Start nostartfiles examples.

Interlink freestanding directories and readme.

README.adoc

@@ -13170,7 +13170,11 @@ The C standard library infrastructure is implemented in the common userland / ba
 
 ==== Freestanding programs
 
-Unlike most our other assembly examples, which use the C standard library for portability, examples under `freestanding/` directories don't link to the C standard library.
+Unlike most our other assembly examples, which use the C standard library for portability, examples under `freestanding/` directories don't link to the C standard library:
+
+* link:userland/arch/x86_64/freestanding/[]
+* link:userland/arch/arm/freestanding/[]
+* link:userland/arch/aarch64/freestanding/[]
 
 As a result, those examples cannot do IO portably, and so they make raw system calls and only be run on one given OS, e.g. <<linux-system-calls>>.
 
@@ -13185,6 +13189,14 @@ In order to GDB step debug those executables, you will want to use `--no-continu
 
 You are now left on the very first instruction of our tiny executable!
 
+===== nostartfiles programs
+
+Assembly examples under `nostartfiles` directories can use the standard library, but they don't use the pre-`main` boilerplate and start directly at our explicitly given `_start`:
+
+* link:userland/arch/aarch64/freestanding/[]
+
+I'm not sure how much stdlib functionality is supposed to work without the pre-main stuff, but I guess we'll just have to find out!
+
 === GCC inline assembly
 
 Examples under `arch/<arch>/c/` directories show to how use inline assembly from higher level languages such as C:

path_properties.py

@@ -260,6 +260,7 @@ gnu_extension_properties = {
     'cc_pedantic': False,
     'cxx_std': 'gnu++17'
 }
+# https://github.com/cirosantilli/linux-kernel-module-cheat#freestanding-programs
 freestanding_properties = {
     'baremetal': False,
     'cc_flags': [
@@ -269,6 +270,13 @@ freestanding_properties = {
     ],
     'extra_objs_lkmc_common': False,
 }
+# https://github.com/cirosantilli/linux-kernel-module-cheat#nostartfiles-programs
+nostartfiles_properties = {
+    'baremetal': False,
+    'cc_flags': [
+        '-nostartfiles', LF,
+    ],
+}
 # See: https://cirosantilli.com/linux-kernel-module-cheat#path-properties
 path_properties_tuples = (
     PathProperties.default_properties,
@@ -405,6 +413,7 @@ path_properties_tuples = (
                                 'freestanding': freestanding_properties,
                                 'lkmc_assert_eq_fail.S': {'signal_received': signal.Signals.SIGABRT},
                                 'lkmc_assert_memcmp_fail.S': {'signal_received': signal.Signals.SIGABRT},
+                                'nostartfiles': nostartfiles_properties,
                                 'udf.S': {
                                     'signal_generated_by_os': True,
                                     'signal_received': signal.Signals.SIGILL,

userland/arch/aarch64/freestanding/README.adoc

@@ -0,0 +1 @@
+https://github.com/cirosantilli/linux-kernel-module-cheat#freestanding-programs

userland/arch/aarch64/nostartfiles/README.adoc

@@ -0,0 +1 @@
+https://github.com/cirosantilli/linux-kernel-module-cheat#nostartfiles-programs

userland/arch/aarch64/nostartfiles/build

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

userland/arch/aarch64/nostartfiles/exit.S

@@ -0,0 +1,4 @@
+.global _start
+_start:
+    mov x0, 0
+    bl exit

userland/arch/aarch64/nostartfiles/test

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

userland/arch/arm/freestanding/README.adoc

@@ -0,0 +1 @@
+https://github.com/cirosantilli/linux-kernel-module-cheat#freestanding-programs

userland/arch/x86_64/freestanding/README.adoc

@@ -0,0 +1 @@
+https://github.com/cirosantilli/linux-kernel-module-cheat#freestanding-programs