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 #include "solib-svr4.h"
  26
  27 #include "alpha-tdep.h"
  28
  29 /* Under GNU/Linux, signal handler invocations can be identified by
  30    the 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 a sequence that copies $sp to $16, loads $0 with the
  33    appropriate syscall number, and finally enters the kernel.
  34
  35    This is somewhat complicated in that:
  36      (1) the expansion of the "mov" assembler macro has changed over
  37          time, from "bis src,src,dst" to "bis zero,src,dst",
  38      (2) the kernel has changed from using "addq" to "lda" to load the
  39          syscall number,
  40      (3) there is a "normal" sigreturn and an "rt" sigreturn which
  41          has a different stack layout.
  42 */
  43
  44 static long
  45 alpha_linux_sigtramp_offset_1 (CORE_ADDR pc)
  46 {
  47   switch (alpha_read_insn (pc))
  48     {
  49     case 0x47de0410:            /* bis $30,$30,$16 */
  50     case 0x47fe0410:            /* bis $31,$30,$16 */
  51       return 0;
  52
  53     case 0x43ecf400:            /* addq $31,103,$0 */
  54     case 0x201f0067:            /* lda $0,103($31) */
  55     case 0x201f015f:            /* lda $0,351($31) */
  56       return 4;
  57
  58     case 0x00000083:            /* call_pal callsys */
  59       return 8;
  60
  61     default:
  62       return -1;
  63     }
  64 }
  65
  66 static LONGEST
  67 alpha_linux_sigtramp_offset (CORE_ADDR pc)
  68 {
  69   long i, off;
  70
  71   if (pc & 3)
  72     return -1;
  73
  74   /* Guess where we might be in the sequence.  */
  75   off = alpha_linux_sigtramp_offset_1 (pc);
  76   if (off < 0)
  77     return -1;
  78
  79   /* Verify that the other two insns of the sequence are as we expect.  */
  80   pc -= off;
  81   for (i = 0; i < 12; i += 4)
  82     {
  83       if (i == off)
  84         continue;
  85       if (alpha_linux_sigtramp_offset_1 (pc + i) != i)
  86         return -1;
  87     }
  88
  89   return off;
  90 }
  91
  92 static int
  93 alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name)
  94 {
  95   return alpha_linux_sigtramp_offset (pc) >= 0;
  96 }
  97
  98 static CORE_ADDR
  99 alpha_linux_sigcontext_addr (struct frame_info *next_frame)
 100 {
 101   CORE_ADDR pc;
 102   ULONGEST sp;
 103   long off;
 104
 105   pc = frame_pc_unwind (next_frame);
 106   frame_unwind_unsigned_register (next_frame, ALPHA_SP_REGNUM, &sp);
 107
 108   off = alpha_linux_sigtramp_offset (pc);
 109   gdb_assert (off >= 0);
 110
 111   /* __NR_rt_sigreturn has a couple of structures on the stack.  This is:
 112
 113         struct rt_sigframe {
 114           struct siginfo info;
 115           struct ucontext uc;
 116         };
 117
 118         offsetof (struct rt_sigframe, uc.uc_mcontext);
 119   */
 120   if (alpha_read_insn (pc - off + 4) == 0x201f015f)
 121     return sp + 176;
 122
 123   /* __NR_sigreturn has the sigcontext structure at the top of the stack.  */
 124   return sp;
 125 }
 126
 127 static void
 128 alpha_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 129 {
 130   struct gdbarch_tdep *tdep;
 131
 132   /* Hook into the DWARF CFI frame unwinder.  */
 133   alpha_dwarf2_init_abi (info, gdbarch);
 134
 135   /* Hook into the MDEBUG frame unwinder.  */
 136   alpha_mdebug_init_abi (info, gdbarch);
 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->pc_in_sigtramp = alpha_linux_pc_in_sigtramp;
 142   tdep->jb_pc = 2;
 143   tdep->jb_elt_size = 8;
 144
 145   /* Enable TLS support.  */
 146   set_gdbarch_fetch_tls_load_module_address (gdbarch,
 147                                              svr4_fetch_objfile_link_map);
 148 }
 149
 150 void
 151 _initialize_alpha_linux_tdep (void)
 152 {
 153   gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_LINUX,
 154                           alpha_linux_init_abi);
 155 }