On Wed, 28 Jun 2017, Palmer Dabbelt wrote:
> +
> +SYSCALL_DEFINE3(sysriscv_cmpxchg32, unsigned long, arg1, unsigned long, arg2,
> + unsigned long, arg3)
> +{
> + unsigned long flags;
> + unsigned long prev;
> + unsigned int *ptr;
> + unsigned int err;
> +
> + ptr = (unsigned int *)arg1;
Errm. Why isn't arg1 a proper pointer type and the arguments arg2/3 u32?
And please give the arguments a proper name, so it's obvious what is what.
SYSCALL_DEFINE3(sysriscv_cmpxchg32, u32 __user *, ptr, u32 new, u32 old)
Hmm?
> + if (!access_ok(VERIFY_WRITE, ptr, sizeof(unsigned int)))
> + return -EFAULT;
> +
> + preempt_disable();
> + raw_local_irq_save(flags);
Why do you want to disable interrupts here? This is thread context and
accessing user space memory, so the only protection this needs is against
preemption.
> + err = __get_user(prev, ptr);
> + if (likely(!err && prev == arg2))
> + err = __put_user(arg3, ptr);
> + raw_local_irq_restore(flags);
> + preempt_enable();
> +
> + return unlikely(err) ? err : prev;
> +}
> +
> +SYSCALL_DEFINE3(sysriscv_cmpxchg64, unsigned long, arg1, unsigned long, arg2,
> + unsigned long, arg3)
This one is even worse. How does this implement cmpxchg64 on a 32bit machine?
Answer: Not at all, because arg2 and 3 are 32bit ....
> +{
> + unsigned long flags;
> + unsigned long prev;
> + unsigned int *ptr;
> + unsigned int err;
> +
> + ptr = (unsigned int *)arg1;
Type casting to random pointer types makes the code more obvious
and safe, right? What the heck has a int pointer to do with u64?
> + if (!access_ok(VERIFY_WRITE, ptr, sizeof(unsigned long)))
> + return -EFAULT;
> +
> + preempt_disable();
> + raw_local_irq_save(flags);
Same as above.
> + err = __get_user(prev, ptr);
Sigh. Type safety is overrated, right?
Thanks,
tglx
