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cd45f6 Bob Green 2026-09-11 09:47:41
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# Assembly Language
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This page describes how gcc passes arguments, which is required when accessing those arguments from inside a piece of assembly.
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Here's an example of how gcc compiled a function
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```
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00c06950 <zobbo>:
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int __attribute__ ((noinline)) zobbo(uint8_t drive_num, uint32_t block_num, uint8_t *buffer) {
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drive_num++;
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if (drive_num == 42) {
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c06950: 0c2f 0029 0007 cmpib #41,%sp@(7)
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c06956: 671e beqs c06976 <zobbo+0x26>
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return NOT_OK;
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}
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block_num--;
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if (block_num == 99) {
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c06958: 7064 moveq #100,%d0
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c0695a: b0af 0008 cmpl %sp@(8),%d0
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c0695e: 670e beqs c0696e <zobbo+0x1e>
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errno = 99;
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return NOT_OK;
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}
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if (*buffer == '!') {
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c06960: 206f 000c moveal %sp@(12),%a0
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c06964: 0c10 0021 cmpib #33,%a0@
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c06968: 57c0 seq %d0
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c0696a: 49c0 extbl %d0
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return NOT_OK;
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}
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return OK;
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}
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c0696c: 4e75 rts
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errno = 99;
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c0696e: 7063 moveq #99,%d0
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c06970: 23c0 0000 1160 movel %d0,1160 <errno>
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return NOT_OK;
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c06976: 70ff moveq #-1,%d0
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}
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c06978: 4e75 rts
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```