x86 asm: move binary arithmetic instructions from x86-assembly-cheat except cmp

userland/arch/x86_64/div.S

@@ -0,0 +1,40 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#x86-binary-arithmetic-instructions
+ *
+ * Unsigned integer division, interface similar to MUL:
+ *
+ * ....
+ * rax = rdx:rax / SRC
+ * rdx = rdx:rax % SRC
+ * ....
+ *
+ * DIV can be used to calculate modulus, but GCC does not use it becaues it is slow, 
+ * and choses alternative techniques instead
+ * http://stackoverflow.com/questions/4361979/how-does-the-gcc-implementation-of-module-work-and-why-does-it-not-use-the
+ */
+
+#include <lkmc.h>
+
+LKMC_PROLOGUE
+    /* 64-bit hello world:
+     *
+     * 5 / 2 = 2 with leftover of 1.
+     */
+    mov $0, %rdx
+    mov $5, %rax
+    mov $2, %rbx
+    div %rbx
+    mov %rax, %r12
+    mov %rdx, %r13
+    LKMC_ASSERT_EQ(%r12, $2)
+    LKMC_ASSERT_EQ(%r13, $1)
+
+    /* Now with a simple carry. */
+    mov $1, %rdx
+    mov $2, %rax
+    mov $2, %rbx
+    div %rbx
+    mov %rax, %r12
+    mov %rdx, %r13
+    LKMC_ASSERT_EQ(%r12, $0x8000000000000001)
+    LKMC_ASSERT_EQ(%r13, $0)
+LKMC_EPILOGUE