From patchwork Fri Jun 17 18:02:18 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Madhavan T. Venkataraman" X-Patchwork-Id: 12885879 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 3026DC433EF for ; Fri, 17 Jun 2022 18:04:51 +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:To:From:Reply-To:Cc:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=GzorDITAt9dG9f0e5t8ZzSjU8123jrPG0wIX/raysdU=; b=iX/AcX+pDbaVlp fc3YD75kMvJCOorfk9PAkoeB3Pqq2KDME8j3dU0rrc76FimLiOScQ3FxIvhT+IrjnNiGraJcvnubO R3M1yDdoZJNFQK1UDRo/M83XAu0U66LrhQQs+VzVfGpWK4l+Sy7ksYLvY24nNV42vnbkhdR8iwd7U P4z3tIj0suoz7Cxk0s0+oBmeSeWrPAj2pKO8jiXUppSGoN0aNJmYoTVubUx8jmjxiAb4K/lPHKh3x iUvYxwsnrIhGof44fX8kcdSt8MMUiIKYhYRNqH84Gd8ijcGa9sdCc7xJ9tKXoYhIqheCEkdZsviy0 8xX+wnSenP5u5Hz4SpYQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o2GJx-008YP2-T4; Fri, 17 Jun 2022 18:03:49 +0000 Received: from linux.microsoft.com ([13.77.154.182]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o2GIv-008Y1b-HJ for linux-arm-kernel@lists.infradead.org; Fri, 17 Jun 2022 18:02:48 +0000 Received: from x64host.home (unknown [47.189.24.195]) by linux.microsoft.com (Postfix) with ESMTPSA id 3189D20C3497; Fri, 17 Jun 2022 11:02:34 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 3189D20C3497 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1655488955; bh=rIRHg9h9dL7P6AtbbpVArTGj3H2jde9z184QDNjMMj4=; h=From:To:Subject:Date:In-Reply-To:References:From; b=kEzyFe/5FapiAAU/JHRWRS34dBuX4CEXuvGcd/o6Dv+tgg+cY6/Pm3McxdLxEpKUG C5ASdPKGiKTsjrBf2J7y99E6+WfAtL+/qTB3a4wG5/QMWJhiGtgdLRwxKDBW1MsBFF ZQFnqKVFtgZzCni31Rp4ZTi52xePkLOS1f4frMOo= From: madvenka@linux.microsoft.com To: broonie@kernel.org, mark.rutland@arm.com, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jamorris@linux.microsoft.com, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, madvenka@linux.microsoft.com Subject: [RFC PATCH v15 5/6] arm64: Create a list of SYM_CODE functions, check return PC against list Date: Fri, 17 Jun 2022 13:02:18 -0500 Message-Id: <20220617180219.20352-6-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220617180219.20352-1-madvenka@linux.microsoft.com> References: <20220617180219.20352-1-madvenka@linux.microsoft.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220617_110245_671683_BBB08F2D X-CRM114-Status: GOOD ( 19.16 ) 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 From: "Madhavan T. Venkataraman" SYM_CODE functions don't follow the usual calling conventions. Check if the return PC in a stack frame falls in any of these. If it does, consider the stack trace unreliable. Define a special section for unreliable functions ================================================= Define a SYM_CODE_END() macro for arm64 that adds the function address range to a new section called "sym_code_functions". Linker file =========== Include the "sym_code_functions" section under read-only data in vmlinux.lds.S. Initialization ============== Define an early_initcall() to create a sym_code_functions[] array from the linker data. Unwinder check ============== Add a reliability check in unwind_check_reliability() that compares a return PC with sym_code_functions[]. If there is a match, then return failure. Signed-off-by: Madhavan T. Venkataraman Reviewed-by: Mark Brown --- arch/arm64/include/asm/linkage.h | 11 +++++++ arch/arm64/include/asm/sections.h | 1 + arch/arm64/kernel/stacktrace.c | 55 +++++++++++++++++++++++++++++++ arch/arm64/kernel/vmlinux.lds.S | 10 ++++++ 4 files changed, 77 insertions(+) diff --git a/arch/arm64/include/asm/linkage.h b/arch/arm64/include/asm/linkage.h index 43f8c25b3fda..d4058de4af78 100644 --- a/arch/arm64/include/asm/linkage.h +++ b/arch/arm64/include/asm/linkage.h @@ -39,4 +39,15 @@ SYM_START(name, SYM_L_WEAK, SYM_A_NONE) \ bti c ; +/* + * Record the address range of each SYM_CODE function in a struct code_range + * in a special section. + */ +#define SYM_CODE_END(name) \ + SYM_END(name, SYM_T_NONE) ;\ +99: .pushsection "sym_code_functions", "aw" ;\ + .quad name ;\ + .quad 99b ;\ + .popsection + #endif diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h index 40971ac1303f..50cfd1083563 100644 --- a/arch/arm64/include/asm/sections.h +++ b/arch/arm64/include/asm/sections.h @@ -22,6 +22,7 @@ extern char __irqentry_text_start[], __irqentry_text_end[]; extern char __mmuoff_data_start[], __mmuoff_data_end[]; extern char __entry_tramp_text_start[], __entry_tramp_text_end[]; extern char __relocate_new_kernel_start[], __relocate_new_kernel_end[]; +extern char __sym_code_functions_start[], __sym_code_functions_end[]; static inline size_t entry_tramp_text_size(void) { diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 5ef2ce217324..eda8581f7dbe 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -62,6 +62,31 @@ struct unwind_state { bool reliable; }; +struct code_range { + unsigned long start; + unsigned long end; +}; + +static struct code_range *sym_code_functions; +static int num_sym_code_functions; + +int __init init_sym_code_functions(void) +{ + size_t size = (unsigned long)__sym_code_functions_end - + (unsigned long)__sym_code_functions_start; + + sym_code_functions = (struct code_range *)__sym_code_functions_start; + /* + * Order it so that sym_code_functions is not visible before + * num_sym_code_functions. + */ + smp_mb(); + num_sym_code_functions = size / sizeof(struct code_range); + + return 0; +} +early_initcall(init_sym_code_functions); + static void unwind_init_common(struct unwind_state *state, struct task_struct *task) { @@ -251,6 +276,10 @@ NOKPROBE_SYMBOL(unwind_next); */ static void unwind_check_reliability(struct unwind_state *state) { + const struct code_range *range; + unsigned long pc; + int i; + if (state->fp == state->final_fp) { /* Final frame; no more unwind, no need to check reliability */ return; @@ -263,6 +292,32 @@ static void unwind_check_reliability(struct unwind_state *state) */ if (!__kernel_text_address(state->pc)) state->reliable = false; + + /* + * Check the return PC against sym_code_functions[]. If there is a + * match, then the consider the stack frame unreliable. + * + * As SYM_CODE functions don't follow the usual calling conventions, + * we assume by default that any SYM_CODE function cannot be unwound + * reliably. + * + * Note that this includes: + * + * - Exception handlers and entry assembly + * - Trampoline assembly (e.g., ftrace, kprobes) + * - Hypervisor-related assembly + * - Hibernation-related assembly + * - CPU start-stop, suspend-resume assembly + * - Kernel relocation assembly + */ + pc = state->pc; + for (i = 0; i < num_sym_code_functions; i++) { + range = &sym_code_functions[i]; + if (pc >= range->start && pc < range->end) { + state->reliable = false; + return; + } + } } static bool notrace unwind(struct unwind_state *state, diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 2d4a8f995175..414dbc82d0a6 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -120,6 +120,14 @@ jiffies = jiffies_64; #define TRAMP_TEXT #endif +#define SYM_CODE_FUNCTIONS \ + . = ALIGN(16); \ + .symcode : AT(ADDR(.symcode) - LOAD_OFFSET) { \ + __sym_code_functions_start = .; \ + KEEP(*(sym_code_functions)) \ + __sym_code_functions_end = .; \ + } + /* * The size of the PE/COFF section that covers the kernel image, which * runs from _stext to _edata, must be a round multiple of the PE/COFF @@ -212,6 +220,8 @@ SECTIONS swapper_pg_dir = .; . += PAGE_SIZE; + SYM_CODE_FUNCTIONS + . = ALIGN(SEGMENT_ALIGN); __init_begin = .; __inittext_begin = .;