gdb/alpha-obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/alpha.
   2
   3    Copyright (C) 2006-2020 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 "alpha-bsd-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 (struct gdbarch *gdbarch, CORE_ADDR pc)
  44 {
  45   return (pc & (alphaobsd_page_size - 1));
  46 }
  47
  48 static int
  49 alphaobsd_pc_in_sigtramp (struct gdbarch *gdbarch,
  50                           CORE_ADDR pc, const 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 (gdbarch, start_pc + 5 * ALPHA_INSN_SIZE);
  60   if (insn != 0x201f0067)
  61     return 0;
  62
  63   /* Check for "".  */
  64   insn = alpha_read_insn (gdbarch, 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 *this_frame)
  73 {
  74   struct gdbarch *gdbarch = get_frame_arch (this_frame);
  75   CORE_ADDR pc = get_frame_pc (this_frame);
  76
  77   if (alphaobsd_sigtramp_offset (gdbarch, pc) < 3 * ALPHA_INSN_SIZE)
  78     {
  79       /* On entry, a pointer the `struct sigcontext' is passed in %a2.  */
  80       return get_frame_register_unsigned (this_frame, ALPHA_A0_REGNUM + 2);
  81     }
  82   else if (alphaobsd_sigtramp_offset (gdbarch, pc) < 4 * ALPHA_INSN_SIZE)
  83     {
  84       /* It is stored on the stack Before calling the signal handler.  */
  85       CORE_ADDR sp;
  86       sp = get_frame_register_unsigned (this_frame, ALPHA_SP_REGNUM);
  87       return get_frame_memory_unsigned (this_frame, sp, 8);
  88     }
  89   else
  90     {
  91       /* It is reloaded into %a0 for the sigreturn(2) call.  */
  92       return get_frame_register_unsigned (this_frame, ALPHA_A0_REGNUM);
  93     }
  94 }
  95 \f
  96
  97 static void
  98 alphaobsd_init_abi(struct gdbarch_info info, struct gdbarch *gdbarch)
  99 {
 100   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 101
 102   /* Hook into the DWARF CFI frame unwinder.  */
 103   alpha_dwarf2_init_abi (info, gdbarch);
 104
 105   /* Hook into the MDEBUG frame unwinder.  */
 106   alpha_mdebug_init_abi (info, gdbarch);
 107
 108   /* OpenBSD/alpha 3.0 and earlier does not provide single step
 109      support via ptrace(2); use software single-stepping for now.  */
 110   set_gdbarch_software_single_step (gdbarch, alpha_software_single_step);
 111
 112   /* OpenBSD/alpha has SVR4-style shared libraries.  */
 113   set_solib_svr4_fetch_link_map_offsets
 114     (gdbarch, svr4_lp64_fetch_link_map_offsets);
 115   set_gdbarch_skip_solib_resolver (gdbarch, obsd_skip_solib_resolver);
 116
 117   tdep->dynamic_sigtramp_offset = alphaobsd_sigtramp_offset;
 118   tdep->pc_in_sigtramp = alphaobsd_pc_in_sigtramp;
 119   tdep->sigcontext_addr = alphaobsd_sigcontext_addr;
 120
 121   tdep->jb_pc = 2;
 122   tdep->jb_elt_size = 8;
 123
 124   set_gdbarch_iterate_over_regset_sections
 125     (gdbarch, alphanbsd_iterate_over_regset_sections);
 126 }
 127 \f
 128
 129 void
 130 _initialize_alphaobsd_tdep (void)
 131 {
 132   gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_OPENBSD,
 133                           alphaobsd_init_abi);
 134 }