From: erik quanstrom <quanstro@quanstro.net>
To: 9fans@9fans.net
Subject: [9fans] sysrfork fp bug?
Date: Mon, 21 Nov 2011 10:08:18 -0500 [thread overview]
Message-ID: <93653898c4ceb27355b5fa1e548176aa@brasstown.quanstro.net> (raw)
sysrfork() does *not* do a procsave before forking. thus the
floating point registers in the new process are just going to
be a copy of whatever was last saved, and perhaps nothing.
on my atom system (but not some others), this attached
program does fault. i wrote a bit of it in assembler to control
what was in F0. the c compiler wasn't keeping things in a
register.
have i missed something or do we need a procsave() in fork?
- erik
---
sed 's/.//' >fp.c <<'//GO.SYSIN DD fp.c'
-#include <u.h>
-#include <libc.h>
-
-char *theformat = "%g\n";
-
-void
-main(void)
-{
- extern void dofp(void);
-
- dofp();
-}
//GO.SYSIN DD fp.c
echo myfp.s
sed 's/.//' >myfp.s <<'//GO.SYSIN DD myfp.s'
-TEXT dofp(SB), $0
- SUBL $12, SP
- FLD1
- CALL fork(SB)
-
- MOVL $2000, AX
- MOVL AX, 0x0(SP)
- CALL sleep(SB)
-
- MOVL theformat(SB), AX
- MOVL AX, 0x0(SP)
- FMOVDP F0,0x4(SP)
- CALL print(SB)
- ADDL $12, SP
- RET
//GO.SYSIN DD myfp.s
next reply other threads:[~2011-11-21 15:08 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-21 15:08 erik quanstrom [this message]
2011-11-21 15:33 ` Charles Forsyth
[not found] ` <CAOw7k5hcpmt26NppfrFENPWS9_g6jD=XMhQzVMeS1usGQrwL0w@mail.gmail.c>
2011-11-21 15:43 ` erik quanstrom
2011-11-21 23:01 ` erik quanstrom
2011-11-21 15:48 ` erik quanstrom
2011-11-21 22:08 ` erik quanstrom
2011-11-21 23:14 ` Charles Forsyth
2011-11-21 23:18 ` Charles Forsyth
[not found] ` <CAOw7k5it_OV56ZNnPygDjh+rA=xC-+-x+DJuSWBCBRC-XhXECw@mail.gmail.c>
2011-11-22 1:52 ` erik quanstrom
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=93653898c4ceb27355b5fa1e548176aa@brasstown.quanstro.net \
--to=quanstro@quanstro.net \
--cc=9fans@9fans.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).