summaryrefslogtreecommitdiff
path: root/payloads/libpayload/arch/x86/exception_asm.S
blob: b3395d0e4b0e5c16828f46a7f94b3c56bca08cea (plain)
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
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
/*
 *
 * Copyright 2013 Google Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

	.align 4
	.global exception_stack_end
exception_stack_end:
	.long 0
	.global exception_state
exception_state:
	.long 0

/* Some temporary variables which are used while saving exception state. */
vector:
	.long 0
error_code:
	.long 0
old_esp:
	.long 0
old_eax:
	.long 0

	.align 8

/*
 * Each exception vector has a small stub associated with it which sets aside
 * the error code, if any, records which vector we entered from, and calls
 * the common exception entry point. Some exceptions have error codes and some
 * don't, so we have a macro for each type.
 */

	.macro stub num
exception_stub_\num:
	movl	$0, error_code
	movl	$\num, vector
	jmp	exception_common
	.endm

	.macro stub_err num
exception_stub_\num:
	popl	error_code
	movl	$\num, vector
	jmp	exception_common
	.endm

	.altmacro
	.macro	user_defined_stubs from, to
	stub	\from
	.if	\to-\from
	user_defined_stubs	%(from+1),\to
	.endif
	.endm

	stub 0
	stub 1
	stub 2
	stub 3
	stub 4
	stub 5
	stub 6
	stub 7
	stub_err 8
	stub 9
	stub_err 10
	stub_err 11
	stub_err 12
	stub_err 13
	stub_err 14
	stub 15
	stub 16
	stub_err 17
	stub 18
	stub 19
	stub 20
	stub 21
	stub 22
	stub 23
	stub 24
	stub 25
	stub 26
	stub 27
	stub 28
	stub 29
	stub_err 30
	stub 31
	/* Split the macro so we avoid a stack overflow. */
	user_defined_stubs 32, 63
	user_defined_stubs 64, 127
	user_defined_stubs 128, 191
	user_defined_stubs 192, 255

exception_common:
	/*
	 * Save off the stack pointer and old eax value and install the
	 * exception stack. eax points to the old stack which has the
	 * exception ip, cs, and flags.
	 */
	mov	%esp, old_esp
	addl	$12, old_esp
	mov	%eax, old_eax
	mov	%esp, %eax
	mov	exception_stack_end, %esp

	/*
	 * Push values onto the top of the exception stack to form an
	 * exception state structure.
	 */
	pushl	vector
	pushl	error_code
	pushl	%gs
	pushl	%fs
	pushl	%es
	pushl	%ds
	pushl	%ss
	pushl	4(%eax)
	pushl	8(%eax)
	pushl	(%eax)
	pushl	%edi
	pushl	%esi
	pushl	%ebp
	pushl	old_esp
	pushl	%ebx
	pushl	%edx
	pushl	%ecx
	pushl	old_eax

	/*
	 * Call the C exception handler. It will find the exception state
	 * using the exception_state global pointer. Not
	 * passing parameters means we don't have to worry about what ABI
	 * is being used.
	 */
	mov	%esp, exception_state
	call	exception_dispatch

	/*
	 * Restore state from the exception state structure, including any
	 * changes that might have been made.
	 */
	popl	old_eax
	popl	%ecx
	popl	%edx
	popl	%ebx
	popl	old_esp

	mov	old_esp, %eax
	subl	$12, %eax

	popl	%ebp
	popl	%esi
	popl	%edi
	popl	(%eax)
	popl	8(%eax)
	popl	4(%eax)
	popl	%ss
	popl	%ds
	popl	%es
	popl	%fs
	popl	%gs

	mov	%eax, %esp
	mov	old_eax, %eax

	/* Return from the exception. */
	iretl

/*
 * We need segment selectors for the IDT, so we need to know where things are
 * in the GDT. We set one up here which is pretty standard and largely copied
 * from coreboot.
 */
	.align 8
gdt:
	/* selgdt 0, unused */
	.word 0x0000, 0x0000
	.byte 0x00, 0x00, 0x00, 0x00

