Re: [PATCH v6 bpf-next 4/6] selftests/bpf: add bpf_snprintf_btf helper tests
From: Alexei Starovoitov <hidden>
Date: 2020-09-25 00:50:57
Also in:
bpf, linux-kselftest, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Shuah Khan, Linus Torvalds
On Wed, Sep 23, 2020 at 06:46:26PM +0100, Alan Maguire wrote:
+static int __strncmp(const void *m1, const void *m2, size_t len)
+{
+ const unsigned char *s1 = m1;
+ const unsigned char *s2 = m2;
+ int i, delta = 0;
+
+#pragma clang loop unroll(full)Shouldn't be needed? The verifier supports bounded loops.
+ for (i = 0; i < len; i++) {
+ delta = s1[i] - s2[i];
+ if (delta || s1[i] == 0 || s2[i] == 0)
+ break;
+ }
+ return delta;
+}
+
+/* Use __builtin_btf_type_id to test snprintf_btf by type id instead of name */
+#if __has_builtin(__builtin_btf_type_id)
+#define TEST_BTF_BY_ID(_str, _typestr, _ptr, _hflags) \
+ do { \
+ int _expected_ret = ret; \
+ _ptr.type = 0; \
+ _ptr.type_id = __builtin_btf_type_id(_typestr, 0); \The test is passing for me, but I don't understand why :) __builtin_btf_type_id(, 0); means btf_id of the bpf program. While bpf_snprintf_btf() is treating it as btf_id of vmlinux_btf. So it really should have been __builtin_btf_type_id(,1); The following diff works:
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c
index b4f96f1f6830..bffa786e3b03 100644
--- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c
+++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c@@ -45,7 +45,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len) do { \ int _expected_ret = ret; \ _ptr.type = 0; \ - _ptr.type_id = __builtin_btf_type_id(_typestr, 0); \ + _ptr.type_id = __builtin_btf_type_id(_typestr, 1); \ ret = bpf_snprintf_btf(_str, STRSIZE, &_ptr, \ sizeof(_ptr), _hflags); \ if (ret != _expected_ret) { \
@@ -88,7 +88,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len) ret = -EBADMSG; \ break; \ } \ - TEST_BTF_BY_ID(_str, #_type, _ptr, _hflags); \ + TEST_BTF_BY_ID(_str, _ptr, _ptr, _hflags); \
But still makes me suspicious of the test. I haven't debugged further.