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selftests/bpf: Add tailcall_bpf2bpf tests
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Add four tests to tailcalls selftest explicitly named
"tailcall_bpf2bpf_X" as their purpose is to validate that combination
of tailcalls with bpf2bpf calls are working properly.
These tests also validate LD_ABS from subprograms.

Signed-off-by: Maciej Fijalkowski <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
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@mfijalko
mfijalko authored and Alexei Starovoitov committed Sep 18, 2020
1 parent 09b28d7 commit 3b03791
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332 changes: 332 additions & 0 deletions tools/testing/selftests/bpf/prog_tests/tailcalls.c
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
#include <test_progs.h>
#include <network_helpers.h>

/* test_tailcall_1 checks basic functionality by patching multiple locations
* in a single program for a single tail call slot with nop->jmp, jmp->nop
Expand Down Expand Up @@ -472,6 +473,329 @@ static void test_tailcall_5(void)
bpf_object__close(obj);
}

/* test_tailcall_bpf2bpf_1 purpose is to make sure that tailcalls are working
* correctly in correlation with BPF subprograms
*/
static void test_tailcall_bpf2bpf_1(void)
{
int err, map_fd, prog_fd, main_fd, i;
struct bpf_map *prog_array;
struct bpf_program *prog;
struct bpf_object *obj;
__u32 retval, duration;
char prog_name[32];

err = bpf_prog_load("tailcall_bpf2bpf1.o", BPF_PROG_TYPE_SCHED_CLS,
&obj, &prog_fd);
if (CHECK_FAIL(err))
return;

prog = bpf_object__find_program_by_title(obj, "classifier");
if (CHECK_FAIL(!prog))
goto out;

main_fd = bpf_program__fd(prog);
if (CHECK_FAIL(main_fd < 0))
goto out;

prog_array = bpf_object__find_map_by_name(obj, "jmp_table");
if (CHECK_FAIL(!prog_array))
goto out;

map_fd = bpf_map__fd(prog_array);
if (CHECK_FAIL(map_fd < 0))
goto out;

/* nop -> jmp */
for (i = 0; i < bpf_map__def(prog_array)->max_entries; i++) {
snprintf(prog_name, sizeof(prog_name), "classifier/%i", i);

prog = bpf_object__find_program_by_title(obj, prog_name);
if (CHECK_FAIL(!prog))
goto out;

prog_fd = bpf_program__fd(prog);
if (CHECK_FAIL(prog_fd < 0))
goto out;

err = bpf_map_update_elem(map_fd, &i, &prog_fd, BPF_ANY);
if (CHECK_FAIL(err))
goto out;
}

err = bpf_prog_test_run(main_fd, 1, &pkt_v4, sizeof(pkt_v4), 0,
0, &retval, &duration);
CHECK(err || retval != 1, "tailcall",
"err %d errno %d retval %d\n", err, errno, retval);

/* jmp -> nop, call subprog that will do tailcall */
i = 1;
err = bpf_map_delete_elem(map_fd, &i);
if (CHECK_FAIL(err))
goto out;

err = bpf_prog_test_run(main_fd, 1, &pkt_v4, sizeof(pkt_v4), 0,
0, &retval, &duration);
CHECK(err || retval != 0, "tailcall", "err %d errno %d retval %d\n",
err, errno, retval);

/* make sure that subprog can access ctx and entry prog that
* called this subprog can properly return
*/
i = 0;
err = bpf_map_delete_elem(map_fd, &i);
if (CHECK_FAIL(err))
goto out;

err = bpf_prog_test_run(main_fd, 1, &pkt_v4, sizeof(pkt_v4), 0,
0, &retval, &duration);
CHECK(err || retval != sizeof(pkt_v4) * 2,
"tailcall", "err %d errno %d retval %d\n",
err, errno, retval);
out:
bpf_object__close(obj);
}

/* test_tailcall_bpf2bpf_2 checks that the count value of the tail call limit
* enforcement matches with expectations when tailcall is preceded with
* bpf2bpf call.
*/
static void test_tailcall_bpf2bpf_2(void)
{
int err, map_fd, prog_fd, main_fd, data_fd, i, val;
struct bpf_map *prog_array, *data_map;
struct bpf_program *prog;
struct bpf_object *obj;
__u32 retval, duration;
char buff[128] = {};

err = bpf_prog_load("tailcall_bpf2bpf2.o", BPF_PROG_TYPE_SCHED_CLS,
&obj, &prog_fd);
if (CHECK_FAIL(err))
return;

prog = bpf_object__find_program_by_title(obj, "classifier");
if (CHECK_FAIL(!prog))
goto out;

