source: trunk/src/gcc/libjava/include/i386-signal.h@ 2

Last change on this file since 2 was 2, checked in by bird, 22 years ago

Initial revision
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  • Property svn:eol-style set to native
  • Property svn:executable set to *
File size: 4.9 KB
Line 
1// i386-signal.h - Catch runtime signals and turn them into exceptions
2// on an i386 based Linux system.
3
4/* Copyright (C) 1998, 1999, 2001, 2002 Free Software Foundation
5
6 This file is part of libgcj.
7
8This software is copyrighted work licensed under the terms of the
9Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
10details. */
11
12
13#ifndef JAVA_SIGNAL_H
14#define JAVA_SIGNAL_H 1
15
16#include <signal.h>
17#include <sys/syscall.h>
18
19#define HANDLE_SEGV 1
20#define HANDLE_FPE 1
21
22#define SIGNAL_HANDLER(_name) \
23static void _name (int _dummy)
24
25#define MAKE_THROW_FRAME(_exception) \
26do \
27{ \
28 void **_p = (void **)&_dummy; \
29 struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p; \
30 \
31 /* Advance the program counter so that it is after the start of the \
32 instruction: the x86 exception handler expects \
33 the PC to point to the instruction after a call. */ \
34 _regs->eip += 2; \
35 \
36} \
37while (0)
38
39#define HANDLE_DIVIDE_OVERFLOW \
40do \
41{ \
42 void **_p = (void **)&_dummy; \
43 struct sigcontext_struct *_regs = (struct sigcontext_struct *)++_p; \
44 \
45 register unsigned char *_eip = (unsigned char *)_regs->eip; \
46 \
47 /* According to the JVM spec, "if the dividend is the negative \
48 * integer of the smallest magnitude and the divisor is -1, then \
49 * overflow occurs and the result is equal to the dividend. Despite \
50 * the overflow, no exception occurs". \
51 \
52 * We handle this by inspecting the instruction which generated the \
53 * signal and advancing eip to point to the following instruction. \
54 * As the instructions are variable length it is necessary to do a \
55 * little calculation to figure out where the following instruction \
56 * actually is. \
57 \
58 */ \
59 \
60 if (_eip[0] == 0xf7) \
61 { \
62 unsigned char _modrm = _eip[1]; \
63 \
64 if (_regs->eax == 0x80000000 \
65 && ((_modrm >> 3) & 7) == 7) /* Signed divide */ \
66 { \
67 _regs->edx = 0; /* the remainder is zero */ \
68 switch (_modrm >> 6) \
69 { \
70 case 0: \
71 if ((_modrm & 7) == 5) \
72 _eip += 4; \
73 break; \
74 case 1: \
75 _eip += 1; \
76 break; \
77 case 2: \
78 _eip += 4; \
79 break; \
80 case 3: \
81 break; \
82 } \
83 _eip += 2; \
84 _regs->eip = (unsigned long)_eip; \
85 return; \
86 } \
87 else \
88 { \
89 /* Advance the program counter so that it is after the start \
90 of the instruction: this is because the x86 exception \
91 handler expects the PC to point to the instruction after a \
92 call. */ \
93 _regs->eip += 2; \
94 } \
95 } \
96} \
97while (0)
98
99/* We use old_kernel_sigaction here because we're calling the kernel
100 directly rather than via glibc. The sigaction structure that the
101 syscall uses is a different shape from the one in userland and not
102 visible to us in a header file so we define it here. */
103
104struct old_i386_kernel_sigaction {
105 void (*k_sa_handler) (int);
106 unsigned long k_sa_mask;
107 unsigned long k_sa_flags;
108 void (*sa_restorer) (void);
109};
110
111#define INIT_SEGV \
112do \
113 { \
114 nullp = new java::lang::NullPointerException (); \
115 struct old_i386_kernel_sigaction kact; \
116 kact.k_sa_handler = catch_segv; \
117 kact.k_sa_mask = 0; \
118 kact.k_sa_flags = 0; \
119 syscall (SYS_sigaction, SIGSEGV, &kact, NULL); \
120 } \
121while (0)
122
123#define INIT_FPE \
124do \
125 { \
126 arithexception = new java::lang::ArithmeticException \
127 (JvNewStringLatin1 ("/ by zero")); \
128 struct old_i386_kernel_sigaction kact; \
129 kact.k_sa_handler = catch_fpe; \
130 kact.k_sa_mask = 0; \
131 kact.k_sa_flags = 0; \
132 syscall (SYS_sigaction, SIGFPE, &kact, NULL); \
133 } \
134while (0)
135
136/* You might wonder why we use syscall(SYS_sigaction) in INIT_FPE
137 * instead of the standard sigaction(). This is necessary because of
138 * the shenanigans above where we increment the PC saved in the
139 * context and then return. This trick will only work when we are
140 * called _directly_ by the kernel, because linuxthreads wraps signal
141 * handlers and its wrappers do not copy the sigcontext struct back
142 * when returning from a signal handler. If we return from our divide
143 * handler to a linuxthreads wrapper, we will lose the PC adjustment
144 * we made and return to the faulting instruction again. Using
145 * syscall(SYS_sigaction) causes our handler to be called directly
146 * by the kernel, bypassing any wrappers.
147
148 * Also, there is at the present time no unwind info in the
149 * linuxthreads library's signal handlers and so we can't unwind
150 * through them anyway.
151
152 * Finally, the code that glibc uses to return from a signal handler
153 * is subject to change. */
154
155#endif /* JAVA_SIGNAL_H */
156
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