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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2420DC43331 for ; Tue, 24 Mar 2020 16:12:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E15B2208DB for ; Tue, 24 Mar 2020 16:12:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="JpkVCL0+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728865AbgCXQMX (ORCPT ); Tue, 24 Mar 2020 12:12:23 -0400 Received: from merlin.infradead.org ([205.233.59.134]:36984 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728506AbgCXQLh (ORCPT ); Tue, 24 Mar 2020 12:11:37 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-Id:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=6YoF6lOc7lq8HzssHakGnaDRnQUZuv12iEDQuZw5FxU=; b=JpkVCL0+VrR88/28J43umZphQu BJDJG74hlxR9rf6JyuF4E/b96DKO9fYjaexpT0qoYAR5qMUrAmoXWjakJSRznPzsG1Fqe3zIhGTYO Du7ELRBGC6VrMIMlmBpy8Sw8dj88LRVbCxWSStgHvIIU/89i+q7cse+919dHowOsHFFO/7q3bm8Ow dj8rmo+StRu4Py4chjSgsH5rrTFS+w0jAArbTfUjXWDhMH1k7PbhTkI8YcfTOFsUvfluynJlwxvKs U6/M+2zMuXp95xEwo98c0gY8Z/s09DNf/5YLsGhLViKoFVB8MFzRmzhqHtckq+zsXYh1AU+7yb1pr Vg9Ilqeg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jGm9M-0006c0-U7; Tue, 24 Mar 2020 16:11:33 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 649D830743D; Tue, 24 Mar 2020 17:11:28 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 5863729A490F5; Tue, 24 Mar 2020 17:11:28 +0100 (CET) Message-Id: <20200324160925.047300866@infradead.org> User-Agent: quilt/0.65 Date: Tue, 24 Mar 2020 16:31:32 +0100 From: Peter Zijlstra To: tglx@linutronix.de, jpoimboe@redhat.com Cc: linux-kernel@vger.kernel.org, x86@kernel.org, peterz@infradead.org, mhiramat@kernel.org, mbenes@suse.cz, brgerst@gmail.com Subject: [PATCH v3 19/26] objtool: Implement noinstr validation References: <20200324153113.098167666@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Validate that any call out of .noinstr.text is in between instr_begin() and instr_end() annotations. This annotation is useful to ensure correct behaviour wrt tracing sensitive code like entry/exit and idle code. When we run code in a sensitive context we want a guarantee no unknown code is ran. Since this validation relies on knowing the section of call destination symbols, we must run it on vmlinux.o instead of on individual object files. Add two options: -d/--duplicate "duplicate validation for vmlinux" -l/--vmlinux "vmlinux.o validation" Where the latter auto-detects when objname ends with "vmlinux.o" and the former will force all validations, also those already done on !vmlinux object files. Signed-off-by: Peter Zijlstra (Intel) --- tools/objtool/builtin-check.c | 11 +++- tools/objtool/builtin.h | 2 tools/objtool/check.c | 97 ++++++++++++++++++++++++++++++++++++++++++ tools/objtool/check.h | 3 + tools/objtool/elf.h | 2 5 files changed, 111 insertions(+), 4 deletions(-) --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -14,10 +14,11 @@ */ #include +#include #include "builtin.h" #include "check.h" -bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats; +bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux; static const char * const check_usage[] = { "objtool check [] file.o", @@ -32,12 +33,14 @@ const struct option check_options[] = { OPT_BOOLEAN('b', "backtrace", &backtrace, "unwind on error"), OPT_BOOLEAN('a', "uaccess", &uaccess, "enable uaccess checking"), OPT_BOOLEAN('s', "stats", &stats, "print statistics"), + OPT_BOOLEAN('d', "duplicate", &validate_dup, "duplicate validation for vmlinux.o"), + OPT_BOOLEAN('l', "vmlinux", &vmlinux, "vmlinux.o validation"), OPT_END(), }; int cmd_check(int argc, const char **argv) { - const char *objname; + const char *objname, *s; argc = parse_options(argc, argv, check_options, check_usage, 0); @@ -46,5 +49,9 @@ int cmd_check(int argc, const char **arg objname = argv[0]; + s = strstr(objname, "vmlinux.o"); + if (s && !s[9]) + vmlinux = true; + return check(objname, false); } --- a/tools/objtool/builtin.h +++ b/tools/objtool/builtin.h @@ -8,7 +8,7 @@ #include extern const struct option check_options[]; -extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats; +extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux; extern int cmd_check(int argc, const char **argv); extern int cmd_orc(int argc, const char **argv); --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -252,6 +252,9 @@ static int decode_instructions(struct ob strncmp(sec->name, ".discard.", 9)) sec->text = true; + if (!strcmp(sec->name, ".noinstr.text")) + sec->noinstr = true; + for (offset = 0; offset < sec->len; offset += insn->len) { insn = malloc(sizeof(*insn)); if (!insn) { @@ -1350,6 +1353,53 @@ static int read_retpoline_hints(struct o return 0; } +static int read_instr_hints(struct objtool_file *file) +{ + struct section *sec; + struct instruction *insn; + struct rela *rela; + + sec = find_section_by_name(file->elf, ".rela.discard.instr_end"); + if (!sec) + return 0; + + list_for_each_entry(rela, &sec->rela_list, list) { + if (rela->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", sec->name); + return -1; + } + + insn = find_insn(file, rela->sym->sec, rela->addend); + if (!insn) { + WARN("bad .discard.instr_end entry"); + return -1; + } + + insn->instr--; + } + + sec = find_section_by_name(file->elf, ".rela.discard.instr_begin"); + if (!sec) + return 0; + + list_for_each_entry(rela, &sec->rela_list, list) { + if (rela->sym->type != STT_SECTION) { + WARN("unexpected relocation symbol type in %s", sec->name); + return -1; + } + + insn = find_insn(file, rela->sym->sec, rela->addend); + if (!insn) { + WARN("bad .discard.instr_begin entry"); + return -1; + } + + insn->instr++; + } + + return 0; +} + static void mark_rodata(struct objtool_file *file) { struct section *sec; @@ -1421,6 +1471,10 @@ static int decode_sections(struct objtoo if (ret) return ret; + ret = read_instr_hints(file); + if (ret) + return ret; + return 0; } @@ -1972,6 +2026,13 @@ static inline const char *call_dest_name static int validate_call(struct instruction *insn, struct insn_state *state) { + if (state->noinstr && state->instr <= 0 && + (!insn->call_dest || insn->call_dest->sec != insn->sec)) { + WARN_FUNC("call to %s() leaves .noinstr.text section", + insn->sec, insn->offset, call_dest_name(insn)); + return 1; + } + if (state->uaccess && !func_uaccess_safe(insn->call_dest)) { WARN_FUNC("call to %s() with UACCESS enabled", insn->sec, insn->offset, call_dest_name(insn)); @@ -2000,6 +2061,12 @@ static int validate_sibling_call(struct static int validate_return(struct symbol *func, struct instruction *insn, struct insn_state *state) { + if (state->noinstr && state->instr > 0) { + WARN_FUNC("return with instrumentation enabled", + insn->sec, insn->offset); + return 1; + } + if (state->uaccess && !func_uaccess_safe(func)) { WARN_FUNC("return with UACCESS enabled", insn->sec, insn->offset); @@ -2082,6 +2149,8 @@ static int apply_insn_hint(struct objtoo state->df = old.df; state->uaccess = old.uaccess; state->uaccess_stack = old.uaccess_stack; + state->noinstr = old.noinstr; + state->instr = old.instr; return 0; } @@ -2444,6 +2513,14 @@ static int validate_section(struct objto CFI_NUM_REGS * sizeof(struct cfi_reg)); state.stack_size = initial_func_cfi.cfa.offset; + /* + * We need the full vmlinux for noinstr validation, otherwise we can + * not correctly determine insn->call_dest->sec (external symbols do + * not have a section). + */ + if (vmlinux) + state.noinstr = sec->noinstr; + list_for_each_entry(func, &sec->symbol_list, list) { if (func->type != STT_FUNC) continue; @@ -2472,6 +2549,17 @@ static int validate_section(struct objto return warnings; } +static int validate_vmlinux_functions(struct objtool_file *file) +{ + struct section *sec; + + sec = find_section_by_name(file->elf, ".noinstr.text"); + if (!sec) + return 0; + + return validate_section(file, sec); +} + static int validate_functions(struct objtool_file *file) { struct section *sec; @@ -2529,6 +2617,15 @@ int check(const char *_objname, bool orc if (list_empty(&file.insn_list)) goto out; + if (vmlinux && !validate_dup) { + ret = validate_vmlinux_functions(&file); + if (ret < 0) + goto out; + + warnings += ret; + goto out; + } + if (retpoline) { ret = validate_retpoline(&file); if (ret < 0) --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -28,6 +28,8 @@ struct insn_state { unsigned char type; bool bp_scratch; bool drap, end, uaccess, df; + bool noinstr; + s8 instr; unsigned int uaccess_stack; int drap_reg, drap_offset; struct cfi_reg vals[CFI_NUM_REGS]; @@ -43,6 +45,7 @@ struct instruction { unsigned long immediate; bool alt_group, dead_end, ignore, hint, save, restore, ignore_alts; bool retpoline_safe; + s8 instr; u8 visited; struct symbol *call_dest; struct instruction *jump_dest; --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -39,7 +39,7 @@ struct section { char *name; int idx; unsigned int len; - bool changed, text, rodata; + bool changed, text, rodata, noinstr; }; struct symbol {