Add description of UFFD_USER_MODE_ONLY flag to userfaultfd(2) manual page, which is required after [1]. Also updated the description of unprivileged_userfaultfd file in proc(5) as per [2]. [1] https://lore.kernel.org/linux-mm/20201215031349.NXimL388W%25akpm@xxxxxxxxxxxxxxxxxxxx/ [2] https://lore.kernel.org/linux-mm/20201215031354.gUsHJUpKo%25akpm@xxxxxxxxxxxxxxxxxxxx/ Signed-off-by: Lokesh Gidra <lokeshgidra@xxxxxxxxxx> --- man2/userfaultfd.2 | 5 +++++ man5/proc.5 | 12 ++++++++++++ 2 files changed, 17 insertions(+) diff --git a/man2/userfaultfd.2 b/man2/userfaultfd.2 index e7dc9f813..792a49d52 100644 --- a/man2/userfaultfd.2 +++ b/man2/userfaultfd.2 @@ -72,6 +72,11 @@ See the description of the .BR O_NONBLOCK flag in .BR open (2). +.TP +.BR UFFD_USER_MODE_ONLY " (Since Linux 5.11)" +Allow handling of user-mode page-faults only. See the description of the +unprivileged_userfaultfd file in +.BR proc (5). .PP When the last file descriptor referring to a userfaultfd object is closed, all memory ranges that were registered with the object are unregistered diff --git a/man5/proc.5 b/man5/proc.5 index f16a29d6e..cb2350c0c 100644 --- a/man5/proc.5 +++ b/man5/proc.5 @@ -5905,6 +5905,18 @@ If this file has the value 0, then only processes that have the capability may employ .BR userfaultfd (2). The default value in this file is 1. +.IP +Starting with Linux 5.11, +.BR userfaultfd (2) +can be used by all processes, however, if this file has the value 0, then +.BR UFFD_USER_MODE_ONLY +flag must be passed to it, which restricts page-fault handling to only +user-mode faults. This restriction is not applicable for processes with +.B CAP_SYS_PTRACE +capability, or if this file has the value 1. Furthermore, the default +value in this file is changed to 0. For further details see the +Linux kernel source file +.I Documentation/admin\-guide/sysctl/vm.rst. .TP .IR /proc/sysrq\-trigger " (since Linux 2.4.21)" Writing a character to this file triggers the same SysRq function as -- 2.30.0.280.ga3ce27912f-goog
