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| author | Eric Dumazet <edumazet@google.com> | 2021-04-13 13:33:50 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-04-14 18:04:09 +0200 |
| commit | 60af388d23889636011488c42763876bcdda3eab (patch) | |
| tree | 9fa22b294c260a515a6243a3cc77090b79ec5ec5 /kernel/rseq.c | |
| parent | 4bad58ebc8bc4f20d89cff95417c9b4674769709 (diff) | |
| download | lwn-60af388d23889636011488c42763876bcdda3eab.tar.gz lwn-60af388d23889636011488c42763876bcdda3eab.zip | |
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@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/20210413203352.71350-2-eric.dumazet@gmail.com
Diffstat (limited to 'kernel/rseq.c')
| -rw-r--r-- | kernel/rseq.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/kernel/rseq.c b/kernel/rseq.c index a4f86a9d6937..f020f18f512a 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) |