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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 | * | |
5f64ec64 | 15 | * Page 0 is deliberately kept safe, since System Management Mode code in |
1da177e4 | 16 | * laptops may need to access the BIOS data stored there. This is also |
5f64ec64 | 17 | * useful for future device drivers that either access the BIOS via VM86 |
1da177e4 LT |
18 | * mode. |
19 | */ | |
20 | ||
21 | /* | |
22 | * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 | |
23 | */ | |
5f64ec64 | 24 | .text |
1da177e4 | 25 | |
1dc818c1 | 26 | #include <linux/init.h> |
1da177e4 LT |
27 | #include <linux/linkage.h> |
28 | #include <asm/segment.h> | |
0341c14d | 29 | #include <asm/page_types.h> |
e69f202d | 30 | #include <asm/boot.h> |
a24e7851 | 31 | #include <asm/asm-offsets.h> |
1da177e4 | 32 | |
1dc818c1 | 33 | __HEAD |
cb425afd | 34 | ENTRY(startup_32) |
bd53147d | 35 | cld |
5f64ec64 PA |
36 | /* |
37 | * Test KEEP_SEGMENTS flag to see if the bootloader is asking | |
38 | * us to not reload segments | |
39 | */ | |
40 | testb $(1<<6), BP_loadflags(%esi) | |
41 | jnz 1f | |
a24e7851 | 42 | |
bd53147d | 43 | cli |
5f64ec64 PA |
44 | movl $__BOOT_DS, %eax |
45 | movl %eax, %ds | |
46 | movl %eax, %es | |
47 | movl %eax, %fs | |
48 | movl %eax, %gs | |
49 | movl %eax, %ss | |
bd53147d | 50 | 1: |
a24e7851 | 51 | |
5f64ec64 PA |
52 | /* |
53 | * Calculate the delta between where we were compiled to run | |
968de4f0 EB |
54 | * at and where we were actually loaded at. This can only be done |
55 | * with a short local call on x86. Nothing else will tell us what | |
56 | * address we are running at. The reserved chunk of the real-mode | |
85414b69 PA |
57 | * data at 0x1e4 (defined as a scratch field) are used as the stack |
58 | * for this calculation. Only 4 bytes are needed. | |
968de4f0 | 59 | */ |
5f64ec64 PA |
60 | leal (BP_scratch+4)(%esi), %esp |
61 | call 1f | |
62 | 1: popl %ebp | |
63 | subl $1b, %ebp | |
968de4f0 | 64 | |
5f64ec64 PA |
65 | /* |
66 | * %ebp contains the address we are loaded at by the boot loader and %ebx | |
e69f202d VG |
67 | * contains the address where we should move the kernel image temporarily |
68 | * for safe in-place decompression. | |
968de4f0 | 69 | */ |
e69f202d | 70 | |
968de4f0 | 71 | #ifdef CONFIG_RELOCATABLE |
5f64ec64 | 72 | movl %ebp, %ebx |
37ba7ab5 PA |
73 | movl BP_kernel_alignment(%esi), %eax |
74 | decl %eax | |
75 | addl %eax, %ebx | |
76 | notl %eax | |
77 | andl %eax, %ebx | |
968de4f0 | 78 | #else |
5f64ec64 | 79 | movl $LOAD_PHYSICAL_ADDR, %ebx |
968de4f0 EB |
80 | #endif |
81 | ||
02a884c0 PA |
82 | /* Target address to relocate to for decompression */ |
83 | addl $z_extract_offset, %ebx | |
968de4f0 | 84 | |
0a137736 PA |
85 | /* Set up the stack */ |
86 | leal boot_stack_end(%ebx), %esp | |
87 | ||
97541912 PA |
88 | /* Zero EFLAGS */ |
89 | pushl $0 | |
90 | popfl | |
91 | ||
5f64ec64 PA |
92 | /* |
93 | * Copy the compressed kernel to the end of our buffer | |
968de4f0 EB |
94 | * where decompression in place becomes safe. |
95 | */ | |
5f64ec64 | 96 | pushl %esi |
