[emily-c]

These are good examples and this might be slightly off topic but I wish that there were more resources on how modern x86 platforms actually work instead of using these legacy interfaces that are either emulated in SMM with IO port trapping or relegated to requiring chipset hacks to keep them working (such as VGA device hacks in the PCI spec or well known chipset legacy IO ports decoding to the LPC bridge).

While it is essentially impossible to truly understand every aspect of todays platforms I think that one can build a lot of intuition about how things work by studying how transaction routing is handled in the platform, e.g. how the uncore and chipset routes TLPs (whether it's raw PCIe or packets essentially wrapped by other interconnect protocols like IF/HyperTransport/DMI/QPI/etc) through the system with various base address registers and decoding windows. This gives way to understanding how modern MSI interrupts and DMA works as well. While I understand that truly going into things like PCI configuration, ACPI, UEFI, chipset interfaces on bus 0, modern booting, DMA and interrupt remapping, DRAM, register locking and security, security processors, power management, various types of runtime firmware, etc is a a many-years-long exercise I think that the core ideas don't need to be spread around all over the place for one to get familiarity with the ideas and patterns that underpin our PCs.

I think that a general conceptual overview on which one can hang more detailed knowledge acquired by reading specs is needed with the amount of complexity that exists today. There are some really good resources that I've collected over the years but there is still something missing. Maybe I or someone else will get around to it some day.

[userbinator]

"legacy" is the reason the PC still remains relatively open despite corporate threats, so don't dismiss it lightly.

https://news.ycombinator.com/item?id=15730113

[emily-c]

I'm not sure why you have legacy in quotes, that is what it is. Modern platforms do not act like a PC AT and there is a ton of cruft to keep those interfaces working which is set up and facilitated by firmware (not so open, at least TianoCore exists regardless of your thoughts on UEFI). Modern x86 systems programming is so much more than these interfaces. I think that it would be beneficial for others to understand how things are actually working on modern platforms.

Regarding your linked post:

For corporate users legacy methods of booting /are/ a security threat. Firmware attacks are a real threat for enterprises. Having IBVs all hand roll things like the S3 boot script or communication with SMM (not using standardized com buffers) is not wise. Secure boot combined with modern security features like using DRTM to remove firmware from the trusted computing base are important and should not be discounted because it's not an 40 year old interface. The PC platform is historically extremely insecure and there is a ton of work still to be done to effectively provide the primitives needed to secure the platform against determined attackers.

If you want to have a USB stack in SMM owning your USB controller to emulate port 60h with IO SMI traps that's fine but it's not a reason to hold the platform back.

[cirosantilli]

I collected some more developed learning OS project at https://github.com/cirosantilli/x86-bare-metal-examples/tree... BTW.

[phendrenad2]

Read about x86-64. There are a few tutorials out there, and most focus on modern systems with the "big four" (UEFI, ACPI, XHCI, PCIE).

[emily-c]

I am talking about the platform more than the ISA. Some interesting resources:

https://sites.google.com/site/pinczakko/system-address-map-i...

https://www.youtube.com/playlist?list=PLBTQvUDSl81dTG_5Uk2my...

http://xillybus.com/tutorials/pci-express-tlp-pcie-primer-tu...

http://xillybus.com/tutorials/pci-express-tlp-pcie-primer-tu...

https://www.amazon.com/Quick-Boot-Pete-Dice/dp/1501515381/

https://opensecuritytraining.info/IntroBIOS.html

https://acpica.org/sites/acpica/files/asl_tutorial_v20190625...

And of course the MindShare books.

[l33t2328]

Could you recommend a tutorial?