From: Eric Dumazet <eric.dumazet@gmail.com>
To: Ingo Molnar <mingo@kernel.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E . McKenney" <paulmck@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>,
Arjun Roy <arjunroy@google.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Eric Dumazet <edumazet@google.com>,
Eric Dumazet <eric.dumazet@gmail.com>
Subject: [PATCH 3/3] rseq: optimise for 64bit arches
Date: Tue, 13 Apr 2021 00:36:57 -0700 [thread overview]
Message-ID: <20210413073657.2308450-4-eric.dumazet@gmail.com> (raw)
In-Reply-To: <20210413073657.2308450-1-eric.dumazet@gmail.com>
From: Eric Dumazet <edumazet@google.com>
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
on 64bit arches is suboptimal.
We might revisit this patch once all 32bit arches support
get_user() and/or put_user() for 8 bytes values.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Arjun Roy <arjunroy@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
---
kernel/rseq.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/kernel/rseq.c b/kernel/rseq.c
index 57344f9abb43905c7dd2b6081205ff508d963e1e..18a75a804008d2f564d1f7789f09216f1a8760bd 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(0ULL, &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
}
/*
--
2.31.1.295.g9ea45b61b8-goog
next prev parent reply other threads:[~2021-04-13 7:37 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 7:36 [PATCH 0/3] rseq: minor optimizations Eric Dumazet
2021-04-13 7:36 ` [PATCH 1/3] rseq: optimize rseq_update_cpu_id() Eric Dumazet
2021-04-13 14:29 ` Mathieu Desnoyers
2021-04-13 15:24 ` Eric Dumazet
2021-04-13 7:36 ` [PATCH 2/3] rseq: remove redundant access_ok() Eric Dumazet
2021-04-13 14:34 ` Mathieu Desnoyers
2021-04-13 15:19 ` Eric Dumazet
2021-04-13 7:36 ` Eric Dumazet [this message]
2021-04-13 9:10 ` [PATCH 3/3] rseq: optimise for 64bit arches Peter Zijlstra
2021-04-13 10:36 ` David Laight
2021-04-13 14:21 ` Mathieu Desnoyers
2021-04-13 15:06 ` David Laight
2021-04-13 15:08 ` Mathieu Desnoyers
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