From 8337ab111e243d1c8f89fb1a789a63b4edd765b0 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benpicco@beuth-hochschule.de>
Date: Mon, 25 Nov 2019 01:34:38 +0100
Subject: [PATCH 1/2] cpu/arm7_common: hook up puf_sram

puf_sram only relies on an uninitialized chunk of memory.
This means to enable it we just have to hook up puf_sram_init().

All memory after __bss_end should be uninitialized at startup, so
just use that.
---
 cpu/arm7_common/Makefile.features | 1 +
 cpu/arm7_common/arm7_init.c       | 9 +++++++++
 cpu/lpc2387/include/cpu_conf.h    | 5 +++++
 3 files changed, 15 insertions(+)

diff --git a/cpu/arm7_common/Makefile.features b/cpu/arm7_common/Makefile.features
index 78b65033f3..f4b17a8c67 100644
--- a/cpu/arm7_common/Makefile.features
+++ b/cpu/arm7_common/Makefile.features
@@ -3,3 +3,4 @@ FEATURES_PROVIDED += arch_arm
 FEATURES_PROVIDED += arch_arm7
 FEATURES_PROVIDED += cpp
 FEATURES_PROVIDED += periph_pm
+FEATURES_PROVIDED += puf_sram
diff --git a/cpu/arm7_common/arm7_init.c b/cpu/arm7_common/arm7_init.c
index c0c1c06938..0dfdf92733 100644
--- a/cpu/arm7_common/arm7_init.c
+++ b/cpu/arm7_common/arm7_init.c
@@ -20,6 +20,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include "thread.h"
+#ifdef MODULE_PUF_SRAM
+#include "puf_sram.h"
+#endif
 
 #include "log.h"
 
@@ -63,6 +66,12 @@ void bootloader(void)
     /* initialize bss and data */
     _init_data();
 
+#ifdef MODULE_PUF_SRAM
+    /* uninitialized heap starts after bss section */
+    extern unsigned int __bss_end;
+    puf_sram_init((uint8_t *) __bss_end, SEED_RAM_LEN);
+#endif
+
     /* cpu specific setup of clocks, peripherals */
     cpu_init();
 
diff --git a/cpu/lpc2387/include/cpu_conf.h b/cpu/lpc2387/include/cpu_conf.h
index 9f37cb9f0f..b7a385ec25 100644
--- a/cpu/lpc2387/include/cpu_conf.h
+++ b/cpu/lpc2387/include/cpu_conf.h
@@ -71,6 +71,11 @@ extern "C" {
 #define CC_CONF_WARN_UNUSED_RESULT      __attribute__((warn_unused_result))
 /** @} */
 
+/**
+ * @brief   Attribute for memory sections required by SRAM PUF
+ */
+#define PUF_SRAM_ATTRIBUTES __attribute__((used, section(".noinit")))
+
 #ifdef __cplusplus
 }
 #endif

From 0da8c8f094a60d7b19ac9691a3c9e0e76b2cc6f1 Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benpicco@beuth-hochschule.de>
Date: Mon, 25 Nov 2019 02:08:59 +0100
Subject: [PATCH 2/2] tests/puf_sram: add newline in printf

puts() will already print the newline itself, but for printf()
we'll have to include it manually.
---
 tests/puf_sram/main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/puf_sram/main.c b/tests/puf_sram/main.c
index 61ac6fc6f7..21050fdf6a 100644
--- a/tests/puf_sram/main.c
+++ b/tests/puf_sram/main.c
@@ -25,7 +25,7 @@ int main(void)
 {
     puts("Start: Test random number generator");
 
-    printf("Success: Data for puf_sram_seed: [0x%08" PRIX32 "]", puf_sram_seed);
+    printf("Success: Data for puf_sram_seed: [0x%08" PRIX32 "]\n", puf_sram_seed);
 
     puts("End: Test finished");
     return 0;