en: add KdCom setup guide.

Author: sunflower2333

WindowsDebug/SetupKDCOM.md

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+# Setup Windbg KdCom
+::: tip Tips
+Sugguest using KdNet for better experience if you can not access your device's uart pins easily.  
+KdCom does not support rdp over it.
+:::
+
+## Preparation
+  - A dev board, or any device with uart test points
+  - An UART->USB bridge, or on board bridge.(Notice: Qualcomm use 1.8V as VDDIO)
+  - Debugging slave installed windows
+  - Debugging host installed [Windbg Preview](https://apps.microsoft.com/detail/9pgjgd53tn86)
+
+## Setup BCD
+  - Mount ESP Partition on you phone with root permission in adb shell or termux.
+    + Simply jump this step if you are using USB mass storage mode.
+    ```bash
+    # Execute on phone
+    mkdir /dev/esp_mnt
+    mount /dev/block/by-name/esp /dev/esp_mnt
+    ```
+  - Copy BCD to your host computer.
+    + If you are using UMS, find the BCD file and copy it to D: or anywhere you want in explorer.
+    + Copy to /sdcard
+    ```bash
+    # Execute on phone
+    cp /dev/esp_mnt/EFI/Microsoft/Boot/BCD /sdcard
+    ```
+    + Pull to computer.
+    ```powershell
+    # Execute on computer, assuming installed adb.
+    # Assuming copy to D:, you can set any path you want.
+    adb pull /sdcard/BCD D:\
+    ```
+  - Open an **administrator** terminal and set bcd configurations.
+    ```powershell
+    cd D:\
+    bcdedit /store BCD /set "{default}" testsigning on
+    bcdedit /store BCD /set "{default}" nointegritychecks on
+    bcdedit /store BCD /set "{default}" debug on 
+    bcdedit /store BCD /dbgsettings serial baudrate:115200 debugport:1
+    ```
+  - Push BCD back to your phone.
+    + If you are using UMS, simply replace the original BCD file.
+    ```powershell
+    # Execute on computer
+    adb push BCD /sdcard
+    # Delete BCD after pushing
+    del D:\BCD
+    ```
+    ```bash
+    # Execute on phone
+    # Backup nomal BCD
+    cp /dev/esp_mnt/EFI/Microsoft/Boot/BCD /dev/esp_mnt/EFI/Microsoft/Boot/NMBCD
+    # Backup kdnet enabled BCD
+    cp /sdcard/BCD /dev/esp_mnt/EFI/Microsoft/Boot/DBGBCD
+    # Replace active BCD
+    cp /sdcard/BCD /dev/esp_mnt/EFI/Microsoft/Boot/BCD
+    ```
+
+## Setup KdCom in Windbg
+  - Open device manager on your computer.
+  - Connect UART->USB bridge to computer, and check the `COMXX` Number under `Serial` section in device manager
+  - Open Windbg Preview, Click **File** button on the top left corner.
+  - Click `Attach to kernel` under `Start debugging`(default section).
+  - Choose `COM` section
+    + Fill `Baud Rate` with `115200`
+    + Fill `Port` with `COMXX`, which you saw in device manager
+    + Others keep default
+  - Click `OK` button and windbg will start waiting for connection.
+
+
+## Connect KdCom
+  - Ensuing DBG2 configuration is correct(No need worry because the address in dbg2 was fixed generally here).
+  - Reboot your phone, and connect it to computer with a usb cable.
+  ```powershell
+  # Execute on computer, boot uefi
+  fastboot boot uefi.img
+  ```
+  - Phone booting windows and hang up for several seconds, you can see windbg print logs if successfully connected.
+
+::: tip Notice
+  - You can close Windbg and open a serial tool like PuTTY or SecureCRT to check if the phone printed some unrecognized messages while windows booting. If it isn't that means BCD configurations were wrong
+:::