Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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> |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 28 | #include <asm/page.h> |
Vivek Goyal | e69f202 | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 29 | #include <asm/boot.h> |
Rusty Russell | a24e785 | 2007-10-21 16:41:35 -0700 | [diff] [blame] | 30 | #include <asm/asm-offsets.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 31 | |
Segher Boessenkool | c6b33cc | 2007-01-02 11:41:47 +0530 | [diff] [blame] | 32 | .section ".text.head","ax",@progbits |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 33 | .globl startup_32 |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 34 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 35 | startup_32: |
Eric W. Biederman | bd53147 | 2007-10-26 11:29:04 -0600 | [diff] [blame] | 36 | cld |
Rusty Russell | a24e785 | 2007-10-21 16:41:35 -0700 | [diff] [blame] | 37 | /* test KEEP_SEGMENTS flag to see if the bootloader is asking |
| 38 | * us to not reload segments */ |
| 39 | testb $(1<<6), BP_loadflags(%esi) |
Eric W. Biederman | bd53147 | 2007-10-26 11:29:04 -0600 | [diff] [blame] | 40 | jnz 1f |
Rusty Russell | a24e785 | 2007-10-21 16:41:35 -0700 | [diff] [blame] | 41 | |
Eric W. Biederman | bd53147 | 2007-10-26 11:29:04 -0600 | [diff] [blame] | 42 | cli |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 43 | movl $(__BOOT_DS),%eax |
| 44 | movl %eax,%ds |
| 45 | movl %eax,%es |
| 46 | movl %eax,%fs |
| 47 | movl %eax,%gs |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 48 | movl %eax,%ss |
Eric W. Biederman | bd53147 | 2007-10-26 11:29:04 -0600 | [diff] [blame] | 49 | 1: |
Rusty Russell | a24e785 | 2007-10-21 16:41:35 -0700 | [diff] [blame] | 50 | |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 51 | /* Calculate the delta between where we were compiled to run |
| 52 | * at and where we were actually loaded at. This can only be done |
| 53 | * with a short local call on x86. Nothing else will tell us what |
| 54 | * address we are running at. The reserved chunk of the real-mode |
H. Peter Anvin | 85414b6 | 2007-07-11 12:18:33 -0700 | [diff] [blame] | 55 | * data at 0x1e4 (defined as a scratch field) are used as the stack |
| 56 | * for this calculation. Only 4 bytes are needed. |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 57 | */ |
H. Peter Anvin | 85414b6 | 2007-07-11 12:18:33 -0700 | [diff] [blame] | 58 | leal (0x1e4+4)(%esi), %esp |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 59 | call 1f |
| 60 | 1: popl %ebp |
| 61 | subl $1b, %ebp |
| 62 | |
Vivek Goyal | e69f202 | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 63 | /* %ebp contains the address we are loaded at by the boot loader and %ebx |
| 64 | * contains the address where we should move the kernel image temporarily |
| 65 | * for safe in-place decompression. |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 66 | */ |
Vivek Goyal | e69f202 | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 67 | |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 68 | #ifdef CONFIG_RELOCATABLE |
Vivek Goyal | e69f202 | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 69 | movl %ebp, %ebx |
| 70 | addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebx |
| 71 | andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebx |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 72 | #else |
Vivek Goyal | e69f202 | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 73 | movl $LOAD_PHYSICAL_ADDR, %ebx |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 74 | #endif |
| 75 | |
| 76 | /* Replace the compressed data size with the uncompressed size */ |
| 77 | subl input_len(%ebp), %ebx |
| 78 | movl output_len(%ebp), %eax |
| 79 | addl %eax, %ebx |
| 80 | /* Add 8 bytes for every 32K input block */ |
| 81 | shrl $12, %eax |
| 82 | addl %eax, %ebx |
| 83 | /* Add 32K + 18 bytes of extra slack */ |
| 84 | addl $(32768 + 18), %ebx |
| 85 | /* Align on a 4K boundary */ |
| 86 | addl $4095, %ebx |
| 87 | andl $~4095, %ebx |
| 88 | |
| 89 | /* Copy the compressed kernel to the end of our buffer |
| 90 | * where decompression in place becomes safe. |
| 91 | */ |
| 92 | pushl %esi |
| 93 | leal _end(%ebp), %esi |
| 94 | leal _end(%ebx), %edi |
| 95 | movl $(_end - startup_32), %ecx |
| 96 | std |
| 97 | rep |
| 98 | movsb |
