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/*
* Copyright (c) 2025 Ian Marco Moffett and the Osmora Team.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Hyra nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdio.h>
#include <errno.h>
#include "rom.h"
#include "cpu/cpu.h"
/*
* Fetch an instruction byte from memory
*
* @core: Core to fetch for
* @byte_res: Result is written here
*
* XXX: Caller is to increment `core->pc'
*
* Returns zero on success
*/
static int
cpu_fetch(struct osmx_core *core, uint8_t *byte_res)
{
uint8_t *rom;
size_t rom_len;
if (core == NULL || byte_res == NULL) {
printf("fatal: bad arg in %s()\n", __func__);
return -1;
}
if ((rom = g_firmware.buf) == NULL) {
printf("fatal: ROM is uninitialized\n");
return -1;
}
rom_len = g_firmware.length;
if (core->pc >= (CPU_BUA_PBASE + rom_len)) {
printf("fatal: PC outside of ROM\n");
return -1;
}
if (core->pc >= CPU_BUA_PBASE) {
*byte_res = rom[core->pc - CPU_BUA_PBASE];
}
return 0;
}
int
cpu_run(struct osmx_core *core)
{
uint8_t opcode;
int error;
if (core == NULL) {
return -EINVAL;
}
core->run = 1;
while (core->run) {
error = cpu_fetch(core, &opcode);
if (error < 0) {
core->run = 0;
break;
}
/* Test opcode cases */
switch (opcode) {
case OP_HLT:
printf("** HALTED **\n");
core->run = false;
continue;
}
++core->pc;
}
}
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