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23 October 2021, 00:29:24 UTC
Revision dbe3ed1c078c193be34326728d494c5c4bc115e2 authored by Linus Torvalds on 19 September 2007, 18:37:14 UTC, committed by Linus Torvalds on 19 September 2007, 18:37:14 UTC 
x86-64: page faults from user mode are always user faults
 
Randy Dunlap noticed an interesting "crashme" behaviour on his dual
Prescott Xeon setup, where he gets page faults with the error code
having a zero "user" bit, but the register state points back to user
mode.

This may be a CPU microcode buglet triggered by some strange instruction
pattern that crashme generates, and loading a microcode update seems to
possibly have fixed it.

Regardless, we really should trust the register state more than the
error code, since it's really the register state that determines whether
we can actually send a signal, or whether we're in kernel mode and need
to oops/kill the process in the case of a page fault.

Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 4f01a75
History
Tip revision: dbe3ed1c078c193be34326728d494c5c4bc115e2 authored by Linus Torvalds on 19 September 2007, 18:37:14 UTC
x86-64: page faults from user mode are always user faults
Tip revision: dbe3ed1
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