linux-kernel - [PATCH 3.16 186/245] Fix built-in early-load Intel microcode alignment

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Message-ID: <lsq.1587683028.212227277@decadent.org.uk>
Date:   Fri, 24 Apr 2020 00:06:53 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Luis Chamberlain" <mcgrof@...nel.org>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Borislav Petkov" <bp@...en8.de>,
        "Fenghua Yu" <fenghua.yu@...el.com>,
        "Jari Ruusu" <jari.ruusu@...il.com>
Subject: [PATCH 3.16 186/245] Fix built-in early-load Intel microcode
 alignment

3.16.83-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jari Ruusu <jari.ruusu@...il.com>

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@...il.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Luis Chamberlain <mcgrof@...nel.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[bwh: Backported to 3.16: adjust filename, context, indentation]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 firmware/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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)\""				>>$@;\
 		  echo "_fw_end:"					>>$@;\