From patchwork Mon Feb 13 04:53:42 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Deepak Gupta X-Patchwork-Id: 13137870 X-Patchwork-Delegate: palmer@dabbelt.com 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 C95A9C64EC7 for ; Mon, 13 Feb 2023 04:54:47 +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:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=2ebUDzgdtDve5sAUG96J5Ua4555U+cNCyu/aTSVa0XM=; b=vllEMGp/YG+cjD XZV+YAl+4oNBcEsoopWob/Qw1abmhsb37ObgvfYKdvdTUBYsoxT+VulVI7KJyrI6sRJXshA8Q8Zy5 InrP0tYVc3U8oUu/X8swE3vDrDQYcfrGxNX0uJ0DG6Ru35UofYbeaDTZb0oRpiQ9OOqyD5d2LM890 VTTDxOUP6QAoiAH53Vt2ixUH3jnC9haSs8QvuVS9MIX0z2D7pjSujc4CzFE9aLgwh7DKwgXpI4Lbj ZvP/GktlCWsifIVcm+mHl9VtxTuXEU+U/01CJbeRpHh7vAE7lYsPNRVxCMY+tlpcULl8S82xA7syN 5A1s3wBc75IlCgiiazkQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pRQrP-00D9e8-7W; Mon, 13 Feb 2023 04:54:39 +0000 Received: from mail-pj1-x1035.google.com ([2607:f8b0:4864:20::1035]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pRQr8-00D9RG-Gk for linux-riscv@lists.infradead.org; Mon, 13 Feb 2023 04:54:24 +0000 Received: by mail-pj1-x1035.google.com with SMTP id mg23so4213015pjb.0 for ; Sun, 12 Feb 2023 20:54:21 -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=ZvCdo+mxIysO24LAIuv6Q8lUy89KKrcbgudJsang1gvN3vGudPaf3LlzkN0ubea7G7 4kcz552T5hk4BEC4jmr/brDUrXLYiirnhrMpyHs413NXQqXmi5gOD3fbZ+uj6mPA+sgV 3vDVxQ7mnMot29hlO3EiAC2tMVhgRWtMFQ+WXgOpVQpQlyW/qXrwZjVHh3AvJTuwaa96 kiUxswIsp9BfEwMZ/tD9mOwxa0Vy4C/cnqfcb4rk1yULCvLbUpAxtXsS126VTmTmgOuU nydfWmeXAvzpEblFGjPT/lo93jKs0qDTHEHTwVuDYFVC4J7rnT/tsFX+VW8hRL89nyuF TxWg== X-Gm-Message-State: AO0yUKUifiGmNKsUeAEOIINViuNSmf/F+XQGs0DLtEBbKucYUGegaA5Q 4MfEOlR65FyeAgIUOnSfDNmS4g== 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230212_205423_199607_51BE2671 X-CRM114-Status: GOOD ( 15.01 ) X-BeenThere: linux-riscv@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-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org 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 signo, 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 bool is_ss_load_store_insn(unsigned long insn) { @@ -112,6 +116,71 @@ bool is_ss_load_store_insn(unsigned long insn) return false; } +bool is_cfi_violation_insn(unsigned long insn) +{ + struct task_struct *task = current; + bool ss_exist = false, lp_exist = false; + + ss_exist = arch_supports_shadow_stack(); + lp_exist = arch_supports_indirect_br_lp_instr(); + + if (ss_exist && (insn == SS_CHECKRA)) { + pr_warn("cfi violation (sschkra): comm = %s, task = %p\n", task->comm, task); + return true; + } + if (lp_exist && ((insn & LP_C_LL) == LP_C_LL)) { + pr_warn("cfi violation (lpcll): comm = %s, task = %p\n", task->comm, task); + return true; + } + if (lp_exist && ((insn & LP_C_ML) == LP_C_ML)) { + pr_warn("cfi violation (lpcml): comm = %s, task = %p\n", task->comm, task); + return true; + } + if (lp_exist && ((insn & LP_C_UL) == LP_C_UL)) { + pr_warn("cfi violation (lpcul): comm = %s, task = %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 = csr_read(stval); + struct thread_info *info = NULL; + struct task_struct *task = current; + + info = current_thread_info(); + /* + * If CFI enabled then following instructions leads to illegal instruction fault + * -- sscheckra: x1 and x5 mismatch + * -- ELP = 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 = 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 = %s, task = %p\n", task->comm, task); + regs->status &= ~(SR_ELP); + return 0; + } + /* if faulting opcode is sscheckra/lpcll/lpcml/lpcll, advance PC and resume */ + if (is_cfi_violation_insn(insn)) { + /* no compressed form for zisslpcfi instructions */ + regs->epc += 4; + return 0; + } + + return 1; +} + ulong get_instruction(ulong epc) { ulong *epc_ptr = (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) {