[POWERPC] PS3: Bootwrapper improvements

Improve the debugging support of the PS3 bootwraper code:

o Increase the size of the PS3 bootwrapper overlay from 256 to 512 bytes to
allow for more debugging code in the overlay.
o Use the dot symbol to set the size of __system_reset_overlay. The
assembler will then emit an error if the overlay code is too big.
o Remove some unused instructions.
o Update the text describing the PS3 bootwrapper overlay.
o Add a check for null pointer writes.
o Change hcall return value from s64.

Signed-off-by: Geoff Levand <[e-mail]>
Signed-off-by: Paul Mackerras <[e-mail]>

arch/powerpc/boot/ps3-head.S

···
 /*
  * __system_reset_overlay - The PS3 first stage entry.
  *
- * The bootwraper build script copies the 0x100 bytes at symbol
- * __system_reset_overlay to offset 0x100 of the rom image.
+ * The bootwraper build script copies the 512 bytes at symbol
+ * __system_reset_overlay to offset 0x100 of the rom image.  This symbol
+ * must occupy 512 or less bytes.
  *
  * The PS3 has a single processor with two threads.
  */
···
 
 	mfspr	r3, 0x88
 	cntlzw.	r3, r3
-	li	r4, 0
-	li	r5, 0
 	beq	1f
 
 	/* Secondary goes to __secondary_hold in kernel. */
···
 	mtctr	r4
 	bctr
 
-	/* Primary delays then goes to _zimage_start in wrapper. */
 1:
+	/* Save the value at addr zero for a null pointer write check later. */
+
+	li	r4, 0
+	lwz	r3, 0(r4)
+
+	/* Primary delays then goes to _zimage_start in wrapper. */
+
 	or	31, 31, 31 /* db16cyc */
 	or	31, 31, 31 /* db16cyc */
 
···
 	mtctr	r4
 	bctr
 
+	. = __system_reset_overlay + 512
+
 /*
  * __system_reset_kernel - Place holder for the kernel reset vector.
  *
- * The bootwrapper build script copies 0x100 bytes from offset 0x100
+ * The bootwrapper build script copies 512 bytes from offset 0x100
  * of the rom image to the symbol __system_reset_kernel.  At runtime
- * the bootwrapper program copies the 0x100 bytes at __system_reset_kernel
- * to ram address 0x100.  This symbol must occupy 0x100 bytes.
+ * the bootwrapper program copies the 512 bytes at __system_reset_kernel
+ * to ram address 0x100.  This symbol must occupy 512 bytes.
  */
 
 	.globl __system_reset_kernel
 __system_reset_kernel:
 
-	. = __system_reset_kernel + 0x100
+	. = __system_reset_kernel + 512

arch/powerpc/boot/ps3.c

···
 #include "page.h"
 #include "ops.h"
 
-extern s64 lv1_panic(u64 in_1);
-extern s64 lv1_get_logical_partition_id(u64 *out_1);
-extern s64 lv1_get_logical_ppe_id(u64 *out_1);
-extern s64 lv1_get_repository_node_value(u64 in_1, u64 in_2, u64 in_3,
+extern int lv1_panic(u64 in_1);
+extern int lv1_get_logical_partition_id(u64 *out_1);
+extern int lv1_get_logical_ppe_id(u64 *out_1);
+extern int lv1_get_repository_node_value(u64 in_1, u64 in_2, u64 in_3,
 	u64 in_4, u64 in_5, u64 *out_1, u64 *out_2);
 
 #ifdef DEBUG
···
  * edit the command line passed to vmlinux (by setting /chosen/bootargs).
  * The buffer is put in it's own section so that tools may locate it easier.
  */
+
 static char cmdline[COMMAND_LINE_SIZE]
 	__attribute__((__section__("__builtin_cmdline")));
 
···
 
 static int ps3_repository_read_rm_size(u64 *rm_size)
 {
-	s64 result;
+	int result;
 	u64 lpar_id;
 	u64 ppe_id;
 	u64 v2;
···
 {
 	extern char __system_reset_kernel[];
 
-	memcpy((void *)0x100, __system_reset_kernel, 0x100);
-	flush_cache((void *)0x100, 0x100);
+	memcpy((void *)0x100, __system_reset_kernel, 512);
+	flush_cache((void *)0x100, 512);
 }
 
-void platform_init(void)
+void platform_init(unsigned long null_check)
 {
 	const u32 heapsize = 0x1000000 - (u32)_end; /* 16MiB */
 	void *chosen;
 	unsigned long ft_addr;
 	u64 rm_size;
+	unsigned long val;
 
 	console_ops.write = ps3_console_write;
 	platform_ops.exit = ps3_exit;
···
 	ps3_copy_vectors();
 
 	printf(" flat tree at 0x%lx\n\r", ft_addr);
+
+	val = *(unsigned long *)0;
+
+	if (val != null_check)
+		printf("null check failed: %lx != %lx\n\r", val, null_check);
 
 	((kernel_entry_t)0)(ft_addr, 0, NULL);
 

arch/powerpc/boot/wrapper

···
     exit 0
     ;;
 ps3)
-    # The ps3's loader supports loading gzipped binary images from flash
-    # rom to addr zero. The loader enters the image at addr 0x100.  A
-    # bootwrapper overlay is use to arrange for the kernel to be loaded
-    # to addr zero and to have a suitable bootwrapper entry at 0x100.
-    # To construct the rom image, 0x100 bytes from offset 0x100 in the
-    # kernel is copied to the bootwrapper symbol __system_reset_kernel.
-    # The 0x100 bytes at the bootwrapper symbol __system_reset_overlay is
-    # then copied to offset 0x100.  At runtime the bootwrapper program
-    # copies the 0x100 bytes at __system_reset_kernel to addr 0x100.
+    # The ps3's loader supports loading a gzipped binary image from flash
+    # rom to ram addr zero. The loader then enters the system reset
+    # vector at addr 0x100.  A bootwrapper overlay is used to arrange for
+    # a binary image of the kernel to be at addr zero, and yet have a
+    # suitable bootwrapper entry at 0x100.  To construct the final rom
+    # image 512 bytes from offset 0x100 is copied to the bootwrapper
+    # place holder at symbol __system_reset_kernel.  The 512 bytes of the
+    # bootwrapper entry code at symbol __system_reset_overlay is then
+    # copied to offset 0x100.  At runtime the bootwrapper program copies
+    # the data at __system_reset_kernel back to addr 0x100.
 
     system_reset_overlay=0x`${CROSS}nm "$ofile" \
         | grep ' __system_reset_overlay$'       \
···
         | cut -d' ' -f1`
     system_reset_kernel=`printf "%d" $system_reset_kernel`
     overlay_dest="256"
-    overlay_size="256"
+    overlay_size="512"
 
     ${CROSS}objcopy -O binary "$ofile" "$ofile.bin"