"Kevin D. Kissell" wrote:
> > > When a new user process is started will its user space be cleared by the
> > > kernel or is there a potential leak from an older user process ?
> >
> > Usually it is defied by the loader. If the data section contents is set to
> > LOAD, then the contents of the section will be loaded from disk (no leak),
> > if not -- whatever values left i nmemory will be there, or exactly, the
> > virtual page of some other proccess that was swapped out or ended.
>
> Note that what you are describing here is the "exec()" behavior.
> I believe Carsten was talking about what happens on a "fork()".
>
> > > What about the registers values, are they cleared for each new user
> > > application or will it simply contain the current value it got when the
> > > user application is started ?
> >
> > It depends on the context switch algorithm of the processor, I think.
>
> On a fork() (or presumably clone()) operation, the set of registers
> is copied. Loading a new program ("exec()") should set up the
> registers that point to the base of the new stack, the environment,
> etc. Historically, it's up to the runtime startup code ("crt0" in old
> Unix systems) to do any other register initialization.
>
> > > How can you flush the data and instruction cashes from a user
> > > application ?
> > >
> >
> > As far as I understand, ASID must take care of it. It contains unique IDs
> > per process virtual space, so that even
> > though virtual addresses may be found in TLB, their ASID will be
> different,
> > causing TLB miss and probably page fault.
>
> That won't necessarily affect the caches, though. While it
> would be possible to do so, I don't believe any existing
> MIPS implementations include ASID in the cache tags.
> Hits are determined by an address match, period.
>
> Back in the Ancient Old Days of System V, every architecture
> had an architecture-specific system call entry, the first parameter
> of which expressed what needed to be done. Do we have
> such a thing in Linux? That would be the logical place to
> things like cache flush and the atomic operations that were
> being discussed here a couple of weeks ago.
I think I just found it.
The system call is sysmips(FLUSH_CACHE).
>
> Regards,
>
> Kevin K.
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