From patchwork Mon Oct 9 12:08:59 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Brown X-Patchwork-Id: 13413569 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D3D18E95A8E for ; Mon, 9 Oct 2023 12:14:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:In-Reply-To:References:Message-Id :MIME-Version:Subject:Date:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=0qwZp8D6efnrZ5VvpdYYsh2YTBq0vXukysYsG4CFMqA=; b=EnejRbmuG5wu4g IREkJkVcX1c/zOJkw/rvGLNfDLPVTn5Mrh/+t1HZccHVG2LQWDZ+tL5BYnU+Ho5NTCCrEVL0/MBi8 kzt/I3UE4KJylSKByngLedDVmI0xNdPj+4G6+Gtpso+rqkrN7m5Ym9o9OE4qlHYeD/LslGANupxBC 8FSPxVYzXLj4gMkLgNCvEVWEFNBXJoTvhIazJIqeXjuO3mfHT4p9uHyIVVw4zb2dRIyzPVQHMXXZo uTb3eLJGG2LkS3bF1DXKjPJqZNStD28Ah6szqp8jz4jaQebuGIJ2bdEy/NDKCfDhHt2DETRkztF1Y Tg+HhgfttyLlo3XsjXwg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qpp95-00AcJp-1i; Mon, 09 Oct 2023 12:13:59 +0000 Received: from sin.source.kernel.org ([145.40.73.55]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qpp8i-00Abto-1t; Mon, 09 Oct 2023 12:13:45 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 31606CE138E; Mon, 9 Oct 2023 12:13:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 311A8C433CC; Mon, 9 Oct 2023 12:13:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1696853613; bh=oHAoMyZjF9g9W2qKAKfFFNVap7j750I1wK7h+SBfGKM=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=dbFRHIfXZnNmV0GH5mjjdcc6Eh0Gm4wTq9OxEWlA02XoukvIMRIthKMA2I63zY/h6 6tT5YzG8dxbZJZKo2nKCwjWLQWTt6E7AoPtUTSy/F1DApuRQ/xbD4e49FvMJfXEpsN pQcRRpbwnzrCBJe20eimpKNVtm/F2z+eeYgynXCY0Yvsj/Q3IWT+5U87czLxfpLEmg nZrWB6rZ62DnIkzuRn+buRggc4ooI8AjdbFmSLK4UKwZR/R58tPy0NXKNv7ezQJpLD lBCgtC9GoXNZq6CwnyDLuuknasB2f7GAA0GhssVQudFnrNzCzr1p6RrrwqypwD6hqG YZ6pVU4TAV8Gw== From: Mark Brown Date: Mon, 09 Oct 2023 13:08:59 +0100 Subject: [PATCH v6 25/38] arm64/signal: Expose GCS state in signal frames MIME-Version: 1.0 Message-Id: <20231009-arm64-gcs-v6-25-78e55deaa4dd@kernel.org> References: <20231009-arm64-gcs-v6-0-78e55deaa4dd@kernel.org> In-Reply-To: <20231009-arm64-gcs-v6-0-78e55deaa4dd@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 , 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, Mark Brown X-Mailer: b4 0.13-dev-0438c X-Developer-Signature: v=1; a=openpgp-sha256; l=5977; i=broonie@kernel.org; h=from:subject:message-id; bh=oHAoMyZjF9g9W2qKAKfFFNVap7j750I1wK7h+SBfGKM=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBlI+2lYDlBWkksdW7TGIp9zwyG9iHJp9RWtj6d3SbY 3m5qMeiJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZSPtpQAKCRAk1otyXVSH0JHPB/ 90gi84qQbtQc2C9jFLZZVlToEfYki5x2CovH76V02l+VZfQqBb/+Ad2dHSY36ROJJ/ekkoDLIgsfRh EGCSmcFXvM084X5xmF40OpBuEjDDsLHndMlD/qEBJnvGXU9Nq6lWkDDIqzVM15dA7ond0LsOhOacai NVxWsDuYwbFt/g8QdVgWxFCqHVRtHdTsRgmCvfzaZeTCwqjETwLNw5wUUursINPs06ns0KHVTq0VXa GaCs4r+m8PrTdFo9OKuw0P0E/kKW8+gjLnG4Zlcl0zQBaWY6DHWEYf1bnl6qcIH3TJPJDwRv2pi38V YWns1T6is4pOsuplsB6xcj0ScKvDLU X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231009_051337_033210_5A5366E9 X-CRM114-Status: GOOD ( 21.01 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 97004c52aea3..78370cf9576a 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) {