gdb/alpha-linux-tdep.c

   1 /* Target-dependent code for GNU/Linux on Alpha.
   2    Copyright 2002, 2003 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include "defs.h"
  22 #include "frame.h"
  23 #include "gdbcore.h"
  24 #include "value.h"
  25 #include "osabi.h"
  26
  27 #include "alpha-tdep.h"
  28
  29 /* Under GNU/Linux, signal handler invocations can be identified by the
  30    designated code sequence that is used to return from a signal
  31    handler.  In particular, the return address of a signal handler
  32    points to the following sequence (the first instruction is quadword
  33    aligned):
  34
  35    bis $30,$30,$16
  36    addq $31,0x67,$0
  37    call_pal callsys
  38
  39    Each instruction has a unique encoding, so we simply attempt to
  40    match the instruction the pc is pointing to with any of the above
  41    instructions.  If there is a hit, we know the offset to the start
  42    of the designated sequence and can then check whether we really are
  43    executing in a designated sequence.  If not, -1 is returned,
  44    otherwise the offset from the start of the desingated sequence is
  45    returned.
  46
  47    There is a slight chance of false hits: code could jump into the
  48    middle of the designated sequence, in which case there is no
  49    guarantee that we are in the middle of a sigreturn syscall.  Don't
  50    think this will be a problem in praxis, though.  */
  51 LONGEST
  52 alpha_linux_sigtramp_offset (CORE_ADDR pc)
  53 {
  54   unsigned int i[3], w;
  55   long off;
  56
  57   if (read_memory_nobpt (pc, (char *) &w, 4) != 0)
  58     return -1;
  59
  60   off = -1;
  61   switch (w)
  62     {
  63     case 0x47de0410:
  64       off = 0;
  65       break;                    /* bis $30,$30,$16 */
  66     case 0x43ecf400:
  67       off = 4;
  68       break;                    /* addq $31,0x67,$0 */
  69     case 0x00000083:
  70       off = 8;
  71       break;                    /* call_pal callsys */
  72     default:
  73       return -1;
  74     }
  75   pc -= off;
  76   if (pc & 0x7)
  77     {
  78       /* designated sequence is not quadword aligned */
  79       return -1;
  80     }
  81   if (read_memory_nobpt (pc, (char *) i, sizeof (i)) != 0)
  82     return -1;
  83
  84   if (i[0] == 0x47de0410 && i[1] == 0x43ecf400 && i[2] == 0x00000083)
  85     return off;
  86
  87   return -1;
  88 }
  89
  90 static int
  91 alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name)
  92 {
  93   return (alpha_linux_sigtramp_offset (pc) >= 0);
  94 }
  95
  96 static CORE_ADDR
  97 alpha_linux_sigcontext_addr (struct frame_info *frame)
  98 {
  99   return (get_frame_base (frame) - 0x298); /* sizeof(struct sigcontext) */
 100 }
 101
 102 static void
 103 alpha_linux_init_abi (struct gdbarch_info info,
 104                       struct gdbarch *gdbarch)
 105 {
 106   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 107
 108   set_gdbarch_pc_in_sigtramp (gdbarch, alpha_linux_pc_in_sigtramp);
 109
 110   tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset;
 111   tdep->sigcontext_addr = alpha_linux_sigcontext_addr;
 112
 113   tdep->jb_pc = 2;
 114   tdep->jb_elt_size = 8;
 115 }
 116
 117 void
 118 _initialize_alpha_linux_tdep (void)
 119 {
 120   gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_LINUX,
 121                           alpha_linux_init_abi);
 122 }