The following commit has been merged into the sched/core branch of tip: Commit-ID: 60af388d23889636011488c42763876bcdda3eab Gitweb: https://git.kernel.org/tip/60af388d23889636011488c42763876bcdda3eab Author: Eric Dumazet <eduma...@google.com> AuthorDate: Tue, 13 Apr 2021 13:33:50 -07:00 Committer: Peter Zijlstra <pet...@infradead.org> CommitterDate: Wed, 14 Apr 2021 18:04:09 +02:00
rseq: Optimize rseq_update_cpu_id() Two put_user() in rseq_update_cpu_id() are replaced by a pair of unsafe_put_user() with appropriate surroundings. This removes one stac/clac pair on x86 in fast path. Signed-off-by: Eric Dumazet <eduma...@google.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Reviewed-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> Link: https://lkml.kernel.org/r/20210413203352.71350-2-eric.duma...@gmail.com --- kernel/rseq.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/kernel/rseq.c b/kernel/rseq.c index a4f86a9..f020f18 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -84,13 +84,20 @@ static int rseq_update_cpu_id(struct task_struct *t) { u32 cpu_id = raw_smp_processor_id(); + struct rseq __user *rseq = t->rseq; - if (put_user(cpu_id, &t->rseq->cpu_id_start)) - return -EFAULT; - if (put_user(cpu_id, &t->rseq->cpu_id)) - return -EFAULT; + if (!user_write_access_begin(rseq, sizeof(*rseq))) + goto efault; + unsafe_put_user(cpu_id, &rseq->cpu_id_start, efault_end); + unsafe_put_user(cpu_id, &rseq->cpu_id, efault_end); + user_write_access_end(); trace_rseq_update(t); return 0; + +efault_end: + user_write_access_end(); +efault: + return -EFAULT; } static int rseq_reset_rseq_cpu_id(struct task_struct *t)
