path: root/include/vdso
diff options
authorAndrei Vagin <avagin@gmail.com>2020-06-24 01:33:18 -0700
committerCatalin Marinas <catalin.marinas@arm.com>2020-07-24 13:15:20 +0100
commit3503d56cc7233ced602e38a4c13caa64f00ab2aa (patch)
treebc7f29974127abc054e722d88dcd1a3c51750140 /include/vdso
parent1b6867d2916bb91e94ddcc9c709e4779419fe391 (diff)
arm64/vdso: Add time namespace page
Allocate the time namespace page among VVAR pages. Provide __arch_get_timens_vdso_data() helper for VDSO code to get the code-relative position of VVARs on that special page. If a task belongs to a time namespace then the VVAR page which contains the system wide VDSO data is replaced with a namespace specific page which has the same layout as the VVAR page. That page has vdso_data->seq set to 1 to enforce the slow path and vdso_data->clock_mode set to VCLOCK_TIMENS to enforce the time namespace handling path. The extra check in the case that vdso_data->seq is odd, e.g. a concurrent update of the VDSO data is in progress, is not really affecting regular tasks which are not part of a time namespace as the task is spin waiting for the update to finish and vdso_data->seq to become even again. If a time namespace task hits that code path, it invokes the corresponding time getter function which retrieves the real VVAR page, reads host time and then adds the offset for the requested clock which is stored in the special VVAR page. The time-namespace page isn't allocated on !CONFIG_TIME_NAMESPACE, but vma is the same size, which simplifies criu/vdso migration between different kernel configs. Signed-off-by: Andrei Vagin <avagin@gmail.com> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Reviewed-by: Dmitry Safonov <dima@arista.com> Cc: Mark Rutland <mark.rutland@arm.com> Link: https://lore.kernel.org/r/20200624083321.144975-4-avagin@gmail.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'include/vdso')
1 files changed, 1 insertions, 0 deletions
diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index 7955c56d6b3c..ee810cae4e1e 100644
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -109,6 +109,7 @@ struct vdso_data {
* relocation, and this is what we need.
extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
+extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden")));
* The generic vDSO implementation requires that gettimeofday.h

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