selftests/bpf: Fix for veristat file/prog filters processing

At the moment veristat filtering behaves unexpectedly for the
following filter expression:

  -f !file/prog

The expression rejects all programs with name 'prog', and all programs
in a file with name 'file'. This commit fixes the expression to
exclude only a program 'prog' from a file 'file'. Additionally,
the commit makes empty filters like '-f ""' or '-f "/"' and error.
Here is the filtering behaviour compared old versus new:

| filter   | file | prog | old verdict | new verdict |
|----------+------+------+-------------+-------------|
| !foo     | foo  | bar  | skipped     | skipped     |
| !foo     | bar  | foo  | skipped     | skipped     |
| !foo     | bar  | bar  | processed   | processed   |
| !foo/bar | foo  | bar  | skipped     | skipped     |
| !foo/bar | foo  | buz  | skipped     | processed   | (!)
| !foo/bar | bar  | bar  | skipped     | processed   | (!)
| !foo/    | foo  | bar  | skipped     | skipped     |
| !foo/    | bar  | bar  | processed   | processed   |
| !/bar    | foo  | bar  | skipped     | skipped     |
| !/bar    | foo  | foo  | processed   | processed   |
| !/       | foo  | bar  | processed   | error       | (!)
| !        | foo  | bar  | processed   | error       | (!)
|----------+------+------+-------------+-------------|
| foo      | foo  | bar  | processed   | processed   |
| foo      | bar  | foo  | processed   | processed   |
| foo      | bar  | bar  | skipped     | skipped     |
| foo/bar  | foo  | bar  | processed   | processed   |
| foo/bar  | foo  | buz  | skipped     | skipped     |
| foo/bar  | bar  | bar  | skipped     | skipped     |
| foo/     | foo  | bar  | processed   | processed   |
| foo/     | bar  | bar  | skipped     | skipped     |
| /bar     | foo  | bar  | processed   | processed   |
| /bar     | foo  | foo  | skipped     | skipped     |
| /        | foo  | bar  | processed   | error       | (!)
|          | foo  | bar  | skipped     | error       | (!)

Fixes: 10b1b3f3e56a ("selftests/bpf: consolidate and improve file/prog filtering in veristat")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260811-veristat-filter-fix-v2-1-6c234c4cd6ef@gmail.com

0 files changed, 0 insertions, 0 deletions