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Commit a4780ade authored by André Hentschel's avatar André Hentschel Committed by Russell King
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ARM: 7735/2: Preserve the user r/w register TPIDRURW on context switch and fork



Since commit 6a1c5312 the user writeable TLS register was zeroed to
prevent it from being used as a covert channel between two tasks.

There are more and more applications coming to Windows RT,
Wine could support them, but mostly they expect to have
the thread environment block (TEB) in TPIDRURW.

This patch preserves that register per thread instead of clearing it.
Unlike the TPIDRURO, which is already switched, the TPIDRURW
can be updated from userspace so needs careful treatment in the case that we
modify TPIDRURW and call fork(). To avoid this we must always read
TPIDRURW in copy_thread.

Signed-off-by: default avatarAndré Hentschel <nerv@dawncrow.de>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarJonathan Austin <jonathan.austin@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 4a1b5733
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