From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 436 invoked by alias); 15 Feb 2013 03:22:14 -0000 Received: (qmail 428 invoked by uid 22791); 15 Feb 2013 03:22:13 -0000 X-SWARE-Spam-Status: No, hits=-3.1 required=5.0 tests=AWL,BAYES_00,KHOP_SPAMHAUS_DROP,KHOP_THREADED,RP_MATCHES_RCVD,TW_EG X-Spam-Check-By: sourceware.org Received: from usmamail.tilera.com (HELO USMAMAIL.TILERA.COM) (12.216.194.151) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Fri, 15 Feb 2013 03:22:07 +0000 Received: from localhost.localdomain (61.139.126.181) by USMAExch2.tad.internal.tilera.com (10.3.0.33) with Microsoft SMTP Server (TLS) id 14.0.694.0; Thu, 14 Feb 2013 22:22:05 -0500 Message-ID: <511DA9D9.7090202@tilera.com> Date: Fri, 15 Feb 2013 03:22:00 -0000 From: Jiong Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 MIME-Version: 1.0 To: Pedro Alves CC: Joel Brobecker , , Walter Lee Subject: Re: [RFC/TileGX 2/6] simplify the handling of skip prologue for plt stub References: <50F91516.6010204@tilera.com> <20130118131511.GF3564@adacore.com> <50F9664D.2090008@tilera.com> <50F9868C.6030905@redhat.com> In-Reply-To: <50F9868C.6030905@redhat.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit 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 X-SW-Source: 2013-02/txt/msg00382.txt.bz2 On 01/19/2013 01:29 AM, Pedro Alves wrote: > On 01/18/2013 03:12 PM, Jiong Wang wrote: >>>> for tilegx, when skip prologue, if the start_pc is a plt stub address, then >>>> stop to go further, just return the start_pc. >>>> >>>> gdb/ChangeLog: >>>> >>>> * tilegx-tdep.c (tilegx_skip_prologue): simplify the handling for >>>> plt stub. >>> Can you provide an example where this becomes necessary? I don't >>> see a problem with the patch per se, but I don't remember seeing >>> other ports doing this... >>> >> yes, there are some tricky thing. >> >> for the simple hello.c >> >> #include >> int main(int argc, char **argv) >> { >> printf("hello, %d\n", argc); >> return 0 >> } >> >> without this patch >> === >> -bash-4.1$ gcc -o hello.tile hello.c >> -bash-4.1$ ./gdb hello.tile >> (gdb) b printf >> Error accessing memory address 0x10a40: Success. >> >> after this patch >> === >> (gdb) b printf >> Breakpoint 1 at 0x10a40 >> >> >> this is because tilegx skip_prologue will invoke tilegx_analyze_prologue, which >> will prefetch 32*8 bytes. >> >> while for when the address is in plt stub, you can see it near the eh_frame_hdr section >> >> [14] .plt 0000000000010a00 000a00 0000a0 28 AX 0 0 64 >> ... >> [16] .eh_frame_hdr 0000000000010ac0 000ac0 000024 00 A 0 0 4 >> [17] .eh_frame 0000000000010ae8 000ae8 0000b4 00 A 0 0 8 >> >> the .eh_frame_hdr aligns to 4, there is a hole between .eh_frame_hdr and .eh_frame, and this >> will cause trouble for section_table_xfer_memory_partial. >> >> after fetch memory starting from 0x10ac0 to 0x10ae4, then the memaddr will be 0x10ae4 in section_table_xfer_memory_partial, >> while this function did not consider this hole situation, so goes to line 666, error occured. > Right. It's this issue that needs solving. Otherwise you're just > papering over the problem. Ping, is this patch OK to commit? --- Regards, Jiong > >> for other targets, like x86, I have done a brief exploration, seems they do not have large prefetch window > > -- Regards, Jiong. Wang Tilera Corporation.