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Last change
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Author Date Id Revision
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File size:
1.3 KB
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| 1 | /* We need a real mode stack that won't be stomped on by Etherboot
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| 2 | which starts at 0x20000. Choose something that's sufficiently high,
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| 3 | but not in DOC territory. Note that we couldn't do this in a real
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| 4 | .com program since stack variables are in the same segment as the
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| 5 | code and data, but this isn't really a .com program, it just looks
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| 6 | like one to make DOS load it into memory. It still has the 64kB
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| 7 | limitation of .com files though. */
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| 8 | #define STACK_SEG 0x7000
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| 9 | #define STACK_SIZE 0x4000
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| 10 |
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| 11 | .text
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| 12 | .code16
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| 13 | .arch i386
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| 14 | .section ".prefix", "ax", @progbits
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| 15 | .globl _prefix
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| 16 |
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| 17 | /* Cheat a little with the relocations: .COM files are loaded at 0x100 */
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| 18 | _prefix:
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| 19 | /* Set up temporary stack */
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| 20 | movw $STACK_SEG, %ax
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| 21 | movw %ax, %ss
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| 22 | movw $STACK_SIZE, %sp
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| 23 |
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| 24 | pushl $0 /* No parameters to preserve for exit path */
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| 25 | pushw $0 /* Dummy return address - use prefix_exit */
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| 26 |
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| 27 | /* Calculate segment address of image start */
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| 28 | pushw %cs
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| 29 | popw %ax
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| 30 | addw $(0x100/16), %ax
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| 31 | pushw %ax
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| 32 | pushw $_start
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| 33 | /* Calculated lcall to _start with %cs:0000 = image start */
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| 34 | lret
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| 35 |
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| 36 | .section ".text16", "ax", @progbits
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| 37 | .globl prefix_exit
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| 38 | prefix_exit:
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| 39 | movw $0x4c00,%ax /* return to DOS */
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| 40 | int $0x21 /* reach this on Quit */
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| 41 | .globl prefix_exit_end
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| 42 | prefix_exit_end:
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| 43 | .previous
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| 44 |
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| 45 | /* The body of etherboot is attached here at build time.
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| 46 | * Force 16 byte alignment
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| 47 | */
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| 48 | .align 16,0
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| 49 | _body:
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