gdb/alphaobsd-tdep.c

   1 /* Target-dependent code for OpenBSD/alpha.
   2
   3    Copyright (C) 2006, 2007, 2008 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 "gdbcore.h"
  23 #include "osabi.h"
  24
  25 #include "obsd-tdep.h"
  26 #include "alpha-tdep.h"
  27 #include "alphabsd-tdep.h"
  28 #include "solib-svr4.h"
  29
  30 /* Signal trampolines.  */
  31
  32 /* The OpenBSD kernel maps the signal trampoline at some random
  33    location in user space, which means that the traditional BSD way of
  34    detecting it won't work.
  35
  36    The signal trampoline will be mapped at an address that is page
  37    aligned.  We recognize the signal trampoline by looking for the
  38    sigreturn system call.  */
  39
  40 static const int alphaobsd_page_size = 8192;
  41
  42 static LONGEST
  43 alphaobsd_sigtramp_offset (CORE_ADDR pc)
  44 {
  45   return (pc & (alphaobsd_page_size - 1));
  46 }
  47
  48 static int
  49 alphaobsd_pc_in_sigtramp (CORE_ADDR pc, char *name)
  50 {
  51   CORE_ADDR start_pc = (pc & ~(alphaobsd_page_size - 1));
  52   unsigned insn;
  53
  54   if (name)
  55     return 0;
  56
  57   /* Check for "".  */
  58   insn = alpha_read_insn (start_pc + 5 * ALPHA_INSN_SIZE);
  59   if (insn != 0x201f0067)
  60     return 0;
  61
  62   /* Check for "".  */
  63   insn = alpha_read_insn (start_pc + 6 * ALPHA_INSN_SIZE);
  64   if (insn != 0x00000083)
  65     return 0;
  66
  67   return 1;
  68 }
  69
  70 static CORE_ADDR
  71 alphaobsd_sigcontext_addr (struct frame_info *next_frame)
  72 {
  73   CORE_ADDR pc = frame_pc_unwind (next_frame);
  74
  75   if (alphaobsd_sigtramp_offset (pc) < 3 * ALPHA_INSN_SIZE)
  76     {
  77       /* On entry, a pointer the `struct sigcontext' is passed in %a2.  */
  78       return frame_unwind_register_unsigned (next_frame, ALPHA_A0_REGNUM + 2);
  79     }
  80   else if (alphaobsd_sigtramp_offset (pc) < 4 * ALPHA_INSN_SIZE)
  81     {
  82       /* It is stored on the stack Before calling the signal handler.  */
  83       CORE_ADDR sp;
  84       sp = frame_unwind_register_unsigned (next_frame, ALPHA_SP_REGNUM);
  85       return get_frame_memory_unsigned (next_frame, sp, 8);
  86     }
  87   else
  88     {
  89       /* It is reloaded into %a0 for the sigreturn(2) call.  */
  90       return frame_unwind_register_unsigned (next_frame, ALPHA_A0_REGNUM);
  91     }
  92 }
  93 \f
  94
  95 static void
  96 alphaobsd_init_abi(struct gdbarch_info info, struct gdbarch *gdbarch)
  97 {
  98   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
  99
 100   /* Hook into the DWARF CFI frame unwinder.  */
 101   alpha_dwarf2_init_abi (info, gdbarch);
 102
 103   /* Hook into the MDEBUG frame unwinder.  */
 104   alpha_mdebug_init_abi (info, gdbarch);
 105
 106   /* OpenBSD/alpha 3.0 and earlier does not provide single step
 107      support via ptrace(2); use software single-stepping for now.  */
 108   set_gdbarch_software_single_step (gdbarch, alpha_software_single_step);
 109
 110   /* OpenBSD/alpha has SVR4-style shared libraries.  */
 111   set_solib_svr4_fetch_link_map_offsets
 112     (gdbarch, svr4_lp64_fetch_link_map_offsets);
 113   set_gdbarch_skip_solib_resolver (gdbarch, obsd_skip_solib_resolver);
 114
 115   tdep->dynamic_sigtramp_offset = alphaobsd_sigtramp_offset;
 116   tdep->pc_in_sigtramp = alphaobsd_pc_in_sigtramp;
 117   tdep->sigcontext_addr = alphaobsd_sigcontext_addr;
 118
 119   tdep->jb_pc = 2;
 120   tdep->jb_elt_size = 8;
 121
 122   set_gdbarch_regset_from_core_section
 123     (gdbarch, alphanbsd_regset_from_core_section);
 124 }
 125 \f
 126
 127 /* Provide a prototype to silence -Wmissing-prototypes.  */
 128 void _initialize_alphaobsd_tdep (void);
 129
 130 void
 131 _initialize_alphaobsd_tdep (void)
 132 {
 133   gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_OPENBSD_ELF,
 134                           alphaobsd_init_abi);
 135 }