On 08/17/2015 10:01 AM, Ingo Molnar wrote: > > (Sorry about the late reply, wasn't around on the weekend.) > > * Linus Torvalds <torva...@linux-foundation.org> wrote: > >> Now that said, I doubt anybody cares. Since we don't support the original >> 80386, >> the only way to ever trigger FP emulation is by having a 486SX or possibly a >> couple of even rarer clone chips. [...] > > Yeah. So when I re-wrote the FPU code I tried to test math-emu by booting > with > 'no387': it turned out that ever since the XSAVE code got merged upstream, > math-emu oopsed reliably during bootup with a NULL reference, because it > wasn't > updated to the dynamic allocation logic in: > > 61c4628b5386 ("x86, fpu: split FPU state from task struct - v5") > > That was 6 years ago, so anything v2.6.26 and later probably has 100% > non-working > math-emu. > > So when I re-introduced static allocations math-emu started working again, to > a > limited degree: on a modern distro, trying to boot /bin/bash I got a prompt, > but > various programs would segfault. I did not investigate it any deeper, I > suppose > the FPU emulation does not go far enough for modern user-space, or maybe it > has > more bugs. > > So in reality nobody has cared about x86 math-emu in the last 6 years
Well... there is this completely crazy x86 javascript emulator by Fabrice Bellard: http://bellard.org/jslinux/tech.html "The CPU is close to a 486 compatible x86 without FPU. The lack of FPU is not a problem when running Linux as Operating System because it contains a FPU emulator." I have it running linux 2.6.20 and busybox here: http://busybox.net/live_bbox/live_bbox.html (or rather, *you* will have it running linux 2.6.20 inside your browser, after you click on that link) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/