Commit 18935a72 authored by Johan Almbladh's avatar Johan Almbladh Committed by Daniel Borkmann
Browse files

bpf/tests: Fix error in tail call limit tests 



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: 874be05f ("bpf, tests: Add tail call test suite")
Reported-by: default avatarPaul Chaignon <paul@cilium.io>
Reported-by: default avatarTiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: default avatarJohan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Tested-by: default avatarTiezhu Yang <yangtiezhu@loongson.cn>
Link: https://lore.kernel.org/bpf/20210914091842.4186267-14-johan.almbladh@anyfinetworks.com
parent f536a7c8

lib/test_bpf.c

+27 −10
Original line number Diff line number Diff line
@@ -12180,10 +12180,15 @@ 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
@@ -12253,32 +12258,38 @@ 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,

	},

};
@@ -12384,6 +12395,8 @@ 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;
@@ -12400,7 +12413,11 @@ 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++;