2003-09-26 Till Strauman <strauman@slac.stanford.edu>

	PR 496/bsps
	* startup/sbrk.c: New file.
	* startup/bspstart.c: This patch implements 'sbrk'
	for the powerpc-shared BSP to work around what's known as the
	'32Mb problem' in combination with run-time loaded code.
	GCC normally generates (PowerPC) code doing 'short jumps' which
	requires all text segments being in the same 32Mb area of memory.
	However, some run-time loaders use (e.g. heap-) memory violating the
	stated limitation on hardware with more than 32Mb of memory.
	(NOTE: portable loaders are probably not even aware of this
	GCC/CPU specific problem.)

	This patch implements a simple workaround: At boot time, the system is
	only provided with 32Mb of memory. The user is supposed to load all
	necessary modules prior to that limit being exhausted. Once that
	happens, newlib/malloc end up trying to 'sbrk()' for more memory and
	the implementation provided by this patch will then make the rest of
	the physical memory available.

3 files changed, 93 insertions, 2 deletions

diff --git a/c/src/lib/libbsp/powerpc/shared/ChangeLog b/c/src/lib/libbsp/powerpc/shared/ChangeLog
index 7443efbdf7..bec24b2a92 100644
--- a/c/src/lib/libbsp/powerpc/shared/ChangeLog
+++ b/c/src/lib/libbsp/powerpc/shared/ChangeLog
@@ -1,3 +1,24 @@
+2003-09-26	Till Strauman <strauman@slac.stanford.edu>
+
+	PR 496/bsps
+	* startup/sbrk.c: New file.
+	* startup/bspstart.c: This patch implements 'sbrk'
+	for the powerpc-shared BSP to work around what's known as the
+	'32Mb problem' in combination with run-time loaded code.
+	GCC normally generates (PowerPC) code doing 'short jumps' which
+	requires all text segments being in the same 32Mb area of memory.
+	However, some run-time loaders use (e.g. heap-) memory violating the
+	stated limitation on hardware with more than 32Mb of memory.
+	(NOTE: portable loaders are probably not even aware of this
+	GCC/CPU specific problem.)
+
+	This patch implements a simple workaround: At boot time, the system is
+	only provided with 32Mb of memory. The user is supposed to load all
+	necessary modules prior to that limit being exhausted. Once that
+	happens, newlib/malloc end up trying to 'sbrk()' for more memory and
+	the implementation provided by this patch will then make the rest of
+	the physical memory available.
+
 2003-09-26  Till Straumann <strauman@slac.stanford.edu>
 
 	PR 497/bsps
diff --git a/c/src/lib/libbsp/powerpc/shared/startup/bspstart.c b/c/src/lib/libbsp/powerpc/shared/startup/bspstart.c
index 3834c6f255..1927ea96db 100644
--- a/c/src/lib/libbsp/powerpc/shared/startup/bspstart.c
+++ b/c/src/lib/libbsp/powerpc/shared/startup/bspstart.c
@@ -132,6 +132,8 @@ void bsp_pretasking_hook(void)
 {
     rtems_unsigned32        heap_start;    
     rtems_unsigned32        heap_size;
+    rtems_unsigned32        heap_sbrk_spared;
+	extern rtems_unsigned32 _bsp_sbrk_init(rtems_unsigned32, rtems_unsigned32*);
 
     heap_start = ((rtems_unsigned32) __rtems_end) +INIT_STACK_SIZE + INTR_STACK_SIZE;
     if (heap_start & (CPU_ALIGNMENT-1))
@@ -139,10 +141,14 @@ void bsp_pretasking_hook(void)
 
     heap_size = (BSP_mem_size - heap_start) - BSP_Configuration.work_space_size;
 
+	heap_sbrk_spared=_bsp_sbrk_init(heap_start, &heap_size);
+
 #ifdef SHOW_MORE_INIT_SETTINGS
-    printk(" HEAP start %x  size %x\n", heap_start, heap_size);
+   	printk(" HEAP start %x  size %x (%x bytes spared for sbrk)\n", heap_start, heap_size, heap_sbrk_spared);
 #endif    
-    bsp_libc_init((void *) heap_start, heap_size, 0);
+
+    bsp_libc_init((void *) 0, heap_size, heap_sbrk_spared);
+
 
 #ifdef RTEMS_DEBUG
     rtems_debug_enable( RTEMS_DEBUG_ALL_MASK );
diff --git a/c/src/lib/libbsp/powerpc/shared/startup/sbrk.c b/c/src/lib/libbsp/powerpc/shared/startup/sbrk.c
new file mode 100644
index 0000000000..276433a5da
--- /dev/null
+++ b/c/src/lib/libbsp/powerpc/shared/startup/sbrk.c
@@ -0,0 +1,64 @@
+/* $Id$ */
+
+/*
+ *  sbrk.c
+ *
+ *  Author: Till Straumann <strauman@slac.stanford.edu>, 2002
+ *
+ *  Hack around the 32bit powerpc 32M problem:
+ *
+ *  GCC by default uses relative branches which can not jump
+ *  farther than 32M. Hence all program text is confined to
+ *  a single 32M segment.
+ *  This hack gives the RTEMS malloc region all memory below
+ *  32M at startup. Only when this region is exhausted will sbrk
+ *  add more memory. Loading modules may fail at that point, hence
+ *  the user is expected to load all modules at startup _prior_
+ *  to malloc()ing lots of memory...
+ *
+ *  NOTE: it would probably be better to have a separate region
+ *        for module code.
+ */
+
+#include <rtems.h>
+
+#include <signal.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+static rtems_unsigned32 remaining_start=0;
+static rtems_unsigned32 remaining_size=0;
+
+#define LIMIT_32M  0x02000000
+
+rtems_unsigned32
+_bsp_sbrk_init(rtems_unsigned32 heap_start, rtems_unsigned32 *heap_size_p)
+{
+  rtems_unsigned32 rval=0;
+
+  remaining_start =  heap_start;
+  remaining_size  =*  heap_size_p;
+  if (remaining_start < LIMIT_32M &&
+      remaining_start + remaining_size > LIMIT_32M) {
+    /* clip at LIMIT_32M */
+    rval = remaining_start + remaining_size - LIMIT_32M;
+    *heap_size_p = LIMIT_32M - remaining_start;
+  }
+  return rval;
+}
+
+void * sbrk(ptrdiff_t incr)
+{
+  void *rval=(void*)-1;
+
+  if (incr <= remaining_size) {
+    remaining_size-=incr;
+    rval = (void*)remaining_start;
+    remaining_start += incr;
+  } else {
+    errno = ENOMEM;
+  }
+  return rval;
+}
+