From patchwork Mon Jul 24 12:46:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13324710 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 CA5DDC0015E for ; Mon, 24 Jul 2023 12:52:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231396AbjGXMwO (ORCPT ); Mon, 24 Jul 2023 08:52:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37908 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231248AbjGXMv0 (ORCPT ); Mon, 24 Jul 2023 08:51:26 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42F5510EB; Mon, 24 Jul 2023 05:49:27 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1629761136; Mon, 24 Jul 2023 12:49:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1EE2C433C7; Mon, 24 Jul 2023 12:49:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690202966; bh=KnBf3819XLYZd+1IcRnGIifcqO5I4WiAi+2WJjL5RP8=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=GHEEhSCjOiAopV0Dt0XrAzErX7cYYm3/SLNrI0NOL1hy+S7ZNKS9y0AxiMl8m4dXP +UjRxSbJpHdeDkYQW5gBc7xoHHqBIhMJ4XrmErqCXuA0MnlgNHJtMvrsSn5z3lCle2 8jNZRV9DvZMIWO+1AArfU+HmcQ43E+1gh6aZoIDeGzYsgYqgfEM3naeK8fSSOdFtjB Qjou0WRgxa6rSjNf+FQO56QQnOgZcGhg6Yccpaf5Kkdgr5wOIYu1Hb1JNas+t+lolh bdfhRq/ZF2YAbeK2b2kYfwWI//Pu5e98Evmhfi4Fhg3ch5SxRRc/qwIELpWLve0Jhr DZYadUqoaOlCw== From: Mark Brown Date: Mon, 24 Jul 2023 13:46:10 +0100 Subject: [PATCH v2 23/35] arm64/signal: Expose GCS state in signal frames MIME-Version: 1.0 Message-Id: <20230724-arm64-gcs-v2-23-dc2c1d44c2eb@kernel.org> References: <20230724-arm64-gcs-v2-0-dc2c1d44c2eb@kernel.org> In-Reply-To: <20230724-arm64-gcs-v2-0-dc2c1d44c2eb@kernel.org> To: 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 Cc: "H.J. Lu" , Paul Walmsley , Palmer Dabbelt , Albert Ou , 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, Mark Brown X-Mailer: b4 0.13-dev-099c9 X-Developer-Signature: v=1; a=openpgp-sha256; l=5977; i=broonie@kernel.org; h=from:subject:message-id; bh=KnBf3819XLYZd+1IcRnGIifcqO5I4WiAi+2WJjL5RP8=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBkvnKmegY3qr/fRcdQfvYRD0xDqu+y/7Y/sF1GauAD 7RYXiruJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZL5ypgAKCRAk1otyXVSH0P72B/ wLF4CRNWKc0HpvKocLcXV3VbYeXJNlhHhIfH/NEaswS6/xq4YOQOpQ0ETsQPFd97Huh3S3vSfC9PEs WS0wxeyVO3J+x9vZZtXaQXVdI4gXHBKNT+JuaSDSiIEqvNyLqDaMgiz9PKLudvlkN6QDU+LTdIcULt lQnbZSvjG0VyRBSDd01Udu4PTVyrFVlbeqJ3TfCulCiCi8UZImIpmE2ia0CK+XHHf209y7rEbjqZfg bSulNjUCeWn2U+/mOF721HihqpGwb2h4+8m/Yy4bruobhz6HplXcXe7STAujFnl86ZfOAVWtdmWBfS NA61lQOkfFNupqB04eeDDWjus0LJ5M X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add a context for the GCS state and include it in the signal context when running on a system that supports GCS. We reuse the same flags that the prctl() uses to specify which GCS features are enabled and also provide the current GCS pointer. We do not support enabling GCS via signal return, there is a conflict between specifying GCSPR_EL0 and allocation of a new GCS and this is not an ancticipated use case. We also enforce GCS configuration locking on signal return. Signed-off-by: Mark Brown --- arch/arm64/include/uapi/asm/sigcontext.h | 9 +++ arch/arm64/kernel/signal.c | 107 +++++++++++++++++++++++++++++++ 2 files changed, 116 insertions(+) diff --git a/arch/arm64/include/uapi/asm/sigcontext.h b/arch/arm64/include/uapi/asm/sigcontext.h index f23c1dc3f002..7b66d245f2d2 100644 --- a/arch/arm64/include/uapi/asm/sigcontext.h +++ b/arch/arm64/include/uapi/asm/sigcontext.h @@ -168,6 +168,15 @@ struct zt_context { __u16 __reserved[3]; }; +#define GCS_MAGIC 0x47435300 + +struct gcs_context { + struct _aarch64_ctx head; + __u64 gcspr; + __u64 features_enabled; + __u64 reserved; +}; + #endif /* !