On 05/28/2013 08:17 PM, David Howells wrote:
> Chen Gang <gang.chen@xxxxxxxxxxx> wrote:
>
>> Your suggestion will improve the speed, but may merge "transferring
>> 'protocol' data" and "processing 'protocol' data" together.
>
> Look at it this way: You're having to step very carefully because you are
> fully expecting the strings not to be NUL-terminated. Therefore you probably
> avoid using string functions if you can.
>
> In fact, looking at the code, why are you copying the data through an
> intermediate buffer at all? Why not just copy directly to userspace:
>
> int len;
> char buf[2];
>
> if (!*lenp || *ppos) {
> *lenp = 0;
> return 0;
> }
> if (!write) {
> - len = sprintf(buf, appldata_timer_active ? "1\n" : "0\n");
> + const char *ptr = appldata_timer_active ? "1\n" : "0\n";
> + size_t len = 2;
> if (len > *lenp)
> len = *lenp;
> if (copy_to_user(buffer, buf, len))
may: "if (copy_to_user(buffer, ptr, len))" ?
:-)
> return -EFAULT;
> goto out;
> }
>
> Put like that, it's fairly obvious what is going on.
>
It seems well fixed (still independent of processing 'protocol' data).
:-)
And how about below:
-------------------------------diff begin------------------------------
diff --git a/arch/s390/appldata/appldata_base.c b/arch/s390/appldata/appldata_base.c
index bae0f40..27f200d 100644
--- a/arch/s390/appldata/appldata_base.c
+++ b/arch/s390/appldata/appldata_base.c
@@ -212,10 +212,9 @@ appldata_timer_handler(ctl_table *ctl, int write,
return 0;
}
if (!write) {
- len = sprintf(buf, appldata_timer_active ? "1\n" : "0\n");
- if (len > *lenp)
- len = *lenp;
- if (copy_to_user(buffer, buf, len))
+ if (copy_to_user(buffer,
+ appldata_timer_active ? "1\n" : "0\n",
+ min(2, *lenp))
return -EFAULT;
goto out;
}
-------------------------------diff end--------------------------------
Thanks
--
Chen Gang
Asianux Corporation
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