1/*
2 *  linux/boot/head.S
3 *
4 *  Copyright (C) 1991, 1992, 1993  Linus Torvalds
5 */
6
7/*
8 *  head.S contains the 32-bit startup code.
9 *
10 * NOTE!!! Startup happens at absolute address 0x00001000, which is also where
11 * the page directory will exist. The startup code will be overwritten by
12 * the page directory. [According to comments etc elsewhere on a compressed
13 * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC]
14 *
15 * Page 0 is deliberately kept safe, since System Management Mode code in
16 * laptops may need to access the BIOS data stored there.  This is also
17 * useful for future device drivers that either access the BIOS via VM86
18 * mode.
19 */
20
21/*
22 * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996
23 */
24	.text
25
26#include <linux/init.h>
27#include <linux/linkage.h>
28#include <asm/segment.h>
29#include <asm/page_types.h>
30#include <asm/boot.h>
31#include <asm/asm-offsets.h>
32
33	__HEAD
34ENTRY(startup_32)
35#ifdef CONFIG_EFI_STUB
36	jmp	preferred_addr
37
38	/*
39	 * We don't need the return address, so set up the stack so
40	 * efi_main() can find its arguments.
41	 */
42ENTRY(efi_pe_entry)
43	add	$0x4, %esp
44
45	call	1f
461:	popl	%esi
47	subl	$1b, %esi
48
49	popl	%ecx
50	movl	%ecx, efi32_config(%esi)	/* Handle */
51	popl	%ecx
52	movl	%ecx, efi32_config+8(%esi)	/* EFI System table pointer */
53
54	/* Relocate efi_config->call() */
55	leal	efi32_config(%esi), %eax
56	add	%esi, 88(%eax)
57	pushl	%eax
58
59	call	make_boot_params
60	cmpl	$0, %eax
61	je	fail
62	movl	%esi, BP_code32_start(%eax)
63	popl	%ecx
64	pushl	%eax
65	pushl	%ecx
66	jmp	2f		/* Skip efi_config initialization */
67
68ENTRY(efi32_stub_entry)
69	add	$0x4, %esp
70	popl	%ecx
71	popl	%edx
72
73	call	1f
741:	popl	%esi
75	subl	$1b, %esi
76
77	movl	%ecx, efi32_config(%esi)	/* Handle */
78	movl	%edx, efi32_config+8(%esi)	/* EFI System table pointer */
79
80	/* Relocate efi_config->call() */
81	leal	efi32_config(%esi), %eax
82	add	%esi, 88(%eax)
83	pushl	%eax
842:
85	call	efi_main
86	cmpl	$0, %eax
87	movl	%eax, %esi
88	jne	2f
89fail:
90	/* EFI init failed, so hang. */
91	hlt
92	jmp	fail
932:
94	movl	BP_code32_start(%esi), %eax
95	leal	preferred_addr(%eax), %eax
96	jmp	*%eax
97
98preferred_addr:
99#endif
100	cld
101	/*
102	 * Test KEEP_SEGMENTS flag to see if the bootloader is asking
103	 * us to not reload segments
104	 */
105	testb	$(1<<6), BP_loadflags(%esi)
106	jnz	1f
107
108	cli
109	movl	$__BOOT_DS, %eax
110	movl	%eax, %ds
111	movl	%eax, %es
112	movl	%eax, %fs
113	movl	%eax, %gs
114	movl	%eax, %ss
1151:
116
117/*
118 * Calculate the delta between where we were compiled to run
119 * at and where we were actually loaded at.  This can only be done
120 * with a short local call on x86.  Nothing  else will tell us what
121 * address we are running at.  The reserved chunk of the real-mode
122 * data at 0x1e4 (defined as a scratch field) are used as the stack
123 * for this calculation. Only 4 bytes are needed.
124 */
125	leal	(BP_scratch+4)(%esi), %esp
126	call	1f
1271:	popl	%ebp
128	subl	$1b, %ebp
129
130/*
131 * %ebp contains the address we are loaded at by the boot loader and %ebx
132 * contains the address where we should move the kernel image temporarily
133 * for safe in-place decompression.
134 */
135
136#ifdef CONFIG_RELOCATABLE
137	movl	%ebp, %ebx
138	movl	BP_kernel_alignment(%esi), %eax
139	decl	%eax
140	addl    %eax, %ebx
141	notl	%eax
142	andl    %eax, %ebx
143	cmpl	$LOAD_PHYSICAL_ADDR, %ebx
144	jge	1f
145#endif
146	movl	$LOAD_PHYSICAL_ADDR, %ebx
1471:
148
149	/* Target address to relocate to for decompression */
150	addl	$z_extract_offset, %ebx
151
152	/* Set up the stack */
153	leal	boot_stack_end(%ebx), %esp
154
155	/* Zero EFLAGS */
156	pushl	$0
157	popfl
158
159/*
160 * Copy the compressed kernel to the end of our buffer
161 * where decompression in place becomes safe.
162 */
163	pushl	%esi
164	leal	(_bss-4)(%ebp), %esi
165	leal	(_bss-4)(%ebx), %edi
166	movl	$(_bss - startup_32), %ecx
167	shrl	$2, %ecx
168	std
169	rep	movsl
170	cld
171	popl	%esi
172
173/*
174 * Jump to the relocated address.
175 */
176	leal	relocated(%ebx), %eax
177	jmp	*%eax
178ENDPROC(startup_32)
179
180	.text
181relocated:
182
183/*
184 * Clear BSS (stack is currently empty)
185 */
186	xorl	%eax, %eax
187	leal	_bss(%ebx), %edi
188	leal	_ebss(%ebx), %ecx
189	subl	%edi, %ecx
190	shrl	$2, %ecx
191	rep	stosl
192
193/*
194 * Adjust our own GOT
195 */
196	leal	_got(%ebx), %edx
197	leal	_egot(%ebx), %ecx
1981:
199	cmpl	%ecx, %edx
200	jae	2f
201	addl	%ebx, (%edx)
202	addl	$4, %edx
203	jmp	1b
2042:
205
206/*
207 * Do the decompression, and jump to the new kernel..
208 */
209				/* push arguments for decompress_kernel: */
210	pushl	$z_run_size	/* size of kernel with .bss and .brk */
211	pushl	$z_output_len	/* decompressed length, end of relocs */
212	leal	z_extract_offset_negative(%ebx), %ebp
213	pushl	%ebp		/* output address */
214	pushl	$z_input_len	/* input_len */
215	leal	input_data(%ebx), %eax
216	pushl	%eax		/* input_data */
217	leal	boot_heap(%ebx), %eax
218	pushl	%eax		/* heap area */
219	pushl	%esi		/* real mode pointer */
220	call	decompress_kernel /* returns kernel location in %eax */
221	addl	$28, %esp
222
223/*
224 * Jump to the decompressed kernel.
225 */
226	xorl	%ebx, %ebx
227	jmp	*%eax
228
229#ifdef CONFIG_EFI_STUB
230	.data
231efi32_config:
232	.fill 11,8,0
233	.long efi_call_phys
234	.long 0
235	.byte 0
236#endif
237
238/*
239 * Stack and heap for uncompression
240 */
241	.bss
242	.balign 4
243boot_heap:
244	.fill BOOT_HEAP_SIZE, 1, 0
245boot_stack:
246	.fill BOOT_STACK_SIZE, 1, 0
247boot_stack_end:
248