add tests that verify bpf_snprintf_btf() behaviour with strings that
- exactly fit the buffer (string size + null terminator == buffer_size)
- overrun the buffer (string size + null terminator == buffer size + 1)
- overrun the buffer (string size + null terminator == buffer size + 2)
These tests require [1] ("bpf: btf: Fix vsnprintf return value check")
...which has not landed yet.
[1] https://lore.kernel.org/bpf/20220711211317.GA1143610@laptop/
Suggested-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
.../selftests/bpf/progs/netif_receive_skb.c | 41 ++++++++++++++++++++--
1 file changed, 38 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c
index 1d8918d..9fc48e4 100644
--- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c
+++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c
@@ -49,7 +49,7 @@ static int __strncmp(const void *m1, const void *m2, size_t len)
}
#if __has_builtin(__builtin_btf_type_id)
-#define TEST_BTF(_str, _type, _flags, _expected, ...) \
+#define TEST_BTF_SIZE(_str, _size, _type, _flags, _expected, ...) \
do { \
static const char _expectedval[EXPECTED_STRSIZE] = \
_expected; \
@@ -69,10 +69,13 @@ static int __strncmp(const void *m1, const void *m2, size_t len)
ret = -EINVAL; \
break; \
} \
- ret = bpf_snprintf_btf(_str, STRSIZE, \
+ ret = bpf_snprintf_btf(_str, _size, \
&_ptr, sizeof(_ptr), _hflags); \
- if (ret) \
+ if (ret < 0) { \
+ bpf_printk("bpf_snprintf_btf_failed (%s): %d\n",\
+ _str, _expectedval, ret); \
break; \
+ } \
_cmp = __strncmp(_str, _expectedval, EXPECTED_STRSIZE); \
if (_cmp != 0) { \
bpf_printk("(%d) got %s", _cmp, _str); \
@@ -82,6 +85,10 @@ static int __strncmp(const void *m1, const void *m2, size_t len)
break; \
} \
} while (0)
+
+#define TEST_BTF(_str, _type, _flags, _expected, ...) \
+ TEST_BTF_SIZE(_str, STRSIZE, _type, _flags, _expected, \
+ __VA_ARGS__)
#endif
/* Use where expected data string matches its stringified declaration */
@@ -98,7 +105,9 @@ int BPF_PROG(trace_netif_receive_skb, struct sk_buff *skb)
static __u64 flags[] = { 0, BTF_F_COMPACT, BTF_F_ZERO, BTF_F_PTR_RAW,
BTF_F_NONAME, BTF_F_COMPACT | BTF_F_ZERO |
BTF_F_PTR_RAW | BTF_F_NONAME };
+ static char _short_str[2] = {};
static struct btf_ptr p = { };
+ char *short_str = _short_str;
__u32 key = 0;
int i, __ret;
char *str;
@@ -141,6 +150,32 @@ int BPF_PROG(trace_netif_receive_skb, struct sk_buff *skb)
TEST_BTF_C(str, int, 0, -4567);
TEST_BTF(str, int, BTF_F_NONAME, "-4567", -4567);
+ /* overflow tests; first string + terminator fits, others do not. */
+ TEST_BTF_SIZE(short_str, sizeof(_short_str), int, BTF_F_NONAME, "1", 1);
+ if (ret != 1) {
+ bpf_printk("bpf_snprintf_btf() should return 1 for '%s'/2-byte array",
+ short_str);
+ ret = -ERANGE;
+ }
+ /* not enough space to write "10", write "1", return 2 for number of bytes we
+ * should have written.
+ */
+ TEST_BTF_SIZE(short_str, sizeof(_short_str), int, BTF_F_NONAME, "1", 10);
+ if (ret != 2) {
+ bpf_printk("bpf_snprintf_btf() should return 2 for '%s'/2-byte array",
+ short_str);
+ ret = -ERANGE;
+ }
+ /* not enough space to write "100", write "1", return 3 for number of bytes we
+ * should have written.
+ */
+ TEST_BTF_SIZE(short_str, sizeof(_short_str), int, BTF_F_NONAME, "1", 100);
+ if (ret != 3) {
+ bpf_printk("bpf_snprintf_btf() should return 3 for '%s'/3-byte array",
+ short_str);
+ ret = -ERANGE;
+ }
+
/* simple char */
TEST_BTF_C(str, char, 0, 100);
TEST_BTF(str, char, BTF_F_NONAME, "100", 100);
--
1.8.3.1
