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x86/iopl: Fake iopl(3) CLI/STI usage
Since commit c8137ac ("x86/iopl: Restrict iopl() permission scope") it's possible to emulate iopl(3) using ioperm(), except for the CLI/STI usage. Userspace CLI/STI usage is very dubious (read broken), since any exception taken during that window can lead to rescheduling anyway (or worse). The IOPL(2) manpage even states that usage of CLI/STI is highly discouraged and might even crash the system. Of course, that won't stop people and HP has the dubious honour of being the first vendor to be found using this in their hp-health package. In order to enable this 'software' to still 'work', have the #GP treat the CLI/STI instructions as NOPs when iopl(3). Warn the user that their program is doing dubious things. Fixes: a24ca99 ("x86/iopl: Remove legacy IOPL option") Reported-by: Ondrej Zary <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> Cc: [email protected] # v5.5+ Link: https://lkml.kernel.org/r/[email protected]
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Peter Zijlstra
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Sep 21, 2021
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