embed_mfs: support embedding mfs into loader

The script originally supported embedding an mfs into ELF files or any
other type of file, because it searched for magic strings to mark the
beginning and end of the embeddable section. It was later modified to
read the section offset and length via readelf, which made it work for
ELF only. Restore the ability to update arbitrary file types by using
the readelf technique for ELF, and the magic string technique for all
others (including PE/COFF files like loader.efi).

Submitted by:	Zakary Nafziger <worldofzak@gmail.com>
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D12746

1 files changed, 32 insertions, 9 deletions

diff --git a/sys/tools/embed_mfs.sh b/sys/tools/embed_mfs.sh
index fc6bacb470d1..c4fea153d561 100644
--- a/sys/tools/embed_mfs.sh
+++ b/sys/tools/embed_mfs.sh
@@ -27,10 +27,10 @@
 #
 # $FreeBSD$ 
 #
-# Embed the MFS image into the kernel body (expects space reserved via 
-# MD_ROOT_SIZE)
+# Embed an MFS image into the kernel body or the loader body (expects space
+# reserved via MD_ROOT_SIZE (kernel) or MD_IMAGE_SIZE (loader))
 #
-# $1: kernel filename
+# $1: kernel or loader filename
 # $2: MFS image filename
 #
 
@@ -47,16 +47,39 @@ mfs_size=`stat -f '%z' $2 2> /dev/null`
 # If we can't determine MFS image size - bail.
 [ -z ${mfs_size} ] && echo "Can't determine MFS image size" && exit 1
 
-sec_info=`elfdump -c $1 2> /dev/null | grep -A 5 -E "sh_name: oldmfs$"`
-# If we can't find the mfs section within the given kernel - bail.
-[ -z "${sec_info}" ] && echo "Can't locate mfs section within $1" && exit 1
+err_no_mfs="Can't locate mfs section within "
 
-sec_size=`echo "${sec_info}" | awk '/sh_size/ {print $2}' 2> /dev/null`
-sec_start=`echo "${sec_info}" | awk '/sh_offset/ {print $2}' 2> /dev/null`
+if [ `file -b $1 | grep -q '^ELF ..-bit .SB executable'` ]; then
+
+	sec_info=`elfdump -c $1 2> /dev/null | grep -A 5 -E "sh_name: oldmfs$"`
+	# If we can't find the mfs section within the given kernel - bail.
+	[ -z "${sec_info}" ] && echo "${err_no_mfs} $1" && exit 1
+
+	sec_size=`echo "${sec_info}" | awk '/sh_size/ {print $2}' 2>/dev/null`
+	sec_start=`echo "${sec_info}" | \
+	    awk '/sh_offset/ {print $2}' 2>/dev/null`
+
+else
+
+	#try to find start byte of MFS start flag otherwise - bail.
+	sec_start=`strings -at d $1 | grep "MFS Filesystem goes here"` || \
+	    { echo "${err_no_mfs} $1"; exit 1; }
+	sec_start=`echo ${sec_start} | awk '{print $1}'`
+
+	#try to find start byte of MFS end flag otherwise - bail.
+	sec_end=`strings -at d $1 | \
+	    grep "MFS Filesystem had better STOP here"` || \
+	    { echo "${err_no_mfs} $1"; exit 1; }
+	sec_end=`echo ${sec_end} | awk '{print $1}'`
+
+	#calculate MFS section size
+	sec_size=`expr ${sec_end} - ${sec_start}`
+
+fi
 
 # If the mfs section size is smaller than the mfs image - bail.
 [ ${sec_size} -lt ${mfs_size} ] && echo "MFS image too large" && exit 1
 
 # Dump the mfs image into the mfs section
 dd if=$2 ibs=8192 of=$1 obs=${sec_start} oseek=1 conv=notrunc 2> /dev/null && \
-    echo "MFS image embedded into kernel" && exit 0
+    echo "MFS image embedded into $1" && exit 0