selftests/nolibc: vfprintf: remove MEMFD_CREATE dependency
The vfprintf test case require to open a temporary file to write, the
old memfd_create() method is perfect but has strong dependency on
MEMFD_CREATE and also TMPFS or HUGETLBFS (see fs/Kconfig):
config MEMFD_CREATE
def_bool TMPFS || HUGETLBFS
And from v6.2, MFD_NOEXEC_SEAL must be passed for the non-executable
memfd, otherwise, The kernel warning will be output to the test result
like this:
Running test 'vfprintf'
0 emptymemfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=1 'init'
"" = "" [OK]
To avoid such warning and also to remove the MEMFD_CREATE dependency,
let's open a file from tmpfs directly.
The /tmp directory is used to detect the existing of tmpfs, if not
there, skip instead of fail.
And further, for pid == 1, the initramfs is loaded as ramfs, which can
be used as tmpfs, so, it is able to further remove TMPFS dependency too.
Suggested-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/lkml/9ad51430-b7c0-47dc-80af-20c86539498d@t-8ch.de
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>