On Thu, Sep 24, 2020 at 5:51 PM Alexei Starovoitov alexei.starovoitov@gmail.com wrote:
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);
Better still to use bpf_core_type_id_kernel() macro from bpf_core_read.h.
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.