36d3793c PA |
97 | leal (_bss-4)(%ebp), %esi |
98 | leal (_bss-4)(%ebx), %edi | |
5b11f1ce | 99 | movl $(_bss - startup_32), %ecx |
36d3793c | 100 | shrl $2, %ecx |
968de4f0 | 101 | std |
36d3793c | 102 | rep movsl |
968de4f0 | 103 | cld |
5f64ec64 | 104 | popl %esi |
968de4f0 | 105 | |
1da177e4 | 106 | /* |
968de4f0 | 107 | * Jump to the relocated address. |
1da177e4 | 108 | */ |
5f64ec64 PA |
109 | leal relocated(%ebx), %eax |
110 | jmp *%eax | |
cb425afd CG |
111 | ENDPROC(startup_32) |
112 | ||
5f64ec64 | 113 | .text |
968de4f0 EB |
114 | relocated: |
115 | ||
1da177e4 | 116 | /* |
0a137736 | 117 | * Clear BSS (stack is currently empty) |
1da177e4 | 118 | */ |
5f64ec64 | 119 | xorl %eax, %eax |
5b11f1ce | 120 | leal _bss(%ebx), %edi |
5f64ec64 PA |
121 | leal _ebss(%ebx), %ecx |
122 | subl %edi, %ecx | |
36d3793c PA |
123 | shrl $2, %ecx |
124 | rep stosl | |
968de4f0 | 125 | |
22a57f58 PA |
126 | /* |
127 | * Adjust our own GOT | |
128 | */ | |
129 | leal _got(%ebx), %edx | |
130 | leal _egot(%ebx), %ecx | |
131 | 1: | |
132 | cmpl %ecx, %edx | |
133 | jae 2f | |
134 | addl %ebx, (%edx) | |
135 | addl $4, %edx | |
136 | jmp 1b | |
137 | 2: | |
138 | ||
1da177e4 LT |
139 | /* |
140 | * Do the decompression, and jump to the new kernel.. | |
141 | */ | |
02a884c0 | 142 | leal z_extract_offset_negative(%ebx), %ebp |
5f64ec64 PA |
143 | /* push arguments for decompress_kernel: */ |
144 | pushl %ebp /* output address */ | |
02a884c0 | 145 | pushl $z_input_len /* input_len */ |
5f64ec64 PA |
146 | leal input_data(%ebx), %eax |
147 | pushl %eax /* input_data */ | |
148 | leal boot_heap(%ebx), %eax | |
149 | pushl %eax /* heap area */ | |
150 | pushl %esi /* real mode pointer */ | |
151 | call decompress_kernel | |
152 | addl $20, %esp | |
968de4f0 EB |
153 | |
154 | #if CONFIG_RELOCATABLE | |
5f64ec64 PA |
155 | /* |
156 | * Find the address of the relocations. | |
968de4f0 | 157 | */ |
02a884c0 | 158 | leal z_output_len(%ebp), %edi |
968de4f0 | 159 | |
5f64ec64 PA |
160 | /* |
161 | * Calculate the delta between where vmlinux was compiled to run | |
968de4f0 EB |
162 | * and where it was actually loaded. |
163 | */ | |
5f64ec64 PA |
164 | movl %ebp, %ebx |
165 | subl $LOAD_PHYSICAL_ADDR, %ebx | |
166 | jz 2f /* Nothing to be done if loaded at compiled addr. */ | |
1da177e4 | 167 | /* |
968de4f0 | 168 | * Process relocations. |
1da177e4 | 169 | */ |
968de4f0 | 170 | |
5f64ec64 PA |
171 | 1: subl $4, %edi |
172 | movl (%edi), %ecx | |
173 | testl %ecx, %ecx | |
174 | jz 2f | |
175 | addl %ebx, -__PAGE_OFFSET(%ebx, %ecx) | |
176 | jmp 1b | |
968de4f0 EB |
177 | 2: |
178 | #endif | |
1da177e4 LT |
179 | |
180 | /* | |
968de4f0 | 181 | * Jump to the decompressed kernel. |
1da177e4 | 182 | */ |
5f64ec64 PA |
183 | xorl %ebx, %ebx |
184 | jmp *%ebp | |
968de4f0 | 185 | |
5f64ec64 PA |
186 | /* |
187 | * Stack and heap for uncompression | |
188 | */ | |
189 | .bss | |
190 | .balign 4 | |
7c539764 AH |
191 | boot_heap: |
192 | .fill BOOT_HEAP_SIZE, 1, 0 | |
193 | boot_stack: | |
194 | .fill BOOT_STACK_SIZE, 1, 0 | |
195 | boot_stack_end: |