bpf/tests: Fix error in tail call limit tests

BugLink: https://bugs.launchpad.net/bugs/1951822
[ Upstream commit 18935a72eb25525b655262579e1652362a3b29bb ]

This patch fixes an error in the tail call limit test that caused the
test to fail on for x86-64 JIT. Previously, the register R0 was used to
report the total number of tail calls made. However, after a tail call
fall-through, the value of the R0 register is undefined. Now, all tail
call error path tests instead use context state to store the count.

Fixes: 874be05f525e ("bpf, tests: Add tail call test suite")
Reported-by: Paul Chaignon <paul@cilium.io>
Reported-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Link: https://lore.kernel.org/bpf/20210914091842.4186267-14-johan.almbladh@anyfinetworks.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/lib/test_bpf.c b/lib/test_bpf.c
index 830a18ecffc8875fafdb58b0cfaf64de365ffa8d..68d125b409f201fcf03f07c82055b0b02f466f32 100644 (file)
--- a/lib/test_bpf.c
+++ b/lib/test_bpf.c
@@ -8992,10 +8992,15 @@ static __init int test_bpf(void)
 struct tail_call_test {
        const char *descr;
        struct bpf_insn insns[MAX_INSNS];
+       int flags;
        int result;
        int stack_depth;
 };
 
+/* Flags that can be passed to tail call test cases */
+#define FLAG_NEED_STATE                BIT(0)
+#define FLAG_RESULT_IN_STATE   BIT(1)
+
 /*
  * Magic marker used in test snippets for tail calls below.
  * BPF_LD/MOV to R2 and R2 with this immediate value is replaced
@@ -9065,32 +9070,38 @@ static struct tail_call_test tail_call_tests[] = {
        {
                "Tail call error path, max count reached",
                .insns = {
-                       BPF_ALU64_IMM(BPF_ADD, R1, 1),
-                       BPF_ALU64_REG(BPF_MOV, R0, R1),
+                       BPF_LDX_MEM(BPF_W, R2, R1, 0),
+                       BPF_ALU64_IMM(BPF_ADD, R2, 1),
+                       BPF_STX_MEM(BPF_W, R1, R2, 0),
                        TAIL_CALL(0),
                        BPF_EXIT_INSN(),
                },
-               .result = MAX_TAIL_CALL_CNT + 1,
+               .flags = FLAG_NEED_STATE | FLAG_RESULT_IN_STATE,
+               .result = (MAX_TAIL_CALL_CNT + 1 + 1) * MAX_TESTRUNS,
        },
        {
                "Tail call error path, NULL target",
                .insns = {
-                       BPF_ALU64_IMM(BPF_MOV, R0, -1),
+                       BPF_LDX_MEM(BPF_W, R2, R1, 0),
+                       BPF_ALU64_IMM(BPF_ADD, R2, 1),
+                       BPF_STX_MEM(BPF_W, R1, R2, 0),
                        TAIL_CALL(TAIL_CALL_NULL),
-                       BPF_ALU64_IMM(BPF_MOV, R0, 1),
                        BPF_EXIT_INSN(),
                },
-               .result = 1,
+               .flags = FLAG_NEED_STATE | FLAG_RESULT_IN_STATE,
+               .result = MAX_TESTRUNS,
        },
        {
                "Tail call error path, index out of range",
                .insns = {
-                       BPF_ALU64_IMM(BPF_MOV, R0, -1),
+                       BPF_LDX_MEM(BPF_W, R2, R1, 0),
+                       BPF_ALU64_IMM(BPF_ADD, R2, 1),
+                       BPF_STX_MEM(BPF_W, R1, R2, 0),
                        TAIL_CALL(TAIL_CALL_INVALID),
-                       BPF_ALU64_IMM(BPF_MOV, R0, 1),
                        BPF_EXIT_INSN(),
                },
-               .result = 1,
+               .flags = FLAG_NEED_STATE | FLAG_RESULT_IN_STATE,
+               .result = MAX_TESTRUNS,
        },
 };
 
@@ -9196,6 +9207,8 @@ static __init int test_tail_calls(struct bpf_array *progs)
        for (i = 0; i < ARRAY_SIZE(tail_call_tests); i++) {
                struct tail_call_test *test = &tail_call_tests[i];
                struct bpf_prog *fp = progs->ptrs[i];
+               int *data = NULL;
+               int state = 0;
                u64 duration;
                int ret;
 
@@ -9212,7 +9225,11 @@ static __init int test_tail_calls(struct bpf_array *progs)
                if (fp->jited)
                        jit_cnt++;
 
-               ret = __run_one(fp, NULL, MAX_TESTRUNS, &duration);
+               if (test->flags & FLAG_NEED_STATE)
+                       data = &state;
+               ret = __run_one(fp, data, MAX_TESTRUNS, &duration);
+               if (test->flags & FLAG_RESULT_IN_STATE)
+                       ret = state;
                if (ret == test->result) {
                        pr_cont("%lld PASS", duration);
                        pass_cnt++;