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bpf, tests: Add tail call test suite

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While BPF_CALL instructions were tested implicitly by the cBPF-to-eBPF
translation, there has not been any tests for BPF_TAIL_CALL instructions.
The new test suite includes tests for tail call chaining, tail call count
tracking and error paths. It is mainly intended for JIT development and
testing.

Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210809091829.810076-15-johan.almbladh@anyfinetworks.com
This commit is contained in:
Johan Almbladh 2021-08-09 11:18:29 +02:00 committed by Daniel Borkmann
parent 6a3b24ca48
commit 874be05f52
1 changed files with 248 additions and 0 deletions
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248
lib/test_bpf.c
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@ -8989,8 +8989,248 @@ static __init int test_bpf(void)
return err_cnt ? -EINVAL : 0;
}
struct tail_call_test {
const char *descr;
struct bpf_insn insns[MAX_INSNS];
int result;
int stack_depth;
};
/*
* Magic marker used in test snippets for tail calls below.
* BPF_LD/MOV to R2 and R2 with this immediate value is replaced
* with the proper values by the test runner.
*/
#define TAIL_CALL_MARKER 0x7a11ca11
/* Special offset to indicate a NULL call target */
#define TAIL_CALL_NULL 0x7fff
/* Special offset to indicate an out-of-range index */
#define TAIL_CALL_INVALID 0x7ffe
#define TAIL_CALL(offset) \
BPF_LD_IMM64(R2, TAIL_CALL_MARKER), \
BPF_RAW_INSN(BPF_ALU | BPF_MOV | BPF_K, R3, 0, \
offset, TAIL_CALL_MARKER), \
BPF_JMP_IMM(BPF_TAIL_CALL, 0, 0, 0)
/*
* Tail call tests. Each test case may call any other test in the table,
* including itself, specified as a relative index offset from the calling
* test. The index TAIL_CALL_NULL can be used to specify a NULL target
* function to test the JIT error path. Similarly, the index TAIL_CALL_INVALID
* results in a target index that is out of range.
*/
static struct tail_call_test tail_call_tests[] = {
{
"Tail call leaf",
.insns = {
BPF_ALU64_REG(BPF_MOV, R0, R1),
BPF_ALU64_IMM(BPF_ADD, R0, 1),
BPF_EXIT_INSN(),
},
.result = 1,
},
{
"Tail call 2",
.insns = {
BPF_ALU64_IMM(BPF_ADD, R1, 2),
TAIL_CALL(-1),
BPF_ALU64_IMM(BPF_MOV, R0, -1),
BPF_EXIT_INSN(),
},
.result = 3,
},
{
"Tail call 3",
.insns = {
BPF_ALU64_IMM(BPF_ADD, R1, 3),
TAIL_CALL(-1),
BPF_ALU64_IMM(BPF_MOV, R0, -1),
BPF_EXIT_INSN(),
},
.result = 6,
},
{
"Tail call 4",
.insns = {
BPF_ALU64_IMM(BPF_ADD, R1, 4),
TAIL_CALL(-1),
BPF_ALU64_IMM(BPF_MOV, R0, -1),
BPF_EXIT_INSN(),
},
.result = 10,
},
{
"Tail call error path, max count reached",
.insns = {
BPF_ALU64_IMM(BPF_ADD, R1, 1),
BPF_ALU64_REG(BPF_MOV, R0, R1),
TAIL_CALL(0),
BPF_EXIT_INSN(),
},
.result = MAX_TAIL_CALL_CNT + 1,
},
{
"Tail call error path, NULL target",
.insns = {
BPF_ALU64_IMM(BPF_MOV, R0, -1),
TAIL_CALL(TAIL_CALL_NULL),
BPF_ALU64_IMM(BPF_MOV, R0, 1),
BPF_EXIT_INSN(),
},
.result = 1,
},
{
"Tail call error path, index out of range",
.insns = {
BPF_ALU64_IMM(BPF_MOV, R0, -1),
TAIL_CALL(TAIL_CALL_INVALID),
BPF_ALU64_IMM(BPF_MOV, R0, 1),
BPF_EXIT_INSN(),
},
.result = 1,
},
};
static void __init destroy_tail_call_tests(struct bpf_array *progs)
{
int i;
for (i = 0; i < ARRAY_SIZE(tail_call_tests); i++)
if (progs->ptrs[i])
bpf_prog_free(progs->ptrs[i]);
kfree(progs);
}
static __init int prepare_tail_call_tests(struct bpf_array **pprogs)
{
int ntests = ARRAY_SIZE(tail_call_tests);
struct bpf_array *progs;
int which, err;
/* Allocate the table of programs to be used for tall calls */
progs = kzalloc(sizeof(*progs) + (ntests + 1) * sizeof(progs->ptrs[0]),
GFP_KERNEL);
if (!progs)
goto out_nomem;
/* Create all eBPF programs and populate the table */
for (which = 0; which < ntests; which++) {
struct tail_call_test *test = &tail_call_tests[which];
struct bpf_prog *fp;
int len, i;
/* Compute the number of program instructions */
for (len = 0; len < MAX_INSNS; len++) {
struct bpf_insn *insn = &test->insns[len];
if (len < MAX_INSNS - 1 &&
insn->code == (BPF_LD | BPF_DW | BPF_IMM))
len++;
if (insn->code == 0)
break;
}
/* Allocate and initialize the program */
fp = bpf_prog_alloc(bpf_prog_size(len), 0);
if (!fp)
goto out_nomem;
fp->len = len;
fp->type = BPF_PROG_TYPE_SOCKET_FILTER;
fp->aux->stack_depth = test->stack_depth;
memcpy(fp->insnsi, test->insns, len * sizeof(struct bpf_insn));
/* Relocate runtime tail call offsets and addresses */
for (i = 0; i < len; i++) {
struct bpf_insn *insn = &fp->insnsi[i];
if (insn->imm != TAIL_CALL_MARKER)
continue;
switch (insn->code) {
case BPF_LD | BPF_DW | BPF_IMM:
insn[0].imm = (u32)(long)progs;
insn[1].imm = ((u64)(long)progs) >> 32;
break;
case BPF_ALU | BPF_MOV | BPF_K:
if (insn->off == TAIL_CALL_NULL)
insn->imm = ntests;
else if (insn->off == TAIL_CALL_INVALID)
insn->imm = ntests + 1;
else
insn->imm = which + insn->off;
insn->off = 0;
}
}
fp = bpf_prog_select_runtime(fp, &err);
if (err)
goto out_err;
progs->ptrs[which] = fp;
}
/* The last entry contains a NULL program pointer */
progs->map.max_entries = ntests + 1;
*pprogs = progs;
return 0;
out_nomem:
err = -ENOMEM;
out_err:
if (progs)
destroy_tail_call_tests(progs);
return err;
}
static __init int test_tail_calls(struct bpf_array *progs)
{
int i, err_cnt = 0, pass_cnt = 0;
int jit_cnt = 0, run_cnt = 0;
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];
u64 duration;
int ret;
cond_resched();
pr_info("#%d %s ", i, test->descr);
if (!fp) {
err_cnt++;
continue;
}
pr_cont("jited:%u ", fp->jited);
run_cnt++;
if (fp->jited)
jit_cnt++;
ret = __run_one(fp, NULL, MAX_TESTRUNS, &duration);
if (ret == test->result) {
pr_cont("%lld PASS", duration);
pass_cnt++;
} else {
pr_cont("ret %d != %d FAIL", ret, test->result);
err_cnt++;
}
}
pr_info("%s: Summary: %d PASSED, %d FAILED, [%d/%d JIT'ed]\n",
__func__, pass_cnt, err_cnt, jit_cnt, run_cnt);
return err_cnt ? -EINVAL : 0;
}
static int __init test_bpf_init(void)
{
struct bpf_array *progs = NULL;
int ret;
ret = prepare_bpf_tests();
@ -9002,6 +9242,14 @@ static int __init test_bpf_init(void)
if (ret)
return ret;
ret = prepare_tail_call_tests(&progs);
if (ret)
return ret;
ret = test_tail_calls(progs);
destroy_tail_call_tests(progs);
if (ret)
return ret;
return test_skb_segment();
}