From nobody Fri Sep 12 08:42:39 2025 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 AC343C636D7 for ; Mon, 13 Feb 2023 04:55:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229921AbjBMEzY (ORCPT ); Sun, 12 Feb 2023 23:55:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51960 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229837AbjBMEy4 (ORCPT ); Sun, 12 Feb 2023 23:54:56 -0500 Received: from mail-pl1-x62c.google.com (mail-pl1-x62c.google.com [IPv6:2607:f8b0:4864:20::62c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AE77C10ABB for ; Sun, 12 Feb 2023 20:54:27 -0800 (PST) Received: by mail-pl1-x62c.google.com with SMTP id z1so12288729plg.6 for ; Sun, 12 Feb 2023 20:54:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Jzh1F9dWgL9z5qWHfkyPDeO9BiBZZOuMNa7E/NQMYRA=; b=hBAMguZTqz8mBO0i9eURw5EVnyTRjZI/TA0b+TvPmhimWAwoztTflfei++MGWOOhhp y9UQAG+6WEpmcozlhgFWPCfcNQEzazPzUc/BX/nwlV3/TfGY4oELgmwTzmcXbl8+8cLl YEyUj++v3tAMb1ug4pKO06rWe166GtjQy4/L6hNDTIxwdYO6Ph9pApQUVXelympLBY5P P2ApcmLSjc979qayu5Jclp/xPesWV0Ux6A2gskrj7yI7PMJAnA8Rupt6ysIl/wy30dGv MavO85rbflXHbv+JQi0NDSiLwIMFGmpAvYbubygtTeUtBxtynv9lE2AP/U0geTFdg9Iz T4Jw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Jzh1F9dWgL9z5qWHfkyPDeO9BiBZZOuMNa7E/NQMYRA=; b=Vjw6KVIDzXdfs6XW+RI8ui3/esW/dYhsM2No1Yr+tHwrGcJysCNpfVOy73Ro0jiVmu 6h3keYVxBMuaFg8AuDzfkFcttj37EpckeFwc5laO62k5UMsEqPqILJmm1TxFPmgR0o6Y JLaQNTOdx1P9hzCAGbhmi/CifQisid8eeIzb7J4ygkWu/HRVOWCAgQhxYsSZGc0tVj4x pjlFCYDzyuLZOfrmCc0CG04ktCcXQJe2MQNL0zbQw5yO1xVzBg47gQvUYcoodhB5q15a mUVA8pNNMgics4oFtjF9P3HhXBovp/x+OC9NUguxbb2JqUowxXn8lcz62CWdKj3FOBLd Njag== X-Gm-Message-State: AO0yUKUsPZ5yM1bwve8EAHeJP4mKXmB2+XtP5hQgW9IPu9ywERyx/4RN Y7jEewxftEddZgPureS3zuzwuf1wUNrdrN/8 X-Google-Smtp-Source: AK7set/ieVh7qhs04S/uXJn79ItEgAaNBhP4tICRnJOHZZuCn+oguG49FVAuZKnOk1MHnr6vz9IICA== X-Received: by 2002:a17:902:e40d:b0:19a:a2f3:e41c with SMTP id m13-20020a170902e40d00b0019aa2f3e41cmr1350325ple.35.1676264061243; Sun, 12 Feb 2023 20:54:21 -0800 (PST) Received: from debug.ba.rivosinc.com ([66.220.2.162]) by smtp.gmail.com with ESMTPSA id e5-20020a170902784500b00189e7cb8b89sm7078303pln.127.2023.02.12.20.54.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Feb 2023 20:54:20 -0800 (PST) From: Deepak Gupta To: linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: Deepak Gupta Subject: [PATCH v1 RFC Zisslpcfi 13/20] riscv: illegal instruction handler for cfi violations Date: Sun, 12 Feb 2023 20:53:42 -0800 Message-Id: <20230213045351.3945824-14-debug@rivosinc.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230213045351.3945824-1-debug@rivosinc.com> References: <20230213045351.3945824-1-debug@rivosinc.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Zisslpcfi spec proposes that cfi violations are reported as illegal instruction exception. Following are the cases - elp missing: An indirect jmp/call landed on instruction which is not `lpcll` - label mismatch: Static label embedded in instr `lpcll/lpcml/lpcul` doesn't match with repsective label in CSR_LPLR - sscheckra: x1 and x5 don't match. Current changes run user code in audit mode. That means that any cfi violation is suppressed and app is allowed to continue. Signed-off-by: Deepak Gupta --- arch/riscv/kernel/traps.c | 79 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 77 insertions(+), 2 deletions(-) diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 