selftests/nolibc: use a pipe to in vfprintf tests

Not all architectures implement lseek(), for example riscv32 only
implements llseek() which is not equivalent to normal lseek().
Remove the need for lseek() by using a pipe instead.

Link: https://lore.kernel.org/r/20241221-nolibc-rv32-v1-3-d9ef6dab7c63@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index 60c50968d3630e4909a5ecb2400770baaf7c2add..3685c13a9a6b8fd5110715b95ff323cdcb29481a 100644 (file)
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -1229,19 +1229,20 @@ int run_stdlib(int min, int max)
 
 static int expect_vfprintf(int llen, int c, const char *expected, const char *fmt, ...)
 {
-       int ret, fd;
+       int ret, pipefd[2];
        ssize_t w, r;
        char buf[100];
        FILE *memfile;
        va_list args;
 
-       fd = open("/tmp", O_TMPFILE | O_EXCL | O_RDWR, 0600);
-       if (fd == -1) {
-               result(llen, SKIPPED);
-               return 0;
+       ret = pipe(pipefd);
+       if (ret == -1) {
+               llen += printf(" pipe() != %s", strerror(errno));
+               result(llen, FAIL);
+               return 1;
        }
 
-       memfile = fdopen(fd, "w+");
+       memfile = fdopen(pipefd[1], "w");
        if (!memfile) {
                result(llen, FAIL);
                return 1;
@@ -1257,13 +1258,10 @@ static int expect_vfprintf(int llen, int c, const char *expected, const char *fm
                return 1;
        }
 
-       fflush(memfile);
-       lseek(fd, 0, SEEK_SET);
-
-       r = read(fd, buf, sizeof(buf) - 1);
-
        fclose(memfile);
 
+       r = read(pipefd[0], buf, sizeof(buf) - 1);
+
        if (r != w) {
                llen += printf(" written(%d) != read(%d)", (int)w, (int)r);
                result(llen, FAIL);