kernel: fork syscall

kernel-src/arch/x86-64/syscall.asm

@@ -10,6 +10,7 @@ extern syscall_write
 extern syscall_getpid
 extern syscall_fstat
 extern syscall_fstatat
+extern syscall_fork
 syscalltab:
 dq syscall_print
 dq syscall_mmap
@@ -22,7 +23,8 @@ dq syscall_write
 dq syscall_getpid
 dq syscall_fstat
 dq syscall_fstatat
-syscallcount equ 11
+dq syscall_fork
+syscallcount equ 12
 section .text
 global arch_syscall_entry
 ; on entry:
@@ -49,7 +51,7 @@ arch_syscall_entry:
 
 	; push context
 	push qword 0x1b ; user SS
-	push qword rcx
+	push qword rcx  ; user RSP
 	add qword [rsp], 8 ; correct the old stack pointer to before the return address push
 	push r11     ; rflags is stored in r11
 	push qword 0x23 ; user CS
@@ -89,6 +91,7 @@ arch_syscall_entry:
 	mov rdx, rsi
 	mov rsi, rdi
 	mov rdi, rsp
+	add rdi, 8 ; context pointer is after r9 argument
 	sti
 
 	cmp rax, syscallcount

kernel-src/sys/syscalls/fork.c

@@ -0,0 +1,63 @@
+#include <kernel/syscalls.h>
+#include <kernel/scheduler.h>
+#include <errno.h>
+#include <kernel/file.h>
+#include <kernel/interrupt.h>
+
+#include <logging.h>
+syscallret_t syscall_fork(context_t *ctx) {
+	syscallret_t ret = {
+		.ret = -1,
+		.errno = 0
+	};
+
+	proc_t *proc = _cpu()->thread->proc;
+	proc_t *nproc = sched_newproc();
+	if (nproc == NULL) {
+		ret.errno = ENOMEM;
+		goto cleanup;
+	}
+
+	thread_t *nthread = sched_newthread((void *)CTX_IP(ctx), 16 * PAGE_SIZE, 1, nproc, (void *)CTX_SP(ctx));
+	if (nthread == NULL) {
+		ret.errno = ENOMEM;
+		goto cleanup;
+	}
+
+	nthread->vmmctx = vmm_fork(_cpu()->thread->vmmctx);
+
+	if (nthread->vmmctx == NULL) {
+		ret.errno = ENOMEM;
+		goto cleanup;
+	}
+
+	ret.errno = fd_clone(nproc);
+	if (ret.errno)
+		goto cleanup;
+
+	bool intstate = interrupt_set(false);
+	spinlock_acquire(&proc->lock);
+
+	nproc->parent = proc;
+	nproc->sibling = proc->child;
+	proc->child = nproc;
+
+	spinlock_release(&proc->lock);
+	interrupt_set(intstate);
+
+	nproc->umask = _cpu()->thread->proc->umask;
+	nproc->root = sched_getroot();
+	nproc->cwd = sched_getcwd();
+
+	ARCH_CONTEXT_THREADSAVE(nthread, ctx);
+
+	CTX_RET(&nthread->context) = 0;
+	CTX_ERRNO(&nthread->context) = 0;
+
+	ret.ret = nproc->pid;
+
+	sched_queue(nthread);
+
+	cleanup:
+	return ret;
+}