The hidden JTAG in a Qualcomm/Snapdragon device’s USB port
Back in February of this year, Qualcomm quietly published the source code for interacting with EUD. This is perhaps one of the most exciting things they’ve done lately - especially if you spend a lot of time debugging the kernel or U-Boot - let’s talk about it. EUD stands for Embedded USB Debug: essentially, this is a debug interface built right into almost every Qualcomm SoC since ~2018. Internally it hooks deep into the SoC, providing debug facilities for not just the CPUs but also the myriad