* Paolo Bonzini (pbonz...@redhat.com) wrote: > > > On 13/03/2015 11:41, Dr. David Alan Gilbert wrote: > >>> > > +#ifdef HOST_X86_64 > >>> > > +#ifndef __NR_userfaultfd > >>> > > +#define __NR_userfaultfd 323 > >> > > >> > Sholdn't this come from the kernel headers imported in the previous > >> > patch? Rather than having an arch-specific hack. > > The header, like the rest of the kernel headers, just provides > > the constant and structure definitions for the call; the syscall numbers > > come from arch specific headers. I guess in the final world I wouldn't > > need this at all since it'll come from the system headers; but what's > > the right way to put this in for new syscalls? > > > > You would just require new _installed_ kernel headers. Then you can use > linux/userfaultfd.h and syscall.h (the latter from glibc, includes > asm/unistd.h to get syscall numbers). > > linux-headers/ is useful for APIs that do not require system calls, or > for APIs that are extensible. However, if a system call is required > (and mandatory) it's simpler to just use installed headers.
OK, so then I could check for ifdef __NR_userfault and then do the include and I think that would be safe. Although then what's the best way to tell people to try it out without an updated libc? Or is it best to modify ./configure to detect it? Dave > > Paolo -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