__ASSEMBLY__ */ #include diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 1c31be0f373e..4cc0c7928cb3 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -87,6 +87,7 @@ struct rt_sigframe_user_layout { unsigned long fpsimd_offset; unsigned long esr_offset; + unsigned long gcs_offset; unsigned long sve_offset; unsigned long tpidr2_offset; unsigned long za_offset; @@ -213,6 +214,8 @@ struct user_ctxs { u32 za_size; struct zt_context __user *zt; u32 zt_size; + struct gcs_context __user *gcs; + u32 gcs_size; }; static int preserve_fpsimd_context(struct fpsimd_context __user *ctx) @@ -605,6 +608,82 @@ 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; + if (task_gcs_el0_enabled(current)) + gcspr -= 8; + + __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(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; + + /* 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); + + return 0; +} + +#else /* ! CONFIG_ARM64_GCS */ + +/* Turn any non-optimised out attempts to use these into a link error: */ +extern int preserve_gcs_context(void __user *ctx); +extern int restore_gcs_context(struct user_ctxs *user); + +#endif /* ! CONFIG_ARM64_GCS */ + static int parse_user_sigframe(struct user_ctxs *user, struct rt_sigframe __user *sf) { @@ -621,6 +700,7 @@ static int parse_user_sigframe(struct user_ctxs *user, user->tpidr2 = NULL; user->za = NULL; user->zt = NULL; + user->gcs = NULL; if (!IS_ALIGNED((unsigned long)base, 16)) goto invalid; @@ -715,6 +795,17 @@ static int parse_user_sigframe(struct user_ctxs *user, user->zt_size = size; break; + case GCS_MAGIC: + if (!system_supports_gcs()) + goto invalid; + + if (user->gcs) + goto invalid; + + user->gcs = (struct gcs_context __user *)head; + user->gcs_size = size; + break; + case EXTRA_MAGIC: if (have_extra_context) goto invalid; @@ -834,6 +925,9 @@ static int restore_sigframe(struct pt_regs *regs, err = restore_fpsimd_context(&user); } + if (err == 0 && system_supports_gcs() && user.gcs) + err = restore_gcs_context(&user); + if (err == 0 && system_supports_tpidr2() && user.tpidr2) err = restore_tpidr2_context(&user); @@ -948,6 +1042,13 @@ static int setup_sigframe_layout(struct rt_sigframe_user_layout *user, return err; } + if (system_supports_gcs()) { + err = sigframe_alloc(user, &user->gcs_offset, + sizeof(struct gcs_context)); + if (err) + return err; + } + if (system_supports_sve() || system_supports_sme()) { unsigned int vq = 0; @@ -1041,6 +1142,12 @@ static int setup_sigframe(struct rt_sigframe_user_layout *user, __put_user_error(current->thread.fault_code, &esr_ctx->esr, err); } + if (system_supports_gcs() && err == 0 && user->gcs_offset) { + struct gcs_context __user *gcs_ctx = + apply_user_offset(user, user->gcs_offset); + err |= preserve_gcs_context(gcs_ctx); + } + /* Scalable Vector Extension state (including streaming), if present */ if ((system_supports_sve() || system_supports_sme()) && err == 0 && user->sve_offset) {