Re: [PATCH v4 0/3] time namespace aware system boot time
On Mon, Oct 19 2020 at 21:52, Michael Weiß wrote: > Michael Weiß (3): > timens: additional helper functions for boottime offset handling > fs/proc: apply the time namespace offset to /proc/stat btime > selftests/timens: added selftest for /proc/stat btime > > fs/proc/array.c | 6 ++- > fs/proc/stat.c | 3 ++ > include/linux/time_namespace.h | 22 ++ > tools/testing/selftests/timens/procfs.c | 58 - > 4 files changed, 86 insertions(+), 3 deletions(-) Acked-by: Thomas Gleixner
Re: [PATCH v4 0/3] time namespace aware system boot time
On Mon, Oct 19, 2020 at 09:52:54PM +0200, Michael Weiß wrote: > Time namespaces make it possible to virtualize time inside of > containers, e.g., it is feasible to reset the uptime of a container > to zero by setting the time namespace offset for boottime to the > negated current value of the CLOCK_BOOTTIME. > > However, the boot time stamp provided by getboottime64() does not > take care of time namespaces. The resulting boot time stamp 'btime' > provided by /proc/stat does not show a plausible time stamp inside > the time namespace of a container. > > We address this by shifting the value returned by getboottime64() > by subtracting the boottime offset of the time namespace. > (A selftest to check the expected /proc/stat 'btime' inside the > namespace is provided.) > > Further, to avoid to show processes as time travelers inside of the > time namespace the boottime offset then needs to be added to the > start_boottime provided by the task_struct. > > v4 Changes: > Avoid type conversions back and forth between timespec64 and ktime_t > in 'proc/stat.c' as suggested by Andrei. > Introduced timens_sub_boottime() in 'time_namespace.h' to provide > better coder readability/consistency. > Reviewed-by: Andrei Vagin Thanks, Andrei
[PATCH v4 0/3] time namespace aware system boot time
Time namespaces make it possible to virtualize time inside of containers, e.g., it is feasible to reset the uptime of a container to zero by setting the time namespace offset for boottime to the negated current value of the CLOCK_BOOTTIME. However, the boot time stamp provided by getboottime64() does not take care of time namespaces. The resulting boot time stamp 'btime' provided by /proc/stat does not show a plausible time stamp inside the time namespace of a container. We address this by shifting the value returned by getboottime64() by subtracting the boottime offset of the time namespace. (A selftest to check the expected /proc/stat 'btime' inside the namespace is provided.) Further, to avoid to show processes as time travelers inside of the time namespace the boottime offset then needs to be added to the start_boottime provided by the task_struct. v4 Changes: Avoid type conversions back and forth between timespec64 and ktime_t in 'proc/stat.c' as suggested by Andrei. Introduced timens_sub_boottime() in 'time_namespace.h' to provide better coder readability/consistency. v3 Changes: leave getboottime64() unchanged and shift the boot timestamp in 'fs/proc/stat.c' as result of the discussion with Andrei and Thomas. v2 Changes: Fixed compile errors with TIME_NS not set in config Michael Weiß (3): timens: additional helper functions for boottime offset handling fs/proc: apply the time namespace offset to /proc/stat btime selftests/timens: added selftest for /proc/stat btime fs/proc/array.c | 6 ++- fs/proc/stat.c | 3 ++ include/linux/time_namespace.h | 22 ++ tools/testing/selftests/timens/procfs.c | 58 - 4 files changed, 86 insertions(+), 3 deletions(-) -- 2.20.1
