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 #include "gdb_assert.h"
  27
  28 #include "alpha-tdep.h"
  29
  30 /* Under GNU/Linux, signal handler invocations can be identified by
  31    the designated code sequence that is used to return from a signal
  32    handler.  In particular, the return address of a signal handler
  33    points to a sequence that copies $sp to $16, loads $0 with the
  34    appropriate syscall number, and finally enters the kernel.
  35
  36    This is somewhat complicated in that:
  37      (1) the expansion of the "mov" assembler macro has changed over
  38          time, from "bis src,src,dst" to "bis zero,src,dst",
  39      (2) the kernel has changed from using "addq" to "lda" to load the
  40          syscall number,
  41      (3) there is a "normal" sigreturn and an "rt" sigreturn which
  42          has a different stack layout.
  43 */
  44
  45 static long
  46 alpha_linux_sigtramp_offset_1 (CORE_ADDR pc)
  47 {
  48   switch (alpha_read_insn (pc))
  49     {
  50     case 0x47de0410:            /* bis $30,$30,$16 */
  51     case 0x47fe0410:            /* bis $31,$30,$16 */
  52       return 0;
  53
  54     case 0x43ecf400:            /* addq $31,103,$0 */
  55     case 0x201f0067:            /* lda $0,103($31) */
  56     case 0x201f015f:            /* lda $0,351($31) */
  57       return 4;
  58
  59     case 0x00000083:            /* call_pal callsys */
  60       return 8;
  61
  62     default:
  63       return -1;
  64     }
  65 }
  66
  67 static LONGEST
  68 alpha_linux_sigtramp_offset (CORE_ADDR pc)
  69 {
  70   long i, off;
  71
  72   if (pc & 3)
  73     return -1;
  74
  75   /* Guess where we might be in the sequence.  */
  76   off = alpha_linux_sigtramp_offset_1 (pc);
  77   if (off < 0)
  78     return -1;
  79
  80   /* Verify that the other two insns of the sequence are as we expect.  */
  81   pc -= off;
  82   for (i = 0; i < 12; i += 4)
  83     {
  84       if (i == off)
  85         continue;
  86       if (alpha_linux_sigtramp_offset_1 (pc + i) != i)
  87         return -1;
  88     }
  89
  90   return off;
  91 }
  92
  93 static int
  94 alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name)
  95 {
  96   return alpha_linux_sigtramp_offset (pc) >= 0;
  97 }
  98
  99 static CORE_ADDR
 100 alpha_linux_sigcontext_addr (struct frame_info *next_frame)
 101 {
 102   CORE_ADDR pc;
 103   ULONGEST sp;
 104   long off;
 105
 106   pc = frame_pc_unwind (next_frame);
 107   frame_unwind_unsigned_register (next_frame, ALPHA_SP_REGNUM, &sp);
 108
 109   off = alpha_linux_sigtramp_offset (pc);
 110   gdb_assert (off >= 0);
 111
 112   /* __NR_rt_sigreturn has a couple of structures on the stack.  This is:
 113
 114         struct rt_sigframe {
 115           struct siginfo info;
 116           struct ucontext uc;
 117         };
 118
 119         offsetof (struct rt_sigframe, uc.uc_mcontext);
 120   */
 121   if (alpha_read_insn (pc - off + 4) == 0x201f015f)
 122     return sp + 176;
 123
 124   /* __NR_sigreturn has the sigcontext structure at the top of the stack.  */
 125   return sp;
 126 }
 127
 128 static void
 129 alpha_linux_init_abi (struct gdbarch_info info,
 130                       struct gdbarch *gdbarch)
 131 {
 132   struct gdbarch_tdep *tdep;
 133
 134   alpha_mdebug_init_abi (info, gdbarch);
 135
 136   set_gdbarch_pc_in_sigtramp (gdbarch, alpha_linux_pc_in_sigtramp);
 137
 138   tdep = gdbarch_tdep (gdbarch);
 139   tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset;
 140   tdep->sigcontext_addr = alpha_linux_sigcontext_addr;
 141   tdep->jb_pc = 2;
 142   tdep->jb_elt_size = 8;
 143 }
 144
 145 void
 146 _initialize_alpha_linux_tdep (void)
 147 {
 148   gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_LINUX,
 149                           alpha_linux_init_abi);
 150 }