On Tue, Sep 26, 2023 at 01:52:34AM +0200, Alejandro Colomar wrote: > Hi Axel, > > On Tue, Sep 19, 2023 at 12:02:03PM -0700, Axel Rasmussen wrote: > > First, it is not correct that repeated UFFDIO_API calls result in > > EINVAL. This is true *if both calls enable features*, but in the case > > where we're doing a two-step feature detection handshake, the kernel > > explicitly expects 2 calls (one with no features set). So, correct this > > description. > > > > Then, some new error cases have been added to the kernel recently, and > > the man page wasn't updated to note these. So, add in descriptions of > > these new error cases. > > > > Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx> > > --- > > man2/ioctl_userfaultfd.2 | 24 +++++++++++++++++++----- > > 1 file changed, 19 insertions(+), 5 deletions(-) > > > > diff --git a/man2/ioctl_userfaultfd.2 b/man2/ioctl_userfaultfd.2 > > index 53b1f473f..1aa9654be 100644 > > --- a/man2/ioctl_userfaultfd.2 > > +++ b/man2/ioctl_userfaultfd.2 > > @@ -280,17 +280,31 @@ refers to an address that is outside the calling process's > > accessible address space. > > .TP > > .B EINVAL > > -The userfaultfd has already been enabled by a previous > > -.B UFFDIO_API > > -operation. > > -.TP > > -.B EINVAL > > The API version requested in the > > .I api > > field is not supported by this kernel, or the > > .I features > > field passed to the kernel includes feature bits that are not supported > > by the current kernel version. > > +.TP > > +.B EPERM > > This EPERM should probably be at the end. Unless you have a good reason > to break alphabetic order. I agree with Alex here, other than that feel free to add Reviewed-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx> > Thanks, > Alex > > > +The > > +.B UFFD_FEATURE_EVENT_FORK > > +feature was enabled, > > +but the calling process doesn't have the > > +.B CAP_SYS_PTRACE > > +capability. > > +.TP > > +.B EINVAL > > +A previous > > +.B UFFDIO_API > > +call already enabled one or more features for this userfaultfd. > > +Calling > > +.B UFFDIO_API > > +twice, > > +the first time with no features set, > > +is explicitly allowed > > +as per the two-step feature detection handshake. > > .\" FIXME In the above error case, the returned 'uffdio_api' structure is > > .\" zeroed out. Why is this done? This should be explained in the manual page. > > .\" > > -- > > 2.42.0.459.ge4e396fd5e-goog > > -- Sincerely yours, Mike.
