1/* Target-dependent code for the GNU C Library (glibc). 2 3 Copyright 2002, 2003 Free Software Foundation, Inc. 4 5 This file is part of GDB. 6 7 This program is free software; you can redistribute it and/or modify 8 it under the terms of the GNU General Public License as published by 9 the Free Software Foundation; either version 2 of the License, or 10 (at your option) any later version. 11 12 This program is distributed in the hope that it will be useful, 13 but WITHOUT ANY WARRANTY; without even the implied warranty of 14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 GNU General Public License for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with this program; if not, write to the Free Software 19 Foundation, Inc., 59 Temple Place - Suite 330, 20 Boston, MA 02111-1307, USA. */ 21 22#include "defs.h" 23#include "frame.h" 24#include "symtab.h" 25#include "symfile.h" 26#include "objfiles.h" 27 28#include "glibc-tdep.h" 29 30/* Calling functions in shared libraries. */ 31 32/* Find the minimal symbol named NAME, and return both the minsym 33 struct and its objfile. This probably ought to be in minsym.c, but 34 everything there is trying to deal with things like C++ and 35 SOFUN_ADDRESS_MAYBE_TURQUOISE, ... Since this is so simple, it may 36 be considered too special-purpose for general consumption. */ 37 38static struct minimal_symbol * 39find_minsym_and_objfile (char *name, struct objfile **objfile_p) 40{ 41 struct objfile *objfile; 42 43 ALL_OBJFILES (objfile) 44 { 45 struct minimal_symbol *msym; 46 47 ALL_OBJFILE_MSYMBOLS (objfile, msym) 48 { 49 if (SYMBOL_LINKAGE_NAME (msym) 50 && strcmp (SYMBOL_LINKAGE_NAME (msym), name) == 0) 51 { 52 *objfile_p = objfile; 53 return msym; 54 } 55 } 56 } 57 58 return 0; 59} 60 61/* See the comments for SKIP_SOLIB_RESOLVER at the top of infrun.c. 62 This function: 63 1) decides whether a PLT has sent us into the linker to resolve 64 a function reference, and 65 2) if so, tells us where to set a temporary breakpoint that will 66 trigger when the dynamic linker is done. */ 67 68CORE_ADDR 69glibc_skip_solib_resolver (struct gdbarch *gdbarch, CORE_ADDR pc) 70{ 71 /* The GNU dynamic linker is part of the GNU C library, and is used 72 by all GNU systems (GNU/Hurd, GNU/Linux). An unresolved PLT 73 entry points to "_dl_runtime_resolve", which calls "fixup" to 74 patch the PLT, and then passes control to the function. 75 76 We look for the symbol `_dl_runtime_resolve', and find `fixup' in 77 the same objfile. If we are at the entry point of `fixup', then 78 we set a breakpoint at the return address (at the top of the 79 stack), and continue. 80 81 It's kind of gross to do all these checks every time we're 82 called, since they don't change once the executable has gotten 83 started. But this is only a temporary hack --- upcoming versions 84 of GNU/Linux will provide a portable, efficient interface for 85 debugging programs that use shared libraries. */ 86 87 struct objfile *objfile; 88 struct minimal_symbol *resolver 89 = find_minsym_and_objfile ("_dl_runtime_resolve", &objfile); 90 91 if (resolver) 92 { 93 struct minimal_symbol *fixup 94 = lookup_minimal_symbol ("fixup", NULL, objfile); 95 96 if (fixup && SYMBOL_VALUE_ADDRESS (fixup) == pc) 97 return frame_pc_unwind (get_current_frame ()); 98 } 99 100 return 0; 101} 102