From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> The signal behavior of pkeys is special compared to many other processor and OS features. Add a special section to describe the behavior. This was previously a part of the pkey_get manpage, but that page was removed from my submission when we removed the syscall itself. I've essentially moved the content from that page to the main pkey.7 page. Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> --- b/man7/pkeys.7 | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff -puN man7/pkeys.7~pkey-signal-behavior man7/pkeys.7 --- a/man7/pkeys.7~pkey-signal-behavior 2016-10-17 08:59:31.081217165 -0700 +++ b/man7/pkeys.7 2016-10-17 13:36:48.525030174 -0700 @@ -135,6 +135,22 @@ appropriate for child threads at the tim .BR clone (2) is called, or ensure that each child thread can perform its own initialization of protection key rights. + +.SS Signal Handler Behavior +Each time a signal handler is invoked (including nested signals), the +thread is temporarily given a new, default set of protection key rights +that override the rights from the interrupted context. +This means that applications must re-establish their desired protection +key rights upon entering a signal handler if the desired rights differ +from the defaults. +The rights of any interrupted context are restored when the signal +handler returns. + +This signal behavior is unusual and is due to the fact that the x86 PKRU +register (which stores protection key access rights) is managed with the +same hardware mechanism (XSAVE) that manages floating-point registers. +The signal behavior is the same as that of floating point registers. + .SS Protection Keys system calls The Linux kernel implements the following pkey-related system calls: .BR pkey_mprotect (2), _ -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
