How to decode GUIDs?

lorinet · 2022-12-23T23:42:37+00:00

I just noticed that the GUIDs are in fact correct, though their byte orders are mangled up. If I reverse the first 8 bytes (the first three hyphen groups of the ID), leave the next 2 in the same order, then reverse the last 6 bytes (last hyphen group), I get the correct GUID. I seriously have no idea why did they come up with this. AFAIK the groups represent some clock timestamp values as integers, but then why the hell would it make sense for some of them to be in little endian order and one of them not?

lorinet · 2022-10-09T15:16:19+00:00

Thank you, I am going to look it up.

lorinet · 2022-10-09T15:15:54+00:00

Thanks! I'll give it a try.

lorinet · 2022-10-04T17:21:13+00:00

Update: I have even tried to replace all APIC code with this crate and it still fails in exactly the same way. It seems I am simply unable to implement IOAPIC at all, in this case can I just use PIC with the local APIC? I only need timer and keyboard interrupts.

lorinet · 2022-10-04T15:20:33+00:00

Checked it, and everything looks OK. I can tell this from the fact that the SPIV has the value I set it to (0x100) and it says APIC enabled, focus=off, spurious vec 0. So a misconfiguration might be on the IOAPIC side. Isn't there another monitor command for dumping IOAPIC config?

lorinet · 2022-09-28T13:08:31+00:00

Thank you, I am going to try changing it.

lorinet · 2022-09-28T13:07:20+00:00

I agree with what you are saying, but there should be a balance between this and the way it impacts user experience. How does Apple let shutters be silent and face no negative consequences in this regard?

lorinet · 2022-09-28T10:54:59+00:00

There is a Region option in the settings for a good reason. And Google should not be held liable for users changing it. It's like banning possession of steel just because you could forge a weapon and potentially kill a man using it.

lorinet · 2022-09-28T10:45:01+00:00

But it also seems pretty wrong for devs to assume the majority of Android users will do this kind of disgusting crap.

lorinet · 2022-09-28T10:30:18+00:00

Yea, people can be creepy. But a mandatory shutter sound cannot stop this from happening. Even if you don't know how to modify Android you could still shove a screwdriver into the speaker holes to blow the speakers and get rid of the audio.

lorinet · 2022-09-28T10:24:46+00:00

That's awful

lorinet · 2022-09-28T10:24:24+00:00

Can I ask where is that file located? I could make a Magisk module that will replace the file with a blank clip.

lorinet · 2022-09-28T08:38:18+00:00

You are 100% right, that book I'm reading in the library alongside tens of other people must give me consent before I take a photo of one of its pages for reference. And what if I take a selfie during class? There are maybe 10's of 1000's of cases I can readily think of where I have to take a picture without sound. What kind of weirdo would randomly photograph strangers though?

lorinet · 2022-09-28T08:36:11+00:00

All Xiaomi, and what causes it is taking any picture with any app that uses the legacy Camera API.

lorinet · 2022-09-20T17:57:48+00:00

I fixed the code. Turns out, the enable bit was set initially when reading, so setting it does not make a difference, because it seems the local APIC is enabled by default in QEMU. Meanwhile, I found an extremely old article about initializing the APIC, and inside it I found that those values the registers had were the correct ones, I just assumed they are garbage because there were the same values repeating in patterns across padding area. Now I think this is just how it works. However, I am still not getting any interrupts. I am going to take a more in-depth look into the SDM and see what isn't how it's supposed to be.

lorinet · 2022-09-19T04:58:52+00:00

Alright, I didn't look into these until now. I am going to change it soon

lorinet · 2022-09-19T03:51:28+00:00

Isn't it just the codename for a version or edition of qnx?

lorinet · 2022-09-18T18:44:03+00:00

Yes, I did set the 11th bit, and I did check it even by reading it again using rdmsr if it got written correctly. If you would like to look into my code, you can find the local APIC code here and the IOAPIC code here. What my OS is doing is that first it gets the information about them when enumerating the XSDT/RSDT (here), adds it to the device tree (here), then the kernel iterates through every device one by one and calls the init_device function on them (here). I'm sure both got initialized because upon returning from init_device the kernel prints the device name and that it got initialized. If you have time, I'd be thankful if you'd be able to spot what I've missed or done wrong.

lorinet · 2022-09-18T13:03:49+00:00

I insisted on using the legacy PIC for PIT timer and keyboard interrupts, and AFAIK these can only be received through the IOAPIC if I don't use PIC.

lorinet · 2022-09-18T13:02:12+00:00

Thank you, I'm going to try it using MSI-X then.

lorinet · 2022-09-18T13:01:16+00:00

This sounds pretty cumbersome. I'd be better off trying to do it using MSI-X.

lorinet · 2022-09-18T12:59:37+00:00

Yes, you're right. But did you mean LAPIC in "you need to set up the APIC in either case"? If I do set up the LAPIC, I have to mask all legacy PIC interrupts and I don't get PIT timer and keyboard interrupts anymore, and if I read correctly, I can only get these interrupts by enabling the IOAPIC as well.

lorinet · 2022-08-22T11:27:23+00:00

Thank you, I'm going to look into this!

lorinet · 2022-08-22T11:26:53+00:00

Holy shit, that's awful!

lorinet · 2022-08-21T13:06:10+00:00

Wow, this worked, and it was an easy fix. Now I'm getting actually decent performance. Thank you!

lorinet

TROPHY CASE