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rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs() 

Commit ec9c82e03a ("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
This commit is contained in:
Eric Dumazet 2021-04-13 13:33:52 -07:00 committed by Peter Zijlstra
parent 0ed9605153
commit 5e0ccd4a3b
1 changed files with 9 additions and 0 deletions
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9
kernel/rseq.c
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@ -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
}
/*