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

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Date:   Sun, 12 Jan 2020 15:03:44 +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: Re: Fix built-in early-load Intel microcode alignment

On 1/12/20, Jari Ruusu <jari.ruusu@...il.com> wrote:
> 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.

Backport of "Fix built-in early-load Intel microcode alignment"
for linux-4.19 and older stable kernels.

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

--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -19,7 +19,7 @@
 		  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)\""				>>$@;\
 		  echo "_fw_end:"					>>$@;\

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