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
alpha_linux_sigtramp_offset_1(CORE_ADDR pc)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
alpha_linux_sigtramp_offset(CORE_ADDR pc)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
alpha_linux_pc_in_sigtramp(CORE_ADDR pc,char * func_name)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
alpha_linux_sigcontext_addr(struct frame_info * next_frame)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
alpha_linux_init_abi(struct gdbarch_info info,struct gdbarch * gdbarch)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 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
145 void
_initialize_alpha_linux_tdep(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 }
151