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| author |   Heiko Carstens <heiko.carstens@de.ibm.com> | 2016-12-28 11:33:48 +0100 |
|---|---|---|
| committer |   Martin Schwidefsky <schwidefsky@de.ibm.com> | 2017-01-16 07:27:48 +0100 |
| commit | e991c24d68b8c0ba297eeb7af80b1e398e98c33f (patch) | |
| tree | 0de08c08b2ecdf7b9a22683ac8cff66331ae7782 /arch/s390/defconfig | |
| parent | Linux 4.10-rc4 (diff) | |
| download | linux-dev-e991c24d68b8c0ba297eeb7af80b1e398e98c33f.tar.xz linux-dev-e991c24d68b8c0ba297eeb7af80b1e398e98c33f.zip | |
s390/ctl_reg: make __ctl_load a full memory barrier
We have quite a lot of code that depends on the order of the
__ctl_load inline assemby and subsequent memory accesses, like
e.g. disabling lowcore protection and the writing to lowcore.
Since the __ctl_load macro does not have memory barrier semantics, nor
any other dependencies the compiler is, theoretically, free to shuffle
code around. Or in other words: storing to lowcore could happen before
lowcore protection is disabled.
In order to avoid this class of potential bugs simply add a full
memory barrier to the __ctl_load macro.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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