With clang build kernel (adding LLVM=1 to kernel and selftests/bpf build
command line), I hit the following test failure:
$ ./test_progs -t btf_dump
...
btf_dump_data:PASS:ensure expected/actual match 0 nsec
btf_dump_data:FAIL:find type id unexpected find type id: actual -2 < expected 0
btf_dump_data:FAIL:find type id unexpected find type id: actual -2 < expected 0
test_btf_dump_int_data:FAIL:dump __int128 unexpected error: -2 (errno 2)
#15/9 btf_dump/btf_dump: int_data:FAIL
Further analysis showed gcc build kernel has type "__int128" in dwarf/BTF
and it doesn't exist in clang build kernel. Code searching for kernel code
found the following:
arch/s390/include/asm/types.h: unsigned __int128 pair;
crypto/ecc.c: unsigned __int128 m = (unsigned __int128)left * right;
include/linux/math64.h: return (u64)(((unsigned __int128)a * mul) >> shift);
include/linux/math64.h: return (u64)(((unsigned __int128)a * mul) >> shift);
lib/ubsan.h:typedef __int128 s_max;
lib/ubsan.h:typedef unsigned __int128 u_max;
In my case, CONFIG_UBSAN is not enabled. Even if we only have "unsigned __int128"
in the code, somehow gcc still put "__int128" in dwarf while clang didn't.
Hence current test works fine for gcc but not for clang.
Enabling CONFIG_UBSAN is an option to provide __int128 type into dwarf
reliably for both gcc and clang, but not everybody enables CONFIG_UBSAN
in their kernel build. So the best choice is to use "unsigned __int128" type
which is available in both clang and gcc build kernels. But clang and gcc
dwarf encoded names for "unsigned __int128" are different:
[$ ~] cat t.c
unsigned __int128 a;
[$ ~] gcc -g -c t.c && llvm-dwarfdump t.o | grep __int128
DW_AT_type (0x00000031 "__int128 unsigned")
DW_AT_name ("__int128 unsigned")
[$ ~] clang -g -c t.c && llvm-dwarfdump t.o | grep __int128
DW_AT_type (0x00000033 "unsigned __int128")
DW_AT_name ("unsigned __int128")
The test change in this patch tries to test type name before
doing actual test.
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
.../selftests/bpf/prog_tests/btf_dump.c | 27 ++++++++++++++-----
1 file changed, 21 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dump.c b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
index 52ccf0cf35e1..87f9df653e4e 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf_dump.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_dump.c
@@ -358,12 +358,27 @@ static void test_btf_dump_int_data(struct btf *btf, struct btf_dump *d,
TEST_BTF_DUMP_DATA_OVER(btf, d, NULL, str, int, sizeof(int)-1, "", 1);
#ifdef __SIZEOF_INT128__
- TEST_BTF_DUMP_DATA(btf, d, NULL, str, __int128, BTF_F_COMPACT,
- "(__int128)0xffffffffffffffff",
- 0xffffffffffffffff);
- ASSERT_OK(btf_dump_data(btf, d, "__int128", NULL, 0, &i, 16, str,
- "(__int128)0xfffffffffffffffffffffffffffffffe"),
- "dump __int128");
+ /* gcc encode unsigned __int128 type with name "__int128 unsigned" in dwarf,
+ * and clang encode it with name "unsigned __int128" in dwarf.
+ * Do an availability test for either variant before doing actual test.
+ */
+ if (btf__find_by_name(btf, "unsigned __int128") > 0) {
+ TEST_BTF_DUMP_DATA(btf, d, NULL, str, unsigned __int128, BTF_F_COMPACT,
+ "(unsigned __int128)0xffffffffffffffff",
+ 0xffffffffffffffff);
+ ASSERT_OK(btf_dump_data(btf, d, "unsigned __int128", NULL, 0, &i, 16, str,
+ "(unsigned __int128)0xfffffffffffffffffffffffffffffffe"),
+ "dump unsigned __int128");
+ } else if (btf__find_by_name(btf, "__int128 unsigned") > 0) {
+ TEST_BTF_DUMP_DATA(btf, d, NULL, str, __int128 unsigned, BTF_F_COMPACT,
+ "(__int128 unsigned)0xffffffffffffffff",
+ 0xffffffffffffffff);
+ ASSERT_OK(btf_dump_data(btf, d, "__int128 unsigned", NULL, 0, &i, 16, str,
+ "(__int128 unsigned)0xfffffffffffffffffffffffffffffffe"),
+ "dump unsigned __int128");
+ } else {
+ ASSERT_TRUE(false, "unsigned_int128_not_found");
+ }
#endif
}
--
2.30.2
