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SubjectRe: Mach-O binary format support and Darwin syscall personality [Was: uts banner changes]


On Wed, 13 Dec 2006, Benjamin Herrenschmidt wrote:
>
> > Secondly, is there a preferred existing field into which I should
> > stick said flag or just stuff it somewhere?
>
> Yes, thread_info->flags.

Well, it may actually make sense to actually stick the whole "syscall
table pointer" in there, rather than a flag that says which pointer to
choose.

We already load the thread_info pointer because we need the flags for
syscall tracing, and since we have the thread_info pointer, it might be
easier to load the syscall table pointer right off there, rather than
loading it as a big constant with "lis + ori" (in fact, on ppc64, we
currently load it off the TOC, which is really sad, since we already
brought in the thread_info into the cache, and usign the TOC is not just a
load, it's a load off a separate cacheline).

So on 64-bit ppc, it could actually speed things up to put the system call
table pointer into thread_info, and make it more flexible at the same
time, without any conditional flags.

Linus
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