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/init.h> 27#include <linux/linkage.h> 28#include <asm/segment.h> 29#include <asm/page_types.h> 30#include <asm/boot.h> 31#include <asm/asm-offsets.h> 32#include <asm/bootparam.h> 33 34 __HEAD 35ENTRY(startup_32) 36#ifdef CONFIG_EFI_STUB 37 jmp preferred_addr 38 39 /* 40 * We don't need the return address, so set up the stack so 41 * efi_main() can find its arguments. 42 */ 43ENTRY(efi_pe_entry) 44 add $0x4, %esp 45 46 call 1f 471: popl %esi 48 subl $1b, %esi 49 50 popl %ecx 51 movl %ecx, efi32_config(%esi) /* Handle */ 52 popl %ecx 53 movl %ecx, efi32_config+8(%esi) /* EFI System table pointer */ 54 55 /* Relocate efi_config->call() */ 56 leal efi32_config(%esi), %eax 57 add %esi, 88(%eax) 58 pushl %eax 59 60 call make_boot_params 61 cmpl $0, %eax 62 je fail 63 movl %esi, BP_code32_start(%eax) 64 popl %ecx 65 pushl %eax 66 pushl %ecx 67 jmp 2f /* Skip efi_config initialization */ 68 69ENTRY(efi32_stub_entry) 70 add $0x4, %esp 71 popl %ecx 72 popl %edx 73 74 call 1f 751: popl %esi 76 subl $1b, %esi 77 78 movl %ecx, efi32_config(%esi) /* Handle */ 79 movl %edx, efi32_config+8(%esi) /* EFI System table pointer */ 80 81 /* Relocate efi_config->call() */ 82 leal efi32_config(%esi), %eax 83 add %esi, 88(%eax) 84 pushl %eax 852: 86 call efi_main 87 cmpl $0, %eax 88 movl %eax, %esi 89 jne 2f 90fail: 91 /* EFI init failed, so hang. */ 92 hlt 93 jmp fail 942: 95 movl BP_code32_start(%esi), %eax 96 leal preferred_addr(%eax), %eax 97 jmp *%eax 98 99preferred_addr: 100#endif 101 cld 102 /* 103 * Test KEEP_SEGMENTS flag to see if the bootloader is asking 104 * us to not reload segments 105 */ 106 testb $KEEP_SEGMENTS, BP_loadflags(%esi) 107 jnz 1f 108 109 cli 110 movl $__BOOT_DS, %eax 111 movl %eax, %ds 112 movl %eax, %es 113 movl %eax, %fs 114 movl %eax, %gs 115 movl %eax, %ss 1161: 117 118/* 119 * Calculate the delta between where we were compiled to run 120 * at and where we were actually loaded at. This can only be done 121 * with a short local call on x86. Nothing else will tell us what 122 * address we are running at. The reserved chunk of the real-mode 123 * data at 0x1e4 (defined as a scratch field) are used as the stack 124 * for this calculation. Only 4 bytes are needed. 125 */ 126 leal (BP_scratch+4)(%esi), %esp 127 call 1f 1281: popl %ebp 129 subl $1b, %ebp 130 131/* 132 * %ebp contains the address we are loaded at by the boot loader and %ebx 133 * contains the address where we should move the kernel image temporarily 134 * for safe in-place decompression. 135 */ 136 137#ifdef CONFIG_RELOCATABLE 138 movl %ebp, %ebx 139 movl BP_kernel_alignment(%esi), %eax 140 decl %eax 141 addl %eax, %ebx 142 notl %eax 143 andl %eax, %ebx 144 cmpl $LOAD_PHYSICAL_ADDR, %ebx 145 jge 1f 146#endif 147 movl $LOAD_PHYSICAL_ADDR, %ebx 1481: 149 150 /* Target address to relocate to for decompression */ 151 addl $z_extract_offset, %ebx 152 153 /* Set up the stack */ 154 leal boot_stack_end(%ebx), %esp 155 156 /* Zero EFLAGS */ 157 pushl $0 158 popfl 159 160/* 161 * Copy the compressed kernel to the end of our buffer 162 * where decompression in place becomes safe. 163 */ 164 pushl %esi 165 leal (_bss-4)(%ebp), %esi 166 leal (_bss-4)(%ebx), %edi 167 movl $(_bss - startup_32), %ecx 168 shrl $2, %ecx 169 std 170 rep movsl 171 cld 172 popl %esi 173 174/* 175 * Jump to the relocated address. 176 */ 177 leal relocated(%ebx), %eax 178 jmp *%eax 179ENDPROC(startup_32) 180 181 .text 182relocated: 183 184/* 185 * Clear BSS (stack is currently empty) 186 */ 187 xorl %eax, %eax 188 leal _bss(%ebx), %edi 189 leal _ebss(%ebx), %ecx 190 subl %edi, %ecx 191 shrl $2, %ecx 192 rep stosl 193 194/* 195 * Adjust our own GOT 196 */ 197 leal _got(%ebx), %edx 198 leal _egot(%ebx), %ecx 1991: 200 cmpl %ecx, %edx 201 jae 2f 202 addl %ebx, (%edx) 203 addl $4, %edx 204 jmp 1b 2052: 206 207/* 208 * Do the decompression, and jump to the new kernel.. 209 */ 210 /* push arguments for decompress_kernel: */ 211 pushl $z_run_size /* size of kernel with .bss and .brk */ 212 pushl $z_output_len /* decompressed length, end of relocs */ 213 leal z_extract_offset_negative(%ebx), %ebp 214 pushl %ebp /* output address */ 215 pushl $z_input_len /* input_len */ 216 leal input_data(%ebx), %eax 217 pushl %eax /* input_data */ 218 leal boot_heap(%ebx), %eax 219 pushl %eax /* heap area */ 220 pushl %esi /* real mode pointer */ 221 call decompress_kernel /* returns kernel location in %eax */ 222 addl $28, %esp 223 224/* 225 * Jump to the decompressed kernel. 226 */ 227 xorl %ebx, %ebx 228 jmp *%eax 229 230#ifdef CONFIG_EFI_STUB 231 .data 232efi32_config: 233 .fill 11,8,0 234 .long efi_call_phys 235 .long 0 236 .byte 0 237#endif 238 239/* 240 * Stack and heap for uncompression 241 */ 242 .bss 243 .balign 4 244boot_heap: 245 .fill BOOT_HEAP_SIZE, 1, 0 246boot_stack: 247 .fill BOOT_STACK_SIZE, 1, 0 248boot_stack_end: 249