From eaaebf3291a12ff65ca5c7f16e0d486fbde10efa Mon Sep 17 00:00:00 2001
From: Damien George
Date: Tue, 23 Sep 2014 10:59:05 +0100
Subject: stmhal: Initialise stack pointer correctly.

Stack is full descending and must be 8-byte aligned.  It must start off
pointing to just above the last byte of RAM.

Previously, stack started pointed to last byte of RAM (eg 0x2001ffff)
and so was not 8-byte aligned.  This caused a bug in combination with
alloca.

This patch also updates some debug printing code.

Addresses issue #872 (among many other undiscovered issues).
---
 stmhal/main.c       | 6 +++---
 stmhal/stm32f405.ld | 8 ++++----
 2 files changed, 7 insertions(+), 7 deletions(-)

(limited to 'stmhal')

diff --git a/stmhal/main.c b/stmhal/main.c
index 6aa7b082d..05b097b7b 100644
--- a/stmhal/main.c
+++ b/stmhal/main.c
@@ -174,9 +174,9 @@ static const char fresh_readme_txt[] =
 int main(void) {
     // TODO disable JTAG
 
-    // Stack limit should be less than real stack size, so we
-    // had chance to recover from limit hit.
-    mp_stack_set_limit(&_ram_end - &_heap_end - 512);
+    // Stack limit should be less than real stack size, so we have a chance
+    // to recover from limit hit.  (Limit is measured in bytes.)
+    mp_stack_set_limit((char*)&_ram_end - (char*)&_heap_end - 1024);
 
     /* STM32F4xx HAL library initialization:
          - Configure the Flash prefetch, instruction and Data caches
diff --git a/stmhal/stm32f405.ld b/stmhal/stm32f405.ld
index 9d9d4d508..5af1d3299 100644
--- a/stmhal/stm32f405.ld
+++ b/stmhal/stm32f405.ld
@@ -16,10 +16,10 @@ MEMORY
 _minimum_stack_size = 2K;
 _minimum_heap_size = 16K;
  
-/* top end of the stack */
-
-/*_stack_end = ORIGIN(RAM) + LENGTH(RAM);*/
-_estack = ORIGIN(RAM) + LENGTH(RAM) - 1;
+/* Define tho top end of the stack.  The stack is full descending so begins just
+   above last byte of RAM.  Note that EABI requires the stack to be 8-byte
+   aligned for a call. */
+_estack = ORIGIN(RAM) + LENGTH(RAM);
 
 /* RAM extents for the garbage collector */
 _ram_end = ORIGIN(RAM) + LENGTH(RAM);
-- 
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