Re: [PATCH v4 bpf-next 2/2] selftests/bpf: add dump type data tests to btf dump tests
From: Andrii Nakryiko <hidden>
Date: 2021-06-05 02:51:36
Also in:
bpf, linux-kselftest, lkml
On Tue, Jun 1, 2021 at 7:37 AM Alan Maguire [off-list ref] wrote:
quoted hunk ↗ jump to hunk
Test various type data dumping operations by comparing expected format with the dumped string; an snprintf-style printf function is used to record the string dumped. Also verify overflow handling where the data passed does not cover the full size of a type, such as would occur if a tracer has a portion of the 8k "struct task_struct". Signed-off-by: Alan Maguire <redacted> --- tools/testing/selftests/bpf/prog_tests/btf_dump.c | 638 ++++++++++++++++++++++ 1 file changed, 638 insertions(+)diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dump.c b/tools/testing/selftests/bpf/prog_tests/btf_dump.c index 1b90e68..b78c308 100644 --- a/tools/testing/selftests/bpf/prog_tests/btf_dump.c +++ b/tools/testing/selftests/bpf/prog_tests/btf_dump.c@@ -232,6 +232,642 @@ void test_btf_dump_incremental(void) btf__free(btf); } +#define STRSIZE 4096 + +void btf_dump_snprintf(void *ctx, const char *fmt, va_list args)
static
+{
+ char *s = ctx, new[STRSIZE];
+
+ vsnprintf(new, STRSIZE, fmt, args);
+ strncat(s, new, STRSIZE);
+}
+
+/* skip "enum "/"struct " prefixes */
+#define SKIP_PREFIX(_typestr, _prefix) \
+ do { \
+ if (strncmp(_typestr, _prefix, strlen(_prefix)) == 0) \
+ _typestr += strlen(_prefix) + 1; \
+ } while (0)
+
+int btf_dump_data(struct btf *btf, struct btf_dump *d,
+ char *name, __u64 flags, void *ptr,
+ size_t ptrsize, char *str, const char *expectedval)static naming nit: expected_val is much easier to read than expected_val, same for ptrsize vs ptr_size; I'm also totally fine with shorter names using common abbreviations (exp_val, ptr_sz, etc).
+{
+ DECLARE_LIBBPF_OPTS(btf_dump_type_data_opts, opts);
+ int ret = 0, cmp;
+ size_t typesize;
+ __s32 type_id;
+
+ if (flags & BTF_F_COMPACT)
+ opts.compact = true;
+ if (flags & BTF_F_NONAME)
+ opts.skip_names = true;
+ if (flags & BTF_F_ZERO)
+ opts.emit_zeroes = true;
nothing wrong with this, but just as an FYI, you could have combined
that with DECLARE_LIBBPF_OPTS above:
DECLARE_LIBBPF_OPTS(btf_dump_type_data_opts, opts,
.compact = flags & BTF_F_COMPACT,
.skip_names = flags & BTF_F_NONAME,
.emit_zeroes = flags & BTF_F_ZERO,
);
+ SKIP_PREFIX(name, "enum");
+ SKIP_PREFIX(name, "struct");
+ SKIP_PREFIX(name, "union");
+ type_id = btf__find_by_name(btf, name);
+ if (CHECK(type_id <= 0, "find type id",
+ "no '%s' in BTF: %d\n", name, type_id)) {
see all the variations of ASSERT_XXX() macros, they are shorter, have
more natural checks and they output argument values automatically if
condition doesn't hold. So this one would be
if (!ASSERT_GT(type_id, 0, "type_id")) {
err = -ENOENT;
goto err;
}
+ ret = -ENOENT;
+ goto err;
+ }
+ typesize = btf__resolve_size(btf, type_id);
+ str[0] = '\0';
+ ret = btf_dump__dump_type_data(d, type_id, ptr, ptrsize, &opts);
+ if (typesize <= ptrsize) {
+ if (CHECK(ret != typesize, "btf_dump__dump_type_data",
+ "failed/unexpected typesize: %d\n", ret))
+ goto err;
+ } else {
+ if (CHECK(ret != -E2BIG, "btf_dump__dump_type_data -E2BIG",
+ "failed to return -E2BIG: %d\n", ret))
+ goto err;
+ ret = 0;
+ }
+
+ cmp = strcmp(str, expectedval);
+ if (CHECK(cmp, "ensure expected/actual match",
+ "'%s' does not match expected '%s': %d\n",
+ str, expectedval, cmp))
+ ret = -EFAULT;here ASSERT_STREQ() is useful
+err:
+ if (ret < 0)
+ btf_dump__free(d);
+ return ret;
+}
+
+#define TEST_BTF_DUMP_DATA(_b, _d, _str, _type, _flags, _expected, ...) \
+ do { \
+ char __ptrtype[64] = #_type; \
+ char *_ptrtype = (char *)__ptrtype; \
+ _type _ptrdata = __VA_ARGS__; \
+ void *_ptr = &_ptrdata; \
+ int _err; \
+ \
+ _err = btf_dump_data(_b, _d, _ptrtype, _flags, _ptr, \
+ sizeof(_type), _str, _expected); \
+ if (_err < 0) \
+ return _err; \
+ } while (0)
+
+/* Use where expected data string matches its stringified declaration */
+#define TEST_BTF_DUMP_DATA_C(_b, _d, _str, _type, _flags, ...) \
+ TEST_BTF_DUMP_DATA(_b, _d, _str, _type, _flags, \
+ "(" #_type ")" #__VA_ARGS__, __VA_ARGS__)
+
+/* overflow test; pass typesize < expected type size, ensure E2BIG returned */
+#define TEST_BTF_DUMP_DATA_OVER(_b, _d, _str, _type, _typesize, _expected, ...)\
+ do { \
+ char __ptrtype[64] = #_type; \
+ char *_ptrtype = (char *)__ptrtype; \
+ _type _ptrdata = __VA_ARGS__; \
+ void *_ptr = &_ptrdata; \
+ int _err; \
+ \
+ _err = btf_dump_data(_b, _d, _ptrtype, 0, _ptr, \
+ _typesize, _str, _expected); \
+ if (_err < 0) \
+ return _err; \
+ } while (0)
+
+#define TEST_BTF_DUMP_VAR(_b, _d, _str, _var, _type, _flags, _expected, ...) \
+ do { \
+ _type _ptrdata = __VA_ARGS__; \
+ void *_ptr = &_ptrdata; \
+ int _err; \
+ \
+ _err = btf_dump_data(_b, _d, _var, _flags, _ptr, \
+ sizeof(_type), _str, _expected); \
+ if (_err < 0) \
+ return _err; \
+ } while (0)
+
+int test_btf_dump_int_data(struct btf *btf, struct btf_dump *d, char *str)static here and in a bunch of places below
+{
+ /* simple int */
+ TEST_BTF_DUMP_DATA_C(btf, d, str, int, BTF_F_COMPACT, 1234);
+ TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT | BTF_F_NONAME,
+ "1234", 1234);
+ TEST_BTF_DUMP_DATA(btf, d, str, int, 0, "(int)1234\n", 1234);do you think it's a good idea to append \n? it seems so simple for user to do that, if necessary; on the other hand, if user doesn't want it, they would need to do strlen() and overwriting last character, which seems like a hassle
+
+ /* zero value should be printed at toplevel */
+ TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT, "(int)0", 0);
+ TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT | BTF_F_NONAME,
+ "0", 0);
+ TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT | BTF_F_ZERO,
+ "(int)0", 0);
+ TEST_BTF_DUMP_DATA(btf, d, str, int,
+ BTF_F_COMPACT | BTF_F_NONAME | BTF_F_ZERO,
+ "0", 0);
+ TEST_BTF_DUMP_DATA_C(btf, d, str, int, BTF_F_COMPACT, -4567);
+ TEST_BTF_DUMP_DATA(btf, d, str, int, BTF_F_COMPACT | BTF_F_NONAME,
+ "-4567", -4567);
+ TEST_BTF_DUMP_DATA(btf, d, str, int, 0, "(int)-4567\n", -4567);
+
+ TEST_BTF_DUMP_DATA_OVER(btf, d, str, int, sizeof(int)-1, "", 1);
+
+ return 0;
+}
+
+/* since the kernel does not likely have any float types in its BTF, we
+ * will need to add some of various sizes.
+ */
+#define TEST_ADD_FLOAT(_btf, _name, _sz) \
+ do { \
+ int _err; \
+ \
+ _err = btf__add_float(_btf, _name, _sz); \
+ if (CHECK(_err < 0, "btf__add_float", \
+ "could not add float of size %d: %d", \
+ _sz, _err)) \
+ return _err; \
+ } while (0)
+
+#define TEST_DUMP_FLOAT(_b, _d, _str, _type, _flags, _data, _sz, \
+ _expectedval) \
+ do { \
+ int _err; \
+ \
+ _err = btf_dump_data(_b, _d, _type, _flags, \
+ _data, _sz, _str, _expectedval); \
+ if (CHECK(_err < 0, "btf_dump float", \
+ "could not dump float data: %d\n", _err)) \
+ return _err; \
+ } while (0)
+
+int test_btf_dump_float_data(struct btf *btf, struct btf_dump *d, char *str)
+{
+ float t1 = 1.234567;
+ float t2 = -1.234567;
+ float t3 = 0.0;
+ double t4 = 5.678912;
+ double t5 = -5.678912;
+ double t6 = 0.0;
+ long double t7 = 9.876543;
+ long double t8 = -9.876543;
+ long double t9 = 0.0;
+
+ TEST_ADD_FLOAT(btf, "test_float", 4);I don't get this love for macros. It makes debugging experience much harder. It makes following the code harder. It doesn't save much typing at all. TEST_BTF_DUMP_DATA at least adds some convenience, but TEST_ADD_FLOAT and TEST_DUMP_FLOAT are completely useless, see below.
+ TEST_DUMP_FLOAT(btf, d, str, "test_float", 0, &t1, 4, + "(test_float)1.234567\n"); + TEST_DUMP_FLOAT(btf, d, str, "test_float", 0, &t2, 4, + "(test_float)-1.234567\n"); + TEST_DUMP_FLOAT(btf, d, str, "test_float", 0, &t3, 4, + "(test_float)0.000000\n");
ASSERT_OK(btf_dump_data(btf, d, "test_float", 0, &t1, 4, str, "(test_float)1.234567\n")); ASSERT_OK(btf_dump_data(btf, d, "test_float", 0, &t2, 4, str, "(test_float)-1.234567\n")); ASSERT_OK(btf_dump_data(btf, d, "test_float", 0, &t3, 4, str, "(test_float)0.000000\n")); It even saved some lines of code.
+ + TEST_ADD_FLOAT(btf, "test_double", 8); + TEST_DUMP_FLOAT(btf, d, str, "test_double", 0, &t4, 8, + "(test_double)5.678912\n"); + TEST_DUMP_FLOAT(btf, d, str, "test_double", 0, &t5, 8, + "(test_double)-5.678912\n"); + TEST_DUMP_FLOAT(btf, d, str, "test_double", 0, &t6, 8, + "(test_double)0.000000\n"); +
[...]
+ TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum,
+ BTF_F_COMPACT | BTF_F_NONAME,
+ "{}",
+ { .name_off = 0, .val = 0,});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum, 0,
+ "(struct btf_enum){\n}\n",
+ { .name_off = 0, .val = 0,});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum,
+ BTF_F_COMPACT | BTF_F_ZERO,
+ "(struct btf_enum){.name_off = (__u32)0,.val = (__s32)0,}",
+ { .name_off = 0, .val = 0,});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct btf_enum,
+ BTF_F_ZERO,
+ "(struct btf_enum){\n\t.name_off = (__u32)0,\n\t.val = (__s32)0,\n}\n",
while for primitive types and enums above are expected strings are
pretty easy to follow, for structs it starts to break apart. For
instance, I find
"(struct btf_enum){\
.name_off = (__u32)0,\
.val = (__s32)0,\
}\
",
much more legible (I can mentally ignore \ at the end quite easily).
This single line \n\t stuff just gets messier for bigger structs.
+ { .name_off = 0, .val = 0,});
+
+ /* struct with pointers */
+ TEST_BTF_DUMP_DATA(btf, d, str, struct list_head, BTF_F_COMPACT,
+ "(struct list_head){.next = (struct list_head *)0x1,}",
+ { .next = (struct list_head *)1 });
+ TEST_BTF_DUMP_DATA(btf, d, str, struct list_head, 0,
+ "(struct list_head){\n\t.next = (struct list_head *)0x1,\n}\n",
+ { .next = (struct list_head *)1 });
+ /* NULL pointer should not be displayed */
+ TEST_BTF_DUMP_DATA(btf, d, str, struct list_head, BTF_F_COMPACT,
+ "(struct list_head){}",
+ { .next = (struct list_head *)0 });
+ TEST_BTF_DUMP_DATA(btf, d, str, struct list_head, 0,
+ "(struct list_head){\n}\n",
+ { .next = (struct list_head *)0 });
+
+ /* struct with function pointers */
+ type_id = btf__find_by_name(btf, "file_operations");
+ if (CHECK(type_id <= 0, "find type id",
+ "no 'struct file_operations' in BTF: %d\n", type_id))
+ return -ENOENT;
+ typesize = btf__resolve_size(btf, type_id);
+ str[0] = '\0';
+
+ ret = btf_dump__dump_type_data(d, type_id, fops, typesize, &opts);
+ if (CHECK(ret != typesize,
+ "dump file_operations is successful",
+ "unexpected return value dumping file_operations '%s': %d\n",
+ str, ret))
+ return -EINVAL;
+
+ cmpstr = "(struct file_operations){\n\t.owner = (struct module *)0xffffffffffffffff,\n\t.llseek = (loff_t(*)(struct file *, loff_t, int))0xffffffffffffffff,";
+ cmp = strncmp(str, cmpstr, strlen(cmpstr));
+ if (CHECK(cmp != 0, "check file_operations dump",
+ "file_operations '%s' did not match expected\n",cmpstr logging is missing here. But I also think it's not the first time there was a need to validate only portiong of string equality, so I wonder if we should just add ASSERT_STRNEQ(actual, expected, len) variant, it should be trivial to add.
+ str))
+ return -EINVAL;
+
+ /* struct with char array */
+ TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info, BTF_F_COMPACT,
+ "(struct bpf_prog_info){.name = (char[])['f','o','o',],}",
+ { .name = "foo",});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info,
+ BTF_F_COMPACT | BTF_F_NONAME,
+ "{['f','o','o',],}",
+ {.name = "foo",});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info, 0,
+ "(struct bpf_prog_info){\n\t.name = (char[])[\n\t\t'f',\n\t\t\'o',\n\t\t'o',\n\t],\n}\n",
+ {.name = "foo",});
+ /* leading null char means do not display string */
+ TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info, BTF_F_COMPACT,
+ "(struct bpf_prog_info){}",
+ {.name = {'\0', 'f', 'o', 'o'}});
+ /* handle non-printable characters */
+ TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_prog_info, BTF_F_COMPACT,
+ "(struct bpf_prog_info){.name = (char[])[1,2,3,],}",
+ { .name = {1, 2, 3, 0}});
+
+ /* struct with non-char array */
+ TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff, BTF_F_COMPACT,
+ "(struct __sk_buff){.cb = (__u32[])[1,2,3,4,5,],}",
+ { .cb = {1, 2, 3, 4, 5,},});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff,
+ BTF_F_COMPACT | BTF_F_NONAME,
+ "{[1,2,3,4,5,],}",
+ { .cb = { 1, 2, 3, 4, 5},});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff, 0,
+ "(struct __sk_buff){\n\t.cb = (__u32[])[\n\t\t1,\n\t\t2,\n\t\t3,\n\t\t4,\n\t\t5,\n\t],\n}\n",As you can see above in my example patch, emit_type_decl would emit this array type as __u32[5]. I think drgn that was used as an inspiration for this format also does that. So I think it's good to stick to __u32[5] here.
