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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 813D6C5320E for ; Sun, 25 Aug 2024 18:36:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 044308D002E; Sun, 25 Aug 2024 14:36:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id F36178D0029; Sun, 25 Aug 2024 14:36:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D89188D002E; Sun, 25 Aug 2024 14:36:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id B83D18D0029 for ; Sun, 25 Aug 2024 14:36:49 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 49542C07E7 for ; Sun, 25 Aug 2024 18:36:49 +0000 (UTC) X-FDA: 82491624138.26.902A1A1 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) by imf20.hostedemail.com (Postfix) with ESMTP id BD5881C001A for ; Sun, 25 Aug 2024 18:36:47 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf20.hostedemail.com: domain of cmarinas@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=cmarinas@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724610913; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=mtdUf22rBq+11BUG9W4yMejiyV/XzJqRkUm54ad8LWQ=; b=PI+XhnChYkOoWaNvzFkWQNhw6NPr6KycP0oN6NOgiwR5EFl1wAC7xEXCxsx/aITpIUW6nN NWSBOpIsamkh8btMTJj5UQC85WXfRnYHPpv7V4oAtvqEDqrBf4YWSXxYTOB9Hmdf+jVMUa uqV3LACvf023isNlUobDFmCCpJm0XXc= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724610913; a=rsa-sha256; cv=none; b=OXaMUsRLC5LndeFK5NtmPQZuHLYjao3ZdzfIheWiDddolNoxeHeuk86gLtbQmZk/yQERbP 0niehjPqPapRHaucCwYyVMX9abU1KZXNWMfE0wTkmEaxKOOVFJcmQngcr2VIf7Ke0IcFGm HHBcxl2rhss19DIW9dv9/ZNXObOSiZU= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf20.hostedemail.com: domain of cmarinas@kernel.org designates 147.75.193.91 as permitted sender) smtp.mailfrom=cmarinas@kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id B8847A41DB2; Wed, 21 Aug 2024 17:40:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A67B2C32781; Wed, 21 Aug 2024 17:40:22 +0000 (UTC) Date: Wed, 21 Aug 2024 18:40:20 +0100 From: Catalin Marinas To: Mark Brown Cc: Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , Kees Cook , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Florian Weimer , Christian Brauner , Thiago Jung Bauermann , Ross Burton , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org Subject: Re: [PATCH v10 24/40] arm64/signal: Expose GCS state in signal frames Message-ID: References: <20240801-arm64-gcs-v10-0-699e2bd2190b@kernel.org> <20240801-arm64-gcs-v10-24-699e2bd2190b@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240801-arm64-gcs-v10-24-699e2bd2190b@kernel.org> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: BD5881C001A X-Stat-Signature: b7nncq5oa6uqxgyuga87k5hcepbs4gjf X-Rspam-User: X-HE-Tag: 1724611007-605779 X-HE-Meta: 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 Te/+JhB5 ZGC2s7B2WQkzW3fCDV7+bwNI+PPra7H0P5fVV5hUVjHZrrBB5bCyhcUuZZhS96ohgxSp3WRwo2OrWAkF+jGpgKqdikg4nxg5nTBkapgEM07tTTeplQNOmA5490Xec7n1O3a7i/QZ5qHvcl/dRH0eu35QH1BnXZNZzhQLMZtp+j+tnUfX0a4yb5Mqgv/yEXKJtQe2eGYpb0Xgq04BWbrRd0vcXfaCOBEDXdATW69NKW6QbK6v22BXKu0s/fkdS6NEFXG9hv5kWkbeNxrDnghFIUlMW9IFkV4+f/9XOpIasIbgY08PDu8ZkAX4VANrZvkMKT04kO58iQDexz2O7u+PRoy9Q/2S9jfSnhP1SGy7+JS+bXHDGntK2+zq51qOnW33+uYoju8XHg4e5EdeHQEsyQUpV81t99IA+jER5EaDDmjAPFUNfL8fAm5JlayddGflOnLo5LfDd+63d/Y0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Aug 01, 2024 at 01:06:51PM +0100, Mark Brown wrote: > @@ -636,6 +639,81 @@ extern int restore_zt_context(struct user_ctxs *user); > > #endif /* ! CONFIG_ARM64_SME */ > > +#ifdef CONFIG_ARM64_GCS > + > +static int preserve_gcs_context(struct gcs_context __user *ctx) > +{ > + int err = 0; > + u64 gcspr; > + > + /* > + * We will add a cap token to the frame, include it in the > + * GCSPR_EL0 we report to support stack switching via > + * sigreturn. > + */ > + gcs_preserve_current_state(); > + gcspr = current->thread.gcspr_el0 - 8; We discussed briefly offline. Not a problem in this patch but gcs_preserve_current_state() only saves it conditionally on GCS being enabled for the task. However, you mentioned that the register is always available to the user, so I'd rather change the preserving function to save it unconditionally. > + > + __put_user_error(GCS_MAGIC, &ctx->head.magic, err); > + __put_user_error(sizeof(*ctx), &ctx->head.size, err); > + __put_user_error(gcspr, &ctx->gcspr, err); > + __put_user_error(0, &ctx->reserved, err); > + __put_user_error(current->thread.gcs_el0_mode, > + &ctx->features_enabled, err); > + > + return err; > +} > + > +static int restore_gcs_context(struct user_ctxs *user) > +{ > + u64 gcspr, enabled; > + int err = 0; > + > + if (user->gcs_size != sizeof(*user->gcs)) > + return -EINVAL; > + > + __get_user_error(gcspr, &user->gcs->gcspr, err); > + __get_user_error(enabled, &user->gcs->features_enabled, err); > + if (err) > + return err; > + > + /* Don't allow unknown modes */ > + if (enabled & ~PR_SHADOW_STACK_SUPPORTED_STATUS_MASK) > + return -EINVAL; > + > + err = gcs_check_locked(current, enabled); > + if (err != 0) > + return err; > + > + /* Don't allow enabling */ > + if (!task_gcs_el0_enabled(current) && > + (enabled & PR_SHADOW_STACK_ENABLE)) > + return -EINVAL; We don't allow enabling and that's fine but we don't restore gcspr either with this early return. > + > + /* If we are disabling disable everything */ > + if (!(enabled & PR_SHADOW_STACK_ENABLE)) > + enabled = 0; > + > + current->thread.gcs_el0_mode = enabled; > + > + /* > + * We let userspace set GCSPR_EL0 to anything here, we will > + * validate later in gcs_restore_signal(). > + */ > + current->thread.gcspr_el0 = gcspr; > + write_sysreg_s(current->thread.gcspr_el0, SYS_GCSPR_EL0); I think you should move this further up unconditionally. -- Catalin