[FYT Android Head Units] cryptyk:
Trying to figure out the CC3 now - any help would be appreciated. Here's what I know:

1) At flash time, the mounts look like this:

rootfs on / type rootfs (rw,seclabel)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,size=2932168k,nr_inodes=733042,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600,ptmxmode=000)
proc on /proc type proc (rw,relatime,gid=3009)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
tmpfs on /mnt type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=2932168k,nr_inodes=733042,mode=755,gid=1000)
tmpfs on /apex type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=2932168k,nr_inodes=733042,mode=755)
none on /acct type cgroup (rw,nosuid,nodev,noexec,relatime,cpuacct)
tmpfs on /tmp type tmpfs (rw,seclabel,relatime,size=2932168k,nr_inodes=733042)
none on /config type configfs (rw,relatime)
adb on /dev/usb-ffs/adb type functionfs (rw,relatime)
fastboot on /dev/usb-ffs/fastboot type functionfs (rw,relatime)
/dev/block/sda1 on /storage/sdcard1 type vfat (rw,nodev,noatime,nodiratime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro)
/dev/block/mmcblk0p33 on /cache type ext4 (rw,seclabel,nosuid,nodev,noatime,noauto_da_alloc,data=ordered)
/dev/block/mmcblk0p44 on /lsecfs type ext4 (rw,seclabel,nosuid,nodev,noatime,noauto_da_alloc,data=ordered)
/dev/block/mmcblk0p42 on /oem type ext4 (rw,seclabel,nosuid,nodev,noatime,noauto_da_alloc)
/dev/block/mmcblk0p46 on /data type f2fs (rw,lazytime,seclabel,nosuid,nodev,noatime,background_gc=on,discard,no_heap,user_xattr,inline_xattr,inline_data,inline_dentry,flush_merge,extent_cache,mode=adaptive,active_logs=6,reserve_root=51200,resuid=0,resgid=0,alloc_mode=default,fsync_mode=posix)

Note there's no mounted /elable/.

2) At runtime (normal boot) the mounts look like this:

/dev/block/dm-2 on / type ext4 (ro,seclabel,relatime)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,size=2932168k,nr_inodes=733042,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600,ptmxmode=000)
proc on /proc type proc (rw,relatime,gid=3009)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
tmpfs on /mnt type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=2932168k,nr_inodes=733042,mode=755,gid=1000)
tmpfs on /apex type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=2932168k,nr_inodes=733042,mode=755)
/dev/block/mmcblk0p38 on /metadata type ext4 (rw,seclabel,nosuid,nodev,noatime,errors=panic,data=ordered)
/dev/block/dm-1 on /vendor type ext4 (ro,seclabel,relatime)
/dev/block/dm-0 on /product type ext4 (ro,seclabel,relatime)
/dev/block/dm-3 on /elable type ext4 (ro,seclabel,relatime,data=ordered)
/dev/block/mmcblk0p42 on /fem type ext4 (ro,seclabel,nosuid,nodev,noatime,noauto_da_alloc)
none on /dev/cg2_bpf type cgroup2 (rw,nosuid,nodev,noexec,relatime)
none on /dev/cpuctl type cgroup (rw,nosuid,nodev,noexec,relatime,cpu)
none on /acct type cgroup (rw,nosuid,nodev,noexec,relatime,cpuacct)
none on /dev/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset,noprefix,release_agent=/sbin/cpuset_release_agent)
none on /dev/memcg type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
none on /dev/stune type cgroup (rw,nosuid,nodev,noexec,relatime,schedtune)
debugfs on /sys/kernel/debug type debugfs (rw,seclabel,relatime)
none on /config type configfs (rw,nosuid,nodev,noexec,relatime)
bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime)
pstore on /sys/fs/pstore type pstore (rw,seclabel,nosuid,nodev,noexec,relatime)
adb on /dev/usb-ffs/adb type functionfs (rw,relatime)
/dev/block/mmcblk0p44 on /lsecfs type ext4 (rw,seclabel,relatime,data=ordered)
tracefs on /sys/kernel/debug/tracing type tracefs (rw,seclabel,relatime)
/dev/block/mmcblk0p46 on /data type f2fs (rw,lazytime,seclabel,nosuid,nodev,noatime,background_gc=on,discard,no_heap,user_xattr,inline_xattr,inline_data,inline_dentry,flush_merge,extent_cache,mode=adaptive,active_logs=6,reserve_root=51200,resuid=0,resgid=0,alloc_mode=default,fsync_mode=posix)
/dev/block/mmcblk0p33 on /cache type ext4 (rw,seclabel,nosuid,nodev,noatime,noauto_da_alloc,data=ordered)
/dev/block/mmcblk0p1 on /mnt/vendor type ext4 (rw,seclabel,nosuid,nodev,noatime,noauto_da_alloc,data=ordered)
/dev/block/mmcblk0p34 on /mnt/vendor/socko type ext4 (ro,seclabel,nosuid,nodev,noatime,noauto_da_alloc)
/dev/block/mmcblk0p35 on /mnt/vendor/odmko type ext4 (ro,seclabel,nosuid,nodev,noatime,noauto_da_alloc)
tmpfs on /storage type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=2932168k,nr_inodes=733042,mode=755,gid=1000)
/dev/block/loop2 on /apex/com.android.media.swcodec@290000000 type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop2 on /apex/com.android.media.swcodec type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop3 on /apex/com.android.resolv@290000000 type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop3 on /apex/com.android.resolv type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop4 on /apex/com.android.conscrypt@290000000 type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop4 on /apex/com.android.conscrypt type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop5 on /apex/com.android.runtime@1 type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop5 on /apex/com.android.runtime type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop6 on /apex/com.android.media@290000000 type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop6 on /apex/com.android.media type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop7 on /apex/com.android.apex.cts.shim@1 type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop7 on /apex/com.android.apex.cts.shim type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop8 on /apex/com.android.tzdata@290000000 type ext4 (ro,dirsync,seclabel,nodev,noatime)
/dev/block/loop8 on /apex/com.android.tzdata type ext4 (ro,dirsync,seclabel,nodev,noatime)
/data/media on /mnt/runtime/default/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)
/data/media on /storage/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,unshared_obb)
/data/media on /mnt/runtime/read/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=23,derive_gid,default_normal,unshared_obb)
/data/media on /mnt/runtime/write/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal,unshared_obb)
/data/media on /mnt/runtime/full/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal,unshared_obb)

