| 1 | /* Target-dependent code for the GNU C Library (glibc). |
| 2 | |
| 3 | Copyright (C) 2002, 2003, 2007 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., 51 Franklin Street, Fifth Floor, |
| 20 | Boston, MA 02110-1301, 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 | |
| 38 | static struct minimal_symbol * |
| 39 | find_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 | |
| 68 | CORE_ADDR |
| 69 | glibc_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 | /* The dynamic linker began using this name in early 2005. */ |
| 94 | struct minimal_symbol *fixup |
| 95 | = lookup_minimal_symbol ("_dl_fixup", NULL, objfile); |
| 96 | |
| 97 | /* This is the name used in older versions. */ |
| 98 | if (! fixup) |
| 99 | fixup = lookup_minimal_symbol ("fixup", NULL, objfile); |
| 100 | |
| 101 | if (fixup && SYMBOL_VALUE_ADDRESS (fixup) == pc) |
| 102 | return frame_pc_unwind (get_current_frame ()); |
| 103 | } |
| 104 | |
| 105 | return 0; |
| 106 | } |