From 5e0ccd4a3b01c5a71732a13186ca110a138516ea Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 13 Apr 2021 13:33:52 -0700 Subject: [PATCH] rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs() Commit ec9c82e03a74 ("rseq: uapi: Declare rseq_cs field as union, update includes") added regressions for our servers. Using copy_from_user() and clear_user() for 64bit values is suboptimal. We can use faster put_user() and get_user() on 64bit arches. Signed-off-by: Eric Dumazet Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Mathieu Desnoyers Link: https://lkml.kernel.org/r/20210413203352.71350-4-eric.dumazet@gmail.com --- kernel/rseq.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/rseq.c b/kernel/rseq.c index cfe01ab5253c..35f7bd0fced0 100644 --- a/kernel/rseq.c +++ b/kernel/rseq.c @@ -127,8 +127,13 @@ static int rseq_get_rseq_cs(struct task_struct *t, struct rseq_cs *rseq_cs) u32 sig; int ret; +#ifdef CONFIG_64BIT + if (get_user(ptr, &t->rseq->rseq_cs.ptr64)) + return -EFAULT; +#else if (copy_from_user(&ptr, &t->rseq->rseq_cs.ptr64, sizeof(ptr))) return -EFAULT; +#endif if (!ptr) { memset(rseq_cs, 0, sizeof(*rseq_cs)); return 0; @@ -211,9 +216,13 @@ static int clear_rseq_cs(struct task_struct *t) * * Set rseq_cs to NULL. */ +#ifdef CONFIG_64BIT + return put_user(0UL, &t->rseq->rseq_cs.ptr64); +#else if (clear_user(&t->rseq->rseq_cs.ptr64, sizeof(t->rseq->rseq_cs.ptr64))) return -EFAULT; return 0; +#endif } /* -- 2.39.5