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 "frame-base.h"
  24 #include "frame-unwind.h"
  25 #include "dwarf2-frame.h"
  26 #include "gdbcore.h"
  27 #include "gdb_assert.h"
  28 #include "osabi.h"
  29 #include "symtab.h"
  30 #include "symfile.h"
  31 #include "value.h"
  32
  33 #include "alpha-tdep.h"
  34
  35 /* Under GNU/Linux, signal handler invocations can be identified by
  36    the designated code sequence that is used to return from a signal
  37    handler.  In particular, the return address of a signal handler
  38    points to a sequence that copies $sp to $16, loads $0 with the
  39    appropriate syscall number, and finally enters the kernel.
  40
  41    This is somewhat complicated in that:
  42      (1) the expansion of the "mov" assembler macro has changed over
  43          time, from "bis src,src,dst" to "bis zero,src,dst",
  44      (2) the kernel has changed from using "addq" to "lda" to load the
  45          syscall number,
  46      (3) there is a "normal" sigreturn and an "rt" sigreturn which
  47          has a different stack layout.
  48 */
  49
  50 static long
  51 alpha_linux_sigtramp_offset_1 (CORE_ADDR pc)
  52 {
  53   switch (alpha_read_insn (pc))
  54     {
  55     case 0x47de0410:            /* bis $30,$30,$16 */
  56     case 0x47fe0410:            /* bis $31,$30,$16 */
  57       return 0;
  58
  59     case 0x43ecf400:            /* addq $31,103,$0 */
  60     case 0x201f0067:            /* lda $0,103($31) */
  61     case 0x201f015f:            /* lda $0,351($31) */
  62       return 4;
  63
  64     case 0x00000083:            /* call_pal callsys */
  65       return 8;
  66
  67     default:
  68       return -1;
  69     }
  70 }
  71
  72 static LONGEST
  73 alpha_linux_sigtramp_offset (CORE_ADDR pc)
  74 {
  75   long i, off;
  76
  77   if (pc & 3)
  78     return -1;
  79
  80   /* Guess where we might be in the sequence.  */
  81   off = alpha_linux_sigtramp_offset_1 (pc);
  82   if (off < 0)
  83     return -1;
  84
  85   /* Verify that the other two insns of the sequence are as we expect.  */
  86   pc -= off;
  87   for (i = 0; i < 12; i += 4)
  88     {
  89       if (i == off)
  90         continue;
  91       if (alpha_linux_sigtramp_offset_1 (pc + i) != i)
  92         return -1;
  93     }
  94
  95   return off;
  96 }
  97
  98 static int
  99 alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name)
 100 {
 101   return alpha_linux_sigtramp_offset (pc) >= 0;
 102 }
 103
 104 static CORE_ADDR
 105 alpha_linux_sigcontext_addr (struct frame_info *next_frame)
 106 {
 107   CORE_ADDR pc;
 108   ULONGEST sp;
 109   long off;
 110
 111   pc = frame_pc_unwind (next_frame);
 112   frame_unwind_unsigned_register (next_frame, ALPHA_SP_REGNUM, &sp);
 113
 114   off = alpha_linux_sigtramp_offset (pc);
 115   gdb_assert (off >= 0);
 116
 117   /* __NR_rt_sigreturn has a couple of structures on the stack.  This is:
 118
 119         struct rt_sigframe {
 120           struct siginfo info;
 121           struct ucontext uc;
 122         };
 123
 124         offsetof (struct rt_sigframe, uc.uc_mcontext);
 125   */
 126   if (alpha_read_insn (pc - off + 4) == 0x201f015f)
 127     return sp + 176;
 128
 129   /* __NR_sigreturn has the sigcontext structure at the top of the stack.  */
 130   return sp;
 131 }
 132
 133 static void
 134 alpha_linux_init_abi (struct gdbarch_info info,
 135                       struct gdbarch *gdbarch)
 136 {
 137   struct gdbarch_tdep *tdep;
 138
 139   /* Hook into the DWARF CFI frame unwinder.  */
 140   frame_unwind_append_predicate (gdbarch, dwarf2_frame_p);
 141   frame_base_append_predicate (gdbarch, dwarf2_frame_base_p);
 142   set_gdbarch_dwarf2_build_frame_info (gdbarch, dwarf2_build_frame_info);
 143
 144   /* Hook into the MDEBUG frame unwinder.  */
 145   alpha_mdebug_init_abi (info, gdbarch);
 146
 147   set_gdbarch_pc_in_sigtramp (gdbarch, alpha_linux_pc_in_sigtramp);
 148
 149   tdep = gdbarch_tdep (gdbarch);
 150   tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset;
 151   tdep->sigcontext_addr = alpha_linux_sigcontext_addr;
 152   tdep->jb_pc = 2;
 153   tdep->jb_elt_size = 8;
 154 }
 155
 156 void
 157 _initialize_alpha_linux_tdep (void)
 158 {
 159   gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_LINUX,
 160                           alpha_linux_init_abi);
 161 }