Messages in this thread |  | | | Date | Tue, 16 Feb 2010 11:23:32 +0100 | | From | Andi Kleen <> | | Subject | Re: x86: get rid of the insane TIF_ABI_PENDING bit |
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On Tue, Feb 16, 2010 at 11:19:03AM +0100, Oleg Nesterov wrote: > On 02/15, H. Peter Anvin wrote: > > > > On 02/15/2010 11:41 AM, Roland McGrath wrote: > > > It affects whatever uses is_compat_task(), but I can't see anything > > > where that matters except inside some particular syscall or for > > > syscall restart after signals. > > > > FWIW, the origin of this is checkin > > 4d9bc79cd28b779610d9590b3a96a28a0f64a25a (2.6.18-rc1), which somewhat > > unhelpfully states "Make sure is_compat_task works early". It doesn't > > specify what the failure is if is_compat_task doesn't work early. > > Perhaps Andi could explain us why this is needed, > > > On > > the other hand, it sure as heck seems better to set it and not need it > > than the other way around. > > Agreed, but otoh it is always good to understand the code. If we > really have a reason for TS_COMPAT, a small comment can help other > readers.
My memory is somewhat fuzzy on this one, but I think it was related to VMA placement (probably for stack randomization or something like that) This happens before the first call. I might be wrong on that.
There might also have been other is_compat_task checks in the exec init path, so partly it was defensive programming.
-Andi
-- ak@linux.intel.com -- Speaking for myself only.
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