lkml.org 
[lkml]   [2021]   [Apr]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip: sched/core] rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs()
The following commit has been merged into the sched/core branch of tip:

Commit-ID: 5e0ccd4a3b01c5a71732a13186ca110a138516ea
Gitweb: https://git.kernel.org/tip/5e0ccd4a3b01c5a71732a13186ca110a138516ea
Author: Eric Dumazet <edumazet@google.com>
AuthorDate: Tue, 13 Apr 2021 13:33:52 -07:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 14 Apr 2021 18:04:09 +02:00

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 <edumazet@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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 cfe01ab..35f7bd0 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
}

/*
\
 
 \ /
  Last update: 2021-04-15 10:39    [W:0.057 / U:1.692 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site