summaryrefslogtreecommitdiffstats
path: root/arch/x86/boot/compressed/head_32.S
blob: 1d7fbbcc196d6f8b661545130972453f109e27d7 (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
/*
 *  linux/boot/head.S
 *
 *  Copyright (C) 1991, 1992, 1993  Linus Torvalds
 */

/*
 *  head.S contains the 32-bit startup code.
 *
 * NOTE!!! Startup happens at absolute address 0x00001000, which is also where
 * the page directory will exist. The startup code will be overwritten by
 * the page directory. [According to comments etc elsewhere on a compressed
 * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
 *
 * Page 0 is deliberately kept safe, since System Management Mode code in
 * laptops may need to access the BIOS data stored there.  This is also
 * useful for future device drivers that either access the BIOS via VM86
 * mode.
 */

/*
 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
 */
	.text

#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/segment.h>
#include <asm/page_types.h>
#include <asm/boot.h>
#include <asm/asm-offsets.h>

	__HEAD
ENTRY(startup_32)
#ifdef CONFIG_EFI_STUB
	jmp	preferred_addr

	/*
	 * We don't need the return address, so set up the stack so
	 * efi_main() can find its arguments.
	 */
ENTRY(efi_pe_entry)
	add	$0x4, %esp

	call	1f
1:	popl	%esi
	subl	$1b, %esi

	popl	%ecx
	movl	%ecx, efi32_config(%esi)	/* Handle */
	popl	%ecx
	movl	%ecx, efi32_config+8(%esi)	/* EFI System table pointer */

	/* Relocate efi_config->call() */
	leal	efi32_config(%esi), %eax
	add	%esi, 88(%eax)
	pushl	%eax

	call	make_boot_params
	cmpl	$0, %eax
	je	fail
	movl	%esi, BP_code32_start(%eax)
	popl	%ecx
	pushl	%eax
	pushl	%ecx
	jmp	2f		/* Skip efi_config initialization */

ENTRY(efi32_stub_entry)
	add	$0x4, %esp
	popl	%ecx
	popl	%edx

	call	1f
1:	popl	%esi
	subl	$1b, %esi

	movl	%ecx, efi32_config(%esi)	/* Handle */
	movl	%edx, efi32_config+8(%esi)	/* EFI System table pointer */

	/* Relocate efi_config->call() */
	leal	efi32_config(%esi), %eax
	add	%esi, 88(%eax)
	pushl	%eax
2:
	call	efi_main
	cmpl	$0, %eax
	movl	%eax, %esi
	jne	2f
fail:
	/* EFI init failed, so hang. */
	hlt
	jmp	fail
2:
	movl	BP_code32_start(%esi), %eax
	leal	preferred_addr(%eax), %eax
	jmp	*%eax

preferred_addr:
#endif
	cld
	/*
	 * Test KEEP_SEGMENTS flag to see if the bootloader is asking
	 * us to not reload segments
	 */
	testb	$(1<<6), BP_loadflags(%esi)
	jnz	1f

	cli
	movl	$__BOOT_DS, %eax
	movl	%eax, %ds
	movl	%eax, %es
	movl	%eax, %fs
	movl	%eax, %gs
	movl	%eax, %ss
1:

/*
 * Calculate the delta between where we were compiled to run
 * at and where we were actually loaded at.  This can only be done
 * with a short local call on x86.  Nothing  else will tell us what
 * address we are running at.  The reserved chunk of the real-mode
 * data at 0x1e4 (defined as a scratch field) are used as the stack
 * for this calculation. Only 4 bytes are needed.
 */
	leal	(BP_scratch+4)(%esi), %esp
	call	1f
1:	popl	%ebp
	subl	$1b, %ebp

/*
 * %ebp contains the address we are loaded at by the boot loader and %ebx
 * contains the address where we should move the kernel image temporarily
 * for safe in-place decompression.
 */

#ifdef CONFIG_RELOCATABLE
	movl	%ebp, %ebx
	movl	BP_kernel_alignment(%esi), %eax
	decl	%eax
	addl    %eax, %ebx
	notl	%eax
	andl    %eax, %ebx
	cmpl	$LOAD_PHYSICAL_ADDR, %ebx
	jge	1f
#endif
	movl	$LOAD_PHYSICAL_ADDR, %ebx
1:

	/* Target address to relocate to for decompression */
	addl	$z_extract_offset, %ebx

	/* Set up the stack */
	leal	boot_stack_end(%ebx), %esp

	/* Zero EFLAGS */
	pushl	$0
	popfl

/*
 * Copy the compressed kernel to the end of our buffer
 * where decompression in place becomes safe.
 */
	pushl	%esi
	leal	(_bss-4)(%ebp), %esi
	leal	(_bss-4)(%ebx), %edi
	movl	$(_bss - startup_32), %ecx
	shrl	$2, %ecx
	std
	rep	movsl
	cld
	popl	%esi

/*
 * Jump to the relocated address.
 */
	leal	relocated(%ebx), %eax
	jmp	*%eax
ENDPROC(startup_32)

	.text
relocated:

/*
 * Clear BSS (stack is currently empty)
 */
	xorl	%eax, %eax
	leal	_bss(%ebx), %edi
	leal	_ebss(%ebx), %ecx
	subl	%edi, %ecx
	shrl	$2, %ecx
	rep	stosl

/*
 * Adjust our own GOT
 */
	leal	_got(%ebx), %edx
	leal	_egot(%ebx), %ecx
1:
	cmpl	%ecx, %edx
	jae	2f
	addl	%ebx, (%edx)
	addl	$4, %edx
	jmp	1b
2:

/*
 * Do the decompression, and jump to the new kernel..
 */
				/* push arguments for decompress_kernel: */
	pushl	$z_run_size	/* size of kernel with .bss and .brk */
	pushl	$z_output_len	/* decompressed length, end of relocs */
	leal	z_extract_offset_negative(%ebx), %ebp
	pushl	%ebp		/* output address */
	pushl	$z_input_len	/* input_len */
	leal	input_data(%ebx), %eax
	pushl	%eax		/* input_data */
	leal	boot_heap(%ebx), %eax
	pushl	%eax		/* heap area */
	pushl	%esi		/* real mode pointer */
	call	decompress_kernel /* returns kernel location in %eax */
	addl	$28, %esp

/*
 * Jump to the decompressed kernel.
 */
	xorl	%ebx, %ebx
	jmp	*%eax

#ifdef CONFIG_EFI_STUB
	.data
efi32_config:
	.fill 11,8,0
	.long efi_call_phys
	.long 0
	.byte 0
#endif

/*
 * Stack and heap for uncompression
 */
	.bss
	.balign 4
boot_heap:
	.fill BOOT_HEAP_SIZE, 1, 0
boot_stack:
	.fill BOOT_STACK_SIZE, 1, 0
boot_stack_end: