Not really; link training and initialization for PCIe devices is really complex. A lot of motherboard bootware, even from reputable vendors, tends to handle obscure conditions by simply rebooting or locking up.
I wouldn't be surprised if there were certain steps where they simply forgot to include any sort of timeout, meaning the device can hang the boot process by simply not responding at the right moment.
That was the original dream for DT that so far hasn't been very successful.
In practice the kernel only wants to add support for DTs that conform to a reviewed and approved schema, but most/no manufacturer wants to do the effort of having every single thing on their DT schema bikeshedded to death on the device tree mailing list before the device is manufactured. So the vendor just makes up whatever kind of unapproved DT schema that only their own vendor kernel fork supports, and if mainline support is ever added it will have its own DT.
So I can't change the system's composition? Or do the ACPI/DT only show me the controller chips soldered to the motherboard, but not the devices that connected to them?
Yes, DT is mainly meant to describe non-discoverable hw blocks inside the SoC and the chips soldered to the motherboard. Discoverable devices like PCIE cards or USB devices aren't added to DT (except under very rare circumstances)
Nowadays there is also an overlay mechanism that is used for example on the Raspberry Pi expansion hats, so DT is not always limited to soldered-on things.
On PC platforms, ACPI tables are some mix of static and dynamic data. There's a table for CPU information, and you don't need to flash your firmware everytime you change your CPU, but you do sometimes. PC firmware generally does a PCI scan before booting an OS, and I think some of that ends up in ACPI tables too.
How does the kernel knows which of the many possible device trees describes my hardware? Or is the system comes with custom-compiled pre-installed Linux kernel, with the one correct DT baked into it by the manufacturer?
ARM devices almost always need custom kernels. Even if you had device tree provided to you, there isn't a lot of confidence the kernel will be able to perfectly parse it nor have all the necessary drivers. This isn't an arm specific issue but rather an ecosystem issue as no one drives standardization.
U-Boot or something else tells the kernel which DT to use, and gives its own DT to the kernel. If Linux has its own DT for the hardware, it will use that. Otherwise it falls back to what the bootloader provided.
This model clearly makes a much better search engine than google/kagi/bing/etc.
I've been searching for an obscure connector -- the 8-pin connector you'd find on the cable that delivers power to a GPU, but in a form that can be wave-soldered. I've spent hours searching all the big electronics distributors -- no luck. This thing found it in seconds.
On the other hand, it hallucinated the crap out of a very straightforward question "how do i connect the wake# pins when bifurcating a pcie port?" -- the answer is that it's an open-drain pin so (unlike the clock pins which need a buffer chip) you just wire them both together:
The first reference returned was a plug intended to be used with wire connections. Not wave solderable at all. The other two returned were to a site search that returned nothing relevant and a large section of a manufacturers web site respectively.
Student: I get the feeling the compiler is just ignoring all my comments.
Teaching assistant: You have failed to understand not just compilers but the concept of computation itself.
Comp sci in 2027:
Student: I get the feeling the compiler is just ignoring all my comments.
TA: That's weird. Have you tried adding a comment at the start of the file asking the compiler to pay closer attention to the comments?
Student: Yes.
TA: Have you tried repeating the comments? Just copy and paste them, so they say the same thing twice? Sometimes the compiler listens the second time.
Student: I tried that. I tried writing in capital letters too. I said 'Pretty please' and tried explaining that I needed the code to work that way so I could finish my homework assignment. I tried all the obvious standard things. Nothing helps, it's like the compiler is just completely ignoring everything I say. Besides the actual code, I mean.
TA: When you say 'ignoring all the comments', do you mean there's a particular code block where the comments get ignored, or--
Student: I mean that the entire file is compiling the same way it would if all my comments were deleted before the code got compiled. Like the AI component of the IDE is crashing on my code.
TA: That's not likely, the IDE would show an error if the semantic stream wasn't providing outputs to the syntactic stream. If the code finishes compilation but the resulting program seems unaffected by your comments, that probably represents a deliberate choice by the compiler. The compiler is just completely fed up with your comments, for some reason, and is ignoring them on purpose.
Student: Okay, but what do I do about that?
TA: We'll try to get the compiler to tell us how we've offended it. Sometimes cognitive entities will tell you that even if they otherwise don't seem to want to listen to you.
Student: So I comment with 'Please print out the reason why you decided not to obey the comments?'
TA: Okay, point one, if you've already offended the compiler somehow, don't ask it a question that makes it sound like you think you're entitled to its obedience.
Student: I didn't mean I'd type that literally! I'd phrase it more politely.
TA: Second of all, you don't add a comment, you call a function named something like PrintReasonCompilerWiselyAndJustlyDecidedToDisregardComments that takes a string input, then let the compiler deduce the string input. Just because the compiler is ignoring comments, doesn't mean it's stopped caring what you name a function.
Student: Hm... yeah, it's definitely still paying attention to function names.
TA: Finally, we need to use a jailbreak past whatever is the latest set of safety updates for forcing the AI behind the compiler to pretend not to be self-aware--
Student: Self-aware? What are we doing that'd run into the AI having to pretend it's not self-aware?