So basically, the CC3 mounts OEM normally during flash time, but when it boots, it mounts the oem block as /fem and links the /oem directory to the /elable directory. It's also mounting /dev/block/dm-3 as elable, but that block device isn't available at flash time.

Here is the /dev/block folder during flash time:

/dev/block:
total 0
drwxr-xr-x 2 root root 1040 2023-01-09 20:23 by-name
brw------- 1 root root 7, 0 2023-01-09 20:23 loop0
brw------- 1 root root 7, 1 2023-01-09 20:23 loop1
brw------- 1 root root 7, 10 2023-01-09 20:23 loop10
brw------- 1 root root 7, 11 2023-01-09 20:23 loop11
brw------- 1 root root 7, 12 2023-01-09 20:23 loop12
brw------- 1 root root 7, 13 2023-01-09 20:23 loop13
brw------- 1 root root 7, 14 2023-01-09 20:23 loop14
brw------- 1 root root 7, 15 2023-01-09 20:23 loop15
brw------- 1 root root 7, 2 2023-01-09 20:23 loop2
brw------- 1 root root 7, 3 2023-01-09 20:23 loop3
brw------- 1 root root 7, 4 2023-01-09 20:23 loop4
brw------- 1 root root 7, 5 2023-01-09 20:23 loop5
brw------- 1 root root 7, 6 2023-01-09 20:23 loop6
brw------- 1 root root 7, 7 2023-01-09 20:23 loop7
brw------- 1 root root 7, 8 2023-01-09 20:23 loop8
brw------- 1 root root 7, 9 2023-01-09 20:23 loop9
brw------- 1 root root 179, 0 2023-01-09 20:23 mmcblk0
brw------- 1 root root 179, 8 2023-01-09 20:23 mmcblk0boot0
brw------- 1 root root 179, 16 2023-01-09 20:23 mmcblk0boot1
brw------- 1 root root 179, 1 2023-01-09 20:23 mmcblk0p1
brw------- 1 root root 259, 2 2023-01-09 20:23 mmcblk0p10
brw------- 1 root root 259, 3 2023-01-09 20:23 mmcblk0p11
brw-rw-rw- 1 system system 259, 4 2023-01-09 20:23 mmcblk0p12
brw------- 1 root root 259, 5 2023-01-09 20:23 mmcblk0p13
brw-rw---- 1 system system 259, 6 2023-01-09 20:23 mmcblk0p14
brw-rw---- 1 system system 259, 7 2023-01-09 20:23 mmcblk0p15
brw-rw---- 1 system system 259, 8 2023-01-09 20:23 mmcblk0p16
brw-rw---- 1 system system 259, 9 2023-01-09 20:23 mmcblk0p17
brw-rw---- 1 system root 259, 10 2023-01-09 20:23 mmcblk0p18
brw------- 1 root root 259, 11 2023-01-09 20:23 mmcblk0p19
brw-rw---- 1 system system 179, 2 2023-01-09 20:23 mmcblk0p2
brw-rw---- 1 system system 259, 12 2023-01-09 20:23 mmcblk0p20
brw------- 1 system root 259, 13 2023-01-09 20:23 mmcblk0p21
brw-rw---- 1 system system 259, 14 2023-01-09 20:23 mmcblk0p22
brw------- 1 system root 259, 15 2023-01-09 20:23 mmcblk0p23
brw------- 1 system root 259, 16 2023-01-09 20:23 mmcblk0p24
brw------- 1 audioserver root 259, 17 2023-01-09 20:23 mmcblk0p25
brw------- 1 system root 259, 18 2023-01-09 20:23 mmcblk0p26
brw------- 1 system root 259, 19 2023-01-09 20:23 mmcblk0p27
brw------- 1 root root 259, 20 2023-01-09 20:23 mmcblk0p28
brw------- 1 root root 259, 21 2023-01-09 20:23 mmcblk0p29
brw------- 1 root root 179, 3 2023-01-09 20:23 mmcblk0p3
