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. 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 >
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