document userland asm syscall interfaces

userland/arch/aarch64/c/freestanding/hello.c

@@ -1,4 +1,6 @@
-/* https://github.com/cirosantilli/arm-assembly-cheat#freestanding-linux-inline-assembly-system-calls */
+/* aarch64 freestanding C inline assemby Linux hello world
+ * https://github.com/cirosantilli/linux-kernel-module-cheat#linux-system-calls
+ */
 
 #include <inttypes.h>
 

userland/arch/aarch64/c/freestanding/hello_clobbers.c

@@ -1,6 +1,8 @@
 /* Like hello.c trying to do it without named register variables.
  * The code is more complicated, and I was not able to get as efficient,
  * so better just stick to named register variables.
+ *
+ * https://github.com/cirosantilli/linux-kernel-module-cheat#linux-system-calls
  */
 
 #include <inttypes.h>

userland/arch/aarch64/freestanding/hello.S

@@ -1,4 +1,6 @@
-/* https://github.com/cirosantilli/arm-assembly-cheat#linux-system-calls */
+/* aarch64 freestanding Linux hello world
+ * https://github.com/cirosantilli/linux-kernel-module-cheat#linux-system-calls
+ */
 
 .text
 .global _start

userland/arch/aarch64/hello_driver.S

@@ -1,3 +1,4 @@
+/* MInimal sanity check of the C driver. */
 .text
 .global asm_main
 asm_main:

userland/arch/arm/c/freestanding/hello.c

@@ -1,3 +1,7 @@
+/* arm freestanding C inline assemby Linux hello world
+ * https://github.com/cirosantilli/linux-kernel-module-cheat#linux-system-calls
+ */
+
 #include <inttypes.h>
 
 void _start(void) {

userland/arch/arm/freestanding/hello.S

@@ -1,4 +1,6 @@
-/* https://github.com/cirosantilli/arm-assembly-cheat#linux-system-calls */
+/* arm freestanding Linux hello world
+ * https://github.com/cirosantilli/linux-kernel-module-cheat#linux-system-calls
+ */
 
 .syntax unified
 .text

userland/arch/x86_64/c/freestanding/hello.c

@@ -1,4 +1,6 @@
-/* Linux freestanding hello world with inline assembly..*/
+/* x86_64 freestanding C inline assemby Linux hello world
+ * https://github.com/cirosantilli/linux-kernel-module-cheat#linux-system-calls
+ */
 
 #define _XOPEN_SOURCE 700
 #include <inttypes.h>

userland/arch/x86_64/c/freestanding/hello_regvar.c

@@ -1,5 +1,5 @@
 /* Same as hello.c, but with explicit register variables, see:
- * https://stackoverflow.com/questions/9506353/how-to-invoke-a-system-call-via-sysenter-in-inline-assembly/54956854#54956854
+ * https://github.com/cirosantilli/linux-kernel-module-cheat#linux-system-calls
  */
 
 #define _XOPEN_SOURCE 700

userland/arch/x86_64/freestanding/hello.S

@@ -1,3 +1,7 @@
+/* x86_64 freestanding Linux hello world
+ * https://github.com/cirosantilli/linux-kernel-module-cheat#linux-system-calls
+ */
+
 .text
 .global _start
 _start: