perf test: Enhance the LLVM test: update basic BPF test program

This patch replaces the original toy BPF program with the previously
introduced bpf-script-example.c. Dynamically embeddeding it into
'llvm-src-base.c'.

The newly introduced BPF program attaches a BPF program to
'sys_epoll_pwait()'. perf itself never use that syscall, so further test
can verify their result with it. The program would generate 1 sample in
every 2 calls of epoll_pwait() system call.

Since the resulting BPF object is useful per se for further tests,
test_llvm__fetch_bpf_obj() is introduced for creating BPF objects from
source. The LLVM test was rewritten to use it.

Committer note:

Running it:

[root@zoo wb]# perf test -v LLVM
35: Test LLVM searching and compiling :
--- start ---
test child forked, pid 17740
Kernel build dir is set to /lib/modules/4.3.0-rc1+/build
set env: KBUILD_DIR=/lib/modules/4.3.0-rc1+/build
unset env: KBUILD_OPTS
include option is set to -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/4.9.2/include -I/home/git/linux/arch/x86/include -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated -I/home/git/linux/include -Iinclude -I/home/git/linux/arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I/home/git/linux/include/uapi -Iinclude/generated/uapi -include /home/git/linux/include/linux/kconfig.h
set env: NR_CPUS=4
set env: LINUX_VERSION_CODE=0x40300
set env: CLANG_EXEC=/usr/libexec/icecc/bin/clang
set env: CLANG_OPTIONS=-xc
set env: KERNEL_INC_OPTIONS= -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/4.9.2/include -I/home/git/linux/arch/x86/include -Iarch/x86/include/generated/uapi -Iarch/x86/include/generated -I/home/git/linux/include -Iinclude -I/home/git/linux/arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I/home/git/linux/include/uapi -Iinclude/generated/uapi -include /home/git/linux/include/linux/kconfig.h
set env: WORKING_DIR=/lib/modules/4.3.0-rc1+/build
set env: CLANG_SOURCE=-
llvm compiling command template: echo '/*
* bpf-script-example.c
* Test basic LLVM building
*/
#ifndef LINUX_VERSION_CODE
# error Need LINUX_VERSION_CODE
# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
#endif
#define BPF_ANY 0
#define BPF_MAP_TYPE_ARRAY 2
#define BPF_FUNC_map_lookup_elem 1
#define BPF_FUNC_map_update_elem 2

static void *(*bpf_map_lookup_elem)(void *map, void *key) =
(void *) BPF_FUNC_map_lookup_elem;
static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
(void *) BPF_FUNC_map_update_elem;

struct bpf_map_def {
unsigned int type;
unsigned int key_size;
unsigned int value_size;
unsigned int max_entries;
};

#define SEC(NAME) __attribute__((section(NAME), used))
struct bpf_map_def SEC("maps") flip_table = {
.type = BPF_MAP_TYPE_ARRAY,
.key_size = sizeof(int),
.value_size = sizeof(int),
.max_entries = 1,
};

SEC("func=sys_epoll_pwait")
int bpf_func__sys_epoll_pwait(void *ctx)
{
int ind =0;
int *flag = bpf_map_lookup_elem(&flip_table, &ind);
int new_flag;
if (!flag)
return 0;
/* flip flag and store back */
new_flag = !*flag;
bpf_map_update_elem(&flip_table, &ind, &new_flag, BPF_ANY);
return new_flag;
}
char _license[] SEC("license") = "GPL";
int _version SEC("version") = LINUX_VERSION_CODE;
' | $CLANG_EXEC -D__KERNEL__ -D__NR_CPUS__=$NR_CPUS -DLINUX_VERSION_CODE=$LINUX_VERSION_CODE $CLANG_OPTIONS $KERNEL_INC_OPTIONS -Wno-unused-value -Wno-pointer-sign -working-directory $WORKING_DIR -c "$CLANG_SOURCE" -target bpf -O2 -o -
test child finished with 0
---- end ----
Test LLVM searching and compiling: Ok
[root@zoo wb]#

Signed-off-by: Wang Nan <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Zefan Li <[e-mail]>
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: He Kuang <[e-mail]>
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/Build

···
 perf-y += parse-no-sample-id-all.o
 perf-y += kmod-path.o
 perf-y += thread-map.o
-perf-y += llvm.o
+perf-y += llvm.o llvm-src-base.o
 perf-y += topology.o
+
+$(OUTPUT)tests/llvm-src-base.c: tests/bpf-script-example.c
+	$(call rule_mkdir)
+	$(Q)echo '#include <tests/llvm.h>' > $@
+	$(Q)echo 'const char test_llvm__bpf_base_prog[] =' >> $@
+	$(Q)sed -e 's/"/\\"/g' -e 's/\(.*\)/"\1\\n"/g' $< >> $@
+	$(Q)echo ';' >> $@
 
 ifeq ($(ARCH),$(filter $(ARCH),x86 arm arm64))
 perf-$(CONFIG_DWARF_UNWIND) += dwarf-unwind.o

tools/perf/tests/bpf-script-example.c

···
+/*
+ * bpf-script-example.c
+ * Test basic LLVM building
+ */
 #ifndef LINUX_VERSION_CODE
 # error Need LINUX_VERSION_CODE
 # error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'

tools/perf/tests/llvm.c

···
 #include <bpf/libbpf.h>
 #include <util/llvm-utils.h>
 #include <util/cache.h>
+#include "llvm.h"
 #include "tests.h"
 #include "debug.h"
 
···
 	return perf_default_config(var, val, arg);
 }
 
-/*
- * Randomly give it a "version" section since we don't really load it
- * into kernel
- */
-static const char test_bpf_prog[] =
-	"__attribute__((section(\"do_fork\"), used)) "
-	"int fork(void *ctx) {return 0;} "
-	"char _license[] __attribute__((section(\"license\"), used)) = \"GPL\";"
-	"int _version __attribute__((section(\"version\"), used)) = 0x40100;";
-
 #ifdef HAVE_LIBBPF_SUPPORT
 static int test__bpf_parsing(void *obj_buf, size_t obj_buf_sz)
 {
···
 
 	obj = bpf_object__open_buffer(obj_buf, obj_buf_sz, NULL);
 	if (IS_ERR(obj))
-		return -1;
+		return TEST_FAIL;
 	bpf_object__close(obj);
-	return 0;
+	return TEST_OK;
 }
 #else
 static int test__bpf_parsing(void *obj_buf __maybe_unused,
 			     size_t obj_buf_sz __maybe_unused)
 {
 	pr_debug("Skip bpf parsing\n");
-	return 0;
+	return TEST_OK;
 }
 #endif
 
-int test__llvm(void)
+static struct {
+	const char *source;
+	const char *desc;
+} bpf_source_table[__LLVM_TESTCASE_MAX] = {
+	[LLVM_TESTCASE_BASE] = {
+		.source = test_llvm__bpf_base_prog,
+		.desc = "Basic BPF llvm compiling test",
+	},
+};
+
+
+int
+test_llvm__fetch_bpf_obj(void **p_obj_buf,
+			 size_t *p_obj_buf_sz,
+			 enum test_llvm__testcase index,
+			 bool force)
 {
-	char *tmpl_new, *clang_opt_new;
-	void *obj_buf;
-	size_t obj_buf_sz;
-	int err, old_verbose;
+	const char *source;
+	const char *desc;
+	const char *tmpl_old, *clang_opt_old;
+	char *tmpl_new = NULL, *clang_opt_new = NULL;
+	int err, old_verbose, ret = TEST_FAIL;
+
+	if (index >= __LLVM_TESTCASE_MAX)
+		return TEST_FAIL;
+
+	source = bpf_source_table[index].source;
+	desc = bpf_source_table[index].desc;
 
 	perf_config(perf_config_cb, NULL);
 
···
 	 * Skip this test if user's .perfconfig doesn't set [llvm] section
 	 * and clang is not found in $PATH, and this is not perf test -v
 	 */
-	if (verbose == 0 && !llvm_param.user_set_param && llvm__search_clang()) {
+	if (!force && (verbose == 0 &&
+		       !llvm_param.user_set_param &&
+		       llvm__search_clang())) {
 		pr_debug("No clang and no verbosive, skip this test\n");
 		return TEST_SKIP;
 	}
 
