[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 <geoffrey.levand@am.sony.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 11 insertions, 10 deletions

diff --git a/arch/powerpc/boot/wrapper b/arch/powerpc/boot/wrapper
index 03b474bfe74..087e120e490 100755
--- a/arch/powerpc/boot/wrapper
+++ b/arch/powerpc/boot/wrapper
@@ -298,15 +298,16 @@ treeboot*)
     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$'       \
@@ -317,7 +318,7 @@ ps3)
         | 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"