From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 21424 invoked by alias); 4 Apr 2012 11:37:10 -0000 Received: (qmail 21229 invoked by uid 22791); 4 Apr 2012 11:37:08 -0000 X-SWARE-Spam-Status: No, hits=-4.1 required=5.0 tests=AWL,BAYES_00,KHOP_RCVD_UNTRUST,KHOP_THREADED,RCVD_IN_HOSTKARMA_W,RCVD_IN_HOSTKARMA_WL X-Spam-Check-By: sourceware.org Received: from relay1.mentorg.com (HELO relay1.mentorg.com) (192.94.38.131) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 04 Apr 2012 11:36:54 +0000 Received: from svr-orw-exc-10.mgc.mentorg.com ([147.34.98.58]) by relay1.mentorg.com with esmtp id 1SFOWD-0006Af-Dl from Maciej_Rozycki@mentor.com ; Wed, 04 Apr 2012 04:36:53 -0700 Received: from SVR-IES-FEM-01.mgc.mentorg.com ([137.202.0.104]) by SVR-ORW-EXC-10.mgc.mentorg.com with Microsoft SMTPSVC(6.0.3790.4675); Wed, 4 Apr 2012 04:36:00 -0700 Received: from [172.30.14.14] (137.202.0.76) by SVR-IES-FEM-01.mgc.mentorg.com (137.202.0.104) with Microsoft SMTP Server id 14.1.289.1; Wed, 4 Apr 2012 12:36:51 +0100 Date: Wed, 04 Apr 2012 11:37:00 -0000 From: "Maciej W. Rozycki" To: Pedro Alves CC: Subject: Re: [PATCH] gdbserver: Handle DT_MIPS_RLD_MAP dynamic tag In-Reply-To: <4F7B6B31.3010203@redhat.com> Message-ID: References: <4F7B6B31.3010203@redhat.com> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" 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: 2012-04/txt/msg00055.txt.bz2 Hi Pedro, > Yeah, I had noticed that on > , but never got > to propose a fix. Sorry about that. Well, I'm supposed to catch this kind of breakage myself these days. ;) > > Index: gdb-fsf-trunk-quilt/gdb/gdbserver/linux-low.c > > =================================================================== > > --- gdb-fsf-trunk-quilt.orig/gdb/gdbserver/linux-low.c 2012-04-03 13:38:58.575561428 +0100 > > +++ gdb-fsf-trunk-quilt/gdb/gdbserver/linux-low.c 2012-04-03 13:39:17.315624148 +0100 > > @@ -5419,7 +5419,9 @@ get_dynamic (const int pid, const int is > > } > > > > /* Return &_r_debug in the inferior, or -1 if not present. Return value > > - can be 0 if the inferior does not yet have the library list initialized. */ > > + can be 0 if the inferior does not yet have the library list initialized. > > + We look for DT_MIPS_RLD_MAP first. MIPS executables use this instead of > > + DT_DEBUG, although they sometimes contain an unused DT_DEBUG entry too. */ > > Can that "unused DT_DEBUG" entry ever appear before DT_MIPS_RLD_MAP in the tags > list? With this patch, we'll stop looking if we see DT_DEBUG first, while > solib-svr4.c in GDB first looks for DT_MIPS_RLD_MAP in all tags, and only > if not found looks for DT_DEBUG (presumably, if there's no DT_MIPS_RLD_MAP, > then there's no DT_DEBUG either; only if DT_MIPS_RLD_MAP exist might there be > a DT_DEBUG). Do we need to worry about this? Hmm, I've double-checked the sources and as you say solib-svr4.c does not rely on the order of the tags indeed. I got mislead by the comment in MIPS BFD that says: /* SGI object has the equivalence of DT_DEBUG in the DT_MIPS_RLD_MAP entry. This must come first because glibc only fills in