On 07/11/2018 13:02, Andrew Cooper wrote:
> On 07/11/18 11:55, Andrew Cooper wrote:
>> On 07/11/18 11:30, Juergen Gross wrote:
>>> + return ret;
>>> }
>>>
>>> static inline int xen_safe_read_ulong(unsigned long *addr, unsigned long
>>> *val)
>>> {
>>> - return __get_user(*val, (unsigned long __user *)addr);
>>> + int ret = 0;
>>> + unsigned long rval;
>>> +
>>> + asm volatile("1: mov"__i" %2,%"__r"1\n"
>>> + "2:\n"
>>> + ".section .fixup,\"ax\"\n"
>>> + "3: mov %3,%0\n"
>>> + " jmp 2b\n"
>>> + ".previous\n"
>>> + _ASM_EXTABLE(1b, 3b)
>>> + : "=r" (ret), "=r" (rval)
>>> + : "m" (*addr), "i" (-1), "0" (ret));
>>> + *val = rval;
>>> + return ret;
>> This also uses rval uninitialised if a fault occurs.
>>
>> Overall, how about:
>>
>> static inline int xen_safe_write_ulong(unsigned long *addr, unsigned
>> long val)
>> {
>> int ret = 0;
>>
>> asm volatile("1: mov %[val], %[ptr]\n"
>> "2:\n"
>> ".section .fixup, \"ax\"\n"
>> "3: mov %[err], %[ret]\n"
>
> Actually, if you want a shorter fixup path, `sub $1, %[ret]` would also
> do, and drop the [err] constraint.
Thanks for the review.
Will send V2 soon.
Juergen
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