| 1 | /* Target-dependent code for OpenBSD/vax. |
| 2 | |
| 3 | Copyright (C) 2005-2015 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 "arch-utils.h" |
| 22 | #include "frame.h" |
| 23 | #include "frame-unwind.h" |
| 24 | #include "osabi.h" |
| 25 | #include "symtab.h" |
| 26 | #include "trad-frame.h" |
| 27 | |
| 28 | #include "vax-tdep.h" |
| 29 | |
| 30 | /* Signal trampolines. */ |
| 31 | |
| 32 | /* Since OpenBSD 3.2, the sigtramp routine is mapped at a random page |
| 33 | in virtual memory. The randomness makes it somewhat tricky to |
| 34 | detect it, but fortunately we can rely on the fact that the start |
| 35 | of the sigtramp routine is page-aligned. We recognize the |
| 36 | trampoline by looking for the code that invokes the sigreturn |
| 37 | system call. The offset where we can find that code varies from |
| 38 | release to release. |
| 39 | |
| 40 | By the way, the mapping mentioned above is read-only, so you cannot |
| 41 | place a breakpoint in the signal trampoline. */ |
| 42 | |
| 43 | /* Default page size. */ |
| 44 | static const int vaxobsd_page_size = 4096; |
| 45 | |
| 46 | /* Offset for sigreturn(2). */ |
| 47 | static const int vaxobsd_sigreturn_offset = 0x11; |
| 48 | |
| 49 | /* Instruction sequence for sigreturn(2). VAX doesn't have |
| 50 | fixed-length instructions so we include the ensuing exit(2) to |
| 51 | reduce the chance of spurious matches. */ |
| 52 | static const gdb_byte vaxobsd_sigreturn[] = { |
| 53 | 0xbc, 0x8f, 0x67, 0x00, /* chmk $SYS_sigreturn */ |
| 54 | 0xbc, 0x01 /* chmk $SYS_exit */ |
| 55 | }; |
| 56 | |
| 57 | static int |
| 58 | vaxobsd_sigtramp_sniffer (const struct frame_unwind *self, |
| 59 | struct frame_info *this_frame, |
| 60 | void **this_cache) |
| 61 | { |
| 62 | CORE_ADDR pc = get_frame_pc (this_frame); |
| 63 | CORE_ADDR start_pc = (pc & ~(vaxobsd_page_size - 1)); |
| 64 | CORE_ADDR sigreturn_addr = start_pc + vaxobsd_sigreturn_offset; |
| 65 | gdb_byte *buf; |
| 66 | const char *name; |
| 67 | |
| 68 | find_pc_partial_function (pc, &name, NULL, NULL); |
| 69 | if (name) |
| 70 | return 0; |
| 71 | |
| 72 | buf = alloca(sizeof vaxobsd_sigreturn); |
| 73 | if (!safe_frame_unwind_memory (this_frame, sigreturn_addr, |
| 74 | buf, sizeof vaxobsd_sigreturn)) |
| 75 | return 0; |
| 76 | |
| 77 | if (memcmp(buf, vaxobsd_sigreturn, sizeof vaxobsd_sigreturn) == 0) |
| 78 | return 1; |
| 79 | |
| 80 | return 0; |
| 81 | } |
| 82 | |
| 83 | static struct trad_frame_cache * |
| 84 | vaxobsd_sigtramp_frame_cache (struct frame_info *this_frame, void **this_cache) |
| 85 | { |
| 86 | struct trad_frame_cache *cache; |
| 87 | CORE_ADDR addr, base, func; |
| 88 | |
| 89 | if (*this_cache) |
| 90 | return *this_cache; |
| 91 | |
| 92 | cache = trad_frame_cache_zalloc (this_frame); |
| 93 | *this_cache = cache; |
| 94 | |
| 95 | func = get_frame_pc (this_frame); |
| 96 | func &= ~(vaxobsd_page_size - 1); |
| 97 | |
| 98 | base = get_frame_register_unsigned (this_frame, VAX_SP_REGNUM); |
