Kconfig and ram.ld: add stack size

Signed-off-by: Alessandro Rubini <rubini@gnudd.com>

Kconfig

@@ -10,6 +10,14 @@ config RAMSIZE
 	 more features you may want to adjust the FPGA size and
 	 choose your preferred value here.
 
+config STACKSIZE
+       int "Size of the stack area needed by this program"
+       default 2048
+       help
+         The linker complains if the code doesn't fit into RAM, but
+	 we must also consider the stack, or the program will crash
+	 badly at run time.
+
 config MPRINTF
 	boolean "Use the old mprintf implementation for printf"
 	default y

arch/lm32/ram.ld.S

@@ -31,7 +31,12 @@ ENTRY(_start)
 
 MEMORY
 {
-    ram : ORIGIN = 0x00000000, LENGTH = CONFIG_RAMSIZE
+    ram :
+	ORIGIN = 0x00000000,
+	LENGTH = CONFIG_RAMSIZE - CONFIG_STACKSIZE
+    stack :
+	ORIGIN = CONFIG_RAMSIZE - CONFIG_STACKSIZE,
+	LENGTH = CONFIG_STACKSIZE
 }
 
 SECTIONS
@@ -54,8 +59,8 @@ SECTIONS
 		_ebss = .;
 	} > ram
 
-	/* First location in stack is highest address in RAM */
-	PROVIDE(_fstack = ORIGIN(ram) + LENGTH(ram) - 4);
+	/* First location in stack is highest address in STACK */
+	PROVIDE(_fstack = ORIGIN(stack) + LENGTH(stack) - 4);
 }
 
 /* We need to provide mprintf to ptp-noposix object files, if missing */