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 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 39739C2BB55 for ; Thu, 16 Apr 2020 11:53:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 151E021D7F for ; Thu, 16 Apr 2020 11:53:40 +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="k3tOsxmk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2634094AbgDPLxi (ORCPT ); Thu, 16 Apr 2020 07:53:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40856 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2506705AbgDPLwh (ORCPT ); Thu, 16 Apr 2020 07:52:37 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 224D1C0610D6 for ; Thu, 16 Apr 2020 04:52:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=ky754+CLVVHlV5y1DSkxULOOeWjje4mqYPKXavtHYsU=; b=k3tOsxmkzivYN/igBlDcBfD6Y7 JmawlBC1GkqtV6DePDaYMGTIMOI52MTAN9bCE+l+nxazY6ugJ1Y5JpMyQa0opMqfy7Dphwo+EkZrr jGqj/5hJLjVxNvmI0MJAPaXJqBqV2qLeZjz31JJr6OnbEtxlOGMXIKCnzfI0oSzwLoSV/8/fkl5XK JBSXGhftt2Yfwg0S3qsTjAXg5sSrBC8keCjMXT3syJxcDP3IWukzxS4SkO/PaW5G4ME3ByxtBwXxD YG/nr+8xwPF+cG30L7lWCSrtUjvDFS5E2Q5XJ6O5yZLFQlARr/ENYbyJvh59RGXqdyX6CeECysqEr 84qgDoxQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jP34D-0004s0-U3; Thu, 16 Apr 2020 11:52:26 +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 38D7B307005; Thu, 16 Apr 2020 13:52:24 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 220392B0DE4C2; Thu, 16 Apr 2020 13:52:24 +0200 (CEST) Message-Id: <20200416115118.631224674@infradead.org> User-Agent: quilt/0.65 Date: Thu, 16 Apr 2020 13:47:08 +0200 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, jthierry@redhat.com, alexandre.chartre@oracle.com Subject: [PATCH v5 02/17] objtool: Better handle IRET References: <20200416114706.625340212@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 Teach objtool a little more about IRET so that we can avoid using the SAVE/RESTORE annotation. In particular, make the weird corner case in insn->restore go away. The purpose of that corner case is to deal with the fact that UNWIND_HINT_RESTORE lands on the instruction after IRET, but that instruction can end up being outside the basic block, consider: if (cond) sync_core() foo(); Then the hint will land on foo(), and we'll encounter the restore hint without ever having seen the save hint. By teaching objtool about the arch specific exception frame size, and assuming that any IRET in an STT_FUNC symbol is an exception frame sized POP, we can remove the use of save/restore hints for this code. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/include/asm/processor.h | 2 -- tools/objtool/arch.h | 1 + tools/objtool/arch/x86/decode.c | 14 ++++++++++++-- tools/objtool/check.c | 29 ++++++++++++++++------------- 4 files changed, 29 insertions(+), 17 deletions(-) --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -727,7 +727,6 @@ static inline void sync_core(void) unsigned int tmp; asm volatile ( - UNWIND_HINT_SAVE "mov %%ss, %0\n\t" "pushq %q0\n\t" "pushq %%rsp\n\t" @@ -737,7 +736,6 @@ static inline void sync_core(void) "pushq %q0\n\t" "pushq $1f\n\t" "iretq\n\t" - UNWIND_HINT_RESTORE "1:" : "=&r" (tmp), ASM_CALL_CONSTRAINT : : "cc", "memory"); #endif --- a/tools/objtool/arch.h +++ b/tools/objtool/arch.h @@ -19,6 +19,7 @@ enum insn_type { INSN_CALL, INSN_CALL_DYNAMIC, INSN_RETURN, + INSN_EXCEPTION_RETURN, INSN_CONTEXT_SWITCH, INSN_STACK, INSN_BUG, --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -435,9 +435,19 @@ int arch_decode_instruction(struct elf * *type = INSN_RETURN; break; + case 0xcf: /* iret */ + *type = INSN_EXCEPTION_RETURN; + + /* add $40, %rsp */ + op->src.type = OP_SRC_ADD; + op->src.reg = CFI_SP; + op->src.offset = 5*8; + op->dest.type = OP_DEST_REG; + op->dest.reg = CFI_SP; + break; + case 0xca: /* retf */ case 0xcb: /* retf */ - case 0xcf: /* iret */ *type = INSN_CONTEXT_SWITCH; break; @@ -483,7 +493,7 @@ int arch_decode_instruction(struct elf * *immediate = insn.immediate.nbytes ? insn.immediate.value : 0; - if (*type == INSN_STACK) + if (*type == INSN_STACK || *type == INSN_EXCEPTION_RETURN) list_add_tail(&op->list, ops_list); else free(op); --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2080,15 +2080,14 @@ static int validate_return(struct symbol * tools/objtool/Documentation/stack-validation.txt. */ static int validate_branch(struct objtool_file *file, struct symbol *func, - struct instruction *first, struct insn_state state) + struct instruction *insn, struct insn_state state) { struct alternative *alt; - struct instruction *insn, *next_insn; + struct instruction *next_insn; struct section *sec; u8 visited; int ret; - insn = first; sec = insn->sec; if (insn->alt_group && list_empty(&insn->alts)) { @@ -2141,16 +2140,6 @@ static int validate_branch(struct objtoo } if (!save_insn->visited) { - /* - * Oops, no state to copy yet. - * Hopefully we can reach this - * instruction from another branch - * after the save insn has been - * visited. - */ - if (insn == first) - return 0; - WARN_FUNC("objtool isn't smart enough to handle this CFI save/restore combo", sec, insn->offset); return 1; @@ -2243,6 +2232,20 @@ static int validate_branch(struct objtoo break; + case INSN_EXCEPTION_RETURN: + if (handle_insn_ops(insn, &state)) + return 1; + + /* + * This handles x86's sync_core() case, where we use an + * IRET to self. All 'normal' IRET instructions are in + * STT_NOTYPE entry symbols. + */ + if (func) + break; + + return 0; + case INSN_CONTEXT_SWITCH: if (func && (!next_insn || !next_insn->hint)) { WARN_FUNC("unsupported instruction in callable function",