Hi Dave, On Tue, May 12, 2020 at 05:36:59PM +0100, Dave Martin wrote: > diff --git a/man2/prctl.2 b/man2/prctl.2 > index dd16227..7ea60e2 100644 > --- a/man2/prctl.2 > +++ b/man2/prctl.2 > @@ -950,6 +950,46 @@ behavior. > A value of 1 indicates > .BR execve (2) > will operate in the privilege-restricting mode described above. > +.\" prctl PR_PAC_RESET_KEYS > +.\" commit ba830885656414101b2f8ca88786524d4bb5e8c1 > +.TP > +.BR PR_PAC_RESET_KEYS " (since Linux 5.0, only on arm64)" > +Securely reset the thread's pointer authentication keys > +to fresh random values generated by the kernel. > +.IP > +The set of keys to be reset is specified by > +.IR arg2 , > +which must be a logical OR of zero or more of the following: > +.RS > +.TP > +.B PR_PAC_APIAKEY > +instruction authentication key A > +.TP > +.B PR_PAC_APIBKEY > +instruction authentication key B > +.TP > +.B PR_PAC_APDAKEY > +data authentication key A > +.TP > +.B PR_PAC_APDBKEY > +data authentication key B > +.TP > +.B PR_PAC_APGAKEY > +generic authentication \(lqA\(rq key. > +.IP > +(Yes folks, there really is no generic B key.) > +.RE > +.IP > +As a special case, if > +.I arg2 > +is zero then all the keys are reset. > +Since new keys could be added in future, > +this is the recommended way to completely wipe the existing keys > +when creating a new execution context. I see what you're saying, but the keys are also reset on exec() iirc, so we don't want to encourage people to issue the prctl() unnecessarily immediately following an exec(). > +.IP > +The remaining arguments > +.IR arg3 ", " arg4 " and " arg5 > +must all be zero. > .\" prctl PR_SET_PDEATHSIG > .TP > .BR PR_SET_PDEATHSIG " (since Linux 2.1.57)" > @@ -1920,6 +1960,27 @@ are not 0. > .B EINVAL > .I option > was > +.B PR_PAC_RESET_KEYS > +and > +.I arg2 > +contains non-zero bits other than > +.BR > +.BR PR_PAC_APIAKEY , > +.BR PR_PAC_APIBKEY , > +.BR PR_PAC_APDAKEY , > +.B PR_PAC_APDBKEY > +and > +.BR PR_PAC_APGAKEY ; > +or > +.IR arg3 , > +.I arg4 > +and > +.I arg5 > +were not all zero. Do we care about other reasons for -EINVAL, such as the system not supporting pointer authentication? Will
