From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 430533A1CD for ; Tue, 20 Feb 2024 02:03:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708394631; cv=none; b=t7rDkZz5n4ohyvsl/8VQPTAKX4O9k8XPRY1zZpMpsm/gFMxXsofiYnz41EzZctBBvQG1LNQ+VitE8BwyBteMTw6jfuyfhs2UOTVsjt4K79v6BWX7Vgm/mtPEUhr3FkCjNvJkkXJia0A9eeeMOduUplhy1aRQ2h8zo9Ytlz6Bh2o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708394631; c=relaxed/simple; bh=tl0G24XOjbGzUHwVuSKAML2L5w2w/ukL5jhI0xL8Wbk=; h=References:From:To:Cc:Subject:In-reply-to:Date:Message-ID: MIME-Version:Content-Type; b=U0GXdL/PGx5hIROnSNdFoJe4Cf22FVFo9CYuIDr1pMCcNSBEwSx6v/a2QxfjDZsQwQArN0ysWJxxbwryuN8+ELxoadgxr4QbgZEbbt28xFG6Qo01rRIkyUgwRPpYYpyqA6vaVBNizqHh44NetBq2I0gMPQJc3W+VHqck8UmtT2o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org; spf=pass smtp.mailfrom=linaro.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b=Suls8slr; arc=none smtp.client-ip=209.85.214.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linaro.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="Suls8slr" Received: by mail-pl1-f169.google.com with SMTP id d9443c01a7336-1d7232dcb3eso26222205ad.2 for ; Mon, 19 Feb 2024 18:03:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1708394628; x=1708999428; darn=vger.kernel.org; h=mime-version:message-id:date:in-reply-to:subject:cc:to:from :user-agent:references:from:to:cc:subject:date:message-id:reply-to; bh=Ut8HYrvCDFac0esrbFqk2cfgA544kkLlPQaAT6Wttz0=; b=Suls8slrlKu1GWrkWeiJyMMq8d8OmJjG4HQRDqGKkDxCGvnQXj3NkpLK8YeFHW7jhR AAgjw2yso4yD4zEgGmYJfcDHbqiouKzolEOKeB9Hpxwi19d8pL2q8lCXZca3vncoL3SQ k1hTGX6ajH2IjdKm0iQkpPvFirt5Q8PlGudv6VB60Whz+Po+CFzEzUCM9fOo5UdvTl46 /WqgZXqtFBCVds2NvymzgcVNOQjTg/hfB6M8TJj69Kh9PyDrR2Elmf2U9h2Hl0j/gZpQ F6wCGVVpNXxcahTQO8wAAuZ+Rk1Z1zsipM4+hqxCKo7TiqlZofPkHZXHt+ViOklVfoLN dfWw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708394628; x=1708999428; h=mime-version:message-id:date:in-reply-to:subject:cc:to:from :user-agent:references:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Ut8HYrvCDFac0esrbFqk2cfgA544kkLlPQaAT6Wttz0=; b=rS/jvLL6A5GMTs+c/uG84a8mXXeR36FzGos0McHVvfExk8Fzly2+QNvh53GASM5xHh ADiaFf7oadLa95V37Zc/VVXDgaE8YGAZpyzE3Ns0C3VxA5urJH8W7HJESlt6GyCgwVyx uR13y8ApypXC5OM75pqXiRVPb9mYwoSeImy119oB/GE2VJMjp2A0Gj3WstOviy70KL0q F6/gwxNLaDLyPcykej9/1m+QHwzoTim/H6/dCRxPxeAJZkOna6x+awHXlgoqAwUpv9wW 90sz5sJ6rfzCwi6gEiWrvAT3/+8Djb79AkxFRfjyUgH0qYYq70dlF/S8PEborhybWnMc bJKQ== X-Forwarded-Encrypted: i=1; AJvYcCUqND80L3eVDSaaxsH8qOXWRy6ZDpZw23CqVrCTiuymPaO8xMuNNrKsgU2BOmrP74ScavkFWnrpRyAk20NdkOz2ID6k0m/S6V7j X-Gm-Message-State: AOJu0YxAWbdUA1h8vfusGiYN3yd/ke8H7vB7LJKDGo9BJaR6Sn72IAFU xEjkHQOO8RfgEFyn/gQwGzZuAjt2xCJWpVQhvOnDUogxZ+A0bszZcQvBFBzwa4Q= X-Google-Smtp-Source: