libtraceevent: bail out of utest if mmap fails

libtraceevent: bail out of utest if mmap fails

[Emil Thorsoe]

Just like, when failing to open the BTF file, failing to
mmap the BTF is testing the test environment, not the code.

This mmap fails with ENODEV on i686 nix build on nixos-unstable.

Just bail out without failing the test, when mmap fails.

Signed-off-by: Emil Thorsoe <ethorsoe@tuxera.com>
---
 utest/traceevent-utest.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/utest/traceevent-utest.c b/utest/traceevent-utest.c
index b62411c..df98fa1 100644
--- a/utest/traceevent-utest.c
+++ b/utest/traceevent-utest.c
@@ -397,8 +397,11 @@ static void test_btf_read(void)
 	CU_TEST(fstat(fd, &st) == 0);
 
 	buf = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
-	CU_TEST(buf != MAP_FAILED);
-
+	if (buf == MAP_FAILED) {
+		printf("[KERNEL DOES NOT ALLOW MMAP OF BTF FILE] ...");
+		close(fd);
+		return;
+	}
 	CU_TEST(tep_load_btf(test_tep, buf, st.st_size) == 0);
 
 	munmap(buf, st.st_size);

Re: libtraceevent: bail out of utest if mmap fails

[Steven Rostedt]

On Tue, 5 May 2026 23:22:44 +0300
Emil Thorsoe <ethorsoe@tuxera.com> wrote:

> Just like, when failing to open the BTF file, failing to
> mmap the BTF is testing the test environment, not the code.
> 
> This mmap fails with ENODEV on i686 nix build on nixos-unstable.
> 
> Just bail out without failing the test, when mmap fails.
> 
> Signed-off-by: Emil Thorsoe <ethorsoe@tuxera.com>
> ---
>  utest/traceevent-utest.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/utest/traceevent-utest.c b/utest/traceevent-utest.c
> index b62411c..df98fa1 100644
> --- a/utest/traceevent-utest.c
> +++ b/utest/traceevent-utest.c
> @@ -397,8 +397,11 @@ static void test_btf_read(void)
>  	CU_TEST(fstat(fd, &st) == 0);
>  
>  	buf = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
> -	CU_TEST(buf != MAP_FAILED);
> -
> +	if (buf == MAP_FAILED) {
> +		printf("[KERNEL DOES NOT ALLOW MMAP OF BTF FILE] ...");

Hmm. Instead of failing, let's instead allocate memory and read it, and
use that instead.

	char *btf_buf = NULL;
	[..]

	if (buf == MAP_FAILED) {
		btf_buf = malloc(st.size);
		/* error check here */
		CU_TEST(read(fd, btf_buf, st.st_size) == st.st_size);
	}
	[..]
	if (btf_buf)
		free(btf_buf);
	else
		munmap(btf, st.st_size); 

or something like that.

Thanks,

-- Steve




> +		close(fd);
> +		return;
> +	}
>  	CU_TEST(tep_load_btf(test_tep, buf, st.st_size) == 0);
>  
>  	munmap(buf, st.st_size);