main_fd = bpf_program__fd(prog);
if (CHECK_FAIL(main_fd < 0))
goto out;

prog_array = bpf_object__find_map_by_name(obj, "jmp_table");
if (CHECK_FAIL(!prog_array))
goto out;

map_fd = bpf_map__fd(prog_array);
if (CHECK_FAIL(map_fd < 0))
goto out;

prog = bpf_object__find_program_by_title(obj, "classifier/0");
if (CHECK_FAIL(!prog))
goto out;

prog_fd = bpf_program__fd(prog);
if (CHECK_FAIL(prog_fd < 0))
goto out;

i = 0;
err = bpf_map_update_elem(map_fd, &i, &prog_fd, BPF_ANY);
if (CHECK_FAIL(err))
goto out;

err = bpf_prog_test_run(main_fd, 1, buff, sizeof(buff), 0,
&duration, &retval, NULL);
CHECK(err || retval != 1, "tailcall", "err %d errno %d retval %d\n",
err, errno, retval);

data_map = bpf_object__find_map_by_name(obj, "tailcall.bss");
if (CHECK_FAIL(!data_map || !bpf_map__is_internal(data_map)))
return;

data_fd = bpf_map__fd(data_map);
if (CHECK_FAIL(map_fd < 0))
return;

i = 0;
err = bpf_map_lookup_elem(data_fd, &i, &val);
CHECK(err || val != 33, "tailcall count", "err %d errno %d count %d\n",
err, errno, val);

i = 0;
err = bpf_map_delete_elem(map_fd, &i);
if (CHECK_FAIL(err))
goto out;

err = bpf_prog_test_run(main_fd, 1, buff, sizeof(buff), 0,
&duration, &retval, NULL);
CHECK(err || retval != 0, "tailcall", "err %d errno %d retval %d\n",
err, errno, retval);
out:
bpf_object__close(obj);
}

/* test_tailcall_bpf2bpf_3 checks that non-trivial amount of stack (up to
* 256 bytes) can be used within bpf subprograms that have the tailcalls
* in them
*/
static void test_tailcall_bpf2bpf_3(void)
{
int err, map_fd, prog_fd, main_fd, i;
struct bpf_map *prog_array;
struct bpf_program *prog;
struct bpf_object *obj;
__u32 retval, duration;
char prog_name[32];

err = bpf_prog_load("tailcall_bpf2bpf3.o", BPF_PROG_TYPE_SCHED_CLS,
&obj, &prog_fd);
if (CHECK_FAIL(err))
return;

prog = bpf_object__find_program_by_title(obj, "classifier");
if (CHECK_FAIL(!prog))
goto out;

main_fd = bpf_program__fd(prog);
if (CHECK_FAIL(main_fd < 0))
goto out;

prog_array = bpf_object__find_map_by_name(obj, "jmp_table");
if (CHECK_FAIL(!prog_array))
goto out;

map_fd = bpf_map__fd(prog_array);
if (CHECK_FAIL(map_fd < 0))
goto out;

for (i = 0; i < bpf_map__def(prog_array)->max_entries; i++) {
snprintf(prog_name, sizeof(prog_name), "classifier/%i", i);

prog = bpf_object__find_program_by_title(obj, prog_name);
if (CHECK_FAIL(!prog))
goto out;

prog_fd = bpf_program__fd(prog);
if (CHECK_FAIL(prog_fd < 0))
goto out;

err = bpf_map_update_elem(map_fd, &i, &prog_fd, BPF_ANY);
if (CHECK_FAIL(err))
goto out;
}

err = bpf_prog_test_run(main_fd, 1, &pkt_v4, sizeof(pkt_v4), 0,
&duration, &retval, NULL);
CHECK(err || retval != sizeof(pkt_v4) * 3,
"tailcall", "err %d errno %d retval %d\n",
err, errno, retval);

i = 1;
err = bpf_map_delete_elem(map_fd, &i);
if (CHECK_FAIL(err))
goto out;

err = bpf_prog_test_run(main_fd, 1, &pkt_v4, sizeof(pkt_v4), 0,
&duration, &retval, NULL);
CHECK(err || retval != sizeof(pkt_v4),
"tailcall", "err %d errno %d retval %d\n",
err, errno, retval);

i = 0;
err = bpf_map_delete_elem(map_fd, &i);
if (CHECK_FAIL(err))
goto out;

err = bpf_prog_test_run(main_fd, 1, &pkt_v4, sizeof(pkt_v4), 0,
&duration, &retval, NULL);
CHECK(err || retval != sizeof(pkt_v4) * 2,
"tailcall", "err %d errno %d retval %d\n",
err, errno, retval);
out:
bpf_object__close(obj);
}

/* test_tailcall_bpf2bpf_4 checks that tailcall counter is correctly preserved
* across tailcalls combined with bpf2bpf calls. for making sure that tailcall
* counter behaves correctly, bpf program will go through following flow:
*
* entry -> entry_subprog -> tailcall0 -> bpf_func0 -> subprog0 ->
* -> tailcall1 -> bpf_func1 -> subprog1 -> tailcall2 -> bpf_func2 ->
* subprog2 [here bump global counter] --------^
*
* We go through first two tailcalls and start counting from the subprog2 where
* the loop begins. At the end of the test make sure that the global counter is
* equal to 31, because tailcall counter includes the first two tailcalls
* whereas global counter is incremented only on loop presented on flow above.
*/
static void test_tailcall_bpf2bpf_4(void)
{
int err, map_fd, prog_fd, main_fd, data_fd, i, val;
struct bpf_map *prog_array, *data_map;
struct bpf_program *prog;
struct bpf_object *obj;
__u32 retval, duration;
char prog_name[32];

err = bpf_prog_load("tailcall_bpf2bpf4.o", BPF_PROG_TYPE_SCHED_CLS,
&obj, &prog_fd);
if (CHECK_FAIL(err))
return;

prog = bpf_object__find_program_by_title(obj, "classifier");
if (CHECK_FAIL(!prog))
goto out;

main_fd = bpf_program__fd(prog);
if (CHECK_FAIL(main_fd < 0))
goto out;

prog_array = bpf_object__find_map_by_name(obj, "jmp_table");
if (CHECK_FAIL(!prog_array))
goto out;

map_fd = bpf_map__fd(prog_array);
if (CHECK_FAIL(map_fd < 0))
goto out;

for (i = 0; i < bpf_map__def(prog_array)->max_entries; i++) {
snprintf(prog_name, sizeof(prog_name), "classifier/%i", i);

prog = bpf_object__find_program_by_title(obj, prog_name);
if (CHECK_FAIL(!prog))
goto out;

prog_fd = bpf_program__fd(prog);
if (CHECK_FAIL(prog_fd < 0))
goto out;

err = bpf_map_update_elem(map_fd, &i, &prog_fd, BPF_ANY);
if (CHECK_FAIL(err))
goto out;
}

err = bpf_prog_test_run(main_fd, 1, &pkt_v4, sizeof(pkt_v4), 0,
&duration, &retval, NULL);
CHECK(err || retval != sizeof(pkt_v4) * 3, "tailcall", "err %d errno %d retval %d\n",
err, errno, retval);

data_map = bpf_object__find_map_by_name(obj, "tailcall.bss");
if (CHECK_FAIL(!data_map || !bpf_map__is_internal(data_map)))
return;

data_fd = bpf_map__fd(data_map);
if (CHECK_FAIL(map_fd < 0))
return;

i = 0;
err = bpf_map_lookup_elem(data_fd, &i, &val);
CHECK(err || val != 31, "tailcall count", "err %d errno %d count %d\n",
err, errno, val);

out:
bpf_object__close(obj);
}

void test_tailcalls(void)
{
if (test__start_subtest("tailcall_1"))
Expand All @@ -484,4 +808,12 @@ void test_tailcalls(void)
test_tailcall_4();
if (test__start_subtest("tailcall_5"))
test_tailcall_5();
if (test__start_subtest("tailcall_bpf2bpf_1"))
test_tailcall_bpf2bpf_1();
if (test__start_subtest("tailcall_bpf2bpf_2"))
test_tailcall_bpf2bpf_2();
if (test__start_subtest("tailcall_bpf2bpf_3"))
test_tailcall_bpf2bpf_3();
if (test__start_subtest("tailcall_bpf2bpf_4"))
test_tailcall_bpf2bpf_4();
}
38 changes: 38 additions & 0 deletions tools/testing/selftests/bpf/progs/tailcall_bpf2bpf1.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,38 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>

struct {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__uint(max_entries, 2);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u32));
} jmp_table SEC(".maps");

#define TAIL_FUNC(x) \
SEC("classifier/" #x) \
int bpf_func_##x(struct __sk_buff *skb) \
{ \
return x; \
}
TAIL_FUNC(0)
TAIL_FUNC(1)

static __noinline
int subprog_tail(struct __sk_buff *skb)
{
bpf_tail_call(skb, &jmp_table, 0);

return skb->len * 2;
}

SEC("classifier")
int entry(struct __sk_buff *skb)
{
bpf_tail_call(skb, &jmp_table, 1);

return subprog_tail(skb);
}

char __license[] SEC("license") = "GPL";
int _version SEC("version") = 1;
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