From patchwork Mon Apr 7 16:19:50 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeremy Linton X-Patchwork-Id: 14041361 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 94230C36010 for ; Mon, 7 Apr 2025 17:15:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=MmJI79xOX++xDBcrvPihMsLbiYiuLuD+bYY7rFVQsyw=; b=p09K0ERd1YKWUgBjEF2ILG8xRE 15Om8w6lOg5dyKDGlonEIG9af5B0gvdo16AaUx3VpG7gai+RIf+uNdz0vwZ/MTbAruRSG49NLAfmR lv3QMoA6uXs5WC76+9sIqXmMTai5itz95i/wFc+LQLcYsRLQG0J1Vr2pvAnYM5UFLNVULuQmfye5e 1Hz4c0JsnIvMrRGJVLqEAdxG0svag2ziyyS2WWMz7ndD99+DomPFXHnEVTyvNoq62rjjDxTSW8MjM m0qUVV0dWgWZ9eeDPLpR8KSC000JBusrAbKtYy16M+UmJQUvPdxkBLb1xwahCFXzUOuo5gY5hiwUC FxpKVUXQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1u1q4B-00000001LC4-0cEg; Mon, 07 Apr 2025 17:15:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1u1pCn-000000019B9-1SSh for linux-arm-kernel@lists.infradead.org; Mon, 07 Apr 2025 16:20:14 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1EAE21BF3; Mon, 7 Apr 2025 09:20:14 -0700 (PDT) Received: from u200865.usa.arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 822873F694; Mon, 7 Apr 2025 09:20:12 -0700 (PDT) From: Jeremy Linton To: linux-trace-kernel@vger.kernel.org Cc: linux-perf-users@vger.kernel.org, mhiramat@kernel.org, oleg@redhat.com, peterz@infradead.org, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, thiago.bauermann@linaro.org, broonie@kernel.org, yury.khrustalev@arm.com, kristina.martsenko@arm.com, liaochang1@huawei.com, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Jeremy Linton , Steve Capper Subject: [PATCH v2 5/6] arm64: uprobes: Add GCS support to uretprobes Date: Mon, 7 Apr 2025 11:19:50 -0500 Message-ID: <20250407161951.560865-6-jeremy.linton@arm.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250407161951.560865-1-jeremy.linton@arm.com> References: <20250407161951.560865-1-jeremy.linton@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250407_092013_417989_36FA97D1 X-CRM114-Status: GOOD ( 15.85 ) 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 Ret probes work by changing the value in the link register at the probe location to return to the probe rather than the calling routine. Thus the GCS needs to be updated with this address as well. Since its possible to insert probes at locations where the current value of the LR doesn't match the GCS state this needs to be detected and handled in order to maintain the existing no-fault behavior. Co-developed-by: Steve Capper Signed-off-by: Steve Capper (updated to use new gcs accessors, and handle LR/GCS mismatches) Signed-off-by: Jeremy Linton --- arch/arm64/kernel/probes/uprobes.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/arch/arm64/kernel/probes/uprobes.c b/arch/arm64/kernel/probes/uprobes.c index cb3d05af36e3..5e72409a255a 100644 --- a/arch/arm64/kernel/probes/uprobes.c +++ b/arch/arm64/kernel/probes/uprobes.c @@ -159,11 +159,41 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs) { unsigned long orig_ret_vaddr; + unsigned long gcs_ret_vaddr; + int err = 0; + u64 gcspr; orig_ret_vaddr = procedure_link_pointer(regs); + + if (task_gcs_el0_enabled(current)) { + gcspr = read_sysreg_s(SYS_GCSPR_EL0); + gcs_ret_vaddr = load_user_gcs((unsigned long __user *)gcspr, &err); + if (err) { + force_sig(SIGSEGV); + goto out; + } + /* + * If the LR and GCS entry don't match, then some kind of PAC/control + * flow happened. Likely because the user is attempting to retprobe + * on something that isn't a function boundary or inside a leaf + * function. Explicitly abort this retprobe because it will generate + * a GCS exception. + */ + if (gcs_ret_vaddr != orig_ret_vaddr) { + orig_ret_vaddr = -1; + goto out; + } + put_user_gcs(trampoline_vaddr, (unsigned long __user *) gcspr, &err); + if (err) { + force_sig(SIGSEGV); + goto out; + } + } + /* Replace the return addr with trampoline addr */ procedure_link_pointer_set(regs, trampoline_vaddr); +out: return orig_ret_vaddr; }