From 96dd24836c1057264a20f88c6b1de6b9db7304e0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Th=C3=A9baudeau?=
 <benoit.thebaudeau.dev@gmail.com>
Date: Wed, 1 Jul 2015 22:15:53 +0200
Subject: [PATCH] cc2538: Use &vectors instead of flash/.text start address
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The current CC2538 linker script in Contiki places the vector table at
the beginning of the flash memory / .text output section. However, this
location is arbitrary (the only requirement is that the vector table is
512-byte aligned), and custom linker scripts may be used with Contiki,
which means that Contiki may be used with a vector table placed
elsewhere. Thus, using the flash/.text start address in the CCA and as
the default NVIC VTABLE value was wrong.

This commit rather uses the address of the vectors[] array from
startup-gcc.c, which makes it possible to freely move around the vector
table without breaking anything or having to use a custom startup-gcc.c
and to configure the NVIC driver for that. Moreover, referencing the
vectors[] array naturally prevents it and its input section from being
garbage-collected by the linker, so this commit also removes the
now-unneeded "used" and "KEEP" keywords from the vector table.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau.dev@gmail.com>
---
 cpu/cc2538/cc2538.lds    |  2 +-
 cpu/cc2538/dev/nvic.h    |  3 ++-
 cpu/cc2538/startup-gcc.c | 29 +++++++++++++----------------
 3 files changed, 16 insertions(+), 18 deletions(-)

diff --git a/cpu/cc2538/cc2538.lds b/cpu/cc2538/cc2538.lds
index a2dd0d209..60a37c796 100644
--- a/cpu/cc2538/cc2538.lds
+++ b/cpu/cc2538/cc2538.lds
@@ -64,7 +64,7 @@ SECTIONS
     .text :
     {
         _text = .;
-        KEEP(*(.vectors))
+        *(.vectors)
         *(.text*)
         *(.rodata*)
         _etext = .;
diff --git a/cpu/cc2538/dev/nvic.h b/cpu/cc2538/dev/nvic.h
index 6c7563680..8f2f68259 100644
--- a/cpu/cc2538/dev/nvic.h
+++ b/cpu/cc2538/dev/nvic.h
@@ -54,7 +54,8 @@
 #ifdef NVIC_CONF_VTABLE_ADDRESS
 #define NVIC_VTABLE_ADDRESS     NVIC_CONF_VTABLE_ADDRESS
 #else
-#define NVIC_VTABLE_ADDRESS     0x200000
+extern void(*const vectors[])(void);
+#define NVIC_VTABLE_ADDRESS     ((uint32_t)&vectors)
 #endif
 /** @} */
 /*---------------------------------------------------------------------------*/
diff --git a/cpu/cc2538/startup-gcc.c b/cpu/cc2538/startup-gcc.c
index 35c2329d2..d3d6ec401 100644
--- a/cpu/cc2538/startup-gcc.c
+++ b/cpu/cc2538/startup-gcc.c
@@ -94,22 +94,7 @@ void pka_isr(void);
 /* Allocate stack space */
 static unsigned long stack[512] __attribute__ ((section(".stack")));
 /*---------------------------------------------------------------------------*/
-/* Linker construct indicating .text section location */
-extern uint8_t _text[0];
-/*---------------------------------------------------------------------------*/
-__attribute__ ((section(".flashcca"), used))
-const flash_cca_lock_page_t __cca = {
-  FLASH_CCA_BOOTLDR_CFG,          /* Boot loader backdoor configuration */
-  FLASH_CCA_IMAGE_VALID,         /* Image valid */
-  &_text,                        /* Vector table located at the start of .text */
-  /* Unlock all pages and debug */
-  { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
-    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }
-};
-/*---------------------------------------------------------------------------*/
-__attribute__ ((section(".vectors"), used))
+__attribute__((__section__(".vectors")))
 void(*const vectors[])(void) =
 {
   (void (*)(void))((unsigned long)stack + sizeof(stack)),   /* Stack pointer */
@@ -277,6 +262,18 @@ void(*const vectors[])(void) =
   default_handler,            /* 162 MACTimer */
 };
 /*---------------------------------------------------------------------------*/
+__attribute__((__section__(".flashcca"), __used__))
+const flash_cca_lock_page_t flash_cca_lock_page = {
+  FLASH_CCA_BOOTLDR_CFG,        /* Boot loader backdoor configuration */
+  FLASH_CCA_IMAGE_VALID,        /* Image valid */
+  &vectors,                     /* Vector table */
+  /* Unlock all pages and debug */
+  { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }
+};
+/*---------------------------------------------------------------------------*/
 /* Linker constructs indicating .data and .bss segment locations */
 extern uint8_t _ldata;
 extern uint8_t _data;