| 99 | addr = get_frame_memory_unsigned (this_frame, base - 4, 4); |
| 100 | |
| 101 | trad_frame_set_reg_addr (cache, VAX_SP_REGNUM, addr + 8); |
| 102 | trad_frame_set_reg_addr (cache, VAX_FP_REGNUM, addr + 12); |
| 103 | trad_frame_set_reg_addr (cache, VAX_AP_REGNUM, addr + 16); |
| 104 | trad_frame_set_reg_addr (cache, VAX_PC_REGNUM, addr + 20); |
| 105 | trad_frame_set_reg_addr (cache, VAX_PS_REGNUM, addr + 24); |
| 106 | |
| 107 | /* Construct the frame ID using the function start. */ |
| 108 | trad_frame_set_id (cache, frame_id_build (base, func)); |
| 109 | |
| 110 | return cache; |
| 111 | } |
| 112 | |
| 113 | static void |
| 114 | vaxobsd_sigtramp_frame_this_id (struct frame_info *this_frame, |
| 115 | void **this_cache, struct frame_id *this_id) |
| 116 | { |
| 117 | struct trad_frame_cache *cache = |
| 118 | vaxobsd_sigtramp_frame_cache (this_frame, this_cache); |
| 119 | |
| 120 | trad_frame_get_id (cache, this_id); |
| 121 | } |
| 122 | |
| 123 | static struct value * |
| 124 | vaxobsd_sigtramp_frame_prev_register (struct frame_info *this_frame, |
| 125 | void **this_cache, int regnum) |
| 126 | { |
| 127 | struct trad_frame_cache *cache = |
| 128 | vaxobsd_sigtramp_frame_cache (this_frame, this_cache); |
| 129 | |
| 130 | return trad_frame_get_register (cache, this_frame, regnum); |
| 131 | } |
| 132 | |
| 133 | static const struct frame_unwind vaxobsd_sigtramp_frame_unwind = { |
| 134 | SIGTRAMP_FRAME, |
| 135 | default_frame_unwind_stop_reason, |
| 136 | vaxobsd_sigtramp_frame_this_id, |
| 137 | vaxobsd_sigtramp_frame_prev_register, |
| 138 | NULL, |
| 139 | vaxobsd_sigtramp_sniffer |
| 140 | }; |
| 141 | \f |
| 142 | |
| 143 | /* OpenBSD a.out. */ |
| 144 | |
| 145 | static void |
| 146 | vaxobsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) |
| 147 | { |
| 148 | frame_unwind_append_unwinder (gdbarch, &vaxobsd_sigtramp_frame_unwind); |
| 149 | } |
| 150 | |
| 151 | /* FIXME: kettenis/20050821: Since OpenBSD/vax binaries are |
| 152 | indistingushable from NetBSD/vax a.out binaries, building a GDB |
| 153 | that should support both these targets will probably not work as |
| 154 | expected. */ |
| 155 | #define GDB_OSABI_OPENBSD_AOUT GDB_OSABI_NETBSD_AOUT |
| 156 | |
| 157 | static enum gdb_osabi |
| 158 | vaxobsd_aout_osabi_sniffer (bfd *abfd) |
| 159 | { |
| 160 | if (strcmp (bfd_get_target (abfd), "a.out-vax-netbsd") == 0) |
| 161 | return GDB_OSABI_OPENBSD_AOUT; |
| 162 | |
| 163 | return GDB_OSABI_UNKNOWN; |
| 164 | } |
| 165 | \f |
| 166 | |
| 167 | /* Provide a prototype to silence -Wmissing-prototypes. */ |
| 168 | void _initialize_vaxobsd_tdep (void); |
| 169 | |
| 170 | void |
| 171 | _initialize_vaxobsd_tdep (void) |
| 172 | { |
| 173 | gdbarch_register_osabi_sniffer (bfd_arch_vax, bfd_target_aout_flavour, |
| 174 | vaxobsd_aout_osabi_sniffer); |
| 175 | |
| 176 | gdbarch_register_osabi (bfd_arch_vax, 0, GDB_OSABI_OPENBSD_AOUT, |
| 177 | vaxobsd_init_abi); |
| 178 | } |