Messages in this thread | | | Date | Wed, 8 Dec 1999 21:32:16 +0100 (CET) | From | Ingo Molnar <> | Subject | Re: 2.3.30pre1 syscall w/6 args support? |
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On Wed, 8 Dec 1999, Brian Gerst wrote:
> As far as I know, Wine currently only uses the extra segments for > Windows code. Any Linux syscalls should only be coming from the main > code segment.
that is great. No changed %ds, %es, %ss either when glibc is called?
> I don't know about Intel's SYSENTER/SYSEXIT, but with AMD's > SYSCALL/SYSRET you cannot return to user space with iret after a > SYSCALL. The CPU sets an internal flag that causes a GPF when > anything modifies %cs except for SYSRET or an interrupt (hardware or > software). This has been a big stumbling block for me with adding > SYSCALL support becuase it interferes with task switching (ie. can't > switch to another task that would do an iret), unless it is restricted > to syscalls that cannot sleep.
i've just tested this on Xeon CPUs, and it works. (i forced the fastcall entry point to reschedule unconditionally, the system still uses int $80)
I agree that this would be a serious showstopper. Are you sure you werent bitten by the stack-MSR issue? (we have to reload the SYSENTER kernel-ESP MSR on every task switch)
-- mingo
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