signal frame ss in a 64-bit process?

[Andy Lutomirski]

How is restoring ss and ds in a 64-bit process supposed to work?
There's this comment:

        /* Kernel saves and restores only the CS segment register on signals,
         * which is the bare minimum needed to allow mixed 32/64-bit code.
         * App's signal handler can save/restore other segments if needed. */

AFAICT this is bogus: syscall (the 64-bit version) sets regs->ss to
__USER_DS.  I think that the actual ss register is untouched until the
syscall returns, so in theory sigreturn could copy ss to regs, but
that seems kind of nasty.

Can we steal __pad0 and put ss in there?

--Andy

-- 
Andy Lutomirski
AMA Capital Management, LLC
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