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 "gdb_assert.h"
  24 #include "osabi.h"
  25
  26 #include "alpha-tdep.h"
  27
  28 /* Under GNU/Linux, signal handler invocations can be identified by
  29    the 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 a sequence that copies $sp to $16, loads $0 with the
  32    appropriate syscall number, and finally enters the kernel.
  33
  34    This is somewhat complicated in that:
  35      (1) the expansion of the "mov" assembler macro has changed over
  36          time, from "bis src,src,dst" to "bis zero,src,dst",
  37      (2) the kernel has changed from using "addq" to "lda" to load the
  38          syscall number,
  39      (3) there is a "normal" sigreturn and an "rt" sigreturn which
  40          has a different stack layout.
  41 */
  42
  43 static long
  44 alpha_linux_sigtramp_offset_1 (CORE_ADDR pc)
  45 {
  46   switch (alpha_read_insn (pc))
  47     {
  48     case 0x47de0410:            /* bis $30,$30,$16 */
  49     case 0x47fe0410:            /* bis $31,$30,$16 */
  50       return 0;
  51
  52     case 0x43ecf400:            /* addq $31,103,$0 */
  53     case 0x201f0067:            /* lda $0,103($31) */
  54     case 0x201f015f:            /* lda $0,351($31) */
  55       return 4;
  56
  57     case 0x00000083:            /* call_pal callsys */
  58       return 8;
  59
  60     default:
  61       return -1;
  62     }
  63 }
  64
  65 static LONGEST
  66 alpha_linux_sigtramp_offset (CORE_ADDR pc)
  67 {
  68   long i, off;
  69
  70   if (pc & 3)
  71     return -1;
  72
  73   /* Guess where we might be in the sequence.  */
  74   off = alpha_linux_sigtramp_offset_1 (pc);
  75   if (off < 0)
  76     return -1;
  77
  78   /* Verify that the other two insns of the sequence are as we expect.  */
  79   pc -= off;
  80   for (i = 0; i < 12; i += 4)
  81     {
  82       if (i == off)
  83         continue;
  84       if (alpha_linux_sigtramp_offset_1 (pc + i) != i)
  85         return -1;
  86     }
  87
  88   return off;
  89 }
  90
  91 static int
  92 alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name)
  93 {
  94   return alpha_linux_sigtramp_offset (pc) >= 0;
  95 }
  96
  97 static CORE_ADDR
  98 alpha_linux_sigcontext_addr (struct frame_info *next_frame)
  99 {
 100   CORE_ADDR pc;
 101   ULONGEST sp;
 102   long off;
 103
 104   pc = frame_pc_unwind (next_frame);
 105   frame_unwind_unsigned_register (next_frame, ALPHA_SP_REGNUM, &sp);
 106
 107   off = alpha_linux_sigtramp_offset (pc);
 108   gdb_assert (off >= 0);
 109
 110   /* __NR_rt_sigreturn has a couple of structures on the stack.  This is:
 111
 112         struct rt_sigframe {
 113           struct siginfo info;
 114           struct ucontext uc;
 115         };
 116
 117         offsetof (struct rt_sigframe, uc.uc_mcontext);
 118   */
 119   if (alpha_read_insn (pc - off + 4) == 0x201f015f)
 120     return sp + 176;
 121
 122   /* __NR_sigreturn has the sigcontext structure at the top of the stack.  */
 123   return sp;
 124 }
 125
 126 static void
 127 alpha_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 128 {
 129   struct gdbarch_tdep *tdep;
 130
 131   /* Hook into the DWARF CFI frame unwinder.  */
 132   alpha_dwarf2_init_abi (info, gdbarch);
 133
 134   /* Hook into the MDEBUG frame unwinder.  */
 135   alpha_mdebug_init_abi (info, gdbarch);
 136
 137   set_gdbarch_deprecated_pc_in_sigtramp (gdbarch, alpha_linux_pc_in_sigtramp);
 138
 139   tdep = gdbarch_tdep (gdbarch);
 140   tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset;
 141   tdep->sigcontext_addr = alpha_linux_sigcontext_addr;
 142   tdep->jb_pc = 2;
 143   tdep->jb_elt_size = 8;
 144 }
 145
 146 void
 147 _initialize_alpha_linux_tdep (void)
 148 {
 149   gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_LINUX,
 150                           alpha_linux_init_abi);
 151 }