From 444852832f835a85fb6d65d79f5b25d84f9da9a8 Mon Sep 17 00:00:00 2001
From: Tiezhu Yang <yangtiezhu@loongson.cn>
Date: Fri, 12 Jan 2024 09:57:00 +0800
Subject: [PATCH] selftests/bpf: Skip callback tests if jit is disabled in
 test_verifier

If CONFIG_BPF_JIT_ALWAYS_ON is not set and bpf_jit_enable is 0, there
exist 6 failed tests.

  [root@linux bpf]# echo 0 > /proc/sys/net/core/bpf_jit_enable
  [root@linux bpf]# echo 0 > /proc/sys/kernel/unprivileged_bpf_disabled
  [root@linux bpf]# ./test_verifier | grep FAIL
  #106/p inline simple bpf_loop call FAIL
  #107/p don't inline bpf_loop call, flags non-zero FAIL
  #108/p don't inline bpf_loop call, callback non-constant FAIL
  #109/p bpf_loop_inline and a dead func FAIL
  #110/p bpf_loop_inline stack locations for loop vars FAIL
  #111/p inline bpf_loop call in a big program FAIL
  Summary: 768 PASSED, 15 SKIPPED, 6 FAILED

The test log shows that callbacks are not allowed in non-JITed programs,
interpreter doesn't support them yet, thus these tests should be skipped
if jit is disabled, copy some check functions from the other places under
tools directory, and then handle this case in do_test_single().

With this patch:

  [root@linux bpf]# echo 0 > /proc/sys/net/core/bpf_jit_enable
  [root@linux bpf]# echo 0 > /proc/sys/kernel/unprivileged_bpf_disabled
  [root@linux bpf]# ./test_verifier | grep FAIL
  Summary: 768 PASSED, 21 SKIPPED, 0 FAILED

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 tools/testing/selftests/bpf/test_verifier.c | 39 +++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index f36e41435be79f..d4e600e3caec2a 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -21,6 +21,7 @@
 #include <sched.h>
 #include <limits.h>
 #include <assert.h>
+#include <fcntl.h>
 
 #include <linux/unistd.h>
 #include <linux/filter.h>
@@ -1397,6 +1398,34 @@ static bool is_skip_insn(struct bpf_insn *insn)
 	return memcmp(insn, &skip_insn, sizeof(skip_insn)) == 0;
 }
 
+static bool is_ldimm64_insn(struct bpf_insn *insn)
+{
+	return insn->code == (BPF_LD | BPF_IMM | BPF_DW);
+}
+
+static bool insn_is_pseudo_func(struct bpf_insn *insn)
+{
+	return is_ldimm64_insn(insn) && insn->src_reg == BPF_PSEUDO_FUNC;
+}
+
+static bool is_jit_enabled(void)
+{
+	const char *jit_sysctl = "/proc/sys/net/core/bpf_jit_enable";
+	bool enabled = false;
+	int sysctl_fd;
+
+	sysctl_fd = open(jit_sysctl, 0, O_RDONLY);
+	if (sysctl_fd != -1) {
+		char tmpc;
+
+		if (read(sysctl_fd, &tmpc, sizeof(tmpc)) == 1)
+			enabled = (tmpc != '0');
+		close(sysctl_fd);
+	}
+
+	return enabled;
+}
+
 static int null_terminated_insn_len(struct bpf_insn *seq, int max_len)
 {
 	int i;
@@ -1662,6 +1691,16 @@ static void do_test_single(struct bpf_test *test, bool unpriv,
 		goto close_fds;
 	}
 
+	if (!is_jit_enabled()) {
+		for (i = 0; i < prog_len; i++, prog++) {
+			if (insn_is_pseudo_func(prog)) {
+				printf("SKIP (callbacks are not allowed in non-JITed programs)\n");
+				skips++;
+				goto close_fds;
+			}
+		}
+	}
+
 	alignment_prevented_execution = 0;
 
 	if (expected_ret == ACCEPT || expected_ret == VERBOSE_ACCEPT) {