gdb/alpha-obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/alpha.
   2
   3    Copyright (C) 2006-2019 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
  22 /* Local non-gdb includes.  */
  23 #include "alpha-bsd-tdep.h"
  24 #include "alpha-tdep.h"
  25 #include "frame.h"
  26 #include "gdbcore.h"
  27 #include "obsd-tdep.h"
  28 #include "osabi.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 (struct gdbarch *gdbarch, CORE_ADDR pc)
  45 {
  46   return (pc & (alphaobsd_page_size - 1));
  47 }
  48
  49 static int
  50 alphaobsd_pc_in_sigtramp (struct gdbarch *gdbarch,
  51                           CORE_ADDR pc, const char *name)
  52 {
  53   CORE_ADDR start_pc = (pc & ~(alphaobsd_page_size - 1));
  54   unsigned insn;
  55
  56   if (name)
  57     return 0;
  58
  59   /* Check for "".  */
  60   insn = alpha_read_insn (gdbarch, start_pc + 5 * ALPHA_INSN_SIZE);
  61   if (insn != 0x201f0067)
  62     return 0;
  63
  64   /* Check for "".  */
  65   insn = alpha_read_insn (gdbarch, start_pc + 6 * ALPHA_INSN_SIZE);
  66   if (insn != 0x00000083)
  67     return 0;
  68
  69   return 1;
  70 }
  71
  72 static CORE_ADDR
  73 alphaobsd_sigcontext_addr (struct frame_info *this_frame)
  74 {
  75   struct gdbarch *gdbarch = get_frame_arch (this_frame);
  76   CORE_ADDR pc = get_frame_pc (this_frame);
  77
  78   if (alphaobsd_sigtramp_offset (gdbarch, pc) < 3 * ALPHA_INSN_SIZE)
  79     {
  80       /* On entry, a pointer the `struct sigcontext' is passed in %a2.  */
  81       return get_frame_register_unsigned (this_frame, ALPHA_A0_REGNUM + 2);
  82     }
  83   else if (alphaobsd_sigtramp_offset (gdbarch, pc) < 4 * ALPHA_INSN_SIZE)
  84     {
  85       /* It is stored on the stack Before calling the signal handler.  */
  86       CORE_ADDR sp;
  87       sp = get_frame_register_unsigned (this_frame, ALPHA_SP_REGNUM);
  88       return get_frame_memory_unsigned (this_frame, sp, 8);
  89     }
  90   else
  91     {
  92       /* It is reloaded into %a0 for the sigreturn(2) call.  */
  93       return get_frame_register_unsigned (this_frame, ALPHA_A0_REGNUM);
  94     }
  95 }
  96 \f
  97
  98 static void
  99 alphaobsd_init_abi(struct gdbarch_info info, struct gdbarch *gdbarch)
 100 {
 101   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 102
 103   /* Hook into the DWARF CFI frame unwinder.  */
 104   alpha_dwarf2_init_abi (info, gdbarch);
 105
 106   /* Hook into the MDEBUG frame unwinder.  */
 107   alpha_mdebug_init_abi (info, gdbarch);
 108
 109   /* OpenBSD/alpha 3.0 and earlier does not provide single step
 110      support via ptrace(2); use software single-stepping for now.  */
 111   set_gdbarch_software_single_step (gdbarch, alpha_software_single_step);
 112
 113   /* OpenBSD/alpha has SVR4-style shared libraries.  */
 114   set_solib_svr4_fetch_link_map_offsets
 115     (gdbarch, svr4_lp64_fetch_link_map_offsets);
 116   set_gdbarch_skip_solib_resolver (gdbarch, obsd_skip_solib_resolver);
 117
 118   tdep->dynamic_sigtramp_offset = alphaobsd_sigtramp_offset;
 119   tdep->pc_in_sigtramp = alphaobsd_pc_in_sigtramp;
 120   tdep->sigcontext_addr = alphaobsd_sigcontext_addr;
 121
 122   tdep->jb_pc = 2;
 123   tdep->jb_elt_size = 8;
 124
 125   set_gdbarch_iterate_over_regset_sections
 126     (gdbarch, alphanbsd_iterate_over_regset_sections);
 127 }
 128 \f
 129
 130 void
 131 _initialize_alphaobsd_tdep (void)
 132 {
 133   gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_OPENBSD,
 134                           alphaobsd_init_abi);
 135 }