jcalvinowens

5 ms·

1.
by jcalvinowens 1mo ago
Location: Bay Area, CA, USA Remote: Yes Willing to relocate: No Technologies: C, C++, Linux, drivers, embedded, HPC, networking, video, radio, yocto Résumé/CV: https://github.com/jcalvinowens/misc/
2.
by jcalvinowens 2mo ago
A much better title would be "A hardware backdoor in a historical VIA x86 CPU".
3.
by jcalvinowens 2mo ago
You stand to the side and pull it with one arm
4.
by jcalvinowens 2mo ago
The preliminary NTSB report: https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/G...
5.
by jcalvinowens 2mo ago
A lawn mower cuts grass whether you push it forward or pull it backwards: my trick when I was a kid was just to push and pull it back and forth across the lawn without changing the direction it faced at all.
6.
by jcalvinowens 2mo ago
Location: Bay Area, CA, USA Remote: Yes Willing to relocate: No Technologies: C, C++, Linux, drivers, embedded, HPC, networking, video, radio, yocto Résumé/CV: https://github.com/jcalvinowens/misc/
7.
by jcalvinowens 2mo ago
Remember that -Os is much much more aggressive in GCC than it is in LLVM, with LLVM you need to use -Oz to get the same result. GCC has historically been a bit of a pig about -Os, my favorite example is on x86 where it will emit a runti
8.
by jcalvinowens 3mo ago
> One thing that concerns me is the possibility of on-die ECC interacting with ECC on the motherboard and reducing it’s effectiveness DDR5 on-die ECC detects and corrects one-bit errors. It cannot detect two-bit errors, so it will miscor
9.
by jcalvinowens 3mo ago
HDCP1 is completely broken, you can buy HDCP2.x strippers on amazon (they're often marketed as "converters").
10.
by jcalvinowens 4mo ago
+1 for btrfs If a NAS has a 1G or even 2.5G NIC, improving the filesystem performance is a waste of time... the network is the bottleneck. My N100 two-disk btrfs-raid1 NAS hits line rate on a 2.5G NIC, that's all that matters to me.
11.
by jcalvinowens 4mo ago
It's actually faster than I remembered: {0}[calvinow@sousa ~/git/linux] git describe v7.1 {0}[calvinow@sousa ~/git/linux] git clean -dffxq {0}[calvinow@sousa ~/git/linux] zcat /proc/con
12.
by jcalvinowens 4mo ago
No, 90 seconds is the clean build time without ccache.
13.
by jcalvinowens 4mo ago
> The build takes about 30-45 minutes If you don't actually need all the drivers, you can use "make localmodconfig" to substantially reduce that. My local kernels build in 90 seconds on a 32-thread desktop machine :) The k
14.
by jcalvinowens 4mo ago
I love keyd, it uses uinput so it works on the vtty too.
15.
by jcalvinowens 4mo ago
https://arxiv.org/pdf/2411.09241
16.
by jcalvinowens 4mo ago
XFS does use /lost+found, it calls it the "orphanage directory" and xfs_repair reparents children of corrupt directories there. Based on comments in the kernel source, it seems like the userspace fsck for JFS and F2FS will al
17.
by jcalvinowens 4mo ago
It is a weirdly common misconception that that fork() is cheap... it is O(N) on the size of the process, and it always has been. Yes, it's copy on write... but there is a linear relationship between the size of the process and the numb
18.
by jcalvinowens 4mo ago
It's unbelievable and it's only getting worse. A 2x32GB DDR5 kit I paid $150 for 11 months ago costs $910 today from the same retailer. A 2x16GB DRR4 kit that was $105 last year is now $230. The RAM alone in my newest machine woul
19.
by jcalvinowens 4mo ago
There's a tradeoff here people often ignore: how much does the power consumption increase? In my experience, you end up using more total power because the SIMD instructions are so much more power hungry. In the cloud, you don't pa
20.
by jcalvinowens 4mo ago
The waymos are so consistently badly overpriced I've stopped even bothering to look. Nobody I know rides them! But they have riders more than half the time I walk by them, so clearly they're making money off somebody ...
21.
by jcalvinowens 5mo ago
Yeah. It's becoming unbelievable how different the prevailing opinions on this site are from those of real people I know and work with. That's always been true to some extent... but good lord, it's like reading the news in a
22.
by jcalvinowens 5mo ago
As others have noted, this usually happens because both sides wrote data and one side didn't read it before calling close(). Here's a little reproducer: https://gist.github.com/jcalvinowens/da57edda9a01ca9f4c4
23.
by jcalvinowens 5mo ago
If the workers weren't forked, the entire process would die to the SIGSEGV, and when it restarted the heap would be at a new address because of ASLR. This exploit couldn't work against a threaded daemon for that reason (only one g
24.
by jcalvinowens 5mo ago
Does anybody else remember the Excel spreadsheet with a bunch of drop down menus that fed 1kloc of embedded visual basic to generate a C function to program the STM32 clock registers based on your selections? Top ten silliest things I'
25.
by jcalvinowens 5mo ago
I mean... you're missing the forest for the trees, but yes I meant "address space" generally not "stack" specifically. The nginx threads are forked, it would not be that terribly complex to set up a heap with a new
26.
by jcalvinowens 5mo ago
> Apache used forked processes; I don't think that's unique or a particular issue. Of course it is... in a typical threaded daemon, the threads have randomized stack addresses. Exactly as you observed, you get unlimited tries b
27.
by jcalvinowens 5mo ago
Both major compilers yell at you for this nowadays... it's pretty unforgivable IMHO for somebody to be asking it as an exam or interview question if the right answer isn't "undefined": <source>:5:10: warning:
28.
by jcalvinowens 5mo ago
I doubt it: aslr is not as easy to break on modern Linux as everyone in this thread wants to pretend it is. And anybody who actually cares so much about security that a compromised web frontend is the end of the world should be doing other
29.
by jcalvinowens 5mo ago
Sure, but I think the github README ought to make it more clear the POC as-is doesn't work against nginx on any current Linux distro.
30.
by jcalvinowens 5mo ago
The POC disables aslr: https://github.com/DepthFirstDisclosures/Nginx-Rift/blob/mai...

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