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