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selftests/bpf: Add test for early update in prog_array_map_poke_run

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Adding test that tries to trigger the BUG_IN during early map update
in prog_array_map_poke_run function.

The idea is to share prog array map between thread that constantly
updates it and another one loading a program that uses that prog
array.

Eventually we will hit a place where the program is ok to be updated
(poke->tailcall_target_stable check) but the address is still not
registered in kallsyms, so the bpf_arch_text_poke returns -EINVAL
and cause imbalance for the next tail call update check, which will
fail with -EBUSY in bpf_arch_text_poke as described in previous fix.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/bpf/20231206083041.1306660-3-jolsa@kernel.org
This commit is contained in:
Jiri Olsa 2023-12-06 09:30:41 +01:00 committed by Daniel Borkmann
parent 4b7de80160
commit ffed24eff9
2 changed files with 116 additions and 0 deletions
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84
tools/testing/selftests/bpf/prog_tests/tailcalls.c
View File

@ -1,6 +1,9 @@
// SPDX-License-Identifier: GPL-2.0
#include <unistd.h>
#include <test_progs.h>
#include <network_helpers.h>
#include "tailcall_poke.skel.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
@ -1105,6 +1108,85 @@ out:
bpf_object__close(tgt_obj);
}
#define JMP_TABLE "/sys/fs/bpf/jmp_table"
static int poke_thread_exit;
static void *poke_update(void *arg)
{
__u32 zero = 0, prog1_fd, prog2_fd, map_fd;
struct tailcall_poke *call = arg;
map_fd = bpf_map__fd(call->maps.jmp_table);
prog1_fd = bpf_program__fd(call->progs.call1);
prog2_fd = bpf_program__fd(call->progs.call2);
while (!poke_thread_exit) {
bpf_map_update_elem(map_fd, &zero, &prog1_fd, BPF_ANY);
bpf_map_update_elem(map_fd, &zero, &prog2_fd, BPF_ANY);
}
return NULL;
}
/*
* We are trying to hit prog array update during another program load
* that shares the same prog array map.
*
* For that we share the jmp_table map between two skeleton instances
* by pinning the jmp_table to same path. Then first skeleton instance
* periodically updates jmp_table in 'poke update' thread while we load
* the second skeleton instance in the main thread.
*/
static void test_tailcall_poke(void)
{
struct tailcall_poke *call, *test;
int err, cnt = 10;
pthread_t thread;
unlink(JMP_TABLE);
call = tailcall_poke__open_and_load();
if (!ASSERT_OK_PTR(call, "tailcall_poke__open"))
return;
err = bpf_map__pin(call->maps.jmp_table, JMP_TABLE);
if (!ASSERT_OK(err, "bpf_map__pin"))
goto out;
err = pthread_create(&thread, NULL, poke_update, call);
if (!ASSERT_OK(err, "new toggler"))
goto out;
while (cnt--) {
test = tailcall_poke__open();
if (!ASSERT_OK_PTR(test, "tailcall_poke__open"))
break;
err = bpf_map__set_pin_path(test->maps.jmp_table, JMP_TABLE);
if (!ASSERT_OK(err, "bpf_map__pin")) {
tailcall_poke__destroy(test);
break;
}
bpf_program__set_autoload(test->progs.test, true);
bpf_program__set_autoload(test->progs.call1, false);
bpf_program__set_autoload(test->progs.call2, false);
err = tailcall_poke__load(test);
tailcall_poke__destroy(test);
if (!ASSERT_OK(err, "tailcall_poke__load"))
break;
}
poke_thread_exit = 1;
ASSERT_OK(pthread_join(thread, NULL), "pthread_join");
out:
bpf_map__unpin(call->maps.jmp_table, JMP_TABLE);
tailcall_poke__destroy(call);
}
void test_tailcalls(void)
{
if (test__start_subtest("tailcall_1"))
@ -1139,4 +1221,6 @@ void test_tailcalls(void)
test_tailcall_bpf2bpf_fentry_fexit();
if (test__start_subtest("tailcall_bpf2bpf_fentry_entry"))
test_tailcall_bpf2bpf_fentry_entry();
if (test__start_subtest("tailcall_poke"))
test_tailcall_poke();
}

32
tools/testing/selftests/bpf/progs/tailcall_poke.c Normal file
View File

@ -0,0 +1,32 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
char _license[] SEC("license") = "GPL";
struct {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__uint(max_entries, 1);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u32));
} jmp_table SEC(".maps");
SEC("?fentry/bpf_fentry_test1")
int BPF_PROG(test, int a)
{
bpf_tail_call_static(ctx, &jmp_table, 0);
return 0;
}
SEC("fentry/bpf_fentry_test1")
int BPF_PROG(call1, int a)
{
return 0;
}
SEC("fentry/bpf_fentry_test1")
int BPF_PROG(call2, int a)
{
return 0;
}