From mboxrd@z Thu Jan 1 00:00:00 1970 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 EFD9EC43334 for ; Sun, 26 Jun 2022 08:48:26 +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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Ft+SuKnhjVlZfIE230HEfK4x/WjZe8luCkWiEvV0pdY=; b=rWlRgBDuwHNdOl jEZdWqvywLipMwE8JfYCnQaRqFXS6t0Ok0BvidMO7ZOWGokkhlgejc35hmSjN4v9MDNoIzq5u28Bf +hfOoFHaDnb3/goSMHU5LF0m/79QntdLTIhUChEiez9UtEBrGEkhyqUoLGSSlYbacpFaKQIJCvXSq 8US6yxOKAO4/+XNZvPajgJJ7IIbfQyltLL3uDPg05liaA8KzqnsJT94hYilanfRPg9mRJxlPdFWoB 51/SIem984me0GdoYsAH1PWMvwN8tKkBYLZ7MMHTQ3DvJUUMnaWErDfEg2ezLwNi1cBDldVqnlub3 9Xm3joO+inWLdkQVMUEg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o5Nv8-00AhXa-D2; Sun, 26 Jun 2022 08:47:06 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1o5Nv4-00AhVa-Lh for linux-arm-kernel@lists.infradead.org; Sun, 26 Jun 2022 08:47:05 +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 67358D6E; Sun, 26 Jun 2022 01:46:59 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.71.61]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5F3CD3F792; Sun, 26 Jun 2022 01:46:57 -0700 (PDT) Date: Sun, 26 Jun 2022 09:46:53 +0100 From: Mark Rutland To: madvenka@linux.microsoft.com Cc: broonie@kernel.org, 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 Subject: Re: [PATCH v15 5/6] arm64: Create a list of SYM_CODE functions, check return PC against list Message-ID: References: <20220617210717.27126-1-madvenka@linux.microsoft.com> <20220617210717.27126-6-madvenka@linux.microsoft.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220617210717.27126-6-madvenka@linux.microsoft.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220626_014702_853771_F96CE840 X-CRM114-Status: GOOD ( 33.95 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Jun 17, 2022 at 04:07:16PM -0500, madvenka@linux.microsoft.com wrote: > 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); There's no reason to need an initcall for this; we can iterate over this directly using __sym_code_functions_start and __sym_code_functions_end, like we do for exception tables today. For example: static inline bool pc_is_sym_code(unsigned long pc) { extern struct code_range *__sym_code_functions_start; extern struct code_range *__sym_code_functions_end; struct code_range *r; for (r = __sym_code_functions_start; r < __sym_code_functions_end; r++) { if (pc >= r->start && pc < r->end) return true; } return false; } Thanks, Mark. > + > 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 = .; > -- > 2.25.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel