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.
~Andrew
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