| 99 | cld |
| 100 | popl %esi |
| 101 | |
| 102 | /* Compute the kernel start address. |
| 103 | */ |
| 104 | #ifdef CONFIG_RELOCATABLE |
Vivek Goyal | e69f202 | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 105 | addl $(CONFIG_PHYSICAL_ALIGN - 1), %ebp |
| 106 | andl $(~(CONFIG_PHYSICAL_ALIGN - 1)), %ebp |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 107 | #else |
Vivek Goyal | e69f202 | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 108 | movl $LOAD_PHYSICAL_ADDR, %ebp |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 109 | #endif |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 110 | |
| 111 | /* |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 112 | * Jump to the relocated address. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 113 | */ |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 114 | leal relocated(%ebx), %eax |
| 115 | jmp *%eax |
| 116 | .section ".text" |
| 117 | relocated: |
| 118 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 119 | /* |
| 120 | * Clear BSS |
| 121 | */ |
| 122 | xorl %eax,%eax |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 123 | leal _edata(%ebx),%edi |
| 124 | leal _end(%ebx), %ecx |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 125 | subl %edi,%ecx |
| 126 | cld |
| 127 | rep |
| 128 | stosb |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 129 | |
| 130 | /* |
| 131 | * Setup the stack for the decompressor |
| 132 | */ |
Alexander van Heukelum | 7c53976 | 2008-04-08 12:54:30 +0200 | [diff] [blame] | 133 | leal boot_stack_end(%ebx), %esp |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 134 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 135 | /* |
| 136 | * Do the decompression, and jump to the new kernel.. |
| 137 | */ |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 138 | movl output_len(%ebx), %eax |
| 139 | pushl %eax |
| 140 | pushl %ebp # output address |
| 141 | movl input_len(%ebx), %eax |
| 142 | pushl %eax # input_len |
| 143 | leal input_data(%ebx), %eax |
| 144 | pushl %eax # input_data |
Alexander van Heukelum | 7c53976 | 2008-04-08 12:54:30 +0200 | [diff] [blame] | 145 | leal boot_heap(%ebx), %eax |
| 146 | pushl %eax # heap area as third argument |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 147 | pushl %esi # real mode pointer as second arg |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 148 | call decompress_kernel |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 149 | addl $20, %esp |
| 150 | popl %ecx |
| 151 | |
| 152 | #if CONFIG_RELOCATABLE |
| 153 | /* Find the address of the relocations. |
| 154 | */ |
| 155 | movl %ebp, %edi |
| 156 | addl %ecx, %edi |
| 157 | |
| 158 | /* Calculate the delta between where vmlinux was compiled to run |
| 159 | * and where it was actually loaded. |
| 160 | */ |
| 161 | movl %ebp, %ebx |
Vivek Goyal | e69f202 | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 162 | subl $LOAD_PHYSICAL_ADDR, %ebx |
| 163 | jz 2f /* Nothing to be done if loaded at compiled addr. */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 164 | /* |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 165 | * Process relocations. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 166 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 167 | |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 168 | 1: subl $4, %edi |
| 169 | movl 0(%edi), %ecx |
| 170 | testl %ecx, %ecx |
| 171 | jz 2f |
| 172 | addl %ebx, -__PAGE_OFFSET(%ebx, %ecx) |
| 173 | jmp 1b |
| 174 | 2: |
| 175 | #endif |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 176 | |
| 177 | /* |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 178 | * Jump to the decompressed kernel. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 179 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 180 | xorl %ebx,%ebx |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 181 | jmp *%ebp |
| 182 | |
| 183 | .bss |
Alexander van Heukelum | 7c53976 | 2008-04-08 12:54:30 +0200 | [diff] [blame] | 184 | /* Stack and heap for uncompression */ |
Eric W. Biederman | 968de4f | 2006-12-07 02:14:04 +0100 | [diff] [blame] | 185 | .balign 4 |
Alexander van Heukelum | 7c53976 | 2008-04-08 12:54:30 +0200 | [diff] [blame] | 186 | boot_heap: |
| 187 | .fill BOOT_HEAP_SIZE, 1, 0 |
| 188 | boot_stack: |
| 189 | .fill BOOT_STACK_SIZE, 1, 0 |
| 190 | boot_stack_end: |