AGHT+IGPIHUy8hPqScHiSoGgxRjrCJE9JJnAWETOMrecbYtciaMsbgwu6AZ9cPzFGRlUwvHmQwNF1w== X-Received: by 2002:a17:902:e5c3:b0:1db:fcc8:7d96 with SMTP id u3-20020a170902e5c300b001dbfcc87d96mr4258933plf.14.1708394628501; Mon, 19 Feb 2024 18:03:48 -0800 (PST) Received: from localhost ([2804:14d:7e39:8470:a328:9cae:8aed:4821]) by smtp.gmail.com with ESMTPSA id kg3-20020a170903060300b001dbbd4ee1f6sm5058425plb.11.2024.02.19.18.03.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Feb 2024 18:03:48 -0800 (PST) References: <20240203-arm64-gcs-v8-0-c9fec77673ef@kernel.org> <20240203-arm64-gcs-v8-23-c9fec77673ef@kernel.org> User-agent: mu4e 1.10.8; emacs 29.1 From: Thiago Jung Bauermann To: Mark Brown Cc: Catalin Marinas , Will Deacon , Jonathan Corbet , Andrew Morton , Marc Zyngier , Oliver Upton , James Morse , Suzuki K Poulose , Arnd Bergmann , Oleg Nesterov , Eric Biederman , Kees Cook , Shuah Khan , "Rick P. Edgecombe" , Deepak Gupta , Ard Biesheuvel , Szabolcs Nagy , "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Florian Weimer , Christian Brauner , 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 v8 23/38] arm64/signal: Set up and restore the GCS context for signal handlers In-reply-to: <20240203-arm64-gcs-v8-23-c9fec77673ef@kernel.org> Date: Mon, 19 Feb 2024 23:03:46 -0300 Message-ID: <87zfvv7uyl.fsf@linaro.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Mark Brown writes: > +#ifdef CONFIG_ARM64_GCS > +static int gcs_restore_signal(void) > +{ > + u64 gcspr_el0, cap; > + int ret; > + > + if (!system_supports_gcs()) > + return 0; > + > + if (!(current->thread.gcs_el0_mode & PR_SHADOW_STACK_ENABLE)) > + return 0; > + > + gcspr_el0 = read_sysreg_s(SYS_GCSPR_EL0); > + > + /* > + * GCSPR_EL0 should be pointing at a capped GCS, read the cap... > + */ > + gcsb_dsync(); > + ret = copy_from_user(&cap, (__user void*)gcspr_el0, sizeof(cap)); > + if (ret) > + return -EFAULT; > + > + /* > + * ...then check that the cap is the actual GCS before > + * restoring it. > + */ > + if (!gcs_signal_cap_valid(gcspr_el0, cap)) > + return -EINVAL; > + > + /* Invalidate the token to prevent reuse */ > + put_user_gcs(0, (__user void*)gcspr_el0, &ret); > + if (ret != 0) > + return -EFAULT; You had mentioned that "ideally we'd be doing a compare and exchange here to substitute in a zero". Is a compare and exchange not necessary anymore, or is it just being left for later? In the latter case, a TODO or FIXME comment mentioning it would be useful here. > + > + current->thread.gcspr_el0 = gcspr_el0 + sizeof(cap); > + write_sysreg_s(current->thread.gcspr_el0, SYS_GCSPR_EL0); > + > + return 0; > +} -- Thiago