From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 122556 invoked by alias); 2 Dec 2016 15:19:26 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 121270 invoked by uid 89); 2 Dec 2016 15:19:25 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy= X-HELO: relay1.mentorg.com Received: from relay1.mentorg.com (HELO relay1.mentorg.com) (192.94.38.131) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Fri, 02 Dec 2016 15:19:15 +0000 Received: from svr-orw-mbx-03.mgc.mentorg.com ([147.34.90.203]) by relay1.mentorg.com with esmtp id 1cCpcH-0001ue-K1 from Luis_Gustavo@mentor.com ; Fri, 02 Dec 2016 07:19:13 -0800 Received: from [172.30.7.172] (147.34.91.1) by svr-orw-mbx-03.mgc.mentorg.com (147.34.90.203) with Microsoft SMTP Server (TLS) id 15.0.1210.3; Fri, 2 Dec 2016 07:19:10 -0800 Reply-To: Luis Machado Subject: Re: [PATCH] AMD64, Prologue: Recognize stack decrementation as prologue operation. References: <1480601804-3128-1-git-send-email-bernhard.heckel@intel.com> <2b71dfb7-0ab8-2440-b102-e8cc6dfc8bef@codesourcery.com> <58413365.50701@intel.com> To: Bernhard Heckel , CC: From: Luis Machado Message-ID: <26ac700b-0a50-e136-8e4f-99e19d64548e@codesourcery.com> Date: Fri, 02 Dec 2016 15:19:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <58413365.50701@intel.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: svr-orw-mbx-01.mgc.mentorg.com (147.34.90.201) To svr-orw-mbx-03.mgc.mentorg.com (147.34.90.203) X-IsSubscribed: yes X-SW-Source: 2016-12/txt/msg00095.txt.bz2 On 12/02/2016 02:40 AM, Bernhard Heckel wrote: > On 01/12/2016 16:31, Luis Machado wrote: >> On 12/01/2016 08:16 AM, Bernhard Heckel wrote: >>> Some compiler decrement stack pointer within the prologue >>> sequence in order to reserve memory for local variables. >>> Recognize this subtraction to stop at the very end of the >>> prologue. >> >> I suppose this was exercised with GCC as well via the testsuite? > Yes > GCC,ICC and Clang 6.0 (llvm 3.5) > > No regression with GCC nor with ICC. > > But, there is a major issue when running with Clang. > Clang associate this "subtraction instruction" with the line after the > prologue sequence. > This causes regressions on Mac. > > I attached disassembly of Clang and GCC for the same program. ICC > behaves like GCC. > I was trying to file a ticket for Clang, but I don't have access to > bugzilla. Auto-registration > is not available and manual account registration is still ongoing. > >> >>> >>> 2016-10-20 Bernhard Heckel >>> >>> gdb/Changelog: >>> amd64-tdep.c (amd64_analyze_prologue): Recognize stack >>> decrementation >>> as prologue operation. >> >> gdb/ChangeLog above the date line, adjust date and add "*" before the >> filename. >> >>> >>> --- >>> gdb/amd64-tdep.c | 30 ++++++++++++++++++++++++++++++ >>> 1 file changed, 30 insertions(+) >>> >>> diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c >>> index a3a1fde..795d78e 100644 >>> --- a/gdb/amd64-tdep.c >>> +++ b/gdb/amd64-tdep.c >>> @@ -2283,6 +2283,12 @@ amd64_analyze_prologue (struct gdbarch *gdbarch, >>> /* Ditto for movl %esp, %ebp. */ >>> static const gdb_byte mov_esp_ebp_1[2] = { 0x89, 0xe5 }; >>> static const gdb_byte mov_esp_ebp_2[2] = { 0x8b, 0xec }; >>> + /* Ditto for subtraction on the stack pointer. */ >>> + static const gdb_byte sub_rsp_imm8[3] = { 0x48, 0x83, 0xec }; >>> + static const gdb_byte sub_rsp_imm32[3] = { 0x48, 0x81, 0xec }; >>> + /* Ditto for subtraction on the stack pointer. */ >>> + static const gdb_byte sub_esp_imm8[2] = { 0x83, 0xec }; >>> + static const gdb_byte sub_esp_imm32[2] = { 0x81, 0xec }; >> >> Should we add a comment making it explicit which instruction patterns >> we're looking at matching here? > You mean, adding it to the function description. There we have > description for push and mov instruction. > To add it to these sub_[esp|rsp|_imm* bits, if meaningful. I don't know if these are documented/used somewhere else in gdb. Just a suggestion that could improve visual identification of such instructions when going through the prologue in disassembly view. >> >> I looked up sub esp imm32, for example, and i got no meaningful hits >> other than some nasm posix entry. >> >>> >>> gdb_byte buf[3]; >>> gdb_byte op; >>> @@ -2316,6 +2322,18 @@ amd64_analyze_prologue (struct gdbarch *gdbarch, >>> { >>> /* OK, we actually have a frame. */ >>> cache->frameless_p = 0; >>> + >>> + /* Some compiler do subtraction on the stack pointer >>> + to reserve memory for local variables. >>> + Two common variants exist to do so. */ >> >> What compiler exactly? Would be nice to know, otherwise this is a bit >> vague. > Actually, GCC, ICC and Clang are using this approach. > I guess you'd want "some compilers" then.