DT_MIPS_RLD_MAP (not DT_DEBUG) and GDB only looks at the first one it sees. */ and which obviously does not stand (anymore?) as far as GDB is concerned. I'll post a proposal to update it to match reality. It is worth noting that current MIPS BFD always adds DT_DEBUG too (and always after DT_MIPS_RLD_MAP, the comment gets this part right). Anyway, I think `gdbserver' should be as liberal as to what it accepts as GDB itself is, so I have updated my change as below. No changes in regression testing. Thanks for your input. Any further comments? 2012-04-03 Maciej W. Rozycki gdb/gdbserver/ * linux-low.c (get_r_debug): Handle DT_MIPS_RLD_MAP. Maciej gdb-gdbserver-rld-map.diff Index: gdb-fsf-trunk-quilt/gdb/gdbserver/linux-low.c =================================================================== --- gdb-fsf-trunk-quilt.orig/gdb/gdbserver/linux-low.c 2012-04-03 16:49:32.000000000 +0100 +++ gdb-fsf-trunk-quilt/gdb/gdbserver/linux-low.c 2012-04-04 11:56:37.405566578 +0100 @@ -5419,7 +5419,9 @@ get_dynamic (const int pid, const int is } /* Return &_r_debug in the inferior, or -1 if not present. Return value - can be 0 if the inferior does not yet have the library list initialized. */ + can be 0 if the inferior does not yet have the library list initialized. + We look for DT_MIPS_RLD_MAP first. MIPS executables use this instead of + DT_DEBUG, although they sometimes contain an unused DT_DEBUG entry too. */ static CORE_ADDR get_r_debug (const int pid, const int is_elf64) @@ -5427,19 +5429,35 @@ get_r_debug (const int pid, const int is CORE_ADDR dynamic_memaddr; const int dyn_size = is_elf64 ? sizeof (Elf64_Dyn) : sizeof (Elf32_Dyn); unsigned char buf[sizeof (Elf64_Dyn)]; /* The larger of the two. */ + CORE_ADDR map = -1; dynamic_memaddr = get_dynamic (pid, is_elf64); if (dynamic_memaddr == 0) - return (CORE_ADDR) -1; + return map; while (linux_read_memory (dynamic_memaddr, buf, dyn_size) == 0) { if (is_elf64) { Elf64_Dyn *const dyn = (Elf64_Dyn *) buf; + union + { + Elf64_Xword map; + unsigned char buf[sizeof (Elf64_Xword)]; + } + rld_map; - if (dyn->d_tag == DT_DEBUG) - return dyn->d_un.d_val; + if (dyn->d_tag == DT_MIPS_RLD_MAP) + { + if (linux_read_memory (dyn->d_un.d_val, + rld_map.buf, sizeof (rld_map.buf)) == 0) + return rld_map.map; + else + break; + } + + if (dyn->d_tag == DT_DEBUG && map == -1) + map = dyn->d_un.d_val; if (dyn->d_tag == DT_NULL) break; @@ -5447,9 +5465,24 @@ get_r_debug (const int pid, const int is else { Elf32_Dyn *const dyn = (Elf32_Dyn *) buf; + union + { + Elf32_Word map; + unsigned char buf[sizeof (Elf32_Word)]; + } + rld_map; - if (dyn->d_tag == DT_DEBUG) - return dyn->d_un.d_val; + if (dyn->d_tag == DT_MIPS_RLD_MAP) + { + if (linux_read_memory (dyn->d_un.d_val, + rld_map.buf, sizeof (rld_map.buf)) == 0) + return rld_map.map; + else + break; + } + + if (dyn->d_tag == DT_DEBUG && map == -1) + map = dyn->d_un.d_val; if (dyn->d_tag == DT_NULL) break; @@ -5458,7 +5491,7 @@ get_r_debug (const int pid, const int is dynamic_memaddr += dyn_size; } - return (CORE_ADDR) -1; + return map; } /* Read one pointer from MEMADDR in the inferior. */