1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
|
/*
* Interrupt Descriptor Table (IDT) setup and interrupt handlers for GDB stub.
*/
#include <librm.h>
#define SIZEOF_I386_REGS 32
#define SIZEOF_I386_FLAGS 4
/****************************************************************************
* Interrupt Descriptor Table
****************************************************************************
*/
.section ".data16", "aw", @progbits
.globl idtr
idtr:
idt_limit:
.word idt_length - 1
idt_base:
.long 0
/* IDT entries have the following format:
* offset_lo, segment selector, flags, offset_hi
*
* Since it is not possible to specify relocations in arbitrary
* expressions like (int_overflow & 0xffff), we initialise the
* IDT with entries in an incorrect format.
*
* The entries are shuffled into the correct format in init_librm().
*/
#define IDT_ENTRY_EMPTY(name) .word 0, 0, 0, 0
#define IDT_ENTRY_PRESENT(name) \
.long int_##name; \
.word 0x8e00, VIRTUAL_CS
.align 16
idt:
IDT_ENTRY_PRESENT(divide_error)
IDT_ENTRY_PRESENT(debug_trap)
IDT_ENTRY_EMPTY(non_maskable_interrupt)
IDT_ENTRY_PRESENT(breakpoint)
IDT_ENTRY_PRESENT(overflow)
IDT_ENTRY_PRESENT(bound_range_exceeded)
IDT_ENTRY_PRESENT(invalid_opcode)
IDT_ENTRY_EMPTY(device_not_available)
IDT_ENTRY_PRESENT(double_fault)
IDT_ENTRY_EMPTY(coprocessor_segment_overrun)
IDT_ENTRY_PRESENT(invalid_tss)
IDT_ENTRY_PRESENT(segment_not_present)
IDT_ENTRY_PRESENT(stack_segment_fault)
IDT_ENTRY_PRESENT(general_protection)
IDT_ENTRY_PRESENT(page_fault)
idt_end:
.equ idt_length, idt_end - idt
/* The IDT entries are fixed up (once) in init_librm() */
idt_fixed:
.byte 0
/****************************************************************************
* idt_init (real-mode near call, 16-bit real-mode near return address)
*
* Initialise the IDT, called from init_librm.
*
* Parameters:
* %eax : IDT base address
*
* Destroys %ax, %bx, and %di.
****************************************************************************
*/
.section ".text16", "ax", @progbits
.code16
.globl idt_init
idt_init:
movl %eax, idt_base
addl $idt, idt_base
/* IDT entries are only fixed up once */
movb idt_fixed, %al
orb %al, %al
jnz 2f
movb $1, idt_fixed
/* Shuffle IDT entries into the correct format */
movb $(idt_length / 8), %al
movw $idt, %bx
or %al, %al
jz 2f
1:
movw 2(%bx), %di
xchg %di, 6(%bx)
movw %di, 2(%bx)
addw $8, %bx
dec %al
jnz 1b
2:
ret
/****************************************************************************
* Interrupt handlers
****************************************************************************
*/
.section ".text", "ax", @progbits
.code32
/* POSIX signal numbers for reporting traps to GDB */
#define SIGILL 4
#define SIGTRAP 5
#define SIGBUS 7
#define SIGFPE 8
#define SIGSEGV 11
#define SIGSTKFLT 16
int_divide_error:
pushl $SIGFPE
jmp do_interrupt
int_debug_trap:
int_breakpoint:
pushl $SIGTRAP
jmp do_interrupt
int_overflow:
int_bound_range_exceeded:
pushl $SIGSTKFLT
jmp do_interrupt
int_invalid_opcode:
pushl $SIGILL
jmp do_interrupt
int_double_fault:
movl $SIGBUS, (%esp)
jmp do_interrupt
int_invalid_tss:
int_segment_not_present:
int_stack_segment_fault:
int_general_protection:
int_page_fault:
movl $SIGSEGV, (%esp)
jmp do_interrupt
/* When invoked, the stack contains: eflags, cs, eip, signo. */
#define IH_OFFSET_GDB_REGS ( 0 )
#define IH_OFFSET_GDB_EIP ( IH_OFFSET_GDB_REGS + SIZEOF_I386_REGS )
#define IH_OFFSET_GDB_EFLAGS ( IH_OFFSET_GDB_EIP + 4 )
#define IH_OFFSET_GDB_SEG_REGS ( IH_OFFSET_GDB_EFLAGS + SIZEOF_I386_FLAGS )
#define IH_OFFSET_GDB_END ( IH_OFFSET_GDB_SEG_REGS + 6 * 4 )
#define IH_OFFSET_SIGNO ( IH_OFFSET_GDB_END )
#define IH_OFFSET_OLD_EIP ( IH_OFFSET_SIGNO + 4 )
#define IH_OFFSET_OLD_CS ( IH_OFFSET_OLD_EIP + 4 )
#define IH_OFFSET_OLD_EFLAGS ( IH_OFFSET_OLD_CS + 4 )
#define IH_OFFSET_END ( IH_OFFSET_OLD_EFLAGS + 4 )
/* We also access the stack whilst still storing or restoring
* the register snapshot. Since ESP is in flux, we need
* special offsets.
*/
#define IH_OFFSET_FLUX_OLD_CS ( IH_OFFSET_OLD_CS - 44 )
#define IH_OFFSET_FLUX_OLD_EFLAGS ( IH_OFFSET_OLD_EFLAGS - 40 )
#define IH_OFFSET_FLUX_OLD_EIP ( IH_OFFSET_OLD_EIP - 36 )
#define IH_OFFSET_FLUX_END ( IH_OFFSET_END - 20 )
do_interrupt:
/* Store CPU state in GDB register snapshot */
pushw $0
pushw %gs
pushw $0
pushw %fs
pushw $0
pushw %es
pushw $0
pushw %ds
pushw $0
pushw %ss
pushw $0
pushw IH_OFFSET_FLUX_OLD_CS + 2(%esp)
pushl IH_OFFSET_FLUX_OLD_EFLAGS(%esp)
pushl IH_OFFSET_FLUX_OLD_EIP(%esp)
pushl %edi
pushl %esi
pushl %ebp
leal IH_OFFSET_FLUX_END(%esp), %edi
pushl %edi /* old ESP */
pushl %ebx
pushl %edx
pushl %ecx
pushl %eax
/* Call GDB stub exception handler */
pushl %esp
pushl (IH_OFFSET_SIGNO + 4)(%esp)
call gdbmach_handler
addl $8, %esp
/* Restore CPU state from GDB register snapshot */
popl %eax
popl %ecx
popl %edx
popl %ebx
addl $4, %esp /* Changing ESP currently not supported */
popl %ebp
popl %esi
popl %edi
popl IH_OFFSET_FLUX_OLD_EIP(%esp)
popl IH_OFFSET_FLUX_OLD_EFLAGS(%esp)
popl IH_OFFSET_FLUX_OLD_CS(%esp)
popl %ss
popl %ds
popl %es
popl %fs
popl %gs
addl $4, %esp /* drop signo */
iret
|
