Commit | Line | Data |
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1da177e4 LT |
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/linkage.h> | |
27 | #include <asm/segment.h> | |
968de4f0 | 28 | #include <asm/page.h> |
e69f202d | 29 | #include <asm/boot.h> |
1da177e4 | 30 | |
c6b33cc4 | 31 | .section ".text.head","ax",@progbits |
1da177e4 | 32 | .globl startup_32 |
968de4f0 | 33 | |
1da177e4 LT |
34 | startup_32: |
35 | cld | |
36 | cli | |
37 | movl $(__BOOT_DS),%eax | |
38 | movl %eax,%ds | |
39 | movl %eax,%es | |
40 | movl %eax,%fs | |
41 | movl %eax,%gs | |
968de4f0 | 42 | movl %eax,%ss |
1da177e4 | 43 | |
968de4f0 EB |
44 | /* Calculate the delta between where we were compiled to run |
45 | * at and where we were actually loaded at. This can only be done | |
46 | * with a short local call on x86. Nothing else will tell us what | |
47 | * address we are running at. The reserved chunk of the real-mode | |
85414b69 PA |
48 | * data at 0x1e4 (defined as a scratch field) are used as the stack |
49 | * for this calculation. Only 4 bytes are needed. | |
968de4f0 | 50 | */ |
85414b69 | 51 | leal (0x1e4+4)(%esi), %esp |
968de4f0 EB |
52 | call 1f |
53 | 1: popl %ebp | |
54 | subl $1b, %ebp | |
55 | ||
e69f202d VG |
56 | /* %ebp contains the address we are loaded at by the boot loader and %ebx |
57 | * contains the address where we should move the kernel image temporarily | |
58 | * for safe in-place decompression. | |
968de4f0 | 59 | */ |
e69f202d | 60 | |
968de4f0 | 61 | #ifdef CONFIG_RELOCATABLE |
e69f202d VG |
62 | movl %ebp, %ebx |
63 | addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebx | |
64 | andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebx | |
968de4f0 | 65 | #else |
e69f202d | 66 | movl $LOAD_PHYSICAL_ADDR, %ebx |
968de4f0 EB |
67 | #endif |
68 | ||
69 | /* Replace the compressed data size with the uncompressed size */ | |
70 | subl input_len(%ebp), %ebx | |
71 | movl output_len(%ebp), %eax | |
72 | addl %eax, %ebx | |
73 | /* Add 8 bytes for every 32K input block */ | |
74 | shrl $12, %eax | |
75 | addl %eax, %ebx | |
76 | /* Add 32K + 18 bytes of extra slack */ | |
77 | addl $(32768 + 18), %ebx | |
78 | /* Align on a 4K boundary */ | |
79 | addl $4095, %ebx | |
80 | andl $~4095, %ebx | |
81 | ||
82 | /* Copy the compressed kernel to the end of our buffer | |
83 | * where decompression in place becomes safe. | |
84 | */ | |
85 | pushl %esi | |
86 | leal _end(%ebp), %esi | |
87 | leal _end(%ebx), %edi | |
88 | movl $(_end - startup_32), %ecx | |
89 | std | |
90 | rep | |
91 | movsb | |
92 | cld | |
93 | popl %esi | |
94 | ||
95 | /* Compute the kernel start address. | |
96 | */ | |
97 | #ifdef CONFIG_RELOCATABLE | |
e69f202d VG |
98 | addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebp |
99 | andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebp | |
968de4f0 | 100 | #else |
e69f202d | 101 | movl $LOAD_PHYSICAL_ADDR, %ebp |
968de4f0 | 102 | #endif |
1da177e4 LT |
103 | |
104 | /* | |
968de4f0 | 105 | * Jump to the relocated address. |
1da177e4 | 106 | */ |
968de4f0 EB |
107 | leal relocated(%ebx), %eax |
108 | jmp *%eax | |
109 | .section ".text" | |
110 | relocated: | |
111 | ||
1da177e4 LT |
112 | /* |
113 | * Clear BSS | |
114 | */ | |
115 | xorl %eax,%eax | |
968de4f0 EB |
116 | leal _edata(%ebx),%edi |
117 | leal _end(%ebx), %ecx | |
1da177e4 LT |
118 | subl %edi,%ecx |
119 | cld | |
120 | rep | |
121 | stosb | |
968de4f0 EB |
122 | |
123 | /* | |
124 | * Setup the stack for the decompressor | |
125 | */ | |
126 | leal stack_end(%ebx), %esp | |
127 | ||
1da177e4 LT |
128 | /* |
129 | * Do the decompression, and jump to the new kernel.. | |
130 | */ | |
968de4f0 EB |
131 | movl output_len(%ebx), %eax |
132 | pushl %eax | |
133 | pushl %ebp # output address | |
134 | movl input_len(%ebx), %eax | |
135 | pushl %eax # input_len | |
136 | leal input_data(%ebx), %eax | |
137 | pushl %eax # input_data | |
138 | leal _end(%ebx), %eax | |
139 | pushl %eax # end of the image as third argument | |
1da177e4 | 140 | pushl %esi # real mode pointer as second arg |
1da177e4 | 141 | call decompress_kernel |
968de4f0 EB |
142 | addl $20, %esp |
143 | popl %ecx | |
144 | ||
145 | #if CONFIG_RELOCATABLE | |
146 | /* Find the address of the relocations. | |
147 | */ | |
148 | movl %ebp, %edi | |
149 | addl %ecx, %edi | |
150 | ||
151 | /* Calculate the delta between where vmlinux was compiled to run | |
152 | * and where it was actually loaded. | |
153 | */ | |
154 | movl %ebp, %ebx | |
e69f202d VG |
155 | subl $LOAD_PHYSICAL_ADDR, %ebx |
156 | jz 2f /* Nothing to be done if loaded at compiled addr. */ | |
1da177e4 | 157 | /* |
968de4f0 | 158 | * Process relocations. |
1da177e4 | 159 | */ |
968de4f0 EB |
160 | |
161 | 1: subl $4, %edi | |
162 | movl 0(%edi), %ecx | |
163 | testl %ecx, %ecx | |
164 | jz 2f | |
165 | addl %ebx, -__PAGE_OFFSET(%ebx, %ecx) | |
166 | jmp 1b | |
167 | 2: | |
168 | #endif | |
1da177e4 LT |
169 | |
170 | /* | |
968de4f0 | 171 | * Jump to the decompressed kernel. |
1da177e4 | 172 | */ |
1da177e4 | 173 | xorl %ebx,%ebx |
968de4f0 EB |
174 | jmp *%ebp |
175 | ||
176 | .bss | |
177 | .balign 4 | |
178 | stack: | |
179 | .fill 4096, 1, 0 | |
180 | stack_end: |