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selftests/nolibc: vfprintf: remove MEMFD_CREATE dependency
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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>
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Zhangjin Wu authored and Willy Tarreau committed Aug 23, 2023
1 parent bbb1454 commit 6861b1a
Showing 1 changed file with 3 additions and 3 deletions.
6 changes: 3 additions & 3 deletions tools/testing/selftests/nolibc/nolibc-test.c
Original file line number Diff line number Diff line change
Expand Up @@ -876,10 +876,10 @@ static int expect_vfprintf(int llen, size_t c, const char *expected, const char
FILE *memfile;
va_list args;

fd = memfd_create("vfprintf", 0);
fd = open("/tmp", O_TMPFILE | O_EXCL | O_RDWR, 0600);
if (fd == -1) {
pad_spc(llen, 64, "[FAIL]\n");
return 1;
pad_spc(llen, 64, "[SKIPPED]\n");
return 0;
}

memfile = fdopen(fd, "w+");
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