emily-c

6 ms·

1.
by emily-c 1mo ago
On commodity PC platforms there are both upsides and downsides of having runtime firmware in a special mode like SMM (or the secure world on ARM64 which is a whole other topic). For hardware errors (e.g. mapping row/bank/column to
2.
by emily-c 2y ago
>In many ways NT was a new, ground up implementation of “VMS NT”. Most definitely. There was a lot of design cleanup from VMS (e.g. fork processes -> DPCs, removing global PTEs and balance slots, etc), optimizations (converging VMS&#x
3.
by emily-c 2y ago
Before VMS there was the family of RSX-11 operating systems which also had ASTs (now called APCs in NT parlance), IRPs, etc. Dave Cutler led the RSX-11M variant which significantly influenced VMS. The various concepts and design styles of t
4.
by emily-c 3y ago
>I don’t think anyone has ever bothered to make FS code async, it’s already quite horrible as it is. Not in a mainstream kernel anyway. [...] Same for Windows disk IO with IOCPs. IOCP merely allows IO completion to happen on worker threa
5.
by emily-c 3y ago
I hope this is a joke.
6.
by emily-c 3y ago
"Embedded software" and "embedded system" also have similar issues with being nebulously defined in various situations. Some things will never perfect and at least firmware is kind of cute.
7.
by emily-c 3y ago
Usually this is still host firmware and not a secondary controller, at least on x86 platforms. To detect/use the USB controller you still need to configure the chipset/root complex and do an initial PCIe bus scan to set up PCIe BA
8.
by emily-c 3y ago
Recording of the opening: https://www.youtube.com/watch?v=Dfd6J3M-FSk
9.
by emily-c 3y ago
Thanks :) I wish there was a consolidated list of what kinds of information gets measured that is easy to point to.
10.
by emily-c 3y ago
Unfortunately, I don't believe there is any up to date and detailed public documentation on the modern DRTM flows that exist on both Intel and AMD platforms. Maybe documentation has been recently updated but I’m not sure if I’m able to
11.
by emily-c 3y ago
DRTM does not remove any malicious firmware provided code or data. Traditionally it is merely a measurement mechanism that happens after ExitBootServices which measures platform state in an unforgable manner. Practically the DRTM event can
12.
by emily-c 3y ago
>Did we mention that a TPM isn’t going to protect you from UEFI malware that was planted on the device by a rogue agent at manufacture time? DRTM, a technology supported by Windows 11 that is layered on top of the TPM, aims to solve this
13.
by emily-c 5y ago
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_
14.
by emily-c 5y ago
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 Ti
15.
by emily-c 5y ago
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
16.
by emily-c 5y ago
A lot of critical system configuration is stored in the SYSTEM hive which isn't explicitly backed by a file mapping and is loaded at boot via firmware services so this will be fast as it is non-paged and mapped in kernel space for the
17.
by emily-c 6y ago
This is awesome. It’s always nice to see new Win32 productivity software. Thank you!
18.
by emily-c 6y ago
This is correct. The functionality of LOADALL now largely happens in the RSM instruction which returns back to normal execution context from an SMI. In modern firmware, before the SMI handler is invoked by the SMM dispatcher the firmware wi
19.
by emily-c 6y ago
Most legacy code is this way unfortunately. The actual techniques employed by the "called out" code are not uncommon. I don't think that people are defending the lack of clarity but rather what the code is doing itself. It co
20.
by emily-c 6y ago
You see similar code to his unconditional executeNoMatch at the end of the table in table based code all the time. Additionally forEachObject is a macro that immediately initializes a variable. For projects like this the code is completely
21.
by emily-c 7y ago
I second every book recommendation here. Another great one is The Standard C Library .
22.
by emily-c 7y ago
This is still pretty common for things like self extracting archives on Windows. copy /b "%windir%\system32\extrac32.exe"+inputarchive.cab selfextract.exe
23.
by emily-c 7y ago
It is still possible but is BIOS dependent :) With UEFI, graphics is preferred to be done with the GOP driver/protocol (which will ultimately interact with video BIOS/graphics card option ROM for you). During early boot setting up
24.
by emily-c 7y ago
You're still relying pretty heavily on the BIOS to write to this region that you otherwise wouldn't be. Getting the legacy framebuffer region set up to be decoded to the graphics card is using some hacks to get it to work over PCI
25.
by emily-c 7y ago
You use WinDbg and do kernel debugging. The newer WinDbgX UI is quite nice lately. However, there's no replacement for live debugging on the same machine the way that SoftICE did it.
26.
by emily-c 7y ago
It's important to realize that you are not your code. Linus' reply comes off as passionate but he clearly cares enough to write such a detailed response.
27.
by emily-c 7y ago
You can thank Jay Miner for that. The Atari is sort of like an Amiga-lite in a lot of respects.
28.
by emily-c 7y ago
This book is great. I would say that it is for beginners as long as they have some semblance of C understanding and spent a few hours (days?) reading up about assembly and machine code topics. These skills take years to truly master and the
29.
by emily-c 7y ago
The CSME is on the PCH[1] (when one exists). (However AMD elected to put their PSP on-die as an IP-block). It is the root of trust of the system and takes the CPU out of reset even though it's not on the CPU itself. x86-based machines
30.
by emily-c 8y ago
This is awesome. If you haven't seen this talk about the AGC you should definitely check it out: https://www.youtube.com/watch?v=xx7Lfh5SKUQ

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