Fix built-in early-load Intel microcode alignment

commit f5ae2ea6347a308cfe91f53b53682ce635497d0d upstream.

Intel Software Developer's Manual, volume 3, chapter 9.11.6 says:

 "Note that the microcode update must be aligned on a 16-byte boundary
  and the size of the microcode update must be 1-KByte granular"

When early-load Intel microcode is loaded from initramfs, userspace tool
'iucode_tool' has already 16-byte aligned those microcode bits in that
initramfs image.  Image that was created something like this:

 iucode_tool --write-earlyfw=FOO.cpio microcode-files...

However, when early-load Intel microcode is loaded from built-in
firmware BLOB using CONFIG_EXTRA_FIRMWARE= kernel config option, that
16-byte alignment is not guaranteed.

Fix this by forcing all built-in firmware BLOBs to 16-byte alignment.

[ If we end up having other firmware with much bigger alignment
  requirements, we might need to introduce some method for the firmware
  to specify it, this is the minimal "just increase the alignment a bit
  to account for this one special case" patch    - Linus ]

Signed-off-by: Jari Ruusu <jari.ruusu@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.16: adjust filename, context, indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/firmware/Makefile b/firmware/Makefile
index 0862d34cf7d1068db9e0d926646b431bf7c2fd4b..3a678382b8cc70088c1d677965539d10173c572d 100644 (file)
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -156,7 +156,7 @@ quiet_cmd_fwbin = MK_FW   $@
                  PROGBITS=$(if $(CONFIG_ARM),%,@)progbits;                  \
                  echo "/* Generated by firmware/Makefile */"           > $@;\
                  echo "    .section .rodata"                           >>$@;\
-                 echo "    .p2align $${ASM_ALIGN}"                     >>$@;\
+                 echo "    .p2align 4"                                 >>$@;\
                  echo "_fw_$${FWSTR}_bin:"                             >>$@;\
                  echo "    .incbin \"$(2)\""                           >>$@;\
                  echo "_fw_end:"                                       >>$@;\