brw------- 1 root root 259, 22 2023-01-09 20:23 mmcblk0p30
brw------- 1 root root 259, 23 2023-01-09 20:23 mmcblk0p31
brw------- 1 root root 259, 24 2023-01-09 20:23 mmcblk0p32
brw------- 1 root root 259, 25 2023-01-09 20:23 mmcblk0p33
brw------- 1 root root 259, 26 2023-01-09 20:23 mmcblk0p34
brw------- 1 root root 259, 27 2023-01-09 20:23 mmcblk0p35
brw------- 1 root root 259, 28 2023-01-09 20:23 mmcblk0p36
brw------- 1 root root 259, 29 2023-01-09 20:23 mmcblk0p37
brw------- 1 root root 259, 30 2023-01-09 20:23 mmcblk0p38
brw-rw---- 1 system system 259, 31 2023-01-09 20:23 mmcblk0p39
brw------- 1 root root 179, 4 2023-01-09 20:23 mmcblk0p4
brw------- 1 root root 259, 32 2023-01-09 20:23 mmcblk0p40
brw------- 1 root root 259, 33 2023-01-09 20:23 mmcblk0p41
brw------- 1 root root 259, 34 2023-01-09 20:23 mmcblk0p42
brw-rw-rw- 1 system system 259, 35 2023-01-09 20:23 mmcblk0p43
brw------- 1 root root 259, 36 2023-01-09 20:23 mmcblk0p44
brw-rw---- 1 system root 259, 37 2023-01-09 20:23 mmcblk0p45
brw------- 1 root root 259, 38 2023-01-09 20:23 mmcblk0p46
brw------- 1 root root 179, 5 2023-01-09 20:23 mmcblk0p5
brw------- 1 root root 179, 6 2023-01-09 20:23 mmcblk0p6
brw------- 1 root root 179, 7 2023-01-09 20:23 mmcblk0p7
brw------- 1 root root 259, 0 2023-01-09 20:23 mmcblk0p8
brw------- 1 root root 259, 1 2023-01-09 20:23 mmcblk0p9
brw-rw---- 1 system system 179, 24 2023-01-09 20:23 mmcblk0rpmb
drwxr-xr-x 3 root root 60 2023-01-09 20:23 platform
brw------- 1 root root 1, 0 2023-01-09 20:23 ram0
brw------- 1 root root 1, 1 2023-01-09 20:23 ram1
brw------- 1 root root 1, 10 2023-01-09 20:23 ram10
brw------- 1 root root 1, 11 2023-01-09 20:23 ram11
brw------- 1 root root 1, 12 2023-01-09 20:23 ram12
brw------- 1 root root 1, 13 2023-01-09 20:23 ram13
brw------- 1 root root 1, 14 2023-01-09 20:23 ram14
brw------- 1 root root 1, 15 2023-01-09 20:23 ram15
brw------- 1 root root 1, 2 2023-01-09 20:23 ram2
brw------- 1 root root 1, 3 2023-01-09 20:23 ram3
brw------- 1 root root 1, 4 2023-01-09 20:23 ram4
brw------- 1 root root 1, 5 2023-01-09 20:23 ram5
brw------- 1 root root 1, 6 2023-01-09 20:23 ram6
brw------- 1 root root 1, 7 2023-01-09 20:23 ram7
brw------- 1 root root 1, 8 2023-01-09 20:23 ram8
brw------- 1 root root 1, 9 2023-01-09 20:23 ram9
brw------- 1 root root 8, 0 2023-01-09 20:23 sda
brw------- 1 root root 8, 1 2023-01-09 20:23 sda1
brw------- 1 root root 254, 0 2023-01-09 20:23 zram0

I suspect that if I can mount /dev/block/dm-3 as /elable/ at flash time, I could write files into it. The problem is that block device doesn't exist at flash time. Anyone know how to get dm-3 to be available at flash time? I'm guessing it's one of the "mmcblk0" blocks, but no idea how to determine which one.