Fix regression introduced in r328806, preventing boot at least on all

PowerPC Apple hardware, and likely all Open Firmware systems.

The loader would allocate memory for its heap at whatever address Open
Firmware gave it, which would in general be the lowest unallocated address,
usually starting a page or two above 0. As the kernel is linked at 1 MB,
and loader insists on running the kernel at its link address, any heap
larger than 1 MB would overlap the kernel, causing loader memory allocations
to corrupt the kernel and vice versa.

Although r328806 made this problem much worse by increasing the heap size
to 8 MB, causing 88% of the loader heap to overlap with the kernel, the
problem has always existed. The old heap size was 1 MB and, unless that
started exactly at zero, which would cause other problems, some number of
pages of the loader heap still overlapped with the kernel.

This patch solves the issue in two ways and cleans up some related code:
- Moves the loader heap inside of the loader. This guarantees that the
  heap will be contiguous with the loader and simplifies the heap
  allocation code at no cost, since the heap lives in BSS.
- Moves the loader, previously at 28 MB and dangerously close to the kernel
  it loads, a bit higher to 44 MB. This has the effect of breaking loader
  on non-embedded PPC machines with < 48 MB of RAM, but we did not support
  those anyway.

The fundamental problem is that the way loader loads ELF files is
incredibly fragile, but that can't be fixed without fundamental
architectural changes.

MFC after:	10 days

stand/ofw/common/main.c

@@ -43,22 +43,16 @@ u_int32_t	acells, scells;
 static char bootargs[128];
 
 #define	HEAP_SIZE	0x800000
+static char heap[HEAP_SIZE]; // In BSS, so uses no space
 
 #define OF_puts(fd, text) OF_write(fd, text, strlen(text))
 
 void
 init_heap(void)
 {
-	void	*base;
-	ihandle_t stdout;
+	bzero(heap, HEAP_SIZE);
 
-	if ((base = ofw_alloc_heap(HEAP_SIZE)) == (void *)0xffffffff) {
-		OF_getprop(chosen, "stdout", &stdout, sizeof(stdout));
-		OF_puts(stdout, "Heap memory claim failed!\n");
-		OF_enter();
-	}
-
-	setheap(base, (void *)((int)base + HEAP_SIZE));
+	setheap(heap, (void *)((int)heap + HEAP_SIZE));
 }
 
 uint64_t

stand/ofw/libofw/elf_freebsd.c

@@ -87,7 +87,6 @@ __elfN(ofw_exec)(struct preloaded_file *fp)
 	printf("Kernel entry at 0x%lx ...\n", e->e_entry);
 
 	dev_cleanup();
-	ofw_release_heap();
 	if (dtbp != 0) {
 		OF_quiesce();
 		((int (*)(u_long, u_long, u_long, void *, u_long))entry)(dtbp, 0, 0,

stand/ofw/libofw/libofw.h

@@ -58,8 +58,6 @@ extern int	ofw_boot(void);
 extern int	ofw_autoload(void);
 
 void	ofw_memmap(int);
-void	*ofw_alloc_heap(unsigned int);
-void	ofw_release_heap(void);
 
 struct preloaded_file;
 struct file_format;

stand/ofw/libofw/ofw_copy.c

@@ -39,7 +39,7 @@ __FBSDID("$FreeBSD$");
 #define	READIN_BUF	(4 * 1024)
 #define	PAGE_SIZE	0x1000
 #define	PAGE_MASK	0x0fff
-#define MAPMEM_PAGE_INC 16
+#define	MAPMEM_PAGE_INC 128 /* Half-MB at a time */
 
 
 #define	roundup(x, y)	((((x)+((y)-1))/(y))*(y))

stand/ofw/libofw/ofw_memory.c

@@ -35,9 +35,6 @@ __FBSDID("$FreeBSD$");
 #include "libofw.h"
 #include "openfirm.h"
 
-static void		*heap_base = NULL;
-static unsigned int	heap_size = 0;
-
 struct ofw_mapping {
         vm_offset_t     va;
         int             len;
@@ -115,32 +112,3 @@ ofw_memmap(int acells)
 	pager_close();
 }
 
-void *
-ofw_alloc_heap(unsigned int size)
-{
-	phandle_t	memoryp, root;
-	cell_t		available[4];
-	cell_t		acells;
-
-	root = OF_finddevice("/");
-	acells = 1;
-	OF_getprop(root, "#address-cells", &acells, sizeof(acells));
-
-	memoryp = OF_instance_to_package(memory);
-	OF_getprop(memoryp, "available", available, sizeof(available));
-
-	heap_base = OF_claim((void *)available[acells-1], size,
-	    sizeof(register_t));
-
-	if (heap_base != (void *)-1) {
-		heap_size = size;
-	}
-
-	return (heap_base);
-}
-
-void
-ofw_release_heap(void)
-{
-	OF_release(heap_base, heap_size);
-}

stand/ofw/libofw/ppc64_elf_freebsd.c

@@ -90,7 +90,6 @@ ppc64_ofw_elf_exec(struct preloaded_file *fp)
 	printf("Kernel entry at 0x%lx ...\n", entry);
 
 	dev_cleanup();
-	ofw_release_heap();
 
 	if (dtbp != 0) {
 		OF_quiesce();

stand/powerpc/ofw/ldscript.powerpc

@@ -9,7 +9,7 @@ PROVIDE (__stack = 0);
 SECTIONS
 {
   /* Read-only sections, merged into text segment: */
-  . = 0x01c00000 + SIZEOF_HEADERS;
+  . = 0x02c00000 + SIZEOF_HEADERS;
   .interp     : { *(.interp) 	}
   .hash          : { *(.hash)		}
   .dynsym        : { *(.dynsym)		}