bslathi19/super6502
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Execute code read from the SD card

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This will read the data from the sd card, copy it to the originally
linked address (no relocation), then execute it.

I am lazy and wrote it in C using weird function pointer casting but
this would probably be more efficient if it were to be written in
assembly instead.

The test program simply returns 'A', but that is enough to prove that it
is actually running.
This commit is contained in:
Byron Lathi
2022-04-16 14:56:41 -05:00
parent 585faa023f
commit 2786ec0940
1 changed files with 57 additions and 0 deletions
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57
sw/main.c
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@@ -1,5 +1,6 @@
#include <stdint.h>
#include <conio.h>
#include <string.h>
#include "board_io.h"
#include "uart.h"
@@ -79,7 +80,15 @@ int main() {
o65_header_t* header;
o65_opt_t* o65_opt;
uint8_t* seg_ptr;
uint16_t code_base;
uint16_t data_base;
uint16_t code_len;
uint16_t data_len;
uint8_t (*exec)(void);
uint8_t ret;
uint16_t reserved_count;
uint32_t sectors_per_fat;
@@ -222,6 +231,12 @@ int main() {
cprintf("stack: %x\n", header->stack);
cprintf("\n");
code_base = header->tbase;
data_base = header->dbase;
code_len = header->tlen;
data_len = header->dlen;
o65_opt = (o65_opt_t*)(buf + sizeof(o65_header_t));
while (o65_opt->olen)
{
@@ -246,6 +261,48 @@ int main() {
cprintf("\n\n");
o65_opt = (o65_opt_t*)((uint8_t*)o65_opt + o65_opt->olen);
}
seg_ptr = (uint8_t*)o65_opt + 1;
cprintf("Code: \n");
for (i = 0; i < code_len; i++) {
cprintf("%x ", seg_ptr[i]);
}
cprintf("\n\n");
memcpy((uint8_t*)code_base, seg_ptr, code_len);
seg_ptr+=code_len;
cprintf("Data: \n");
for (i = 0; i < data_len; i++) {
cprintf("%x ", seg_ptr[i]);
}
cprintf("\n\n");
memcpy((uint8_t*)data_base, seg_ptr, data_len);
cprintf("Memory Copied!\n");
cprintf("Code: \n");
for (i = 0; i < code_len; i++) {
cprintf("%x ", ((uint8_t*)code_base)[i]);
}
cprintf("\n\n");
cprintf("Data: \n");
for (i = 0; i < data_len; i++) {
cprintf("%x ", ((uint8_t*)data_base)[i]);
}
cprintf("\n\n");
exec = (int(*)(void))code_base;
ret = 0;
ret = (*exec)();
cprintf("ret: %x\n", ret);
}