Add documentation for the PR_PAC_RESET_KEYS ioctl added in Linux 5.0 for arm64. Signed-off-by: Dave Martin <Dave.Martin@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Amit Daniel Kachhap <amit.kachhap@xxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> --- Note that the comment about PR_PAC_RESET_KEYS(0) being the recommended way to set up a fresh execution context is not present in the existing kernel documentation. I vaguely remember some discussion to this effect; in any case, it seems sensible, given that there must have been _some_ rationale for this feature... Shout if it sounds wrong! --- man2/prctl.2 | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) 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. +.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. +.TP +.B EINVAL +.I option +was .B PR_SVE_SET_VL and .I arg2 -- 2.1.4
