kernel: munmap syscall

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

@@ -14,6 +14,7 @@ extern syscall_fork
 extern syscall_execve
 extern syscall_exit
 extern syscall_waitpid
+extern syscall_munmap
 syscalltab:
 dq syscall_print
 dq syscall_mmap
@@ -30,7 +31,8 @@ dq syscall_fork
 dq syscall_execve
 dq syscall_exit
 dq syscall_waitpid
-syscallcount equ 15
+dq syscall_munmap
+syscallcount equ 16
 section .text
 global arch_syscall_entry
 ; on entry:

kernel-src/sys/syscalls/munmap.c

@@ -0,0 +1,27 @@
+#include <kernel/syscalls.h>
+#include <kernel/vmm.h>
+#include <errno.h>
+
+syscallret_t syscall_munmap(context_t *ctx, void *addr, size_t length) {
+	syscallret_t ret = {
+		.ret = -1,
+		.errno = 0
+	};
+
+	if (addr > USERSPACE_END) {
+		ret.errno = EFAULT;
+		return ret;
+	}
+
+	if (length == 0 || length % PAGE_SIZE > 0) {
+		ret.errno = EINVAL;
+		return ret;
+	}
+
+	vmm_unmap(addr, length / PAGE_SIZE, 0);
+
+	ret.ret = 0;
+	ret.errno = 0;
+
+	return ret;
+}