OpenSystemsDevelopment / usbboot

documentation: Secure boot quick start / walkthough

The secure-boot-example/boot.img has been replaced with the
mass-storage-gadget Linux OS image because it already supported
login, hdmi and ethernet.

Typo fixes from @dp111 (who obviously has too much time on his hands).

Revert binary to usbboot 4608d57c4d57dde19cc14988ee14702868d394bd

msd: Fix support for older EEPROM release in on 2711

Update EEPROM, recovery.bin and bootcode4.bin to 2022-04-26

Previously two commits added a fallback fmemopen for OS X/BSD that
didn't support fmemopen, then fixed some of the ifdef logic around it.
Unforunately the logic was backwards, as libc implementations do not
define _POSIX_C_SOURCE in order to advertise features.  Instead the
user defines _POSIX_C_SOURCE to control which definitions are
available.

Check _POSIX_VERSION to see if the libc is new enough to implement
fmemopen.  If it is too old, assume that we're on a BSD compatible
system and use the fallback fmemopen that depends on funopen.
This solves the problem for some environments, but is still incorrect
as it will try to use the fallback even on a system that does not
include funopen.

Fixes: 45c7237 (Fixup for recent firmware inclusion changes (#34))
Fixes: 17f6b01 (Fix cross-platform building)

Add inline comments about boot order

Add no sudo hint

When not signing the configuration (no -k option), there's no
$TMP_CONFIG file and `test -f "$TMP_CONFIG"` is false. The whole line
becomes false and the script exists 1 for `set -e`.

This commit fixes that by moving the test to `if` condition.

Fixes: d1a9a5c659e8 ("beta: Add support for secure-boot - see Readme.md")
Signed-off-by: Wojtek Porczyk <woju@invisiblethingslab.com>

Include the new imager applications and fix the recursive File
operations to stop the installer pulling in the .git directory.

Add a few tidyups and a note about initramfs

Create a new rpiboot mode that uses a Linux initramfs to
implement mass-storage-gadget mode supporting EMMC and NVMe
block devices.

To use:
cd usbboot/mass-storage/gadget
../rpiboot -d .

Replace the example boot.img with a slightly more useful version
64-bit version that boots to a minimal busybox initrd with
USB enabled.

See https://github.com/raspberrypi/usbboot/issues/116

Fix help -c and -i default option

pieeprom-2022-02-08: Fix boot failure in locked secure-boot

The previous version would fail to boot if secure-boot mode was
locked via OTP settings.

recovery.bin prevent revoke_devkey from being set before the
customer key has been programmed.