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Thursday, 15 August 2019

10:42:35 <Prf_Jakob> j`ey: Hey thanks for the help!
10:42:48 <j`ey> Prf_Jakob: did you get it working?
10:42:52 <Prf_Jakob> Yupp
10:43:15 <Prf_Jakob> https://github.com/VoltLang/Volta/blob/master/rt/src/vrt/aarch64.s#L19-L51
10:43:16 <j`ey> can you link the code again?
10:43:17 <j`ey> o
10:43:35 <j`ey> awesome
10:44:34 <Prf_Jakob> When I looked the compiler output things like "stp x3, x4, [sp, #-256]!" The '!' being post add value to register inside of [].
10:44:53 <j`ey> yeah
10:45:23 <Prf_Jakob> I mean it was a bit confusing, but reading the docs a bit more I figured it out
10:46:30 <zid`> That's a silly syntax
10:46:34 <zid`> Try a real arch
10:47:00 <Prf_Jakob> The syntax is a bit silly, but the instruction makes a lot of sense.
10:47:18 <zid`> godbolt doesn't do aarch apparently
10:47:38 <j`ey> Prf_Jakob: turns out your in the same city as me
10:47:43 <j`ey> *you're
10:47:49 <j`ey> zid`: it does
10:47:55 <zid`> what's it called
10:48:12 <j`ey> ARM GCC
10:48:18 <zid`> arm64?
10:48:21 <j`ey> right at the top of the list
10:48:21 <j`ey> yeah
10:48:31 <Prf_Jakob> arm64 aka aarch64
10:50:31 <zid`> The interrupt attribute is not available for A64 code.
11:05:46 <Prf_Jakob> j`ey: Small world! :D
13:26:06 <zid`> guys my mind has gone blank on a word
13:26:13 <zid`> ___ case, where everything that could be awful is awful
13:27:42 <j`ey> camel
13:27:46 <zid`> funny
13:27:50 <eryjus> worst
13:28:48 <zid`> pathological
13:29:49 <zid`> thanks for nothing *shakes fist angrily*
13:30:11 <Bitweasil> Intel?
13:30:12 <Bitweasil> SNAFU?
13:30:33 <Bitweasil> Test?
13:30:44 <Bitweasil> Normal?
13:30:45 <zid`> It was pathological.
13:30:46 <Bitweasil> :)
13:31:04 <Bitweasil> I know. I'm just particularly irritated by Intel, and Microsoft patching a /20 year/ local root exploit isn't improving my day.
13:31:11 <Bitweasil> (that they patched it, yes, that it's existed this long...)
13:31:17 <zid`> what was it
13:31:48 <zid`> https://googleprojectzero.blogspot.com/2019/08/down-rabbit-hole.html this one?
13:31:58 <Bitweasil> Yeah.
13:39:02 <Bitweasil> So, to recap, for the last 20 years, Windows has had a quality little local root exploit that's dead-reliable, and for the past 10 years, Intel has shipped chips that can't keep secrets if you ask politely.
13:39:16 <Bitweasil> Let's just skip pretending that computers can run untrusted tasks on the same hardware and go back to physically separate servers.
13:40:19 <zid`> The cloud was always a bad idea
13:40:26 <zid`> it's not exactly news
13:40:48 <Bitweasil> Sure, but now we know exactly /why/ instead of those people being regarded as tinfoil hat paranoid for no good reason.
13:40:56 <Bitweasil> (Theo was right about hyperthreading, for instance)
13:40:59 <zid`> like vmsplice etc didn't exist?
13:41:11 <Bitweasil> Eh, yeah. Hypervisors are gross too.
13:41:12 <zid`> shellshock, etc?
13:41:26 <zid`> it's not like the bugs need to be old to make it a bad idea
13:41:41 <zid`> new bugs get found all the time and every client on a VPS gets hacked instantly by all the other clients
13:42:02 <Bitweasil> Yeah, but people treat hardware bugs differently.
13:42:06 <Bitweasil> They're a lot harder to patch.
13:43:32 <zid`> so yea, looks like they never even attempted to make this "ship shape"
13:43:39 <zid`> just slapped it on to make IMEs work
13:44:32 <zid`> The IME shit just needs to be a service and use the regular token system winapi uses and generate 'fake' window messages, why they have megs of stupid broken code idk
14:47:59 <azonenberg> Bitweasil: yeeeah
14:48:40 <azonenberg> this is why i run my public facing services on a separate raspberry pi each
14:48:58 <azonenberg> hanging off a physically separate router interface from the rest of the network
14:49:31 <azonenberg> And then i run my web browsers etc in a bunch of separate xen instances on a semi-trusted server, not perfect but better than nothing
14:49:49 <azonenberg> it at least raises the bar until have the budget to move them to a totally separate dmz box
15:01:44 <Bitweasil> Qubes? or your own thing?
15:19:03 <bytefire> hi, in arm, does gic have a concept of max number of interrupt lines it can support?
