Comment 8 for bug 1285363

Doing this only for aarch64 targets seems like a bad idea to me -- this isn't an aarch64 specific issue. QEMU needs SIGSEGV to go to its own handler (so we can unprotect pages we've marked as read-only in order to catch guest writes to them so we can throw away invalidated translated code), and that's true for all targets. It probably just happens more often on the aarch64 target than others you've tested because aarch64 has a signal-return trampoline on the stack frame, so we'll often see that page get translated and thrown away again. (Other targets with a trampoline include sparc, cris, openrisc and ppc.)

PS: the comment "this is not required for qemu to work" just means that QEMU will work fine whether we tell the guest a lie about what's going on with SIGSEGV in one way (saying "it's blocked") or the other (saying "it's not blocked").