+ { .cb = { 1, 2, 3, 4, 5},});
+ /* For non-char, arrays, show non-zero values only */
+ TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff, BTF_F_COMPACT,
+ "(struct __sk_buff){.cb = (__u32[])[0,0,1,0,0,],}",
+ { .cb = { 0, 0, 1, 0, 0},});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct __sk_buff, 0,
+ "(struct __sk_buff){\n\t.cb = (__u32[])[\n\t\t0,\n\t\t0,\n\t\t1,\n\t\t0,\n\t\t0,\n\t],\n}\n",
+ { .cb = { 0, 0, 1, 0, 0},});
+
+ /* struct with bitfields */
+ TEST_BTF_DUMP_DATA_C(btf, d, str, struct bpf_insn, BTF_F_COMPACT,
+ {.code = (__u8)1,.dst_reg = (__u8)0x2,.src_reg = (__u8)0x3,.off = (__s16)4,.imm = (__s32)5,});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_insn,
+ BTF_F_COMPACT | BTF_F_NONAME,
+ "{1,0x2,0x3,4,5,}",
+ { .code = 1, .dst_reg = 0x2, .src_reg = 0x3, .off = 4,
+ .imm = 5,});
+ TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_insn, 0,
+ "(struct bpf_insn){\n\t.code = (__u8)1,\n\t.dst_reg = (__u8)0x2,\n\t.src_reg = (__u8)0x3,\n\t.off = (__s16)4,\n\t.imm = (__s32)5,\n}\n",
+ {.code = 1, .dst_reg = 2, .src_reg = 3, .off = 4, .imm = 5});
+
+ /* zeroed bitfields should not be displayed */
+ TEST_BTF_DUMP_DATA(btf, d, str, struct bpf_insn, BTF_F_COMPACT,
+ "(struct bpf_insn){.dst_reg = (__u8)0x1,}",
+ { .code = 0, .dst_reg = 1});
+
+ /* struct with enum bitfield */
+ type_id = btf__find_by_name(btf, "nft_cmp_expr");This nft_cmp_expr breaks our CI ([0]) because we don't build kernels with CONFIG_NF_TABLES=y. Can you please find some other struct that would be in a core kernel configuration? If not, you can just do the same trick as with floats and generate your own struct with bitfields. [0] https://travis-ci.com/github/kernel-patches/bpf/builds/227876698
+ if (CHECK(type_id <= 0, "find nft_cmp_expr", + "no 'struct nft_cmp_expr' in BTF: %d\n", type_id)) + return -ENOENT; + typesize = btf__resolve_size(btf, type_id); + str[0] = '\0'; +
[...]
+void test_btf_dump_data(void)
+{
+ struct btf *btf = libbpf_find_kernel_btf();
+ char str[STRSIZE];
+ struct btf_dump_opts opts = { .ctx = str };
+ struct btf_dump *d;
+
+ if (CHECK(!btf, "get kernel BTF", "no kernel BTF found"))
+ return;
+
+ d = btf_dump__new(btf, NULL, &opts, btf_dump_snprintf);
+
+ if (CHECK(!d, "new dump", "could not create BTF dump"))
+ return;
+
+ /* Verify type display for various types. */
+ if (test_btf_dump_int_data(btf, d, str))
+ return;
+ if (test_btf_dump_float_data(btf, d, str))
+ return;
+ if (test_btf_dump_char_data(btf, d, str))
+ return;
+ if (test_btf_dump_typedef_data(btf, d, str))
+ return;
+ if (test_btf_dump_enum_data(btf, d, str))
+ return;
+ if (test_btf_dump_struct_data(btf, d, str))
+ return;
+ if (test_btf_dump_var_data(btf, d, str))
+ return;it would be more convenient for each of those to be a subtest, and there is no need to exit early if one of them fails, so don't return early.
quoted hunk ↗ jump to hunk
+ btf_dump__free(d); + btf__free(btf); + + /* verify datasec display */ + if (test_btf_dump_datasec_data(str)) + return; + +} + void test_btf_dump() { int i;@@ -245,4 +881,6 @@ void test_btf_dump() { } if (test__start_subtest("btf_dump: incremental")) test_btf_dump_incremental(); + if (test__start_subtest("btf_dump: data"))
so instead of testing subtest name here, just do it for every test_btf_dump_*_data above
+ test_btf_dump_data(); } -- 1.8.3.1