userland: support arch specific examples

userland/arch/aarch64/Makefile

@@ -0,0 +1 @@
+../../Makefile

userland/arch/aarch64/asm_hello.c

@@ -0,0 +1,8 @@
+#include <assert.h>
+#include <inttypes.h>
+
+int main(void) {
+    register uint32_t x0 __asm__ ("x0");
+    __asm__ ("mov x0, #1;" : : : "%x0");
+    assert(x0 == 1);
+}

userland/arch/aarch64/params.mk

@@ -0,0 +1 @@
+COMMON_DIR = ../../..

userland/arch/x86_64/Makefile

@@ -0,0 +1 @@
+../../Makefile

userland/arch/x86_64/asm_hello.c

@@ -0,0 +1,16 @@
+#include <assert.h>
+#include <inttypes.h>
+
+int main(void) {
+	uint32_t in = 1;
+	uint32_t out = 0;
+	__asm__ (
+		"movl %1, %%eax;"
+		"inc %%eax;"
+		"movl %%eax, %0"
+		: "=m" (out)
+		: "m" (in)
+		: "%eax"
+	);
+	assert(out == in + 1);
+}

userland/arch/x86_64/freestanding/hello.S

@@ -0,0 +1,19 @@
+.data
+    s:
+        .ascii "hello\n"
+        len = . - s
+.text
+    .global _start
+    _start:
+
+    /* Write. */
+    mov $1, %rax
+    mov $1, %rdi
+    mov $s, %rsi
+    mov $len, %rdx
+    syscall
+
+    /* Exit. */
+    mov $60, %rax
+    mov $0, %rdi
+    syscall

userland/arch/x86_64/params.mk

@@ -0,0 +1 @@
+COMMON_DIR = ../../..