A Linux system running over JavaScript [LWN.net]

A Linux system running over JavaScript

Posted May 17, 2011 19:11 UTC (Tue) by Aissen (subscriber, #59976)
Parent article: A Linux system running over JavaScript

Anyone know the reason why Bellard stopped at the 4 years old 2.6.20 kernel ?

I tried reproducing what he did by re-compiling a kernel to run in the jslinux, it works with 2.6.20.21, but didn't work with 2.6.38.6. I didn't have time to bisect it.

So I guess it's something that was introduced after 2.6.20 that cannot be emulated by jslinux. Is it the tickless kernel ? The merging of i386 and x86_68 architectures ? The CFS scheduler ? Or something else ?

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A Linux system running over JavaScript

Posted May 17, 2011 19:15 UTC (Tue) by tzafrir (subscriber, #11501) [Link] (4 responses)

FPU emulation. See the notes.

A Linux system running over JavaScript

Posted May 18, 2011 4:15 UTC (Wed) by jdub (guest, #27) [Link] (3 responses)

Why, was kernel FPU emulation removed?

A Linux system running over JavaScript

Posted May 18, 2011 19:10 UTC (Wed) by rahvin (guest, #16953) [Link] (2 responses)

How many x86 CPU's have you run into that don't have FPU's?

The simple reality is that such a piece of hardware hasn't existed for a very long time and I believe the kernel dev's took the opinion that it was causing needless pain to leave it in when no one was using it. Not to mention that there are still all those old kernels that can do it which IMO are much more suited to all that old hardware than the newer kernels. Finally, that the vast majority of people didn't even notice it was gone until someone built a fancy little emulator without FPU support is also indicative that they made the right decision in excising the code.

A Linux system running over JavaScript

Posted May 19, 2011 0:26 UTC (Thu) by Darkmere (subscriber, #53695) [Link] (1 responses)

What? They are all over the place, especially in the x86-embedded market, 486SX (VorteX86 and similar SoC chipsets) is a very capable little controller that works exceptionally well.

Also, FPU emulation works on newer kernels than 6.20, so that's just fine too.

A Linux system running over JavaScript

Posted May 19, 2011 7:13 UTC (Thu) by richard_weinberger (subscriber, #38938) [Link]

JSLinux has problems with newer kernels because it passes the kernel command line in an old-styled way.
Commit fa76dab9 (x86: clean up setup.h and the boot code) "broke" Linux >= 2.6.24 on JSLinux.

Fabrice Bellard has to update his linuxstart.bin bootloader...