linux-kernel - Fix built-in early-load Intel microcode alignment

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Date:   Sun, 12 Jan 2020 15:00:53 +0200
From:   Jari Ruusu <jari.ruusu@...il.com>
To:     Borislav Petkov <bp@...en8.de>, Fenghua Yu <fenghua.yu@...el.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Fix built-in early-load Intel microcode alignment

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.

Signed-off-by: Jari Ruusu <jari.ruusu@...il.com>

--- a/drivers/base/firmware_loader/builtin/Makefile
+++ b/drivers/base/firmware_loader/builtin/Makefile
@@ -17,7 +17,7 @@
 filechk_fwbin = \
 	echo "/* Generated by $(src)/Makefile */"		;\
 	echo "    .section .rodata"				;\
-	echo "    .p2align $(ASM_ALIGN)"			;\
+	echo "    .p2align 4"					;\
 	echo "_fw_$(FWSTR)_bin:"				;\
 	echo "    .incbin \"$(fwdir)/$(FWNAME)\""		;\
 	echo "_fw_end:"						;\

-- 
Jari Ruusu  4096R/8132F189 12D6 4C3A DCDA 0AA4 27BD  ACDF F073 3C80 8132 F189