selftests/bpf: test_progs: switch to open_memstream

Use open_memstream to override stdout during test execution.
The copy of the original stdout is held in env.stdout and used
to print subtest info and dump failed log.

test_{v,}printf are now simple wrappers around stdout and will be
removed in the next patch.

v5:
* fix -v crash by always setting env.std{in,err} (Alexei Starovoitov)
* drop force_log check from stdio_hijack (Andrii Nakryiko)

v4:
* one field per line for stdout/stderr (Andrii Nakryiko)

v3:
* don't do strlen over log_buf, log_cnt has it already (Andrii Nakryiko)

v2:
* add ifdef __GLIBC__ around open_memstream (maybe pointless since
  we already depend on glibc for argp_parse)
* hijack stderr as well (Andrii Nakryiko)
* don't hijack for every test, do it once (Andrii Nakryiko)
* log_cap -> log_size (Andrii Nakryiko)
* do fseeko in a proper place (Andrii Nakryiko)
* check open_memstream returned value (Andrii Nakryiko)

Cc: Andrii Nakryiko <andriin@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
index afd14962456f..541f9eab5eed 100644
--- a/tools/testing/selftests/bpf/test_progs.h
+++ b/tools/testing/selftests/bpf/test_progs.h
@@ -56,9 +56,10 @@ struct test_env {
 	bool jit_enabled;
 
 	struct prog_test_def *test;
+	FILE *stdout;
+	FILE *stderr;
 	char *log_buf;
 	size_t log_cnt;
-	size_t log_cap;
 
 	int succ_cnt; /* successful tests */
 	int sub_succ_cnt; /* successful sub-tests */