64 lines
1.2 KiB
C
64 lines
1.2 KiB
C
#include <stdint.h>
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#include <string.h>
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/* x86 memory map
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0x00000 - 0x003FF IVT 0x400
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0x00400 - 0x9FFFF FREE 0x9FC00
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0xA0000 - 0xBFFFF VGA 0x20000
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0xC0000 - 0xFFFFF FREE 0x40000
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total freemem - 0xDFC00 - 916480 bytes/895.0K
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*/
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typedef struct { // pointer into program data into which load segment is added
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uint16_t offset,
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segment;
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} __attribute__((packed)) reloc;
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typedef struct { // no endian checks - this will only work on x86+vm anyway
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uint16_t mz,
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bytes,
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pages,
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relsz,
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len,
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minalloc, // can easily ignore - we have 895k free
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maxalloc,
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ss,
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sp,
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sum,
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ip,
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cs,
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rel, // pointer to
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overlay; // zero if main binary
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reloc r[];
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} __attribute__((packed)) mz;
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typedef struct {
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uint16_t ss, sp, ip, cs;
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} mz_start;
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#define m8 ((uint8_t*)m) // access mz by byte
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uint32_t loadmz(mz* m, uint8_t* mem, uint32_t seg, mz_start* m) {
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uint32_t sz = (((uint32_t)m->pages) << 9) + m->bytes;
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memcpy( // copy mz to memory
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mem + (seg << 4),
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m8 + (m->len << 4),
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sz
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);
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for(int i = 0; i < m->relsz; i++) *(uint16_t*)(
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m8 +
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(seg << 4) +
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((uint32_t)m->r[i].segment << 4) +
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(uint32_t)m->r[i].offset
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) += seg;
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*m = (mz_start) {
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m->ss+seg,
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m->sp,
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m->ip,
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m->cs+seg
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};
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}
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