5553b8d48ba5..a292699f4f25 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -97,6 +97,10 @@ static void do_trap_error(struct pt_regs *regs, int sign= o, int code, /* Zisslpcfi instructions encodings */ #define SS_PUSH_POP 0x81C04073 #define SS_AMOSWAP 0x82004073 +#define SS_CHECKRA 0x8A12C073 +#define LP_C_LL 0x83004073 +#define LP_C_ML 0x86804073 +#define LP_C_UL 0x8B804073 =20 bool is_ss_load_store_insn(unsigned long insn) { @@ -112,6 +116,71 @@ bool is_ss_load_store_insn(unsigned long insn) return false; } =20 +bool is_cfi_violation_insn(unsigned long insn) +{ + struct task_struct *task =3D current; + bool ss_exist =3D false, lp_exist =3D false; + + ss_exist =3D arch_supports_shadow_stack(); + lp_exist =3D arch_supports_indirect_br_lp_instr(); + + if (ss_exist && (insn =3D=3D SS_CHECKRA)) { + pr_warn("cfi violation (sschkra): comm =3D %s, task =3D %p\n", task->com= m, task); + return true; + } + if (lp_exist && ((insn & LP_C_LL) =3D=3D LP_C_LL)) { + pr_warn("cfi violation (lpcll): comm =3D %s, task =3D %p\n", task->comm,= task); + return true; + } + if (lp_exist && ((insn & LP_C_ML) =3D=3D LP_C_ML)) { + pr_warn("cfi violation (lpcml): comm =3D %s, task =3D %p\n", task->comm,= task); + return true; + } + if (lp_exist && ((insn & LP_C_UL) =3D=3D LP_C_UL)) { + pr_warn("cfi violation (lpcul): comm =3D %s, task =3D %p\n", task->comm,= task); + return true; + } + + return false; +} + +int handle_illegal_instruction(struct pt_regs *regs) +{ + /* stval should hold faulting opcode */ + unsigned long insn =3D csr_read(stval); + struct thread_info *info =3D NULL; + struct task_struct *task =3D current; + + info =3D current_thread_info(); + /* + * If CFI enabled then following instructions leads to illegal instructio= n fault + * -- sscheckra: x1 and x5 mismatch + * -- ELP =3D 1, Any instruction other than lpcll will fault + * -- lpcll will fault if lower label don't match with LPLR.LL + * -- lpcml will fault if lower label don't match with LPLR.ML + * -- lpcul will fault if lower label don't match with LPLR.UL + */ + + /* If fcfi enabled and ELP =3D 1, suppress ELP (audit mode) and resume = */ + if (arch_supports_indirect_br_lp_instr() && +#ifdef CONFIG_USER_INDIRECT_BR_LP + info->user_cfi_state.ufcfi_en && +#endif + (regs->status & SR_ELP)) { + pr_warn("cfi violation (elp): comm =3D %s, task =3D %p\n", task->comm, t= ask); + regs->status &=3D ~(SR_ELP); + return 0; + } + /* if faulting opcode is sscheckra/lpcll/lpcml/lpcll, advance PC and resu= me */ + if (is_cfi_violation_insn(insn)) { + /* no compressed form for zisslpcfi instructions */ + regs->epc +=3D 4; + return 0; + } + + return 1; +} + ulong get_instruction(ulong epc) { ulong *epc_ptr =3D (ulong *) epc; @@ -190,8 +259,14 @@ DO_ERROR_INFO(do_trap_insn_misaligned, SIGBUS, BUS_ADRALN, "instruction address misaligned"); DO_ERROR_INFO(do_trap_insn_fault, SIGSEGV, SEGV_ACCERR, "instruction access fault"); -DO_ERROR_INFO(do_trap_insn_illegal, - SIGILL, ILL_ILLOPC, "illegal instruction"); + +asmlinkage void __trap_section do_trap_insn_illegal(struct pt_regs *regs) +{ + if (!handle_illegal_instruction(regs)) + return; + do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->epc, + "illegal instruction"); +} #ifdef CONFIG_USER_SHADOW_STACK asmlinkage void __trap_section do_trap_load_fault(struct pt_regs *regs) { --=20 2.25.1