| 1 | /* Target-dependent code for GNU/Linux on Alpha. |
| 2 | Copyright 2002 Free Software Foundation, Inc. |
| 3 | |
| 4 | This file is part of GDB. |
| 5 | |
| 6 | This program is free software; you can redistribute it and/or modify |
| 7 | it under the terms of the GNU General Public License as published by |
| 8 | the Free Software Foundation; either version 2 of the License, or |
| 9 | (at your option) any later version. |
| 10 | |
| 11 | This program is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | GNU General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License |
| 17 | along with this program; if not, write to the Free Software |
| 18 | Foundation, Inc., 59 Temple Place - Suite 330, |
| 19 | Boston, MA 02111-1307, USA. */ |
| 20 | |
| 21 | #include "defs.h" |
| 22 | #include "gdbcore.h" |
| 23 | #include "value.h" |
| 24 | |
| 25 | #include "alpha-tdep.h" |
| 26 | |
| 27 | /* Under GNU/Linux, signal handler invocations can be identified by the |
| 28 | designated code sequence that is used to return from a signal |
| 29 | handler. In particular, the return address of a signal handler |
| 30 | points to the following sequence (the first instruction is quadword |
| 31 | aligned): |
| 32 | |
| 33 | bis $30,$30,$16 |
| 34 | addq $31,0x67,$0 |
| 35 | call_pal callsys |
| 36 | |
| 37 | Each instruction has a unique encoding, so we simply attempt to |
| 38 | match the instruction the pc is pointing to with any of the above |
| 39 | instructions. If there is a hit, we know the offset to the start |
| 40 | of the designated sequence and can then check whether we really are |
| 41 | executing in a designated sequence. If not, -1 is returned, |
| 42 | otherwise the offset from the start of the desingated sequence is |
| 43 | returned. |
| 44 | |
| 45 | There is a slight chance of false hits: code could jump into the |
| 46 | middle of the designated sequence, in which case there is no |
| 47 | guarantee that we are in the middle of a sigreturn syscall. Don't |
| 48 | think this will be a problem in praxis, though. */ |
| 49 | LONGEST |
| 50 | alpha_linux_sigtramp_offset (CORE_ADDR pc) |
| 51 | { |
| 52 | unsigned int i[3], w; |
| 53 | long off; |
| 54 | |
| 55 | if (read_memory_nobpt (pc, (char *) &w, 4) != 0) |
| 56 | return -1; |
| 57 | |
| 58 | off = -1; |
| 59 | switch (w) |
| 60 | { |
| 61 | case 0x47de0410: |
| 62 | off = 0; |
| 63 | break; /* bis $30,$30,$16 */ |
| 64 | case 0x43ecf400: |
| 65 | off = 4; |
| 66 | break; /* addq $31,0x67,$0 */ |
| 67 | case 0x00000083: |
| 68 | off = 8; |
| 69 | break; /* call_pal callsys */ |
| 70 | default: |
| 71 | return -1; |
| 72 | } |
| 73 | pc -= off; |
| 74 | if (pc & 0x7) |
| 75 | { |
| 76 | /* designated sequence is not quadword aligned */ |
| 77 | return -1; |
| 78 | } |
| 79 | if (read_memory_nobpt (pc, (char *) i, sizeof (i)) != 0) |
| 80 | return -1; |
| 81 | |
| 82 | if (i[0] == 0x47de0410 && i[1] == 0x43ecf400 && i[2] == 0x00000083) |
| 83 | return off; |
| 84 | |
| 85 | return -1; |
| 86 | } |
| 87 | |
| 88 | static int |
| 89 | alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name) |
| 90 | { |
| 91 | return (alpha_linux_sigtramp_offset (pc) >= 0); |
| 92 | } |
| 93 | |
| 94 | static void |
| 95 | alpha_linux_init_abi (struct gdbarch_info info, |
| 96 | struct gdbarch *gdbarch) |
| 97 | { |
| 98 | struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); |
| 99 | |
| 100 | set_gdbarch_pc_in_sigtramp (gdbarch, alpha_linux_pc_in_sigtramp); |
| 101 | |
| 102 | tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset; |
| 103 | |
| 104 | tdep->jb_pc = 2; |
| 105 | tdep->jb_elt_size = 8; |
| 106 | } |
| 107 | |
| 108 | void |
| 109 | _initialize_alpha_linux_tdep (void) |
| 110 | { |
| 111 | alpha_gdbarch_register_os_abi (ALPHA_ABI_LINUX, alpha_linux_init_abi); |
| 112 | } |