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 <edumazet@xxxxxxxxxx>
AuthorDate: Tue, 13 Apr 2021 13:33:50 -07:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
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 <edumazet@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20210413203352.71350-2-eric.dumazet@xxxxxxxxx
---
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)
|