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
43static long
44alpha_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
65static LONGEST
66alpha_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
91static int
92alpha_linux_pc_in_sigtramp (CORE_ADDR pc, char *func_name)
93{
94  return alpha_linux_sigtramp_offset (pc) >= 0;
95}
96
97static CORE_ADDR
98alpha_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
126static void
127alpha_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  tdep = gdbarch_tdep (gdbarch);
138  tdep->dynamic_sigtramp_offset = alpha_linux_sigtramp_offset;
139  tdep->sigcontext_addr = alpha_linux_sigcontext_addr;
140  tdep->pc_in_sigtramp = alpha_linux_pc_in_sigtramp;
141  tdep->jb_pc = 2;
142  tdep->jb_elt_size = 8;
143}
144
145void
146_initialize_alpha_linux_tdep (void)
147{
148  gdbarch_register_osabi (bfd_arch_alpha, 0, GDB_OSABI_LINUX,
149                          alpha_linux_init_abi);
150}
151