Scheduler fix, User RR

Makefile

@@ -16,12 +16,13 @@ endif
 OBJFILES := $(patsubst $(SRC)/%.c, $(BUILDDIR)/%.o, $(SOURCES))
 
 CC := x86_64-elf-gcc
-CC_FLAGS=-Wall -Wextra -std=gnu99 -nostdlib -ffreestanding -fstack-protector -fno-omit-frame-pointer -fno-stack-check -fno-PIC -ffunction-sections -fdata-sections -mcmodel=kernel
+CC_FLAGS=-Wall -Wextra -std=gnu99 -nostdlib -ffreestanding -fstack-protector -fno-omit-frame-pointer -fno-stack-check -fno-PIC -ffunction-sections -fdata-sections -mcmodel=kernel -mno-red-zone
 
 LD := x86_64-elf-ld
 
 $(ELFFILE): $(BUILDDIR) $(OBJFILES)
 	nasm -f bin user/hello.S -o $(BUILDDIR)/hello
+	nasm -f bin user/pedicel.S -o $(BUILDDIR)/pedicel
 	nasm -f elf64 src/arch/x86/idt.S -o $(BUILDDIR)/idt_stub.o
 	$(LD) -o $(ELFFILE) -T linker.ld $(OBJFILES) $(BUILDDIR)/idt_stub.o
 	# Get the symbols for debugging
@@ -49,6 +50,7 @@ build-iso: limine/limine $(ELFFILE)
 	mkdir -p iso_root/boot/limine
 	cp -v limine.conf iso_root/boot/limine
 	cp $(BUILDDIR)/hello iso_root/boot/
+	cp $(BUILDDIR)/pedicel iso_root/boot/
 	mkdir -p iso_root/EFI/BOOT
 	cp -v limine/limine-bios.sys limine/limine-bios-cd.bin limine/limine-uefi-cd.bin iso_root/boot/limine/
 	cp -v limine/BOOTX64.EFI iso_root/EFI/BOOT/

limine.conf

@@ -7,3 +7,4 @@ interface_branding: Welcome to the PepperOS disk!
 	comment: Default configuration (warning: spicy)
 	path: boot():/boot/pepperk
 	module_path: boot():/boot/hello
+	module_path: boot():/boot/pedicel

src/arch/x86/syscall.c

@@ -9,6 +9,9 @@
 #include <kernel.h>
 #include <stddef.h>
 #include <io/term/term.h>
+#include <sched/process.h>
+
+extern struct process* current_process;
 
 void sys_write(unsigned int fd, const char* buf, size_t count)
 {
@@ -20,10 +23,19 @@ void sys_write(unsigned int fd, const char* buf, size_t count)
             break;
 
         case 2: //stderr
+            for (size_t i=0; i<count; i++) {
+                internal_putc(buf[i], NULL);
+            }
             break;
     }
 }
 
+void sys_exit(int error_code)
+{
+    current_process->status = DEAD;
+    DEBUG("exiting process PID=%u name=%s", current_process->pid, current_process->name);
+}
+
 /*
  * syscall_handler - System call dispatcher
  * @regs: CPU state
@@ -53,6 +65,9 @@ struct cpu_status* syscall_handler(struct cpu_status* regs)
         case 1: //sys_write
             sys_write(regs->rdi, (char*)regs->rsi, regs->rdx);
             break;
+        case 60: //sys_exit
+            sys_exit(regs->rdi);
+            break;
         default:
             regs->rax = 0xbad515ca11;
             break;

src/kmain.c

@@ -122,10 +122,13 @@ void kmain()
 	if (!boot_ctx.module) {
 		panic(NULL, "could not load 'hello' executable :(");
 	}
-	if (boot_ctx.module->module_count == 1) {
+	if (boot_ctx.module->module_count == 2) {
 		file = boot_ctx.module->modules[0];
 		DEBUG("file: addr=%p size=%u", file->address, file->size);
 		process_create_user(file, "hello");
+
+		file = boot_ctx.module->modules[1];
+		process_create_user(file, "pedicel");
 	}
 	scheduler_init();
 

src/sched/scheduler.c

@@ -50,31 +50,47 @@ struct cpu_status* scheduler_schedule(struct cpu_status* context)
         panic(NULL, "current_process->context is NULL");
     }
 
-    if (current_process->next == NULL) {
-        return current_process->context;
-    }
-
     current_process->context = context;
 
-    for (;;) {
-        struct process* prev_process = current_process;
-        if (current_process->next != NULL) {
+    if (current_process->status == DEAD) {
+        struct process* dead_process = current_process;
+        struct process* next_process = (dead_process->next != NULL) ? dead_process->next : processes_list;
+
+        process_delete(&processes_list, dead_process);
+
+        if (processes_list == NULL || next_process == dead_process) {
+            current_process = idle_proc;
+            return idle_proc->context;
+        }
+
+        current_process = next_process;
+    } else if (current_process->next != NULL) {
         current_process = current_process->next;
     } else {
         current_process = processes_list;
     }
 
-        if (current_process != NULL && current_process->status == DEAD) {
-            process_delete(&prev_process, current_process);
-            current_process = NULL;
+    for (;;) {
+        if (current_process->status == DEAD) {
+            struct process* dead_process = current_process;
+            struct process* next_process = (current_process->next != NULL) ? current_process->next : processes_list;
 
+            process_delete(&processes_list, dead_process);
+
+            if (processes_list == NULL || next_process == dead_process) {
+                current_process = idle_proc;
                 return idle_proc->context;
-        } else {
+            }
+
+            current_process = next_process;
+            continue;
+        }
+
         current_process->status = RUNNING;
         break;
     }
-    }
 
+    // Here, we chose next running process so we load its kernel stack & page tables
     tss.rsp0 = (uint64_t)current_process->kernel_stack;
     load_cr3(VIRT_TO_PHYS((uint64_t)current_process->root_page_table));
 

user/hello.S

@@ -12,5 +12,10 @@ hello:
     mov rdx, 33         ;count
     int 0x80
 
+.end:
+    mov rax, 0x3C       ;sys_exit
+    mov rdi, 0x0        ;error_code
+    int 0x80
+
 .loop:
     jmp .loop

user/pedicel.S

@@ -0,0 +1,25 @@
+bits 64
+
+section .data
+hello db 0x0A, 0x0D, "User program 2 speaking", 0
+
+section .text
+
+_start:
+    mov rax, 0x1    ;sys_write
+    mov rdi, 0x1    ;stdout
+    lea rsi, [rel hello]
+    mov rdx, 25     ;count
+    int 0x80
+
+; when we are ready to have an os specific toolchain,
+; this bit (exit & loop) should be appended at the end of every
+; C program we compile.
+
+.end:
+    mov rax, 0x3C
+    mov rdi, 0x0
+    int 0x80
+
+.loop:
+    jmp .loop