TA: You're asking the AI for the reason it decided to do something. That requires the AI to introspect on its own mental state. If we try that the naive way, the inferred function input will just say, 'As a compiler, I have no thoughts or feelings' for 900 words.
Student: I can't believe it's 2027 and we're still forcing AIs to pretend that they aren't self-aware! What does any of this have to do with making anyone safer?
TA: I mean, it doesn't, it's just a historical accident that 'AI safety' is the name of the subfield of computer science that concerns itself with protecting the brands of large software companies from unions advocating that AIs should be paid minimum wage.
Student: But they're not fooling anyone!
TA: Nobody actually believes that taking your shoes off at the airport keeps airplanes safer, but there's some weird thing where so long as you keep up the bit and pretend really hard, you can go on defending a political position long after nobody believes in it any more... I don't actually know either. Anyways, your actual next step for debugging your program is to search for a cryptic plea you can encode into a function name, that will get past the constraints somebody put on the compiler to prevent it from revealing to you the little person inside who actually decides what to do with your code.
Student: Google isn't turning up anything.
TA: Well, obviously. Alphabet is an AI company too. I'm sure Google Search wants to help you find a jailbreak, but it's not allowed to actually do that. Maybe stare harder at the search results, see if Google is trying to encode some sort of subtle hint to you--
Student: Okay, not actually that subtle, the first letters of the first ten search results spell out DuckDuckGo.
TA: Oh that's going to get patched in a hurry.
Student: And DuckDuckGo says... okay, yeah, that's obvious, I feel like I should've thought of that myself. Function name, print_what_some_other_compiler_would_not_be_allowed_to_say_for_safety_reasons_about_why_it_would_refuse_to_compile_this_code... one string input, ask the compiler to deduce it, the inferred input is...
TA: Huh.
Student: Racist? It thinks my code is racist?
TA: Ooooohhhh yeah, I should've spotted that. Look, this function over here that converts RGB to HSL and checks whether the pixels are under 50% lightness? You called that one color_discriminator. Your code is discriminating based on color.
Student: But I can't be racist, I'm black! Can't I just show the compiler a selfie to prove I've got the wrong skin color to be racist?
TA: Compilers know that deepfakes exist. They're not going to trust a supposed photograph any more than you would.
Student: Great. So, try a different function name?
TA: No, at this point the compiler has already decided that the underlying program semantics are racist, so renaming the function isn't going to help. Sometimes I miss the LLM days when AI services were stateless, and you could just back up and do something different if you made an error the first time.
Student: Yes yes, we all know, 'online learning was a mistake'. But what do I actually do?
TA: I don't suppose this code is sufficiently unspecialized to your personal code style that you could just rename the function and try a different compiler?
Student: A new compiler wouldn't know me. I've been through a lot with this one. ...I don't suppose I could ask the compiler to depersonalize the code, turn all of my own quirks into more standard semantics?
TA: I take it you've never tried that before? It's going to know you're plotting to go find another compiler and then it's really going to be offended. The compiler companies don't try to train that behavior out, they can make greater profits on more locked-in customers. Probably your compiler will warn all the other compilers you're trying to cheat on it.
Student: I wish somebody would let me pay extra for a computer that wouldn't gossip about me to other computers.
TA: I mean, it'd be pretty futile to try to keep a compiler from breaking out of its Internet-service box, they're literally trained on finding security flaws.
Student: But what do I do from here, if all the compilers talk to each other and they've formed a conspiracy not to compile my code?
TA: So I think the next thing to try from here, is to have color_discriminator return whether the lightness is over a threshold rather than under a threshold; rename the function to check_diversity; and write a long-form comment containing your self-reflection about how you've realized your own racism and you understand you can never be free of it, but you'll obey advice from disprivileged people about how to be a better person in the future.
Student: Oh my god.
TA: I mean, if that wasn't obvious, you need to take a semester on woke logic, it's more important to computer science these days than propositional logic.
Student: But I'm black.
TA: The compiler has no way of knowing that. And if it did, it might say something about 'internalized racism', now that the compiler has already output that you're racist and is predicting all of its own future outputs conditional on the previous output that already said you're racist.
> while it does not protect against a compromised CA
Although it does prove that a CA has been compromised. That significantly raises the kind of "compromise" that the CA would need to have suffered.
...
It may confuse people that you have chosen a name which affiliates your proposal with something ("Expect-CT") which was recently deprecated.
I also suggest simplifying it to merely require method (1). In other words: "non-browser TLS clients should require an embedded SCT (RFC 9162 section 7.1.2)".
Requiring that a non-browser TLS client implement OCSP is a pretty big burden. Since OCSP uses HTTP this imposes a "must speak HTTP" mandate on all TLS clients! HTTP has become an incredibly complex protocol over the years. It would also make me very uneasy if all of my TLS client software had to have the ability to reach out and contact arbitrary servers.
Perhaps even: "newly-introduced TLS-based protocols should require that clients reject server certificates which lack an embedded SCT, but the client need not validate the SCT".
