[PATCH 5.15 365/917] bpf/tests: Fix error in tail call limit tests

Greg Kroah-Hartman
2021-11-16T00:54:43Z

From: Johan Almbladh <johan.almbladh@anyfinetworks.com>

[ 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>
---
lib/test_bpf.c | 37 +++++++++++++++++++++++++++----------
1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/lib/test_bpf.c b/lib/test_bpf.c
index 830a18ecffc88..68d125b409f20 100644
--- 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++;
--
2.33.0