x86 asm: move NOP in from x86-assembly-cheat

Author: cirosantilli

README.adoc

@@ -12473,6 +12473,20 @@ link:userland/arch/x86_64/loop.S[LOOP]
 
 Vs <<x86-jcc-instructions,Jcc>>: https://stackoverflow.com/questions/6805692/x86-assembly-programming-loops-with-ecx-and-loop-instruction-versus-jmp-jcond Holy CISC!
 
+=== x86 miscellaneous instructions
+
+<<intel-manual-1>> 7.3.16 "Miscellaneous Instructions"
+
+==== x86 NOP instruction
+
+link:userland/arch/x86_64/nop.S[NOP]
+
+No OPeration.
+
+Does nothing except take up one processor cycle and occupy some instruction memory.
+
+Applications: http://stackoverflow.com/questions/234906/whats-the-purpose-of-the-nop-opcode
+
 === x86 random number generator instructions
 
 <<intel-manual-1>> 5.1.15 Random Number Generator Instructions

userland/arch/x86_64/nop.S

@@ -0,0 +1,13 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#x86-nop-instruction */
+
+#include <lkmc.h>
+
+LKMC_PROLOGUE
+    nop
+    nop
+
+    /* Other nops
+     * http://stackoverflow.com/questions/11910501/why-did-gcc-generate-mov-eax-eax-and-what-does-it-mean
+     */
+    mov %rax, %rax
+LKMC_EPILOGUE