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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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/linkage.h>
27#include <asm/segment.h>
Eric W. Biederman968de4f2006-12-07 02:14:04 +010028#include <asm/page.h>
Vivek Goyale69f2022006-12-07 02:14:04 +010029#include <asm/boot.h>
Rusty Russella24e7852007-10-21 16:41:35 -070030#include <asm/asm-offsets.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070031
Segher Boessenkoolc6b33cc2007-01-02 11:41:47 +053032.section ".text.head","ax",@progbits
Linus Torvalds1da177e2005-04-16 15:20:36 -070033 .globl startup_32
Eric W. Biederman968de4f2006-12-07 02:14:04 +010034
Linus Torvalds1da177e2005-04-16 15:20:36 -070035startup_32:
Eric W. Biedermanbd531472007-10-26 11:29:04 -060036 cld
Rusty Russella24e7852007-10-21 16:41:35 -070037 /* test KEEP_SEGMENTS flag to see if the bootloader is asking
38 * us to not reload segments */
39 testb $(1<<6), BP_loadflags(%esi)
Eric W. Biedermanbd531472007-10-26 11:29:04 -060040 jnz 1f
Rusty Russella24e7852007-10-21 16:41:35 -070041
Eric W. Biedermanbd531472007-10-26 11:29:04 -060042 cli
Linus Torvalds1da177e2005-04-16 15:20:36 -070043 movl $(__BOOT_DS),%eax
44 movl %eax,%ds
45 movl %eax,%es
46 movl %eax,%fs
47 movl %eax,%gs
Eric W. Biederman968de4f2006-12-07 02:14:04 +010048 movl %eax,%ss
Eric W. Biedermanbd531472007-10-26 11:29:04 -0600491:
Rusty Russella24e7852007-10-21 16:41:35 -070050
Eric W. Biederman968de4f2006-12-07 02:14:04 +010051/* Calculate the delta between where we were compiled to run
52 * at and where we were actually loaded at. This can only be done
53 * with a short local call on x86. Nothing else will tell us what
54 * address we are running at. The reserved chunk of the real-mode
H. Peter Anvin85414b62007-07-11 12:18:33 -070055 * data at 0x1e4 (defined as a scratch field) are used as the stack
56 * for this calculation. Only 4 bytes are needed.
Eric W. Biederman968de4f2006-12-07 02:14:04 +010057 */
H. Peter Anvin85414b62007-07-11 12:18:33 -070058 leal (0x1e4+4)(%esi), %esp
Eric W. Biederman968de4f2006-12-07 02:14:04 +010059 call 1f
601: popl %ebp
61 subl $1b, %ebp
62
Vivek Goyale69f2022006-12-07 02:14:04 +010063/* %ebp contains the address we are loaded at by the boot loader and %ebx
64 * contains the address where we should move the kernel image temporarily
65 * for safe in-place decompression.
Eric W. Biederman968de4f2006-12-07 02:14:04 +010066 */
Vivek Goyale69f2022006-12-07 02:14:04 +010067
Eric W. Biederman968de4f2006-12-07 02:14:04 +010068#ifdef CONFIG_RELOCATABLE
Vivek Goyale69f2022006-12-07 02:14:04 +010069 movl %ebp, %ebx
70 addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebx
71 andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebx
Eric W. Biederman968de4f2006-12-07 02:14:04 +010072#else
Vivek Goyale69f2022006-12-07 02:14:04 +010073 movl $LOAD_PHYSICAL_ADDR, %ebx
Eric W. Biederman968de4f2006-12-07 02:14:04 +010074#endif
75
76 /* Replace the compressed data size with the uncompressed size */
77 subl input_len(%ebp), %ebx
78 movl output_len(%ebp), %eax
79 addl %eax, %ebx
80 /* Add 8 bytes for every 32K input block */
81 shrl $12, %eax
82 addl %eax, %ebx
83 /* Add 32K + 18 bytes of extra slack */
84 addl $(32768 + 18), %ebx
85 /* Align on a 4K boundary */
86 addl $4095, %ebx
87 andl $~4095, %ebx
88
89/* Copy the compressed kernel to the end of our buffer
90 * where decompression in place becomes safe.
91 */
92 pushl %esi
93 leal _end(%ebp), %esi
94 leal _end(%ebx), %edi
95 movl $(_end - startup_32), %ecx
96 std
97 rep
98 movsb
99 cld
100 popl %esi
101
102/* Compute the kernel start address.
103 */
104#ifdef CONFIG_RELOCATABLE
Vivek Goyale69f2022006-12-07 02:14:04 +0100105 addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebp
106 andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebp
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100107#else
Vivek Goyale69f2022006-12-07 02:14:04 +0100108 movl $LOAD_PHYSICAL_ADDR, %ebp
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100109#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110
111/*
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100112 * Jump to the relocated address.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 */
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100114 leal relocated(%ebx), %eax
115 jmp *%eax
116.section ".text"
117relocated:
118
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119/*
120 * Clear BSS
121 */
122 xorl %eax,%eax
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100123 leal _edata(%ebx),%edi
124 leal _end(%ebx), %ecx
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125 subl %edi,%ecx
126 cld
127 rep
128 stosb
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100129
130/*
131 * Setup the stack for the decompressor
132 */
Alexander van Heukelum7c539762008-04-08 12:54:30 +0200133 leal boot_stack_end(%ebx), %esp
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100134
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135/*
136 * Do the decompression, and jump to the new kernel..
137 */
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100138 movl output_len(%ebx), %eax
139 pushl %eax
140 pushl %ebp # output address
141 movl input_len(%ebx), %eax
142 pushl %eax # input_len
143 leal input_data(%ebx), %eax
144 pushl %eax # input_data
Alexander van Heukelum7c539762008-04-08 12:54:30 +0200145 leal boot_heap(%ebx), %eax
146 pushl %eax # heap area as third argument
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147 pushl %esi # real mode pointer as second arg
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148 call decompress_kernel
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100149 addl $20, %esp
150 popl %ecx
151
152#if CONFIG_RELOCATABLE
153/* Find the address of the relocations.
154 */
155 movl %ebp, %edi
156 addl %ecx, %edi
157
158/* Calculate the delta between where vmlinux was compiled to run
159 * and where it was actually loaded.
160 */
161 movl %ebp, %ebx
Vivek Goyale69f2022006-12-07 02:14:04 +0100162 subl $LOAD_PHYSICAL_ADDR, %ebx
163 jz 2f /* Nothing to be done if loaded at compiled addr. */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700164/*
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100165 * Process relocations.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167
Eric W. Biederman968de4f2006-12-07 02:14:04 +01001681: subl $4, %edi
169 movl 0(%edi), %ecx
170 testl %ecx, %ecx
171 jz 2f
172 addl %ebx, -__PAGE_OFFSET(%ebx, %ecx)
173 jmp 1b
1742:
175#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176
177/*
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100178 * Jump to the decompressed kernel.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180 xorl %ebx,%ebx
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100181 jmp *%ebp
182
183.bss
Alexander van Heukelum7c539762008-04-08 12:54:30 +0200184/* Stack and heap for uncompression */
Eric W. Biederman968de4f2006-12-07 02:14:04 +0100185.balign 4
Alexander van Heukelum7c539762008-04-08 12:54:30 +0200186boot_heap:
187 .fill BOOT_HEAP_SIZE, 1, 0
188boot_stack:
189 .fill BOOT_STACK_SIZE, 1, 0
190boot_stack_end: