tests/boot-serial-test: Fix problem with timeout due to dropped characters

Commit 92b540dac9fc3a5 introduce a counter to handle the timeouts in a
better way. But in case ccnt reaches 512, the current read character is
ignored - and if that character is part of the string that we are looking
for, the test fails to match the string.

Almost all of the tests look for a string within the first 512 bytes of
firmware output, so the problem never triggered there. But the hppa test
that has been added recently looks for a longer string at the very end of
a long output, thus there's a chance that we miss a character there so
that the test fails unexpectedly. Fix it by *not* reading and dropping a
character if the counter reaches 512.

Fixes: 92b540dac9fc3a572c7342edd0b073000f5a6abf
Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-id: 1518761564-9899-1-git-send-email-thuth@redhat.com
[PMM: added initializer for nbd to silence false-positive warning
 from OpenBSD 6 compiler]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/tests/boot-serial-test.c b/tests/boot-serial-test.c
index 511bf314a3689c69646ca54fb2d6a2e55aa516bd..ece25c694f994d3264a6beff70a52b96718d06c7 100644 (file)
--- a/tests/boot-serial-test.c
+++ b/tests/boot-serial-test.c
@@ -111,13 +111,13 @@ static testdef_t tests[] = {
 static void check_guest_output(const testdef_t *test, int fd)
 {
     bool output_ok = false;
-    int i, nbr, pos = 0, ccnt;
+    int i, nbr = 0, pos = 0, ccnt;
     char ch;
 
     /* Poll serial output... Wait at most 60 seconds */
     for (i = 0; i < 6000; ++i) {
         ccnt = 0;
-        while ((nbr = read(fd, &ch, 1)) == 1 && ccnt++ < 512) {
+        while (ccnt++ < 512 && (nbr = read(fd, &ch, 1)) == 1) {
             if (ch == test->expect[pos]) {
                 pos += 1;
                 if (test->expect[pos] == '\0') {