From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4A21C4167B for ; Wed, 30 Nov 2022 02:35:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232322AbiK3Cfz (ORCPT ); Tue, 29 Nov 2022 21:35:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230293AbiK3Cft (ORCPT ); Tue, 29 Nov 2022 21:35:49 -0500 Received: from mail-pj1-x102b.google.com (mail-pj1-x102b.google.com [IPv6:2607:f8b0:4864:20::102b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A17EA13CD1 for ; Tue, 29 Nov 2022 18:35:47 -0800 (PST) Received: by mail-pj1-x102b.google.com with SMTP id 3-20020a17090a098300b00219041dcbe9so581917pjo.3 for ; Tue, 29 Nov 2022 18:35:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20210112.gappssmtp.com; s=20210112; h=to:from:cc:content-transfer-encoding:mime-version:references :in-reply-to:message-id:date:subject:from:to:cc:subject:date :message-id:reply-to; bh=WK41owb8xQar3YPAMlOv6Q9IlVxICe86b2kCZ83CjmI=; b=NYaY1njFT+Iv04FROrsPA9asr8bF0H1T04E0ghH8zlytybXdGXaucom+/NQFSJL3iN efDS5zB46j0rOji8pcj485H1bPAwEnbMedmSqSEmf9B0wOaK9y7b1cF2ad77M3muEnbi qstWPWEJs/VJ5jCtWTtcb7YUXNolbQ28uZPsHenqV73ygMFTNij1XXA1rKcB0p91dDSg +bpgfhsHSzWV1Tyhw4e43BlxsTlU2cGT7GoXFBSE8FPrEOI9hkNdf7a2KEI+vkMrrO1l AJvx8bfKnp+cn/ARJvoFo0ELvjUsXydRIUgT9uh8J5GQOc3rLSUsST/k+m1AtfbnbM4a FzgA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=to:from:cc:content-transfer-encoding:mime-version:references :in-reply-to:message-id:date:subject:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=WK41owb8xQar3YPAMlOv6Q9IlVxICe86b2kCZ83CjmI=; b=VVImN6ohPGy4S+917QZsiO3P6oPr3/0CUnpuznIF7Uo568+vRrQy2xnkoK4xlMLyPm MkF8/x/vt61q50vdtNSjP5wDEOhsSpCDJPbsf1eayAFsxwrtluDd5zbOTU3rcoF3dnL5 ccZnKY/kVvVSu/u48gyUcjtxbHBOsNlZwMAMUp/hoYa/2b6/rJ13Fsaj+BB57RaB/UiQ ej6PrI9k6T5VvEcP19Y+0RUF76yuHfAr2WBeH+8i2d5JwqNPUbdNKsU+GxCtnXKb3F8y ld/ysOq0Gi+dwZHOuhnX7Jlpva5ER7sEAn+xa9HvDiMMnnH5eQBcy3HUJLloEnMcsnBT du+Q== X-Gm-Message-State: ANoB5pl6CN1imuTECeuM6VdqG5LWNcYWRKqIjG+rGaOLc9NJt6DrcDWV 4gzz665WOawb9/k4EiGOEa3CyTZuNXNIaQ== X-Google-Smtp-Source: AA0mqf5bUTnWIeZUMTYfWzcYyQ2Ayw75862olJovnwQkgFAZMu4TKHAv/LhckeZcuq6IEBmsNETSfA== X-Received: by 2002:a17:903:120c:b0:188:fc5f:84f3 with SMTP id l12-20020a170903120c00b00188fc5f84f3mr51970782plh.2.1669775747099; Tue, 29 Nov 2022 18:35:47 -0800 (PST) Received: from localhost ([50.221.140.188]) by smtp.gmail.com with ESMTPSA id v11-20020a63464b000000b00476b165ff8bsm15069pgk.57.2022.11.29.18.35.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Nov 2022 18:35:46 -0800 (PST) Subject: [PATCH 2/2] RISC-V: Add some comments about the shadow and overflow stacks Date: Tue, 29 Nov 2022 18:35:15 -0800 Message-Id: <20221130023515.20217-2-palmer@rivosinc.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221130023515.20217-1-palmer@rivosinc.com> References: <20221130023515.20217-1-palmer@rivosinc.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Palmer Dabbelt From: Palmer Dabbelt To: jszhang@kernel.org, guoren@kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It took me a while to page all this back in when trying to review the recent spin_shadow_stack, so I figured I'd just write up some comments. Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/traps.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index acdfcacd7e57..336d4aadadb1 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -200,18 +200,18 @@ void __init trap_init(void) } #ifdef CONFIG_VMAP_STACK +/* + * Extra stack space that allows us to provide panic messages when the kernel + * has overflowed its stack. + */ static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)], overflow_stack)__aligned(16); /* - * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used - * to get per-cpu overflow stack(get_overflow_stack). + * A temporary stack for use by handle_kernel_stack_overflow. This is used so + * we can call into C code to get the per-hart overflow stack. Usage of this + * stack must be protected by spin_shadow_stack. */ long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16); -asmlinkage unsigned long get_overflow_stack(void) -{ - return (unsigned long)this_cpu_ptr(overflow_stack) + - OVERFLOW_STACK_SIZE; -} /* * A pseudo spinlock to protect the shadow stack from being used by multiple @@ -222,6 +222,12 @@ asmlinkage unsigned long get_overflow_stack(void) */ unsigned long spin_shadow_stack; +asmlinkage unsigned long get_overflow_stack(void) +{ + return (unsigned long)this_cpu_ptr(overflow_stack) + + OVERFLOW_STACK_SIZE; +} + asmlinkage void handle_bad_stack(struct pt_regs *regs) { unsigned long tsk_stk = (unsigned long)current->stack; -- 2.38.1