15:19:25 <bytefire> i mean max number of interrupt lines going from gic to cpu
15:22:25 <eryjus> i don't believe so. From what I am aware of (rpi) there are Fast IRQ (FIQ) and and IRQ lines only. only 1 IRQ can be tagged as fast, and if you get any other IRQ you need to figure out what triggered it
15:23:35 <eryjus> now, the rpi does not have a GIC, so I may be way off base here as well
15:28:23 <bytefire> i see
15:29:29 <bytefire> i'm trying to see if and how gic limits the number of interrupt lines it can support
15:54:21 <geist> yay new case for my rpi 4 is very nice and cool
15:54:29 <geist> otherwise that thing will run really really hot
15:55:55 * Ameisen is reporting a missed optimization bug for GCC, LLVM, and half for MSVC
15:55:58 <Ameisen> I'm surprised
15:56:08 <Ameisen> MSVC doesn't miss the optimization in the trivial case, but does in the easy case
15:58:29 <Ameisen> I forget, is anyone in here a developer at MS for MSVC?
15:58:48 <Ameisen> I'm unaware of any channels or subreddits or whatnot for MSVC in particular
15:59:47 <Mutabah> I've seen MSVC devs on /r/cpp
16:01:20 <Ameisen> same, I messaged a few of them as I don't know who else to ask :)
16:01:42 <geist> not that i know of
16:01:50 <Ameisen> basically, adding a __builtin_assume or __builtin_unreachable to force the compiler to presume a return value from a function prohibits tail call optimization
16:02:02 <geist> i do kinda wonder how big that team is
16:02:10 <Ameisen> for GCC, LLVM in both the unreachable and assume case
16:02:16 <Ameisen> and in MSVC... only in the assume case
16:02:19 <Ameisen> unreachable works fine
16:02:39 <Ameisen> I suspect that's less MSVC doing better, and more MSVC not knowing that the assume(0) for unreachable actually means something
16:03:09 <Ameisen> well, I don't know any of the optimizer developers for MSVC... only stdlib devs
16:03:10 <Ameisen> like STL
16:03:25 <Ameisen> his initials are extremely convnient. He was born for the job.
16:19:51 <geist> yah i was a little surprised that MSVC would even understand those __builtins
16:20:13 <geist> though i ahve no particular reason to assume its less sophisticated, but more like it doesn't necessarily align with gcc/clang for stuff like that
16:31:09 <Ameisen> MSVC doesn't call them the same, but __assume does actually work
16:57:21 <Ameisen> all righty, finished reporting
16:59:20 <Ameisen> It's always nice to report the same missed optimization for gcc, llvm, and msvc.
18:07:31 <eau> hoi
18:07:42 <eau> anyone familiar with acpi/aml and such?
18:09:10 <zid`> don't ask to ask or do polls :/
18:13:39 <aalm> .theo
18:13:39 <glenda> No. You have it wrong. Go back to reading school.
18:19:51 <eau> ?
18:53:39 <knebulae> @eau: just ask your question
19:03:48 <eau> knebulae: looking for an introduction to acpi & aml, in order to grasp how it works, how to deal and how to debug etc.. documentation & links to read to familiarize with it
19:04:55 <knebulae> @eau: have you tried the resources from the wiki @ https://wiki.osdev.org?
19:06:40 <knebulae> @eau: https://wiki.osdev.org/ACPI specifically.
19:06:42 <eau> knebulae: i was starting there yes.
19:07:09 <eau> ok i ll keeping browsing and ask more specifics once i read thx!
19:07:24 <knebulae> there is an AML page too: https://wiki.osdev.org/AML
19:07:41 <knebulae> not much info though
19:08:29 <eau> i found this just now :
19:08:31 <eau> https://acpica.org/sites/acpica/files/ACPI-Introduction.pdf
19:08:44 <eau> might be useful as an additional link
21:15:36 <Ameisen> cccccciftricbietrufeukjetjdfeftfcejefbldctbv
21:15:52 <Ameisen> no clue why my keyboard just typed that.
21:22:24 <mrvn> cat got your keyboard?
21:24:10 <Ameisen> No. No cats in my office atm.
21:24:16 <Ameisen> I switched my keyboard from one PC to another
21:24:19 <Ameisen> might have been that
21:28:58 <jjuran> Make sure the keyboard and the PC are set to the same baud rate
21:47:23 <Bitweasil> You might have been around serial links too long if you can look at the nonsense generated and know what the mismatch is. :/
22:12:59 <FireFly> Ameisen: yubikey OTP?
22:49:47 <mrvn> also keyboards get a clock signal from the controler and don't have a baud rate
22:54:23 <bcos_> I think PS/2 was "sender provides clock" (so when keyboard sends to host it provides clock), and used 9600 baud.
22:54:48 <bcos_> Of course USB is different (probably uses a faster baud!)
23:45:03 <azonenberg> bcos_: usb keyboards are probably 12 Mbps
23:45:18 <azonenberg> and both sides have their own clocks but they need to be approximately the same frequency
23:45:37 <azonenberg> Bitweasil: i can look at a uart link that's mismatched and tell you it's mismatched
23:45:40 <azonenberg> but not in which direction
23:45:50 <azonenberg> if i have any doubts i just drop a scope on the uart and measure the baud rate