selftests/bpf: Add tests for libbpf-provided externs

Add a set of tests validating libbpf-provided extern variables. One crucial
feature that's tested is dead code elimination together with using invalid BPF
helper. CONFIG_MISSING is not supposed to exist and should always be specified
by libbpf as zero, which allows BPF verifier to correctly do branch pruning
and not fail validation, when invalid BPF helper is called from dead if branch.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191214014710.3449601-5-andriin@fb.com

1 files changed, 195 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/core_extern.c b/tools/testing/selftests/bpf/prog_tests/core_extern.c
new file mode 100644
index 000000000000..30a7972e9012
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/core_extern.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook */
+
+#include <test_progs.h>
+#include <sys/mman.h>
+#include <sys/utsname.h>
+#include <linux/version.h>
+#include "test_core_extern.skel.h"
+
+static uint32_t get_kernel_version(void)
+{
+	uint32_t major, minor, patch;
+	struct utsname info;
+
+	uname(&info);
+	if (sscanf(info.release, "%u.%u.%u", &major, &minor, &patch) != 3)
+		return 0;
+	return KERNEL_VERSION(major, minor, patch);
+}
+
+#define CFG "CONFIG_BPF_SYSCALL=n\n"
+
+static struct test_case {
+	const char *name;
+	const char *cfg;
+	const char *cfg_path;
+	bool fails;
+	struct test_core_extern__data data;
+} test_cases[] = {
+	{ .name = "default search path", .cfg_path = NULL,
+	  .data = { .bpf_syscall = true } },
+	{ .name = "/proc/config.gz", .cfg_path = "/proc/config.gz",
+	  .data = { .bpf_syscall = true } },
+	{ .name = "missing config", .fails = true,
+	  .cfg_path = "/proc/invalid-config.gz" },
+	{
+		.name = "custom values",
+		.cfg = "CONFIG_BPF_SYSCALL=y\n"
+		       "CONFIG_TRISTATE=m\n"
+		       "CONFIG_BOOL=y\n"
+		       "CONFIG_CHAR=100\n"
+		       "CONFIG_USHORT=30000\n"
+		       "CONFIG_INT=123456\n"
+		       "CONFIG_ULONG=0xDEADBEEFC0DE\n"
+		       "CONFIG_STR=\"abracad\"\n"
+		       "CONFIG_MISSING=0",
+		.data = {
+			.bpf_syscall = true,
+			.tristate_val = TRI_MODULE,
+			.bool_val = true,
+			.char_val = 100,
+			.ushort_val = 30000,
+			.int_val = 123456,
+			.ulong_val = 0xDEADBEEFC0DE,
+			.str_val = "abracad",
+		},
+	},
+	/* TRISTATE */
+	{ .name = "tristate (y)", .cfg = CFG"CONFIG_TRISTATE=y\n",
+	  .data = { .tristate_val = TRI_YES } },
+	{ .name = "tristate (n)", .cfg = CFG"CONFIG_TRISTATE=n\n",
+	  .data = { .tristate_val = TRI_NO } },
+	{ .name = "tristate (m)", .cfg = CFG"CONFIG_TRISTATE=m\n",
+	  .data = { .tristate_val = TRI_MODULE } },
+	{ .name = "tristate (int)", .fails = 1, .cfg = CFG"CONFIG_TRISTATE=1" },
+	{ .name = "tristate (bad)", .fails = 1, .cfg = CFG"CONFIG_TRISTATE=M" },
+	/* BOOL */
+	{ .name = "bool (y)", .cfg = CFG"CONFIG_BOOL=y\n",
+	  .data = { .bool_val = true } },
+	{ .name = "bool (n)", .cfg = CFG"CONFIG_BOOL=n\n",
+	  .data = { .bool_val = false } },
+	{ .name = "bool (tristate)", .fails = 1, .cfg = CFG"CONFIG_BOOL=m" },
+	{ .name = "bool (int)", .fails = 1, .cfg = CFG"CONFIG_BOOL=1" },
+	/* CHAR */
+	{ .name = "char (tristate)", .cfg = CFG"CONFIG_CHAR=m\n",
+	  .data = { .char_val = 'm' } },
+	{ .name = "char (bad)", .fails = 1, .cfg = CFG"CONFIG_CHAR=q\n" },
+	{ .name = "char (empty)", .fails = 1, .cfg = CFG"CONFIG_CHAR=\n" },
+	{ .name = "char (str)", .fails = 1, .cfg = CFG"CONFIG_CHAR=\"y\"\n" },
+	/* STRING */
+	{ .name = "str (empty)", .cfg = CFG"CONFIG_STR=\"\"\n",
+	  .data = { .str_val = "\0\0\0\0\0\0\0" } },
+	{ .name = "str (padded)", .cfg = CFG"CONFIG_STR=\"abra\"\n",
+	  .data = { .str_val = "abra\0\0\0" } },
+	{ .name = "str (too long)", .cfg = CFG"CONFIG_STR=\"abracada\"\n",
