gdb/alpha-obsd-tdep.c

   1 /* Target-dependent code for OpenBSD/alpha.
   2
   3    Copyright (C) 2006-2024 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 "frame.h"
  21 #include "gdbcore.h"
  22 #include "osabi.h"
  23
  24 #include "obsd-tdep.h"
  25 #include "alpha-tdep.h"
  26 #include "alpha-bsd-tdep.h"
  27 #include "solib-svr4.h"
  28
  29 /* Signal trampolines.  */
  30
  31 /* The OpenBSD kernel maps the signal trampoline at some random
  32    location in user space, which means that the traditional BSD way of
  33    detecting it won't work.
  34
  35    The signal trampoline will be mapped at an address that is page
  36    aligned.  We recognize the signal trampoline by looking for the
  37    sigreturn system call.  */
  38
  39 static const int alphaobsd_page_size = 8192;
  40
  41 static LONGEST
  42 alphaobsd_sigtramp_offset (struct gdbarch *gdbarch, CORE_ADDR pc)
  43 {
  44   return (pc & (alphaobsd_page_size - 1));
  45 }
  46
  47 static int
  48 alphaobsd_pc_in_sigtramp (struct gdbarch *gdbarch,
  49                           CORE_ADDR pc, const 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 (gdbarch, start_pc + 5 * ALPHA_INSN_SIZE);
  59   if (insn != 0x201f0067)
  60     return 0;
  61
  62   /* Check for "".  */
  63   insn = alpha_read_insn (gdbarch, 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 (const frame_info_ptr &this_frame)
  72 {
  73   struct gdbarch *gdbarch = get_frame_arch (this_frame);
  74   CORE_ADDR pc = get_frame_pc (this_frame);
  75
  76   if (alphaobsd_sigtramp_offset (gdbarch, pc) < 3 * ALPHA_INSN_SIZE)
  77     {
  78       /* On entry, a pointer the `struct sigcontext' is passed in %a2.  */
  79       return get_frame_register_unsigned (this_frame, ALPHA_A0_REGNUM + 2);
  80     }
  81   else if (alphaobsd_sigtramp_offset (gdbarch, pc) < 4 * ALPHA_INSN_SIZE)
  82     {
  83       /* It is stored on the stack Before calling the signal handler.  */
  84       CORE_ADDR sp;
  85       sp = get_frame_register_unsigned (this_frame, ALPHA_SP_REGNUM);
  86       return get_frame_memory_unsigned (this_frame, sp, 8);
  87     }
  88   else
  89     {
  90       /* It is reloaded into %a0 for the sigreturn(2) call.  */
  91       return get_frame_register_unsigned (this_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   alpha_gdbarch_tdep *tdep = gdbarch_tdep<alpha_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   set_gdbarch_skip_solib_resolver (gdbarch, obsd_skip_solib_resolver);
 115
 116   tdep->dynamic_sigtramp_offset = alphaobsd_sigtramp_offset;
 117   tdep->pc_in_sigtramp = alphaobsd_pc_in_sigtramp;
 118   tdep->sigcontext_addr = alphaobsd_sigcontext_addr;
 119
 120   tdep->jb_pc = 2;
 121   tdep->jb_elt_size = 8;
 122
 123   set_gdbarch_iterate_over_regset_sections
 124     (gdbarch, alphanbsd_iterate_over_regset_sections);
 125 }
 126 \f
 127
 128 void _initialize_alphaobsd_tdep ();
 129 void
 130 _initialize_alphaobsd_tdep ()
 131 {
 132   gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_OPENBSD,
 133                           alphaobsd_init_abi);
 134 }