On Fri, Aug 14, 2015 at 1:55 PM, Cyrill Gorcunov <gorcunov@xxxxxxxxx> wrote: > 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). Don't bother testing yet. I'm waffling between trying something like this and adding SA_SAVE_SS. I have partially written patches for the latter. --Andy -- Andy Lutomirski AMA Capital Management, LLC -- 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
