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 1EA90C2BB55 for ; Thu, 16 Apr 2020 11:55:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EE5BC21D7F for ; Thu, 16 Apr 2020 11:55:38 +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="18gIha6P" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2634424AbgDPLzd (ORCPT ); Thu, 16 Apr 2020 07:55:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40918 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2633981AbgDPLwx (ORCPT ); Thu, 16 Apr 2020 07:52:53 -0400 Received: from merlin.infradead.org (unknown [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7594FC0610D5 for ; Thu, 16 Apr 2020 04:52:53 -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=j0vVLpAsgisOvtLlJu5Oc9txbLzNwPvNwKAnEr4oqLg=; b=18gIha6Pp+8MbzmQi6FRpSvFA5 bvx0HPAZFL+zfBdJEqqYkjN+cB0LkA7zOz5Y/lnk/le2cTkmB0QonmTpPF7JZ+NplXGJT+HkN1Jmc 0r+bNcNwwFt4ltYPTovxMkPaR2yR3fWSpYUMaD1OLHtRjRRX7YfT8fhXkeL6usNNf3hvn66M5nrwr 5VUXbwGtSh6YoUbTpE76eXaaLS2//JUcq47GIYWbD4uCzZTOioOPddLqbqsNaawchSfRpdOk6uXqt +QfqLr1s/a1Jg1xHYuT/wMwqWCcUkPMWgVk9oc5d5aoatpQ3ynf01w2QiJc4dhFfm1GLcvrOWMdns 8sBDSUeg==; 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 1jP34F-0006jL-2Z; Thu, 16 Apr 2020 11:52:27 +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 3CB6F307016; Thu, 16 Apr 2020 13:52:24 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 272692B0DE4C4; Thu, 16 Apr 2020 13:52:24 +0200 (CEST) Message-Id: <20200416115118.690601403@infradead.org> User-Agent: quilt/0.65 Date: Thu, 16 Apr 2020 13:47:09 +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 03/17] objtool: Introduce HINT_RET_OFFSET 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 Normally objtool ensures a function keeps the stack layout invariant. But there is a useful exception, it is possible to stuff the return stack in order to 'inject' a 'call': push $fun ret In this case the invariant mentioned above is violated. Add an objtool HINT to annotate this and allow a function exit with a modified stack frame. Signed-off-by: Peter Zijlstra (Intel) --- arch/x86/include/asm/orc_types.h | 1 + arch/x86/include/asm/unwind_hints.h | 10 ++++++++++ tools/arch/x86/include/asm/orc_types.h | 1 + tools/objtool/check.c | 24 ++++++++++++++++-------- tools/objtool/check.h | 4 +++- 5 files changed, 31 insertions(+), 9 deletions(-) --- a/arch/x86/include/asm/orc_types.h +++ b/arch/x86/include/asm/orc_types.h @@ -60,6 +60,7 @@ #define ORC_TYPE_REGS_IRET 2 #define UNWIND_HINT_TYPE_SAVE 3 #define UNWIND_HINT_TYPE_RESTORE 4 +#define UNWIND_HINT_TYPE_RET_OFFSET 5 #ifndef __ASSEMBLY__ /* --- a/arch/x86/include/asm/unwind_hints.h +++ b/arch/x86/include/asm/unwind_hints.h @@ -94,6 +94,16 @@ UNWIND_HINT type=UNWIND_HINT_TYPE_RESTORE .endm + +/* + * RET_OFFSET: Used on instructions that terminate a function; mostly RETURN + * and sibling calls. On these, sp_offset denotes the expected offset from + * initial_func_cfi. + */ +.macro UNWIND_HINT_RET_OFFSET sp_offset=8 + UNWIND_HINT type=UNWIND_HINT_TYPE_RET_OFFSET sp_offset=\sp_offset +.endm + #else /* !__ASSEMBLY__ */ #define UNWIND_HINT(sp_reg, sp_offset, type, end) \ --- a/tools/arch/x86/include/asm/orc_types.h +++ b/tools/arch/x86/include/asm/orc_types.h @@ -60,6 +60,7 @@ #define ORC_TYPE_REGS_IRET 2 #define UNWIND_HINT_TYPE_SAVE 3 #define UNWIND_HINT_TYPE_RESTORE 4 +#define UNWIND_HINT_TYPE_RET_OFFSET 5 #ifndef __ASSEMBLY__ /* --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1253,6 +1253,9 @@ static int read_unwind_hints(struct objt } else if (hint->type == UNWIND_HINT_TYPE_RESTORE) { insn->restore = true; insn->hint = true; + + } else if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) { + insn->ret_offset = hint->sp_offset; continue; } @@ -1416,20 +1419,25 @@ static bool is_fentry_call(struct instru return false; } -static bool has_modified_stack_frame(struct insn_state *state) +static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state) { + u8 ret_offset = insn->ret_offset; int i; - if (state->cfa.base != initial_func_cfi.cfa.base || - state->cfa.offset != initial_func_cfi.cfa.offset || - state->stack_size != initial_func_cfi.cfa.offset || - state->drap) + if (state->cfa.base != initial_func_cfi.cfa.base || state->drap) + return true; + + if (state->cfa.offset != initial_func_cfi.cfa.offset + ret_offset) return true; - for (i = 0; i < CFI_NUM_REGS; i++) + if (state->stack_size != initial_func_cfi.cfa.offset + ret_offset) + return true; + + for (i = 0; i < CFI_NUM_REGS; i++) { if (state->regs[i].base != initial_func_cfi.regs[i].base || state->regs[i].offset != initial_func_cfi.regs[i].offset) return true; + } return false; } @@ -1971,7 +1979,7 @@ static int validate_call(struct instruct static int validate_sibling_call(struct instruction *insn, struct insn_state *state) { - if (has_modified_stack_frame(state)) { + if (has_modified_stack_frame(insn, state)) { WARN_FUNC("sibling call from callable instruction with modified stack frame", insn->sec, insn->offset); return 1; @@ -2000,7 +2008,7 @@ static int validate_return(struct symbol return 1; } - if (func && has_modified_stack_frame(state)) { + if (func && has_modified_stack_frame(insn, state)) { WARN_FUNC("return with modified stack frame", insn->sec, insn->offset); return 1; --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -33,9 +33,11 @@ struct instruction { unsigned int len; enum insn_type type; unsigned long immediate; - bool alt_group, dead_end, ignore, hint, save, restore, ignore_alts; + bool alt_group, dead_end, ignore, ignore_alts; + bool hint, save, restore; bool retpoline_safe; u8 visited; + u8 ret_offset; struct symbol *call_dest; struct instruction *jump_dest; struct instruction *first_jump_src;