[LTP] [PATCH 4/5] API: Add tst_clone

[Richard Palethorpe]

Hello,

Cyril Hrubis <chrubis@suse.cz> writes:

> Hi!
>> +	int flags;
>> +	pid_t pid = -1;
>> +
>> +	tst_flush();
>> +
>> +	errno = ENOSYS;
>> +	if (__NR_clone3 != __LTP__NR_INVALID_SYSCALL)
>> +		pid = syscall(__NR_clone3, &args, sizeof(args));
>> +
>> +	if (pid == -1 && errno != ENOSYS)
>> +		return -1;
>
> As far as I can tell when kernel is too old we would get EINVAL because
> the syscall number is not allocated. ENOSYS happens mostly when syscall
> number is allocated and kernel does not implement the functionality,
> e.g. it's disabled in .config.
>
> I wonder if it's even menaningful to handle ENOSYS here, I doubt that
> clone3() can be disabled, or do I miss something?

AFAICT it should return ENOSYS if the syscall number is greater than the
current maximum. This is certainly true for riscv and also apears to be
true for arm64 and x86. It is also written in a kernel book I have from
2010 :-p

-- 
Thank you,
Richard.