[RFC] handle_vm86_fault

[Kasper Dupont <kasperd@daimi.au.dk>]

Recently some changes were made to arch/i386/kernel/vm86.c in order to
prevent some Oopses. Currently handle_vm86_fault returns VM86_UNKNOWN
in those cases. But that is a little broken, rather than returning
this value, it should send a SIGSEGV to usermode.

That is however not trivial, there is a problem with the si_addr field
in the siginfo_t struct. The do_page_fault function in
arch/i386/mm/fault.c will fill this field in such a struct with the
local variable address. But that only happens if the trap comes from
usermode, in this case the trap comes from kernelmode. That means that
do_page_fault just finds the fixup address and returns loosing the
value of the local variable address.

How can I pass that variable back from do_page_fault to
handle_vm86_fault? There might also be a problem with the si_code
field, I'm not sure exactly from where I should get that value.
Perhaps it will turn out to be some known constant.

Would it be safe to fill the address in tsk->thread.cr2 like the
usermode case?

-- 
Kasper Dupont -- der bruger for meget tid på usenet.
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