* startup/bspstart.c, start/start.S: Since the crude

memory autodetection code can easily fail (boards with
	'reserved' regions - I experienced a hard lockup on a
	dell precision 490 when writing past the bios-reported
	memory size) I added code that a) tries to save
	and use multiboot info, if present b) allows applications
	to override/set memory size via a weak alias.

c/src/lib/libbsp/i386/pc386/ChangeLog

@@ -1,3 +1,13 @@
+2006-09-04	Till Straumann <strauman@slac.stanford.edu>
+
+	* startup/bspstart.c, start/start.S: Since the crude
+	memory autodetection code can easily fail (boards with
+	'reserved' regions - I experienced a hard lockup on a
+	dell precision 490 when writing past the bios-reported
+	memory size) I added code that a) tries to save
+	and use multiboot info, if present b) allows applications
+	to override/set memory size via a weak alias.
+
 2006-09-04	Till Straumann <strauman@slac.stanford.edu>
 
 	* startup/linkcmds: added *(.text.*) *(.data.*) *(.bss.*)

c/src/lib/libbsp/i386/pc386/start/start.S

@@ -87,6 +87,22 @@ speakl:	jmp	speakl             # and SPIN!!!
         nop
         cli			# DISABLE INTERRUPTS!!!
 	cld
+
+		/* Save multiboot info */
+		cmp 	$0x2badb002,eax
+		jne		1f
+		/* We have multiboot info; let's hope DS and ES are OK... */
+		movl	ebx, SYM(_boot_multiboot_info_p)
+		/* Check for memory size info and save */
+		movl	ebx, esi
+		movl	$SYM(_boot_multiboot_info), edi
+		movsd
+		/* only save flag 1 since that's the only data we save */
+		and		$1,-4(edi)
+		je		1f
+		movl	$2,ecx
+		rep movsd
+1:
 #ifdef DEBUG_EARLY_START
 	/*
 	 * Must get video attribute to have a working printk.
@@ -178,6 +194,15 @@ SYM (zero_bss):
 END_CODE
 
 BEGIN_DATA
+	PUBLIC(_boot_multiboot_info_p)
+SYM(_boot_multiboot_info_p):
+	.long 0
+
+	PUBLIC(_boot_multiboot_info)
+SYM(_boot_multiboot_info):
+	.long 0	/* flags */
+	.long 0 /* mem_lower */
+	.long 0 /* mem_upper */
 
 	PUBLIC(_stack_size)
 SYM(_stack_size):

c/src/lib/libbsp/i386/pc386/startup/bspstart.c

@@ -40,12 +40,28 @@
 | Global Variables
 +--------------------------------------------------------------------------*/
 extern uint32_t         _end;         /* End of BSS. Defined in 'linkcmds'. */
+
+/* rudimentary multiboot info */
+struct multiboot_info {
+	uint32_t	flags;		/* start.S only raises flags for items actually saved; this allows us to check for the size of the data structure */
+	uint32_t	mem_lower;	/* avail kB in lower memory */
+	uint32_t	mem_upper;	/* avail kB in lower memory */
+	/* ... (unimplemented) */
+};
+
+extern struct multiboot_info _boot_multiboot_info;
 /*
  * Size of heap if it is 0 it will be dynamically defined by memory size,
  * otherwise the value should be changed by binary patch
  */
 uint32_t         _heap_size = 0;
 
+/* Alternative way to hardcode the board's memory size [rather than heap size].
+ * Can easily be overridden by application.
+ */
+extern uint32_t bsp_mem_size __attribute__ ((weak, alias("bsp_mem_size_default")));
+uint32_t bsp_mem_size_default = 0;
+
 /* Size of stack used during initialization. Defined in 'start.s'.  */
 extern uint32_t         _stack_size;
 
@@ -92,26 +108,43 @@ void bsp_pretasking_hook(void)
   if ( lowest  < 2 )
       lowest = 2;
 
+  /* The memory detection algorithm is very crude; try
+   * to use multiboot info, if possible (set from start.S)
+   */
+  if (   bsp_mem_size == 0
+      && (_boot_multiboot_info.flags & 1)
+      && _boot_multiboot_info.mem_upper ) {
+    bsp_mem_size = _boot_multiboot_info.mem_upper * 1024;
+  }
+
   if (_heap_size == 0) {
-    /*
-     * We have to dynamically size memory. Memory size can be anything
-     * between no less than 2M and 2048M.
-     * let us first write
-     */
-    for (i=2048; i>=lowest; i--) {
-      topAddr = i*1024*1024 - 4;
-      *(volatile uint32_t*)topAddr = topAddr;
-    }
 
-   for(i=lowest; i<=2048; i++) {
+    if ( bsp_mem_size == 0 ) {
-     topAddr = i*1024*1024 - 4;
+        /*
-     val =  *(uint32_t*)topAddr;
+         * We have to dynamically size memory. Memory size can be anything
-     if (val != topAddr) {
+         * between no less than 2M and 2048M.
-       break;
+         * let us first write
-     }
+         */
-   }
+        for (i=2048; i>=lowest; i--) {
+          topAddr = i*1024*1024 - 4;
+          *(volatile uint32_t*)topAddr = topAddr;
+        }
 
-    topAddr = (i-1)*1024*1024 - 4;
+        for(i=lowest; i<=2048; i++) {
+          topAddr = i*1024*1024 - 4;
+          val =  *(uint32_t*)topAddr;
+          if (val != topAddr) {
+            break;
+          }
+        }
+      
+        topAddr = (i-1)*1024*1024 - 4;
+
+      } else {
+
+        topAddr = bsp_mem_size;
+
+      }
 
     _heap_size = topAddr - rtemsFreeMemStart;
   }
@@ -143,8 +176,8 @@ void bsp_start_default( void )
    */
   Calibrate_loop_1ms();
 
+  /* set the value of start of free memory. */
   rtemsFreeMemStart = (uint32_t)&_end + _stack_size;
-                                    /* set the value of start of free memory. */
 
   /* If we don't have command line arguments set default program name. */