alt Hacker NewsThis is a much better experience than the previous Qualcomm debug experience, which was a hand-rolled set of read/write/execute primitives exposed over USB. It was hilariously undersecured, allowing a few of us to continually get root on various Qualcomm models.
In seriousness, these debug ports are seriously lacking in most mobile chipsets. MediaTek still has the old-style approach in many of their devices, requiring some incantations which expose serial over USB, but not in the way you think -- it's serial over USB pins!
I've done tonnes of work with mobile chipsets and security and this seems like they've finally started down the road to making this functionality accessible. Don't be surprised if you don't see this supported out of the box in most places, though. Most OEMs will certainly disable this once they've adapted their bootloaders to it. The big G doesn't like debuggability in end user devices.
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You bring me back to the olden days of QXDM in my adolescence, when I used it to save myself from bricking my phone, and again when I had my first internship working on an MDM9x50 device
Most of those boards have a separate physical JTAG connector (at least in development kits, this article indicates JTAG over USB is disabled in production systems anyways so no difference there) which is what they are expecting you to use for low-level debugging. It only costs like 1,000 $ for a JTAG probe which is like 1 fully-burdened engineer-day of cost. Even fully featured probes enabling hardware trace and time-travel debugging only cost like 1 engineer-week.
MediaTek still has the old-style approach in many of their devices, requiring some incantations which expose serial over USB, but not in the way you think -- it's serial over USB pins!
Wasn't that only in their old feature-phone (MT62xx) SoCs? All the smartphone ones AFAIK (at least since the MT657x days) use USB CDC in their BootROM and preloader.
at work we adapted to "usb c debug accessory mode", which should be a standard everyone should follow.
Google exposes serial Serial over the SBU pins on all the Pixel devices