212,11 @@ do { \ * Set up a signal frame. */ +/* x86 ABI requires 16-byte alignment */ +#define FRAME_ALIGNMENT 16UL + +#define MAX_FRAME_PADDING (FRAME_ALIGNMENT - 1) + /* * Determine which stack to use.. */ @@ -222,9 +227,9 @@ static unsigned long align_sigframe(unsigned long sp) * Align the stack pointer according to the i386 ABI, * i.e. so that on function entry ((sp + 4) & 15) == 0. */ - sp = ((sp + 4) & -16ul) - 4; + sp = ((sp + 4) & -FRAME_ALIGNMENT) - 4; #else /* !CONFIG_X86_32 */ - sp = round_down(sp, 16) - 8; + sp = round_down(sp, FRAME_ALIGNMENT) - 8; #endif return sp; } @@ -663,6 +668,54 @@ SYSCALL_DEFINE0(rt_sigreturn) return 0; } +/* + * There are four different struct types for signal frame: sigframe_ia32, + * rt_sigframe_ia32, rt_sigframe_x32, and rt_sigframe. Use the worst case + * -- the largest size. It means the size for 64-bit apps is a bit more + * than needed, but this keeps the code simple. + */ +#if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) +# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct sigframe_ia32) +#else +# define MAX_FRAME_SIGINFO_UCTXT_SIZE sizeof(struct rt_sigframe) +#endif + +/* + * The FP state frame contains an XSAVE buffer which must be 64-byte aligned. + * If a signal frame starts at an unaligned address, extra space is required. + * This is the max alignment padding, conservatively. + */ +#define MAX_XSAVE_PADDING 63UL + +/* + * The frame data is composed of the following areas and laid out as: + * + * ------------------------- + * | alignment padding | + * ------------------------- + * | (f)xsave frame | + * ------------------------- + * | fsave header | + * ------------------------- + * | alignment padding | + * ------------------------- + * | siginfo + ucontext | + * ------------------------- + */ + +/* max_frame_size tells userspace the worst case signal stack size. */ +static unsigned long __ro_after_init max_frame_size; + +void __init init_sigframe_size(void) +{ + max_frame_size = MAX_FRAME_SIGINFO_UCTXT_SIZE + MAX_FRAME_PADDING; + + max_frame_size += fpu__get_fpstate_size() + MAX_XSAVE_PADDING; + + /* Userspace expects an aligned size. */ + max_frame_size = round_up(max_frame_size, FRAME_ALIGNMENT); +} + static inline int is_ia32_compat_frame(struct ksignal *ksig) { return IS_ENABLED(CONFIG_IA32_EMULATION) &&