Re: [9fans] go floating point exception

[Ron Minnich <rminnich@p9f.org>]

btw, cdid you get a stack trace from the go runtime? or just that one
l ine diagnostic?

On Fri, Jan 2, 2026 at 8:19 AM ron minnich <rminnich@gmail.com> wrote:
>
> I wonder why that exception is enabled? I wonder what is enabling it?
> Does the go runtime turn it on?
>
> on linux, mxcsr is 0x1f80, all exceptions masked, and in particular, 0x20 is not set -- no precision exceptions.
>
> On Fri, Jan 2, 2026 at 6:23 AM <hahahahacker2009@gmail.com> wrote:
>> 
>> Hello,
>> I don't know go, just have it to compile some programs.
>> I cross-compiled this http server from arm for amd64:
>> https://mkws.sh/https/https.go
>> 
>> Running it on 9legacy/amd64 (under qemu) will raise this error 50% of
>> the time (otherwise it works pretty well):
>> gohttp 177: suicide: sys: fp: Precision Exception mxcsr=0x20 pc=0x215443
>> 
>> Plan 9
>> mmuinit: vmstart 0xfffffffff0000000 vmunused 0xfffffffff03cc000 vmunmapped 0xfffffffff0400000 vmend 0xfffffffffe000000
>> sys->pd 0x108003 0x108023
>> l 3 0xffffff7fbfdfeff8 107023
>> l 2 0xffffff7fbfdffff8 108023
>> l 1 0xffffff7fbffffc00 e3
>> l 1 0xffffff7fbffffc00 e3
>> base 0xfffffffff03d0000 ptr 0xfffffffff03d0000 nunits 14430208
>> physalloc color=0 base=0xe000000 size=0x71fe0000
>> apic0: hz 998949300 max 9989493 min 99894 div 3
>> intrenable: nil handler for 11, tbdf 0xc001800 for ether0
>> #l0: virtio10: 1Gbps port 0xfe000000 irq 11: 525400123456
>> 2044M memory: 2800K+220M kernel, 1822M user, 0M lost
>> pickmethod...read #e/nobootprompt...pickmethod done
>> bind #æ...bind #S...partinit...part plan9 63 67103505
>> p9part /dev/sdC0/data plan9
>> part 9fat 63 204863
>> part nvram 204863 204864
>> part fossil 204864 10573102
>> part arenas 10573102 62414293
>> part isect 62414293 65006353
>> part bloom 65006353 65530641
>> auth...mount usbd...can't open /srv/usbtime...
>> venti...2026/0102 11:36:29 venti: conf.../boot/venti: mem 2,236,962 bcmem 4,473,924 icmem 6,710,886...httpd tcp!127.1!8000...init...icache 6,710,886 bytes = 66,728 entries; 4 scache
>> sync...announce tcp!127.1!17034...serving.
>> fossil(#S/sdC0/fossil)...fsys: dialing venti at tcp!127.1!17034
>> version...can't stat /srv/partfs.sdXX: '/srv/partfs.sdXX' file does not exist
>> 
>> init: starting /bin/rc
>> secstore
>> mkvbe: '/dev/realmode' file does not exist
>> aux/vga: controller not in /lib/vgadb, not vesa
>> 0xC0000 55 AA 4D E9 90 55 CC 00 00 00 00 00 00 00 00 00  U.M..U..........
>> 0xC0010 00 00 00 00 00 00 00 00 5C 98 00 00 00 00 49 42  ........\.....IB
>> 0xC0020 4D 00 2E 8B 16 E8 98 85 D2 74 01 EE C2 02 00 84  M........t......
>> 0xC0030 C0 74 34 66 55 66 89 E5 66 53 66 89 C3 66 B8 00  .t4fUf..fSf..f..
>> 0xC0040 40 00 00 FE CB 74 37 66 0F B7 D2 66 0F B7 C9 66  @....t7f...f...f
>> 0xC0050 0F AF D1 66 C1 FA 03 66 89 D0 9C 66 05 FF 1F 00  ...f...f...f....
>> 0xC0060 00 9D 25 00 E0 EB 17 0F AF CA 66 89 C8 9C 66 D1  ..%.......f...f.
>> 0xC0070 E0 66 05 FF 07 00 00 9D 25 00 F8 C2 02 00 66 5B  .f......%.....f[
>> 0xC0080 66 5D C2 02 00 66 55 66 89 E5 66 56 66 53 66 89  f]...fUf..fVfSf.
>> 0xC0090 C6 66 89 D3 66 89 CA 67 66 8B 4D 08 67 8A 45 0C  .f..f..gf.M.g.E.
>> 0xC00A0 66 C1 E6 10 66 0F B7 DB 66 09 F3 66 31 F6 8E C6  f...f...f..f1...
>> 0xC00B0 26 66 89 1E 0C 01 80 F9 01 74 0D 80 F9 03 74 0C  &f.......t....t.
>> 0xC00C0 84 C9 74 0A B0 19 EB 06 B0 0E EB 02 B0 2B 66 B9  ..t..........+f.
>> 0xC00D0 40 00 00 00 8E C1 66 48 26 A2 84 00 8E C1 66 0F  @.....fH&.....f.
>> 0xC00E0 B6 D2 26 89 16 85 00 66 5B 66 5E 66 5D C2 02 00  ..&....f[f^f]...
>> 0xC00F0 66 55 66 89 E5 66 57 66 56 66 53 66 53 66 89 C3  fUf..fWfVfSfSf..
>> aux/vga: main: vga@1024x768x1 not in /lib/vgadb
>> rio: can't open display: initdisplay: /dev/draw/new: no frame buffer
>> init: rc exit status: rio 41: display open
>> 
>> init: starting /bin/rc
>> term%
>> 
>
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