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=-3.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 5CC8BC2BB55 for ; Thu, 16 Apr 2020 15:15:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 32BCE214D8 for ; Thu, 16 Apr 2020 15:15:59 +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="TYfep7er" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2503487AbgDPPP6 (ORCPT ); Thu, 16 Apr 2020 11:15:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S2395070AbgDPPMS (ORCPT ); Thu, 16 Apr 2020 11:12:18 -0400 Received: from merlin.infradead.org (unknown [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3173FC061A0F for ; Thu, 16 Apr 2020 08:12:18 -0700 (PDT) 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=VO8OgZtTlpanMZN2sQJ/dRFzTr62tn4AjfwviFGlzT4=; b=TYfep7erSM+2EBYCzjis1tAedJ xpXq5szVbZYnLk8Ieb7Q5uaMG6kHqPggeZFeqcU0/ZBDLsAtClpYiOQumYkr+K53AWY0POcq699jH Xk3XMN/IKl9L+dVDJOuvPxaAzITm3ngbw0oQ7mZriZsaDijOXaj00sp2KeD218hyMO5mbfa7u5T1r zL1T/VfuO+iEaqqkUJHFYsYiL/eScYNYU1cjw6JsuIne8H6QluJLL9iEmdOogGuWo+nFi9FjDPcae 5qy5XszowiEqj/yXk0NJYxZr1G/sMpZ6b1yskWBWizzlFysdPM/R8Vrd2d4YlW2QhZrWGZ7lQuv/n eUOPGfmQ==; 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 1jP6BJ-00046v-3u; Thu, 16 Apr 2020 15:11:57 +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 277A9307456; Thu, 16 Apr 2020 17:11:54 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 10A492B0DE4BF; Thu, 16 Apr 2020 17:11:54 +0200 (CEST) Message-Id: <20200416151024.944613249@infradead.org> User-Agent: quilt/0.65 Date: Thu, 16 Apr 2020 17:07:56 +0200 From: Peter Zijlstra To: jpoimboe@redhat.com, alexandre.chartre@oracle.com Cc: linux-kernel@vger.kernel.org, jthierry@redhat.com, tglx@linutronix.de, x86@kernel.org, peterz@infradead.org Subject: [RFC][PATCH 4/7] objtool: Add support for intra-function calls References: <20200416150752.569029800@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 From: Alexandre Chartre Change objtool to support intra-function calls. On x86, an intra-function call is represented in objtool as a push onto the stack (of the return address), and a jump to the destination address. That way the stack information is correctly updated and the call flow is still accurate. Signed-off-by: Alexandre Chartre Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200414103618.12657-4-alexandre.chartre@oracle.com --- include/linux/frame.h | 11 + tools/objtool/Documentation/stack-validation.txt | 8 + tools/objtool/arch/x86/decode.c | 17 ++- tools/objtool/check.c | 129 ++++++++++++++++++----- tools/objtool/check.h | 1 5 files changed, 140 insertions(+), 26 deletions(-) --- a/include/linux/frame.h +++ b/include/linux/frame.h @@ -15,9 +15,20 @@ static void __used __section(.discard.func_stack_frame_non_standard) \ *__func_stack_frame_non_standard_##func = func +/* + * This macro indicates that the following intra-function call is valid. + * Any non-annotated intra-function call will cause objtool to issue warning. + */ +#define ANNOTATE_INTRA_FUNCTION_CALL \ + 999: \ + .pushsection .discard.intra_function_calls; \ + .long 999b; \ + .popsection; + #else /* !CONFIG_STACK_VALIDATION */ #define STACK_FRAME_NON_STANDARD(func) +#define ANNOTATE_INTRA_FUNCTION_CALL #endif /* CONFIG_STACK_VALIDATION */ --- a/tools/objtool/Documentation/stack-validation.txt +++ b/tools/objtool/Documentation/stack-validation.txt @@ -290,6 +290,14 @@ they mean, and suggestions for how to fi https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646 +9. file.o: warning: unsupported intra-function call + + This warning means that a direct call is done to a destination which + is not at the beginning of a function. If this is a legit call, you + can remove this warning by putting the ANNOTATE_INTRA_FUNCTION_CALL + directive right before the call. + + If the error doesn't seem to make sense, it could be a bug in objtool. Feel free to ask the objtool maintainer for help. --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -453,6 +453,12 @@ int arch_decode_instruction(struct elf * case 0xe8: *type = INSN_CALL; + /* + * For the impact on the stack, a call behaves like + * a push of an immediate value (the return address). + */ + op->src.type = OP_SRC_CONST; + op->dest.type = OP_DEST_PUSH; break; case 0xfc: @@ -493,10 +499,17 @@ int arch_decode_instruction(struct elf * *immediate = insn.immediate.nbytes ? insn.immediate.value : 0; - if (*type == INSN_STACK || *type == INSN_EXCEPTION_RETURN) + switch (*type) { + case INSN_STACK: + case INSN_EXCEPTION_RETURN: + case INSN_CALL: list_add_tail(&op->list, ops_list); - else + break; + + default: free(op); + break; + } return 0; } --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -691,44 +691,51 @@ static int add_jump_destinations(struct return 0; } +static int setup_call_dest(struct objtool_file *file, struct instruction *insn) +{ + unsigned long dest_off; + + dest_off = insn->offset + insn->len + insn->immediate; + insn->call_dest = find_func_by_offset(insn->sec, dest_off); + if (!insn->call_dest) + insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); + + if (!insn->call_dest) { + /* intra-function call */ + if (insn->intra_function_call) + return 0; + + WARN_FUNC("intra-function call", insn->sec, insn->offset); + return -1; + } + + /* regular call */ + if (insn->func && insn->call_dest->type != STT_FUNC) { + WARN_FUNC("unsupported call to non-function", + insn->sec, insn->offset); + return -1; + } + + return 0; +} + /* * Find the destination instructions for all calls. */ static int add_call_destinations(struct objtool_file *file) { struct instruction *insn; - unsigned long dest_off; struct rela *rela; for_each_insn(file, insn) { - if (insn->type != INSN_CALL) + if (insn->type != INSN_CALL || insn->ignore) continue; rela = find_rela_by_dest_range(file->elf, insn->sec, insn->offset, insn->len); if (!rela) { - dest_off = insn->offset + insn->len + insn->immediate; - insn->call_dest = find_func_by_offset(insn->sec, dest_off); - if (!insn->call_dest) - insn->call_dest = find_symbol_by_offset(insn->sec, dest_off); - - if (insn->ignore) - continue; - - if (!insn->call_dest) { - WARN_FUNC("unsupported intra-function call", - insn->sec, insn->offset); - if (retpoline) - WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE."); - return -1; - } - - if (insn->func && insn->call_dest->type != STT_FUNC) { - WARN_FUNC("unsupported call to non-function", - insn->sec, insn->offset); + if (setup_call_dest(file, insn)) return -1; - } - } else if (rela->sym->type == STT_SECTION) { insn->call_dest = find_func_by_offset(rela->sym->sec, rela->addend+4); @@ -1414,6 +1421,52 @@ static int read_instr_hints(struct objto return 0; } +static int read_intra_function_calls(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + struct rela *rela; + + sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls"); + if (!sec) + return 0; + + list_for_each_entry(rela, &sec->rela_list, list) { + unsigned long dest_off; + + 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.intra_function_call entry"); + return -1; + } + + if (insn->type != INSN_CALL) { + WARN_FUNC("intra_function_call not a direct call", + insn->sec, insn->offset); + return -1; + } + + insn->intra_function_call = true; + + dest_off = insn->offset + insn->len + insn->immediate; + insn->jump_dest = find_insn(file, insn->sec, dest_off); + if (!insn->jump_dest) { + WARN_FUNC("can't find call dest at %s+0x%lx", + insn->sec, insn->offset, + insn->sec->name, dest_off); + return -1; + } + } + + return 0; +} + static void mark_rodata(struct objtool_file *file) { struct section *sec; @@ -1469,6 +1522,10 @@ static int decode_sections(struct objtoo if (ret) return ret; + ret = read_intra_function_calls(file); + if (ret) + return ret; + ret = add_call_destinations(file); if (ret) return ret; @@ -2260,7 +2317,8 @@ static int validate_branch(struct objtoo return ret; if (!no_fp && func && !is_fentry_call(insn) && - !has_valid_stack_frame(&state)) { + !has_valid_stack_frame(&state) && + !insn->intra_function_call) { WARN_FUNC("call without frame pointer save/setup", sec, insn->offset); return 1; @@ -2269,6 +2327,29 @@ static int validate_branch(struct objtoo if (dead_end_function(file, insn->call_dest)) return 0; + if (insn->intra_function_call) { + /* + * The call instruction can update the stack + * state. Then make the intra-function call + * behaves like and unconditional jump. + */ + ret = handle_insn_ops(insn, &state); + if (ret) + return ret; + + ret = validate_branch(file, func, insn, + insn->jump_dest, state); + if (ret) { + if (backtrace) { + BT_FUNC("(intra-function call)", + insn); + } + return ret; + } + + return 0; + } + break; case INSN_JUMP_CONDITIONAL: --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -33,6 +33,7 @@ struct instruction { int alt_group; bool dead_end, ignore, ignore_alts; bool hint; + bool intra_function_call; bool retpoline_safe; s8 instr; u8 visited;