linux-kernel - [PATCH] x86/boot: fix make hdimage with older versions of mtools

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Message-Id: <20210911003906.2700218-1-hpa@zytor.com>
Date:   Fri, 10 Sep 2021 17:39:06 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc:     x86 mailing list <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "H. Peter Anvin (Intel)" <hpa@...or.com>
Subject: [PATCH] x86/boot: fix make hdimage with older versions of mtools

From: "H. Peter Anvin (Intel)" <hpa@...or.com>

Some versions of mtools (fixed somewhere between 4.0.31 and 4.0.35)
generates bad output for mformat when used with the partition=
option. Use the offset= option instead, but we *also* need an
mtools.conf entry with partition= to support mpartition; combining
them in one entry does not work either.

Don't specify the -t option to mpartition; it is unnecessary and seems
to confuse mpartition under some circumstances.

Also do a few minor optimizations:

Use a larger cluster size; there is no reason for the typical 4K
clusters when we are dealing mainly with comparatively huge files.

Start the partition at 32K. There is no reason to align it more than
that, since the internal FAT filesystem structures will at best be
cluster-aligned, and 32K is the maximum FAT cluster size.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
---
 arch/x86/boot/genimage.sh    | 15 ++++++++-------
 arch/x86/boot/mtools.conf.in |  5 +++--
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/x86/boot/genimage.sh b/arch/x86/boot/genimage.sh
index 0673fdfc1a11..c9299aeb7333 100644
--- a/arch/x86/boot/genimage.sh
+++ b/arch/x86/boot/genimage.sh
@@ -120,12 +120,13 @@ efiarch() {
 }
 
 # Get the combined sizes in bytes of the files given, counting sparse
-# files as full length, and padding each file to a 4K block size
+# files as full length, and padding each file to cluster size
+cluster=16384
 filesizes() {
 	local t=0
 	local s
 	for s in $(ls -lnL "$@" 2>/dev/null | awk '/^-/{ print $5; }'); do
-		t=$((t + ((s+4095)/4096)*4096))
+		t=$((t + ((s+cluster-1)/cluster)*cluster))
 	done
 	echo $t
 }
@@ -230,14 +231,14 @@ genhdimage() {
 		ptype='-T 0xef'	# EFI system partition, no GPT
 	fi
 	sizes=$(filesizes "$FBZIMAGE" "${FDINITRDS[@]}" "$efishell")
-	# Allow 1% + 1 MiB for filesystem and partition table overhead,
-	# syslinux, and config files
+	# Allow 1% + 2 MiB for filesystem and partition table overhead,
+	# syslinux, and config files; this is probably excessive...
 	megs=$(((sizes + sizes/100 + 2*1024*1024 - 1)/(1024*1024)))
 	$dd if=/dev/zero of="$FIMAGE" bs=$((1024*1024)) count=$megs 2>/dev/null
-	mpartition -I -c -s 32 -h 64 -t $megs $ptype -b 512 -a h:
+	mpartition -I -c -s 32 -h 64 $ptype -b 64 -a p:
 	$dd if="$mbr" of="$FIMAGE" bs=440 count=1 conv=notrunc 2>/dev/null
-	mformat -v 'LINUX_BOOT' -s 32 -h 64 -t $megs h:
-	syslinux --offset $((512*512)) "$FIMAGE"
+	mformat -v 'LINUX_BOOT' -s 32 -h 64 -c $((cluster/512)) -t $megs h:
+	syslinux --offset $((64*512)) "$FIMAGE"
 	do_mcopy h:
 }
 
diff --git a/arch/x86/boot/mtools.conf.in b/arch/x86/boot/mtools.conf.in
index 9e2662d01364..174c60508766 100644
--- a/arch/x86/boot/mtools.conf.in
+++ b/arch/x86/boot/mtools.conf.in
@@ -14,7 +14,8 @@ drive v:
 drive w:
   file="@OBJ@...image" cylinders=80 heads=2 sectors=36 filter
 
-# Hard disk
+# Hard disk (h: for the filesystem, p: for format - old mtools bug?)
 drive h:
+  file="@OBJ@...image" offset=32768 mformat_only
+drive p:
   file="@OBJ@...image" partition=1 mformat_only
-
-- 
2.31.1