On Thu, Aug 13, 2015 at 01:18:50PM -0700, Andy Lutomirski wrote: > This adds two new uc_flags flags. UC_SAVED_SS will be set for all > 64-bit signals (including x32). It indicates that the saved SS field > is valid and that the kernel understands UC_RESTORE_SS. > > The kernel will *not* set UC_RESTORE_SS. User signal handlers can > set UC_RESTORE_SS themselves to indicate that sigreturn should > restore SS from the sigcontext. > > 64-bit programs that use segmentation are encouraged to check > UC_SAVED_SS and set UC_RESTORE_SS in their signal handlers. This is > the only straightforward way to cause sigreturn to restore SS. (The > only non-test program that I know of that uses segmentation in a > 64-bit binary is DOSEMU, and DOSEMU currently uses a nasty > trampoline to work around the lack of this mechanism in old kernels. > It could detect UC_RESTORE_SS and use it to avoid needing a > trampoline. > > Cc: Stas Sergeev <stsp@xxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxx> > Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx> Looks reasonable to me. Andy, Linus, what the final conclusion -- are we about to introduce this flag or simply continue with revert? Should I test this one? (from the code I don't excpect it break criu anyhow but still). -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