	/* selgdt 8, unused */
	.word 0x0000, 0x0000
	.byte 0x00, 0x00, 0x00, 0x00

	/* selgdt 0x10, flat 4GB code segment */
        .word 0xffff, 0x0000
	.byte 0x00, 0x9b, 0xcf, 0x00

	/* selgdt 0x18, flat 4GB data segment */
	.word 0xffff, 0x0000
	.byte 0x00, 0x93, 0xcf, 0x00
gdt_end:

/* GDT pointer for use with lgdt */
gdt_ptr:
	.word	gdt_end - gdt - 1
	.long	gdt

	/*
	 * Record the target and construct the actual entry at init time. This
	 * is necessary because the linker doesn't want to construct the entry
	 * for us.
	 */
	.macro interrupt_gate target
	.long \target
	.long \target
	.endm

	.altmacro
	.macro	user_defined_gates from, to
	interrupt_gate	exception_stub_\from
	.if	\to-\from
	user_defined_gates	%(from+1),\to
	.endif
	.endm

	.align 8
	.global	idt
idt:
	interrupt_gate exception_stub_0
	interrupt_gate exception_stub_1
	interrupt_gate exception_stub_2
	interrupt_gate exception_stub_3
	interrupt_gate exception_stub_4
	interrupt_gate exception_stub_5
	interrupt_gate exception_stub_6
	interrupt_gate exception_stub_7
	interrupt_gate exception_stub_8
	interrupt_gate exception_stub_9
	interrupt_gate exception_stub_10
	interrupt_gate exception_stub_11
	interrupt_gate exception_stub_12
	interrupt_gate exception_stub_13
	interrupt_gate exception_stub_14
	interrupt_gate exception_stub_15
	interrupt_gate exception_stub_16
	interrupt_gate exception_stub_17
	interrupt_gate exception_stub_18
	interrupt_gate exception_stub_19
	interrupt_gate exception_stub_20
	interrupt_gate exception_stub_21
	interrupt_gate exception_stub_22
	interrupt_gate exception_stub_23
	interrupt_gate exception_stub_24
	interrupt_gate exception_stub_25
	interrupt_gate exception_stub_26
	interrupt_gate exception_stub_27
	interrupt_gate exception_stub_28
	interrupt_gate exception_stub_29
	interrupt_gate exception_stub_30
	interrupt_gate exception_stub_31
	user_defined_gates 32, 63
	user_defined_gates 64, 127
	user_defined_gates 128, 191
	user_defined_gates 192, 255
idt_end:

/* IDT pointer for use with lidt */
idt_ptr:
	.word idt_end - idt - 1
	.long idt

	.global exception_init_asm
exception_init_asm:
	/* Save eax so we can use it as a temporary variable. */
	pushl	%eax

	/* Install the GDT. */
	lgdt	gdt_ptr
	/* Load the segment registers from it. */
	ljmp	$0x10, $1f
1:	movl	$0x18, %eax
	movl	%eax, %ds
	movl	%eax, %es
	movl	%eax, %ss
	movl	%eax, %fs
	movl	%eax, %gs

	/*
	 * Loop over the entries which start out as two copies of the target
	 * address. We can turn them into real interrupt gates by selectively
	 * replacing certain bit fields.
	 */
	movl	$idt, %eax
1:
	andl	$0x0000ffff, (%eax)
	orl	$0x00100000, (%eax)
	andl	$0xffff0000, 4(%eax)
	orl	$0x0000ee00, 4(%eax)
	addl	$8, %eax
	cmp	$idt_end, %eax
	jne	1b

	/* Install the IDT. */
	lidt	idt_ptr

	/* Restore eax and return to the caller. */
	popl	%eax
	ret