Re: [PATCH] Implement the mlock2 function

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 27/11/2017 14:07, Florian Weimer wrote:
> On 11/27/2017 02:11 PM, Adhemerval Zanella wrote:
>> This is a reasonable approach and I am ok with this patch with the
>> INLINE_SYSCALL_CALL change. I wonder if it is worth to add a similar
>> change to p{read,write}v2 to return ENOSUP in the case of ENOSYS.
> 
> My copy of the manual page says that EINVAL is used there as well.
> 
> Thanks,
> Florian

Indeed manpages [1] states that EINVAL is returned, but our documentation
states otherwise:

manual/llio.texi

1286 @item EOPNOTSUPP
1287 
1288 @c The default sysdeps/posix code will return it for any flags value
1289 @c different than 0.
1290 An unsupported @var{flags} was used.

Also, "tst-preadvwritev" on a 4.13.0-17-generic indeed generates Linux
EOPNOTSUPP (ENOSUP):

[pid  7896] preadv2(3,  <unfinished ...>
[pid  7895] <... rt_sigaction resumed> {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0
[pid  7896] <... preadv2 resumed> [{iov_base=0x7ffca77846d0, iov_len=32}], 1, 0, 0x10 /* RWF_??? */) = -1 EOPNOTSUPP (Operation not supported)
[pid  7895] wait4(7896,  <unfinished ...>
[pid  7896] pwritev2(3, [{iov_base="\0\0\0\0\0\0\0\0\241H\363?\244\177\0\0@Gx\247\374\177\0\0\0\0\0\0\0\0\0\0", iov_len=32}], 1, 0, 0x10 /* RWF_??? */) = -1 EOPNOTSUPP (Operation not supported)

So I think it would be worth to change p{read,write}v2 on GLIBC to 
return EINVAL for invalid flags. I will prepare a patch.

[1] http://man7.org/linux/man-pages/man2/preadv2.2.html