From cec9625ff4a5f576139d230d562a8851916e251b Mon Sep 17 00:00:00 2001
From: Kaspar Schleiser <kaspar@schleiser.de>
Date: Wed, 23 Sep 2015 17:26:31 +0200
Subject: [PATCH] cpu: provide link-time random value, use as fake cpuid

---
 Makefile.cflags                       | 3 +++
 Makefile.include                      | 8 ++++++++
 boards/Makefile.include.msp430_common | 3 +++
 drivers/include/periph/cpuid.h        | 9 ++++++++-
 4 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/Makefile.cflags b/Makefile.cflags
index 3755c1028bbe..4ac6ac2f61b7 100644
--- a/Makefile.cflags
+++ b/Makefile.cflags
@@ -64,3 +64,6 @@ endif
 ifeq ($(origin ARFLAGS),default)
   ARFLAGS = rcs
 endif
+
+# define random number at link stage
+LINKFLAGS += -Wl,--defsym=RANDOM=$(RANDOM)
diff --git a/Makefile.include b/Makefile.include
index 0c0622888b95..d5f0c29a3f94 100644
--- a/Makefile.include
+++ b/Makefile.include
@@ -72,6 +72,14 @@ else
   AD=
 endif
 
+# get a random value
+ifeq ($(OS),Darwin)
+  RANDOM ?= 0x$(shell jot -r -w%08x 1 0 0xffffffff)
+else
+  RANDOM ?= 0x$(shell </dev/urandom tr -dc 0-9a-f | dd bs=8 count=1 status=none)
+endif
+export RANDOM
+
 # Fail on warnings. Can be overridden by `make WERROR=0`.
 WERROR ?= 1
 export WERROR
diff --git a/boards/Makefile.include.msp430_common b/boards/Makefile.include.msp430_common
index 385f771f1003..f327efe5eade 100644
--- a/boards/Makefile.include.msp430_common
+++ b/boards/Makefile.include.msp430_common
@@ -17,5 +17,8 @@ export LINKFLAGS += $(CFLAGS_CPU) -lgcc
 # Import all toolchain settings
 include $(RIOTBOARD)/Makefile.include.gnu
 
+# as msp430 is 16bit only, cut the 32bit wide random number
+RANDOM := $(shell echo $(RANDOM) | cut -c -6)
+
 # export board specific includes to the global includes-listing
 export INCLUDES += -I$(RIOTBOARD)/$(BOARD)/include
diff --git a/drivers/include/periph/cpuid.h b/drivers/include/periph/cpuid.h
index 7929659019a6..ab6372cf5269 100644
--- a/drivers/include/periph/cpuid.h
+++ b/drivers/include/periph/cpuid.h
@@ -45,7 +45,14 @@ extern "C" {
  *                  defined in the CPU's cpu_conf.h)
  */
 void cpuid_get(void *id);
-#endif /* CPUID_ID_LEN */
+#else
+extern unsigned *RANDOM;
+#define CPUID_ID_LEN (sizeof(&RANDOM))
+static inline void cpuid_get(void* id)
+{
+    *(unsigned*)id = (unsigned) &RANDOM;
+}
+#endif
 
 #ifdef __cplusplus
 }