+	  .data = { .str_val = "abracad" } },
+	{ .name = "str (no value)", .fails = 1, .cfg = CFG"CONFIG_STR=\n" },
+	{ .name = "str (bad value)", .fails = 1, .cfg = CFG"CONFIG_STR=bla\n" },
+	/* INTEGERS */
+	{
+		.name = "integer forms",
+		.cfg = CFG
+		       "CONFIG_CHAR=0xA\n"
+		       "CONFIG_USHORT=0462\n"
+		       "CONFIG_INT=-100\n"
+		       "CONFIG_ULONG=+1000000000000",
+		.data = {
+			.char_val = 0xA,
+			.ushort_val = 0462,
+			.int_val = -100,
+			.ulong_val = 1000000000000,
+		},
+	},
+	{ .name = "int (bad)", .fails = 1, .cfg = CFG"CONFIG_INT=abc" },
+	{ .name = "int (str)", .fails = 1, .cfg = CFG"CONFIG_INT=\"abc\"" },
+	{ .name = "int (empty)", .fails = 1, .cfg = CFG"CONFIG_INT=" },
+	{ .name = "int (mixed)", .fails = 1, .cfg = CFG"CONFIG_INT=123abc" },
+	{ .name = "int (max)", .cfg = CFG"CONFIG_INT=2147483647",
+	  .data = { .int_val = 2147483647 } },
+	{ .name = "int (min)", .cfg = CFG"CONFIG_INT=-2147483648",
+	  .data = { .int_val = -2147483648 } },
+	{ .name = "int (max+1)", .fails = 1, .cfg = CFG"CONFIG_INT=2147483648" },
+	{ .name = "int (min-1)", .fails = 1, .cfg = CFG"CONFIG_INT=-2147483649" },
+	{ .name = "ushort (max)", .cfg = CFG"CONFIG_USHORT=65535",
+	  .data = { .ushort_val = 65535 } },
+	{ .name = "ushort (min)", .cfg = CFG"CONFIG_USHORT=0",
+	  .data = { .ushort_val = 0 } },
+	{ .name = "ushort (max+1)", .fails = 1, .cfg = CFG"CONFIG_USHORT=65536" },
+	{ .name = "ushort (min-1)", .fails = 1, .cfg = CFG"CONFIG_USHORT=-1" },
+	{ .name = "u64 (max)", .cfg = CFG"CONFIG_ULONG=0xffffffffffffffff",
+	  .data = { .ulong_val = 0xffffffffffffffff } },
+	{ .name = "u64 (min)", .cfg = CFG"CONFIG_ULONG=0",
+	  .data = { .ulong_val = 0 } },
+	{ .name = "u64 (max+1)", .fails = 1, .cfg = CFG"CONFIG_ULONG=0x10000000000000000" },
+};
+
+BPF_EMBED_OBJ(core_extern, "test_core_extern.o");
+
+void test_core_extern(void)
+{
+	const uint32_t kern_ver = get_kernel_version();
+	int err, duration = 0, i, j;
+	struct test_core_extern *skel = NULL;
+	uint64_t *got, *exp;
+	int n = sizeof(*skel->data) / sizeof(uint64_t);
+
+	for (i = 0; i < ARRAY_SIZE(test_cases); i++) {
+		char tmp_cfg_path[] = "/tmp/test_core_extern_cfg.XXXXXX";
+		struct test_case *t = &test_cases[i];
+		DECLARE_LIBBPF_OPTS(bpf_object_open_opts, opts,
+			.kconfig_path = t->cfg_path,
+		);
+
+		if (!test__start_subtest(t->name))
+			continue;
+
+		if (t->cfg) {
+			size_t n = strlen(t->cfg) + 1;
+			int fd = mkstemp(tmp_cfg_path);
+			int written;
+
+			if (CHECK(fd < 0, "mkstemp", "errno: %d\n", errno))
+				continue;
+			printf("using '%s' as config file\n", tmp_cfg_path);
+			written = write(fd, t->cfg, n);
+			close(fd);
+			if (CHECK_FAIL(written != n))
+				goto cleanup;
+			opts.kconfig_path = tmp_cfg_path;
+		}
+
+		skel = test_core_extern__open_opts(&core_extern_embed, &opts);
+		if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
+			goto cleanup;
+		err = test_core_extern__load(skel);
+		if (t->fails) {
+			CHECK(!err, "skel_load",
+			      "shouldn't succeed open/load of skeleton\n");
+			goto cleanup;
+		} else if (CHECK(err, "skel_load",
+				 "failed to open/load skeleton\n")) {
+			goto cleanup;
+		}
+		err = test_core_extern__attach(skel);
+		if (CHECK(err, "attach_raw_tp", "failed attach: %d\n", err))
+			goto cleanup;
+
+		usleep(1);
+
+		t->data.kern_ver = kern_ver;
+		t->data.missing_val = 0xDEADC0DE;
+		got = (uint64_t *)skel->data;
+		exp = (uint64_t *)&t->data;
+		for (j = 0; j < n; j++) {
+			CHECK(got[j] != exp[j], "check_res",
+			      "result #%d: expected %lx, but got %lx\n",
+			       j, exp[j], got[j]);
+		}
+cleanup:
+		if (t->cfg)
+			unlink(tmp_cfg_path);
+		test_core_extern__destroy(skel);
+		skel = NULL;
+	}
+}