selftests/bpf: fix test_bpffs

Currently this tests tries to umount /sys/kernel/debug (TDIR) but the
system it is running on may have mounts below.

For example, danobi/vmtest [0] VMs have
mount -t tracefs tracefs /sys/kernel/debug/tracing
as part of their init.

This change instead creates a "random" directory under /tmp and uses this
as TDIR.
If the directory already exists, ignore the error and keep moving on.

Test:

Originally:

$ vmtest -k $KERNEL_REPO/arch/x86_64/boot/bzImage "./test_progs -vv -a test_bpffs"
=> bzImage
===> Booting
===> Setting up VM
===> Running command
[ 2.138818] bpf_testmod: loading out-of-tree module taints kernel.
[ 2.140913] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
bpf_testmod.ko is already unloaded.
Loading bpf_testmod.ko...
Successfully loaded bpf_testmod.ko.
test_test_bpffs:PASS:clone 0 nsec
fn:PASS:unshare 0 nsec
fn:PASS:mount / 0 nsec
fn:FAIL:umount /sys/kernel/debug unexpected error: -1 (errno 16)
bpf_testmod.ko is already unloaded.
Loading bpf_testmod.ko...
Successfully loaded bpf_testmod.ko.
test_test_bpffs:PASS:clone 0 nsec
test_test_bpffs:PASS:waitpid 0 nsec
test_test_bpffs:FAIL:bpffs test failed 255#282 test_bpffs:FAIL
Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED
Successfully unloaded bpf_testmod.ko.
Command failed with exit code: 1

After this change:

$ vmtest -k $(make image_name) 'cd tools/testing/selftests/bpf && ./test_progs -vv -a test_bpffs'
=> bzImage
===> Booting
===> Setting up VM
===> Running command
[ 2.295696] bpf_testmod: loading out-of-tree module taints kernel.
[ 2.296468] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
bpf_testmod.ko is already unloaded.
Loading bpf_testmod.ko...
Successfully loaded bpf_testmod.ko.
test_test_bpffs:PASS:clone 0 nsec
fn:PASS:unshare 0 nsec
fn:PASS:mount / 0 nsec
fn:PASS:mount tmpfs 0 nsec
fn:PASS:mkdir /tmp/test_bpffs_testdir/fs1 0 nsec
fn:PASS:mkdir /tmp/test_bpffs_testdir/fs2 0 nsec
fn:PASS:mount bpffs /tmp/test_bpffs_testdir/fs1 0 nsec
fn:PASS:mount bpffs /tmp/test_bpffs_testdir/fs2 0 nsec
fn:PASS:reading /tmp/test_bpffs_testdir/fs1/maps.debug 0 nsec
fn:PASS:reading /tmp/test_bpffs_testdir/fs2/progs.debug 0 nsec
fn:PASS:creating /tmp/test_bpffs_testdir/fs1/a 0 nsec
fn:PASS:creating /tmp/test_bpffs_testdir/fs1/a/1 0 nsec
fn:PASS:creating /tmp/test_bpffs_testdir/fs1/b 0 nsec
fn:PASS:create_map(ARRAY) 0 nsec
fn:PASS:pin map 0 nsec
fn:PASS:stat(/tmp/test_bpffs_testdir/fs1/a) 0 nsec
fn:PASS:renameat2(/fs1/a, /fs1/b, RENAME_EXCHANGE) 0 nsec
fn:PASS:stat(/tmp/test_bpffs_testdir/fs1/b) 0 nsec
fn:PASS:b should have a's inode 0 nsec
fn:PASS:access(/tmp/test_bpffs_testdir/fs1/b/1) 0 nsec
fn:PASS:stat(/tmp/test_bpffs_testdir/fs1/map) 0 nsec
fn:PASS:renameat2(/fs1/c, /fs1/b, RENAME_EXCHANGE) 0 nsec
fn:PASS:stat(/tmp/test_bpffs_testdir/fs1/b) 0 nsec
fn:PASS:b should have c's inode 0 nsec
fn:PASS:access(/tmp/test_bpffs_testdir/fs1/c/1) 0 nsec
fn:PASS:renameat2(RENAME_NOREPLACE) 0 nsec
fn:PASS:access(/tmp/test_bpffs_testdir/fs1/b) 0 nsec
bpf_testmod.ko is already unloaded.
Loading bpf_testmod.ko...
Successfully loaded bpf_testmod.ko.
test_test_bpffs:PASS:clone 0 nsec
test_test_bpffs:PASS:waitpid 0 nsec
test_test_bpffs:PASS:bpffs test 0 nsec
#282 test_bpffs:OK
Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED
Successfully unloaded bpf_testmod.ko.

[0] https://github.com/danobi/vmtest

This is a follow-up of https://lore.kernel.org/bpf/20231024201852.1512720-1-chantr4@gmail.com/T/

v1 -> v2:
- use a TDIR name that is related to test
- use C-style comments

Signed-off-by: Manu Bretelle <chantr4@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20231031223606.2927976-1-chantr4@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

selftests/bpf: Prevent out-of-bounds stack access in test_bpffs

Buf can be not zero-terminated leading to strstr() to access data beyond
the intended buf[] array. Fix by forcing zero termination.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-12-andrii@kernel.org

selftests/bpf: Migrate selftests to bpf_map_create()

Conversion is straightforward for most cases. In few cases tests are
using mutable map_flags and attribute structs, but bpf_map_create_opts
can be used in the similar fashion, so there were no problems. Just lots
of repetitive conversions.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124193233.3115996-5-andrii@kernel.org

selftests/bpf: Test RENAME_EXCHANGE and RENAME_NOREPLACE on bpffs

Add tests to exercise the behaviour of RENAME_EXCHANGE and RENAME_NOREPLACE
on bpffs. The former checks that after an exchange the inode of two
directories has changed. The latter checks that the source still exists
after a failed rename. Generally, having support for renameat2(RENAME_EXCHANGE)
in bpffs fixes atomic upgrades of our sk_lookup control plane.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211028094724.59043-5-lmb@cloudflare.com

selftests/bpf: Convert test_bpffs to ASSERT macros

Remove usage of deprecated CHECK macros.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211028094724.59043-4-lmb@cloudflare.com

selftests/bpf: Add bpffs preload test.

Add a test that mounts two bpffs instances and checks progs.debug
and maps.debug for sanity data.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200819042759.51280-5-alexei.starovoitov@gmail.com