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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 | /* * linux/boot/head.S * * Copyright (C) 1991, 1992, 1993 Linus Torvalds */ /* * head.S contains the 32-bit startup code. * * NOTE!!! Startup happens at absolute address 0x00001000, which is also where * the page directory will exist. The startup code will be overwritten by * the page directory. [According to comments etc elsewhere on a compressed * kernel it will end up at 0x1000 + 1Mb I hope so as I assume this. - AC] * * Page 0 is deliberately kept safe, since System Management Mode code in * laptops may need to access the BIOS data stored there. This is also * useful for future device drivers that either access the BIOS via VM86 * mode. */ /* * High loaded stuff by Hans Lermen & Werner Almesberger, Feb. 1996 */ .text #include <linux/linkage.h> #include <asm/segment.h> .globl startup_32 startup_32: cld cli movl $(__KERNEL_DS),%eax movl %eax,%ds movl %eax,%es movl %eax,%fs movl %eax,%gs lss SYMBOL_NAME(stack_start),%esp xorl %eax,%eax 1: incl %eax # check that A20 really IS enabled movl %eax,0x000000 # loop forever if it isn't cmpl %eax,0x100000 je 1b /* * Initialize eflags. Some BIOS's leave bits like NT set. This would * confuse the debugger if this code is traced. * XXX - best to initialize before switching to protected mode. */ pushl $0 popfl /* * Clear BSS */ xorl %eax,%eax movl $ SYMBOL_NAME(_edata),%edi movl $ SYMBOL_NAME(_end),%ecx subl %edi,%ecx cld rep stosb /* * Do the decompression, and jump to the new kernel.. */ subl $16,%esp # place for structure on the stack movl %esp,%eax pushl %esi # real mode pointer as second arg pushl %eax # address of structure as first arg call SYMBOL_NAME(decompress_kernel) orl %eax,%eax jnz 3f popl %esi # discard address popl %esi # real mode pointer xorl %ebx,%ebx ljmp $(__KERNEL_CS), $0x100000 /* * We come here, if we were loaded high. * We need to move the move-in-place routine down to 0x1000 * and then start it with the buffer addresses in registers, * which we got from the stack. */ 3: movl $move_routine_start,%esi movl $0x1000,%edi movl $move_routine_end,%ecx subl %esi,%ecx addl $3,%ecx shrl $2,%ecx cld rep movsl popl %esi # discard the address popl %ebx # real mode pointer popl %esi # low_buffer_start popl %ecx # lcount popl %edx # high_buffer_start popl %eax # hcount movl $0x100000,%edi cli # make sure we don't get interrupted ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine /* * Routine (template) for moving the decompressed kernel in place, * if we were high loaded. This _must_ PIC-code ! */ move_routine_start: movl %ecx,%ebp shrl $2,%ecx rep movsl movl %ebp,%ecx andl $3,%ecx rep movsb movl %edx,%esi movl %eax,%ecx # NOTE: rep movsb won't move if %ecx == 0 addl $3,%ecx shrl $2,%ecx rep movsl movl %ebx,%esi # Restore setup pointer xorl %ebx,%ebx ljmp $(__KERNEL_CS), $0x100000 move_routine_end: |