-	old_verbose = verbose;
 	/*
 	 * llvm is verbosity when error. Suppress all error output if
 	 * not 'perf test -v'.
 	 */
+	old_verbose = verbose;
 	if (verbose == 0)
 		verbose = -1;
 
+	*p_obj_buf = NULL;
+	*p_obj_buf_sz = 0;
+
 	if (!llvm_param.clang_bpf_cmd_template)
-		return -1;
+		goto out;
 
 	if (!llvm_param.clang_opt)
 		llvm_param.clang_opt = strdup("");
 
-	err = asprintf(&tmpl_new, "echo '%s' | %s", test_bpf_prog,
-		       llvm_param.clang_bpf_cmd_template);
+	err = asprintf(&tmpl_new, "echo '%s' | %s%s", source,
+		       llvm_param.clang_bpf_cmd_template,
+		       old_verbose ? "" : " 2>/dev/null");
 	if (err < 0)
-		return -1;
+		goto out;
 	err = asprintf(&clang_opt_new, "-xc %s", llvm_param.clang_opt);
 	if (err < 0)
-		return -1;
+		goto out;
 
+	tmpl_old = llvm_param.clang_bpf_cmd_template;
 	llvm_param.clang_bpf_cmd_template = tmpl_new;
+	clang_opt_old = llvm_param.clang_opt;
 	llvm_param.clang_opt = clang_opt_new;
-	err = llvm__compile_bpf("-", &obj_buf, &obj_buf_sz);
+
+	err = llvm__compile_bpf("-", p_obj_buf, p_obj_buf_sz);
+
+	llvm_param.clang_bpf_cmd_template = tmpl_old;
+	llvm_param.clang_opt = clang_opt_old;
 
 	verbose = old_verbose;
 	if (err)
-		return TEST_FAIL;
+		goto out;
 
-	err = test__bpf_parsing(obj_buf, obj_buf_sz);
-	free(obj_buf);
-	return err;
+	ret = TEST_OK;
+out:
+	free(tmpl_new);
+	free(clang_opt_new);
+	if (ret != TEST_OK)
+		pr_debug("Failed to compile test case: '%s'\n", desc);
+	return ret;
+}
+
+int test__llvm(void)
+{
+	enum test_llvm__testcase i;
+
+	for (i = 0; i < __LLVM_TESTCASE_MAX; i++) {
+		int ret;
+		void *obj_buf = NULL;
+		size_t obj_buf_sz = 0;
+
+		ret = test_llvm__fetch_bpf_obj(&obj_buf, &obj_buf_sz,
+					       i, false);
+
+		if (ret == TEST_OK) {
+			ret = test__bpf_parsing(obj_buf, obj_buf_sz);
+			if (ret != TEST_OK)
+				pr_debug("Failed to parse test case '%s'\n",
+					 bpf_source_table[i].desc);
+		}
+		free(obj_buf);
+
+		switch (ret) {
+		case TEST_SKIP:
+			return TEST_SKIP;
+		case TEST_OK:
+			break;
+		default:
+			/*
+			 * Test 0 is the basic LLVM test. If test 0
+			 * fail, the basic LLVM support not functional
+			 * so the whole test should fail. If other test
+			 * case fail, it can be fixed by adjusting
+			 * config so don't report error.
+			 */
+			if (i == 0)
+				return TEST_FAIL;
+			else
+				return TEST_SKIP;
+		}
+	}
+	return TEST_OK;
 }

tools/perf/tests/llvm.h

···
+#ifndef PERF_TEST_LLVM_H
+#define PERF_TEST_LLVM_H
+
+#include <stddef.h> /* for size_t */
+#include <stdbool.h> /* for bool */
+
+extern const char test_llvm__bpf_base_prog[];
+
+enum test_llvm__testcase {
+	LLVM_TESTCASE_BASE,
+	__LLVM_TESTCASE_MAX,
+};
+
+int test_llvm__fetch_bpf_obj(void **p_obj_buf, size_t *p_obj_buf_sz,
+			     enum test_llvm__testcase index, bool force);
+#endif