Re: [RFC] x86: xsave/xrstor support, ucontext_t extensions
From: H. Peter Anvin
Date: Thu May 22 2008 - 22:32:32 EST
Suresh Siddha wrote:
No. You CANNOT restore from a frame that doesn't have the full state -
you don't have enough information to do so!
The kernel needs to accept one(*) of the formats it can produce, which
is not necessarily what it last produced. It's not inconceivable that
user-space will construct sigframes on the fly (to emulate setcontext),
or that it will mangle sigframes (e.g. to map non-rt to rt before
(*) The format is determined by which version of sys_sigreturn the
What I was doing in the RFC is: restore the state what ever that was present and
init the state that was not present in the stack frame.
Either way, I find it somewhat surprising that the user would invoke a
different sys_sigreturn especially if using a restorer function (which
gcc always does.)
I really think I need to understand your application better,
*especially* in the light of the fact you wouldn't at the moment know
how even get the size of the frame.
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