selftests/bpf: Add variable-length data concat pattern less than test

Extend original variable-length tests with a case to catch a common
existing pattern of testing for < 0 for errors. Note because
verifier also tracks upper bounds and we know it can not be greater
than MAX_LEN here we can skip upper bound check.

In ALU64 enabled compilation converting from long->int return types
in probe helpers results in extra instruction pattern, <<= 32, s >>= 32.
The trade-off is the non-ALU64 case works. If you really care about
every extra insn (XDP case?) then you probably should be using original
int type.

In addition adding a sext insn to bpf might help the verifier in the
general case to avoid these types of tricks.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200623032224.4020118-3-andriin@fb.com

diff --git a/tools/testing/selftests/bpf/prog_tests/varlen.c b/tools/testing/selftests/bpf/prog_tests/varlen.c
index 7533565..c75525e 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/varlen.c
+++ b/tools/testing/selftests/bpf/prog_tests/varlen.c
@@ -51,6 +51,18 @@ void test_varlen(void)
        CHECK_VAL(data->total2, size1 + size2);
        CHECK(memcmp(data->payload2, exp_str, size1 + size2), "content_check",
              "doesn't match!");
+
+       CHECK_VAL(data->payload3_len1, size1);
+       CHECK_VAL(data->payload3_len2, size2);
+       CHECK_VAL(data->total3, size1 + size2);
+       CHECK(memcmp(data->payload3, exp_str, size1 + size2), "content_check",
+             "doesn't match!");
+
+       CHECK_VAL(data->payload4_len1, size1);
+       CHECK_VAL(data->payload4_len2, size2);
+       CHECK_VAL(data->total4, size1 + size2);
+       CHECK(memcmp(data->payload4, exp_str, size1 + size2), "content_check",
+             "doesn't match!");
 cleanup:
        test_varlen__destroy(skel);
 }

diff --git a/tools/testing/selftests/bpf/progs/test_varlen.c b/tools/testing/selftests/bpf/progs/test_varlen.c
index 0969185..cd4b72c 100644 (file)
--- a/tools/testing/selftests/bpf/progs/test_varlen.c
+++ b/tools/testing/selftests/bpf/progs/test_varlen.c
@@ -26,8 +26,18 @@ int payload2_len2 = -1;
 int total2 = -1;
 char payload2[MAX_LEN + MAX_LEN] = { 1 };
 
+int payload3_len1 = -1;
+int payload3_len2 = -1;
+int total3= -1;
+char payload3[MAX_LEN + MAX_LEN] = { 1 };
+
+int payload4_len1 = -1;
+int payload4_len2 = -1;
+int total4= -1;
+char payload4[MAX_LEN + MAX_LEN] = { 1 };
+
 SEC("raw_tp/sys_enter")
-int handler64(void *regs)
+int handler64_unsigned(void *regs)
 {
        int pid = bpf_get_current_pid_tgid() >> 32;
        void *payload = payload1;
@@ -54,8 +64,34 @@ int handler64(void *regs)
        return 0;
 }
 
-SEC("tp_btf/sys_enter")
-int handler32(void *regs)
+SEC("raw_tp/sys_exit")
+int handler64_signed(void *regs)
+{
+       int pid = bpf_get_current_pid_tgid() >> 32;
+       void *payload = payload3;
+       long len;
+
+       /* ignore irrelevant invocations */
+       if (test_pid != pid || !capture)
+               return 0;
+
+       len = bpf_probe_read_kernel_str(payload, MAX_LEN, &buf_in1[0]);
+       if (len >= 0) {
+               payload += len;
+               payload3_len1 = len;
+       }
+       len = bpf_probe_read_kernel_str(payload, MAX_LEN, &buf_in2[0]);
+       if (len >= 0) {
+               payload += len;
+               payload3_len2 = len;
+       }
+       total3 = payload - (void *)payload3;
+
+       return 0;
+}
+
+SEC("tp/raw_syscalls/sys_enter")
+int handler32_unsigned(void *regs)
 {
        int pid = bpf_get_current_pid_tgid() >> 32;
        void *payload = payload2;
@@ -82,7 +118,33 @@ int handler32(void *regs)
        return 0;
 }
 
-SEC("tp_btf/sys_exit")
+SEC("tp/raw_syscalls/sys_exit")
+int handler32_signed(void *regs)
+{
+       int pid = bpf_get_current_pid_tgid() >> 32;
+       void *payload = payload4;
+       int len;
+
+       /* ignore irrelevant invocations */
+       if (test_pid != pid || !capture)
+               return 0;
+
+       len = bpf_probe_read_kernel_str(payload, MAX_LEN, &buf_in1[0]);
+       if (len >= 0) {
+               payload += len;
+               payload4_len1 = len;
+       }
+       len = bpf_probe_read_kernel_str(payload, MAX_LEN, &buf_in2[0]);
+       if (len >= 0) {
+               payload += len;
+               payload4_len2 = len;
+       }
+       total4 = payload - (void *)payload4;
+
+       return 0;
+}
+
+SEC("tp/syscalls/sys_exit_getpid")
 int handler_exit(void *regs)
 {
        long bla;