On Tue, Sep 08, 2020 at 12:59:49AM -0400, Gabriel Krisman Bertazi wrote:
Christian Brauner christian.brauner@ubuntu.com writes:
On Fri, Sep 04, 2020 at 04:31:39PM -0400, Gabriel Krisman Bertazi wrote:
index afe01e232935..3511c98a7849 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -959,7 +959,11 @@ struct task_struct { kuid_t loginuid; unsigned int sessionid; #endif
- struct seccomp seccomp;
- struct {
unsigned int syscall_intercept;struct seccomp seccomp;- };
If there's no specific reason to do this I'd not wrap this in an anonymous struct. It doesn't really buy anything and there doesn't seem to be precedent in struct task_struct right now. Also, if this somehow adds padding it seems you might end up increasing the size of struct task_struct more than necessary by accident? (I might be wrong though.)
Hi Christian,
Thanks for your review on this and on the other patches of this series.
I wrapped these to prevent struct layout randomization from separating the flags field from seccomp, as they are going to be used together and I was trying to reduce overhead to seccomp entry due to two cache misses when reading this structure. Measuring it seccomp_benchmark didn't show any difference with the unwrapped version, so perhaps it was a bit of premature optimization?
That should not be a thing to think about here. Structure randomization already has a mode to protect against cache line issues. I would leave this as just a new member; no wrapping struct.