Update README.md after various lessons learned.

Namely:

* `AppleSerialShim` must be disabled not just for Monterey but any older
  macOS version; emphasize that point,

* SIP must be disabled; while the user is there, you might as well have
  them run through the startup security downgrade steps while they are
  there,

* the list of "except" ports on https://support.apple.com/en-us/111336
  seems to be a hint to which are the DFU ports, add the link for
  reference in case this is true,

* `cu` on macOS doesn't work well for the debug console port; this
  slightly adjusted `picocom` invocation found from the IRC archives
  works much better.

* you likely need to install a corresponding KDK; you may need to upgrade
  macOS to do that.

The commit also makes some other light wording tweaks. This doc could be
further improved still, but it's a start.

Signed-off-by: 3405691582 <[email protected]>

README.md

@@ -15,29 +15,31 @@ This is based on portions of [ThunderboltPatcher](https://github.com/osy/Thunder
 
 Thanks to t8012.dev and mrarm for assistance with the VDM and Ace2 host interface commands.
 
-## Note about macOS 12
+## Note about macOS versions 12 and up
 
-To have access to the serial console device on macOS Monterey (12), you need to disable the `AppleSerialShim` extension.
+To have access to the serial console device on macOS Monterey (12) or any later version, you need to disable the `AppleSerialShim` kernel extension.
 
 **Note:** This requires downgrading the system security and may cause problems with upgrades. Use it at your own risk!
 
-Start by generating a new kernel cache, without the `AppleSerialShim` extension:
+Start by booting into 1TR:
+
+1. Power off your Mac
+2. Press and hold the Power button until the boot menu appears
+3. Select “Options”, then (if necessary) select your macOS volume and enter your administrative password.
+
+Disable System Integrity Protection (SIP). Select Utilities > Terminal and run `csrutil disable`. While you are here, select Utilities > Startup security and switch the macOS installation to reduced security. 
+
+Back in macOS, generate a new kernel cache without the `AppleSerialShim` extension:
 
 ```
 sudo kmutil create -n boot -a arm64e -B /Library/KernelCollections/kc.noshim.macho -V release  -k /System/Library/Kernels/kernel.release.<soc> -r /System/Library/Extensions -r /System/Library/DriverExtensions -x $(kmutil inspect -V release --no-header | awk '!/AppleSerialShim/ { print " -b "$1; }')
 ```
 
 Replace `<soc>` with `t8101` on M1 Macs and `t6000` on M1 Pro/Max Macs. If you’re unsure, `uname -v` and look at the end of the version string (`RELEASE_ARM64_<soc>`).
 
-Then, enter 1TR:
+If you are prompted with an error message to download a KDK for your kernel, note the version it gives you, then either download and install the corresponding KDK [from Apple directly](https://developer.apple.com/download/all/) or [unofficially from KdkSupportPkg](https://github.com/dortania/KdkSupportPkg/releases). You may also need to upgrade your macOS install to get to a kernel version that has a corresponding KDK.
 
-1. Power off your Mac
-2. Press and hold the Power button until the boot menu appears
-3. Select “Options”, then (if necessary) select your macOS volume and enter your administrative password.
-
-Select Utilities>Startup security and switch the macOS installation to reduced security. Exit Startup security.
-
-Select Utilities>Terminal and install your custom kernel:
+Go back to 1TR, select Utilities>Terminal and install your custom kernel:
 
 ```
 kmutil configure-boot -c /Volume/<volume>/Library/KernelCollections/kc.noshim.macho -C -v /Volume/<volume>
@@ -47,7 +49,7 @@ Replace `<volume>` with the name of your boot volume.
 
 You can now reboot: macOS should start as normal, and the serial device `/dev/cu.debug-console` should be available.
 
-To revert back to the default kernel, enter 1TR again, access Utilities>Startup security and switch to full or reduced security.
+To revert back to the default kernel, enter 1TR again, access Utilities>Startup security and switch to full or reduced security, as well as reenabling SIP with `csrutil enable`.
 
 ## Building
 
@@ -60,6 +62,8 @@ Connect the two devices via their DFU ports. That's:
  - the port next to the MagSafe connector on the 14" and 16" MacBook Pro
  - the port nearest to the power plug on Mac Mini
 
+([This list of ports](https://support.apple.com/en-us/111336#connect) might also be useful for other hardware not listed here.) 
+
 You need to use a *USB 3.0 compatible* (SuperSpeed) Type C cable. USB 2.0-only cables, including most cables meant for charging, will not work, as they do not have the required pins. Thunderbolt cables work too.
 
 Run it as root (`sudo ./macvdmtool`).
@@ -74,6 +78,6 @@ Commands:
   nop - do nothing
 ```
 
-Use `/dev/cu.debug_console` on the local machine as your serial device. To use it with m1n1, `export M1N1DEVICE=/dev/cu.debug-console`.
+Use `/dev/cu.debug_console` on the local machine as your serial device. To use it with m1n1, `export M1N1DEVICE=/dev/cu.debug-console`. `picocom` generally works better than `cu` for this; use something like `sudo picocom -q --omap crlf --imap lfcrlf -b 115200 /dev/cu.debug-console`.
 
 For typical development, the command you want to use is `macvdmtool reboot serial`. This will reboot the target, and immediately put it back into serial mode, with the right timing to make it work.