gdb/alphaobsd-tdep.c

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