| 1 | /* Target-dependent code for the GNU C Library (glibc). |
| 2 | |
| 3 | Copyright (C) 2002-2017 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 3 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, see <http://www.gnu.org/licenses/>. */ |
| 19 | |
| 20 | #include "defs.h" |
| 21 | #include "frame.h" |
| 22 | #include "symtab.h" |
| 23 | #include "symfile.h" |
| 24 | #include "objfiles.h" |
| 25 | |
| 26 | #include "glibc-tdep.h" |
| 27 | |
| 28 | /* Calling functions in shared libraries. */ |
| 29 | |
| 30 | /* See the comments for SKIP_SOLIB_RESOLVER at the top of infrun.c. |
| 31 | This function: |
| 32 | 1) decides whether a PLT has sent us into the linker to resolve |
| 33 | a function reference, and |
| 34 | 2) if so, tells us where to set a temporary breakpoint that will |
| 35 | trigger when the dynamic linker is done. */ |
| 36 | |
| 37 | CORE_ADDR |
| 38 | glibc_skip_solib_resolver (struct gdbarch *gdbarch, CORE_ADDR pc) |
| 39 | { |
| 40 | /* The GNU dynamic linker is part of the GNU C library, and is used |
| 41 | by all GNU systems (GNU/Hurd, GNU/Linux). An unresolved PLT |
| 42 | entry points to "_dl_runtime_resolve", which calls "fixup" to |
| 43 | patch the PLT, and then passes control to the function. |
| 44 | |
| 45 | We look for the symbol `_dl_runtime_resolve', and find `fixup' in |
| 46 | the same objfile. If we are at the entry point of `fixup', then |
| 47 | we set a breakpoint at the return address (at the top of the |
| 48 | stack), and continue. |
| 49 | |
| 50 | It's kind of gross to do all these checks every time we're |
| 51 | called, since they don't change once the executable has gotten |
| 52 | started. But this is only a temporary hack --- upcoming versions |
| 53 | of GNU/Linux will provide a portable, efficient interface for |
| 54 | debugging programs that use shared libraries. */ |
| 55 | |
| 56 | struct bound_minimal_symbol resolver |
| 57 | = lookup_minimal_symbol_and_objfile ("_dl_runtime_resolve"); |
| 58 | |
| 59 | if (resolver.minsym) |
| 60 | { |
| 61 | /* The dynamic linker began using this name in early 2005. */ |
| 62 | struct bound_minimal_symbol fixup |
| 63 | = lookup_minimal_symbol ("_dl_fixup", NULL, resolver.objfile); |
| 64 | |
| 65 | /* This is the name used in older versions. */ |
| 66 | if (! fixup.minsym) |
| 67 | fixup = lookup_minimal_symbol ("fixup", NULL, resolver.objfile); |
| 68 | |
| 69 | if (fixup.minsym && BMSYMBOL_VALUE_ADDRESS (fixup) == pc) |
| 70 | return frame_unwind_caller_pc (get_current_frame ()); |
| 71 | } |
| 72 | |
| 73 | return 0; |
| 74 | } |