sched: implement passing arguments to user-mode threads

arch/x86_64/thread.c

@@ -1,6 +1,14 @@
 #include <kernel/machine/cpu.h>
 #include <kernel/machine/thread.h>
 
+#define MAX_REG_ARGS 6
+#define REG_ARG_0    rdi
+#define REG_ARG_1    rsi
+#define REG_ARG_2    rdx
+#define REG_ARG_3    rcx
+#define REG_ARG_4    r8
+#define REG_ARG_5    r9
+
 /* this is the context information restored by ml_thread_switch.
  * since ml_thread_switch only jumps to kernel-mode, IRETQ isn't used,
  * and the extra register values needed by IRETQ aren't present. */
@@ -23,10 +31,12 @@ void ml_thread_prepare_kernel_context(uintptr_t ip, uintptr_t *sp)
 	ctx->rfl = 0x202;
 }
 
-extern void ml_thread_prepare_user_context(
+extern kern_status_t ml_thread_prepare_user_context(
 	virt_addr_t ip,
 	virt_addr_t user_sp,
-	virt_addr_t *kernel_sp)
+	virt_addr_t *kernel_sp,
+	const uintptr_t *args,
+	size_t nr_args)
 {
 	(*kernel_sp) -= sizeof(struct ml_cpu_context);
 
@@ -39,4 +49,31 @@ extern void ml_thread_prepare_user_context(
 	ctx->rflags = 0x202;
 	ctx->rdi = 0;   // arg 0
 	ctx->rsi = 0;   // arg 1
+
+	for (size_t i = 0; i < nr_args; i++) {
+		switch (i) {
+		case 0:
+			ctx->REG_ARG_0 = args[i];
+			break;
+		case 1:
+			ctx->REG_ARG_1 = args[i];
+			break;
+		case 2:
+			ctx->REG_ARG_2 = args[i];
+			break;
+		case 3:
+			ctx->REG_ARG_3 = args[i];
+			break;
+		case 4:
+			ctx->REG_ARG_4 = args[i];
+			break;
+		case 5:
+			ctx->REG_ARG_5 = args[i];
+			break;
+		default:
+			return KERN_INVALID_ARGUMENT;
+		}
+	}
+
+	return KERN_OK;
 }