[PATCH bpf] selftests/bpf: fix test_btf_dump with O=

[Ilya Leoshkevich <iii@linux.ibm.com>]

test_btf_dump fails when run with O=, because it needs to access source
files and assumes they live in ./progs/, which is not the case in this
scenario.

Fix by instructing kselftest to copy btf_dump_test_case_*.c files to the
test directory. Since kselftest does not preserve directory structure,
adjust the test to look in ./progs/ and then in ./.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tools/testing/selftests/bpf/Makefile        | 3 +++
 tools/testing/selftests/bpf/test_btf_dump.c | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index c085964e1d05..69b98d8d3b5b 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -34,6 +34,9 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
 BPF_OBJ_FILES = $(patsubst %.c,%.o, $(notdir $(wildcard progs/*.c)))
 TEST_GEN_FILES = $(BPF_OBJ_FILES)
 
+BTF_C_FILES = $(wildcard progs/btf_dump_test_case_*.c)
+TEST_FILES = $(BTF_C_FILES)
+
 # Also test sub-register code-gen if LLVM has eBPF v3 processor support which
 # contains both ALU32 and JMP32 instructions.
 SUBREG_CODEGEN := $(shell echo "int cal(int a) { return a > 0; }" | \
diff --git a/tools/testing/selftests/bpf/test_btf_dump.c b/tools/testing/selftests/bpf/test_btf_dump.c
index 8f850823d35f..6e75dd3cb14f 100644
--- a/tools/testing/selftests/bpf/test_btf_dump.c
+++ b/tools/testing/selftests/bpf/test_btf_dump.c
@@ -97,6 +97,13 @@ int test_btf_dump_case(int n, struct btf_dump_test_case *test_case)
 	}
 
 	snprintf(test_file, sizeof(test_file), "progs/%s.c", test_case->name);
+	if (access(test_file, R_OK) == -1)
+		/*
+		 * When the test is run with O=, kselftest copies TEST_FILES
+		 * without preserving the directory structure.
+		 */
+		snprintf(test_file, sizeof(test_file), "%s.c",
+			test_case->name);
 	/*
 	 * Diff test output and expected test output, contained between
 	 * START-EXPECTED-OUTPUT and END-EXPECTED-OUTPUT lines in test case.
-- 
2.21.0