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 | ||
78 | /* Replace the compressed data size with the uncompressed size */ | |
5f64ec64 PA |
79 | subl input_len(%ebp), %ebx |
80 | movl output_len(%ebp), %eax | |
81 | addl %eax, %ebx | |
968de4f0 | 82 | /* Add 8 bytes for every 32K input block */ |
5f64ec64 PA |
83 | shrl $12, %eax |
84 | addl %eax, %ebx | |
968de4f0 | 85 | /* Add 32K + 18 bytes of extra slack */ |
5f64ec64 | 86 | addl $(32768 + 18), %ebx |
968de4f0 | 87 | /* Align on a 4K boundary */ |
5f64ec64 PA |
88 | addl $4095, %ebx |
89 | andl $~4095, %ebx | |
968de4f0 | 90 | |
0a137736 PA |
91 | /* Set up the stack */ |
92 | leal boot_stack_end(%ebx), %esp | |
93 | ||
97541912 PA |
94 | /* Zero EFLAGS */ |
95 | pushl $0 | |
96 | popfl | |
97 | ||
5f64ec64 PA |
98 | /* |
99 | * Copy the compressed kernel to the end of our buffer | |
968de4f0 EB |
100 | * where decompression in place becomes safe. |
101 | */ | |
5f64ec64 | 102 | pushl %esi |
5b11f1ce PA |
103 | leal _bss(%ebp), %esi |
104 | leal _bss(%ebx), %edi | |
105 | movl $(_bss - startup_32), %ecx | |
968de4f0 | 106 | std |
5f64ec64 | 107 | rep movsb |
968de4f0 | 108 | cld |
5f64ec64 | 109 | popl %esi |
968de4f0 | 110 | |
5f64ec64 PA |
111 | /* |
112 | * Compute the kernel start address. | |
968de4f0 EB |
113 | */ |
114 | #ifdef CONFIG_RELOCATABLE | |
e69f202d VG |
115 | addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebp |
116 | andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebp | |
968de4f0 | 117 | #else |
e69f202d | 118 | movl $LOAD_PHYSICAL_ADDR, %ebp |
968de4f0 | 119 | #endif |
1da177e4 LT |
120 | |
121 | /* | |
968de4f0 | 122 | * Jump to the relocated address. |
1da177e4 | 123 | */ |
5f64ec64 PA |
124 | leal relocated(%ebx), %eax |
125 | jmp *%eax | |
cb425afd CG |
126 | ENDPROC(startup_32) |
127 | ||
5f64ec64 | 128 | .text |
968de4f0 EB |
129 | relocated: |
130 | ||
1da177e4 | 131 | /* |
0a137736 | 132 | * Clear BSS (stack is currently empty) |
1da177e4 | 133 | */ |
5f64ec64 | 134 | xorl %eax, %eax |
5b11f1ce | 135 | leal _bss(%ebx), %edi |
5f64ec64 PA |
136 | leal _ebss(%ebx), %ecx |
137 | subl %edi, %ecx | |
1da177e4 | 138 | cld |
5f64ec64 | 139 | rep stosb |
968de4f0 | 140 | |
1da177e4 LT |
141 | /* |
142 | * Do the decompression, and jump to the new kernel.. | |
143 | */ | |
5f64ec64 PA |
144 | movl output_len(%ebx), %eax |
145 | pushl %eax | |
146 | /* push arguments for decompress_kernel: */ | |
147 | pushl %ebp /* output address */ | |
148 | movl input_len(%ebx), %eax | |
149 | pushl %eax /* input_len */ | |
150 | leal input_data(%ebx), %eax | |
151 | pushl %eax /* input_data */ | |
152 | leal boot_heap(%ebx), %eax | |
153 | pushl %eax /* heap area */ | |
154 | pushl %esi /* real mode pointer */ | |
155 | call decompress_kernel | |
156 | addl $20, %esp | |
157 | popl %ecx | |
968de4f0 EB |
158 | |
159 | #if CONFIG_RELOCATABLE | |
5f64ec64 PA |
160 | /* |
161 | * Find the address of the relocations. | |
968de4f0 | 162 | */ |
5f64ec64 PA |
163 | movl %ebp, %edi |
164 | addl %ecx, %edi | |
968de4f0 | 165 | |
5f64ec64 PA |
166 | /* |
167 | * Calculate the delta between where vmlinux was compiled to run | |
968de4f0 EB |
168 | * and where it was actually loaded. |
169 | */ | |
5f64ec64 PA |
170 | movl %ebp, %ebx |
171 | subl $LOAD_PHYSICAL_ADDR, %ebx | |
172 | jz 2f /* Nothing to be done if loaded at compiled addr. */ | |
1da177e4 | 173 | /* |
968de4f0 | 174 | * Process relocations. |
1da177e4 | 175 | */ |
968de4f0 | 176 | |
5f64ec64 PA |
177 | 1: subl $4, %edi |
178 | movl (%edi), %ecx | |
179 | testl %ecx, %ecx | |
180 | jz 2f | |
181 | addl %ebx, -__PAGE_OFFSET(%ebx, %ecx) | |
182 | jmp 1b | |
968de4f0 EB |
183 | 2: |
184 | #endif | |
1da177e4 LT |
185 | |
186 | /* | |
968de4f0 | 187 | * Jump to the decompressed kernel. |
1da177e4 | 188 | */ |
5f64ec64 PA |
189 | xorl %ebx, %ebx |
190 | jmp *%ebp | |
968de4f0 | 191 | |
5f64ec64 PA |
192 | /* |
193 | * Stack and heap for uncompression | |
194 | */ | |
195 | .bss | |
196 | .balign 4 | |
7c539764 AH |
197 | boot_heap: |
198 | .fill BOOT_HEAP_SIZE, 1, 0 | |
199 | boot_stack: | |
200 | .fill BOOT_STACK_SIZE, 1, 0 | |
201 | boot_stack_end: |