75 lines
2.1 KiB
C
75 lines
2.1 KiB
C
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#include<stdint.h>
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#include<stdlib.h>
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typedef int uint24_t;
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typedef struct Process {
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uint16_t stack_pointer;
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uint24_t stack_pointer_frame;
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struct Process* next_process;
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struct Process* prev_process;
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uint16_t pid;
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uint24_t page_mappings[16];
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} Process;
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static Process* ready_to_run_head = NULL;
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static Process* ready_to_run_tail = NULL;
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static Process* current_process = NULL;
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static uint16_t next_pid = 0;
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Process processes[4];
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extern uint24_t get_free_frame();
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extern void switch_to_process_asm();
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extern Process* switch_to_process_asm_arg;
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void new_process(uint24_t* page_mappings, uint16_t entry_point) {
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uint16_t pid = next_pid;
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next_pid++;
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processes[pid].pid = pid;
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processes[pid].stack_pointer_frame = get_free_frame();
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set_frame(0xE, processes[pid].stack_pointer_frame);
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processes[pid].stack_pointer = 0xFFEA;
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*((uint16_t*)(0xEFFE)) = entry_point;
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for (int i = 0; i<16; i++) {
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processes[pid].page_mappings[i] = page_mappings[i];
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}
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processes[pid].next_process = NULL;
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processes[pid].prev_process = NULL;
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if (ready_to_run_head) {
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ready_to_run_head->prev_process = &processes[pid];
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processes[pid].next_process = ready_to_run_head;
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ready_to_run_head = &processes[pid];
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} else if (current_process) {
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ready_to_run_head = &processes[pid];
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ready_to_run_tail = &processes[pid];
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} else {
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current_process = &processes[pid];
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}
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}
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void yield() {
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if (ready_to_run_head) {
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Process* process = ready_to_run_head;
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ready_to_run_head = ready_to_run_head->next_process;
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if (ready_to_run_head==NULL) {
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ready_to_run_head = current_process;
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ready_to_run_tail = current_process;
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} else {
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ready_to_run_head->prev_process = current_process;
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current_process->next_process = ready_to_run_head;
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ready_to_run_head = current_process;
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}
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process->prev_process=NULL;
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process->next_process=NULL;
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for (int i=0; i<16; i++) {
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current_process->page_mappings[i] = get_frame(i);
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}
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for (int i=0; i<16; i++) {
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set_frame(i, process->page_mappings[i]);
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}
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switch_to_process_asm_arg = process;
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switch_to_process_asm();
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}
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}
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