[PATCH] libtraceevent utest: exit test if mmap fails

[PATCH] libtraceevent utest: exit test if mmap fails

[Sudip Mukherjee]

CU_TEST() continues execution even if the test fails. It just records
that the test has failed and moves on.
So, when libtraceevent is built in a chroot, it can open
/sys/kernel/btf/vmlinux but fails in mmap stage and since CU_TEST()
does not stop so we get a segfault when tep_load_btf() tries to use
the mapped buffer.

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 utest/traceevent-utest.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/utest/traceevent-utest.c b/utest/traceevent-utest.c
index b62411c..547619d 100644
--- a/utest/traceevent-utest.c
+++ b/utest/traceevent-utest.c
@@ -397,6 +397,12 @@ static void test_btf_read(void)
 	CU_TEST(fstat(fd, &st) == 0);
 
 	buf = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	if (buf == MAP_FAILED) {
+		printf("kernel has btf, but it might be a chroot and mmap has failed\n");
+		close(fd);
+		return;
+	}
+
 	CU_TEST(buf != MAP_FAILED);
 
 	CU_TEST(tep_load_btf(test_tep, buf, st.st_size) == 0);
-- 
2.39.5

Re: [PATCH] libtraceevent utest: exit test if mmap fails

[Steven Rostedt]

On Tue, 26 May 2026 19:42:19 +0100
Sudip Mukherjee <sudipm.mukherjee@gmail.com> wrote:

> CU_TEST() continues execution even if the test fails. It just records
> that the test has failed and moves on.
> So, when libtraceevent is built in a chroot, it can open
> /sys/kernel/btf/vmlinux but fails in mmap stage and since CU_TEST()
> does not stop so we get a segfault when tep_load_btf() tries to use
> the mapped buffer.
> 
> Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>

Thanks, but the real fix is here and I'm applying that one:

  https://lore.kernel.org/all/d6e07cd6-cb78-4119-a048-920ca58b4830@tuxera.com/

-- Steve