[PATCH AUTOSEL 5.10 058/176] samples: bpf: Fix tracex7 error raised on the missing argument

From: Sasha Levin
Date: Thu Sep 09 2021 - 08:39:28 EST

From: Juhee Kang <claudiajkang@xxxxxxxxx>

[ Upstream commit 7d07006f05922b95518be403f08ef8437b67aa32 ]

The current behavior of 'tracex7' doesn't consist with other bpf samples
tracex{1..6}. Other samples do not require any argument to run with, but
tracex7 should be run with btrfs device argument. (it should be executed
with test_override_return.sh)

Currently, tracex7 doesn't have any description about how to run this
program and raises an unexpected error. And this result might be
confusing since users might not have a hunch about how to run this

// Current behavior
# ./tracex7
sh: 1: Syntax error: word unexpected (expecting ")")
// Fixed behavior
# ./tracex7
ERROR: Run with the btrfs device argument!

In order to fix this error, this commit adds logic to report a message
and exit when running this program with a missing argument.

Additionally in test_override_return.sh, there is a problem with
multiple directory(tmpmnt) creation. So in this commit adds a line with
removing the directory with every execution.

Signed-off-by: Juhee Kang <claudiajkang@xxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
Link: https://lore.kernel.org/bpf/20210727041056.23455-1-claudiajkang@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
samples/bpf/test_override_return.sh | 1 +
samples/bpf/tracex7_user.c | 5 +++++
2 files changed, 6 insertions(+)

diff --git a/samples/bpf/test_override_return.sh b/samples/bpf/test_override_return.sh
index e68b9ee6814b..35db26f736b9 100755
--- a/samples/bpf/test_override_return.sh
+++ b/samples/bpf/test_override_return.sh
@@ -1,5 +1,6 @@

+rm -r tmpmnt
rm -f testfile.img
dd if=/dev/zero of=testfile.img bs=1M seek=1000 count=1
DEVICE=$(losetup --show -f testfile.img)
diff --git a/samples/bpf/tracex7_user.c b/samples/bpf/tracex7_user.c
index fdcd6580dd73..8be7ce18d3ba 100644
--- a/samples/bpf/tracex7_user.c
+++ b/samples/bpf/tracex7_user.c
@@ -14,6 +14,11 @@ int main(int argc, char **argv)
int ret = 0;
FILE *f;

+ if (!argv[1]) {
+ fprintf(stderr, "ERROR: Run with the btrfs device argument!\n");
+ return 0;
+ }
snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
obj = bpf_object__open_file(filename, NULL);
if (libbpf_get_error(obj)) {