gdb/alpha-linux-tdep.c

   1 /* Target-dependent code for GNU/Linux on Alpha.
   2    Copyright 2002 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
  26 #include "alpha-tdep.h"
  27
  28 /* Under GNU/Linux, signal handler invocations can be identified by the
  29    designated code sequence that is used to return from a signal
  30    handler.  In particular, the return address of a signal handler
  31    points to the following sequence (the first instruction is quadword
  32    aligned):
  33
  34    bis $30,$30,$16
  35    addq $31,0x67,$0
  36    call_pal callsys
  37
  38    Each instruction has a unique encoding, so we simply attempt to
  39    match the instruction the pc is pointing to with any of the above
  40    instructions.  If there is a hit, we know the offset to the start
  41    of the designated sequence and can then check whether we really are
  42    executing in a designated sequence.  If not, -1 is returned,
  43    otherwise the offset from the start of the desingated sequence is
  44    returned.
  45
  46    There is a slight chance of false hits: code could jump into the
  47    middle of the designated sequence, in which case there is no
  48    guarantee that we are in the middle of a sigreturn syscall.  Don't
  49    think this will be a problem in praxis, though.  */
  50 LONGEST
  51 alpha_linux_sigtramp_offset (CORE_ADDR pc)
  52 {
  53   unsigned int i[3], w;
  54   long off;
  55
  56   if (read_memory_nobpt (pc, (char *) &w, 4) != 0)
  57     return -1;
  58
  59   off = -1;
  60   switch (w)
  61     {
  62     case 0x47de0410:
  63       off = 0;
  64       break;                    /* bis $30,$30,$16 */
  65     case 0x43ecf400:
  66       off = 4;
  67       break;                    /* addq $31,0x67,$0 */
  68     case 0x00000083:
  69       off = 8;
  70       break;                    /* call_pal callsys */
  71     default:
  72       return -1;
  73     }
  74   pc -= off;
  75   if (pc & 0x7)
  76     {
  77       /* designated sequence is not quadword aligned */
  78       return -1;
  79     }
  80   if (read_memory_nobpt (pc, (char *) i, sizeof (i)) != 0)
  81     return -1;
  82
  83   if (i[0] == 0x47de0410 && i[1] == 0x43ecf400 && i[2] == 0x00000083)
  84     return off;
  85
  86   return -1;
  87 }
  88
  89 static int
  90 alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name)
  91 {
  92   return (alpha_linux_sigtramp_offset (pc) >= 0);
  93 }
  94
  95 static CORE_ADDR
  96 alpha_linux_sigcontext_addr (struct frame_info *frame)
  97 {
  98   return (frame->frame - 0x298); /* sizeof(struct sigcontext) */
  99 }
 100
 101 static void
 102 alpha_linux_init_abi (struct gdbarch_info info,
 103                       struct gdbarch *gdbarch)
 104 {
 105   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 106
 107   set_gdbarch_pc_in_sigtramp (gdbarch, alpha_linux_pc_in_sigtramp);
 108
 109   tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset;
 110   tdep->sigcontext_addr = alpha_linux_sigcontext_addr;
 111
 112   tdep->jb_pc = 2;
 113   tdep->jb_elt_size = 8;
 114 }
 115
 116 void
 117 _initialize_alpha_linux_tdep (void)
 118 {
 119   alpha_gdbarch_register_os_abi (ALPHA_ABI_LINUX, alpha_linux_init_abi);
 120 }