From: Daniel Borkmann <daniel@iogearbox.net>
Date: Fri, 10 Sep 2021 11:19:00 +0200
Subject: bpf, selftests: Replicate tailcall limit test for indirect call case
Patch-mainline: v5.16-rc1
Git-commit: dbd7eb14e0607afa1dd3aee7175f37022ecc5f03
References: jsc#PED-1377
The tailcall_3 test program uses bpf_tail_call_static() where the JIT
would patch a direct jump. Add a new tailcall_6 test program replicating
exactly the same test just ensuring that bpf_tail_call() uses a map
index where the verifier cannot make assumptions this time.
In other words, this will now cover both on x86-64 JIT, meaning, JIT
images with emit_bpf_tail_call_direct() emission as well as JIT images
with emit_bpf_tail_call_indirect() emission.
# echo 1 > /proc/sys/net/core/bpf_jit_enable
# ./test_progs -t tailcalls
#136/1 tailcalls/tailcall_1:OK
#136/2 tailcalls/tailcall_2:OK
#136/3 tailcalls/tailcall_3:OK
#136/4 tailcalls/tailcall_4:OK
#136/5 tailcalls/tailcall_5:OK
#136/6 tailcalls/tailcall_6:OK
#136/7 tailcalls/tailcall_bpf2bpf_1:OK
#136/8 tailcalls/tailcall_bpf2bpf_2:OK
#136/9 tailcalls/tailcall_bpf2bpf_3:OK
#136/10 tailcalls/tailcall_bpf2bpf_4:OK
#136/11 tailcalls/tailcall_bpf2bpf_5:OK
#136 tailcalls:OK
Summary: 1/11 PASSED, 0 SKIPPED, 0 FAILED
# echo 0 > /proc/sys/net/core/bpf_jit_enable
# ./test_progs -t tailcalls
#136/1 tailcalls/tailcall_1:OK
#136/2 tailcalls/tailcall_2:OK
#136/3 tailcalls/tailcall_3:OK
#136/4 tailcalls/tailcall_4:OK
#136/5 tailcalls/tailcall_5:OK
#136/6 tailcalls/tailcall_6:OK
[...]
For interpreter, the tailcall_1-6 tests are passing as well. The later
tailcall_bpf2bpf_* are failing due lack of bpf2bpf + tailcall support
in interpreter, so this is expected.
Also, manual inspection shows that both loaded programs from tailcall_3
and tailcall_6 test case emit the expected opcodes:
* tailcall_3 disasm, emit_bpf_tail_call_direct():
[...]
b: push %rax
c: push %rbx
d: push %r13
f: mov %rdi,%rbx
12: movabs $0xffff8d3f5afb0200,%r13
1c: mov %rbx,%rdi
1f: mov %r13,%rsi
22: xor %edx,%edx _
24: mov -0x4(%rbp),%eax | limit check
2a: cmp $0x20,%eax |
2d: ja 0x0000000000000046 |
2f: add $0x1,%eax |
32: mov %eax,-0x4(%rbp) |_
38: nopl 0x0(%rax,%rax,1)
3d: pop %r13
3f: pop %rbx
40: pop %rax
41: jmpq 0xffffffffffffe377
[...]
* tailcall_6 disasm, emit_bpf_tail_call_indirect():
[...]
47: movabs $0xffff8d3f59143a00,%rsi
51: mov %edx,%edx
53: cmp %edx,0x24(%rsi)
56: jbe 0x0000000000000093 _
58: mov -0x4(%rbp),%eax | limit check
5e: cmp $0x20,%eax |
61: ja 0x0000000000000093 |
63: add $0x1,%eax |
66: mov %eax,-0x4(%rbp) |_
6c: mov 0x110(%rsi,%rdx,8),%rcx
74: test %rcx,%rcx
77: je 0x0000000000000093
79: pop %rax
7a: mov 0x30(%rcx),%rcx
7e: add $0xb,%rcx
82: callq 0x000000000000008e
87: pause
89: lfence
8c: jmp 0x0000000000000087
8e: mov %rcx,(%rsp)
92: retq
[...]
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Tested-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Acked-by: Paul Chaignon <paul@cilium.io>
Link: https://lore.kernel.org/bpf/CAM1=_QRyRVCODcXo_Y6qOm1iT163HoiSj8U2pZ8Rj3hzMTT=HQ@mail.gmail.com
Link: https://lore.kernel.org/bpf/20210910091900.16119-1-daniel@iogearbox.net
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
tools/testing/selftests/bpf/prog_tests/tailcalls.c | 25 ++++++++++++---
tools/testing/selftests/bpf/progs/tailcall6.c | 34 +++++++++++++++++++++
2 files changed, 54 insertions(+), 5 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/tailcall6.c
--- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c
+++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c
@@ -219,10 +219,7 @@ out:
bpf_object__close(obj);
}
-/* test_tailcall_3 checks that the count value of the tail call limit
- * enforcement matches with expectations.
- */
-static void test_tailcall_3(void)
+static void test_tailcall_count(const char *which)
{
int err, map_fd, prog_fd, main_fd, data_fd, i, val;
struct bpf_map *prog_array, *data_map;
@@ -231,7 +228,7 @@ static void test_tailcall_3(void)
__u32 retval, duration;
char buff[128] = {};
- err = bpf_prog_load("tailcall3.o", BPF_PROG_TYPE_SCHED_CLS, &obj,
+ err = bpf_prog_load(which, BPF_PROG_TYPE_SCHED_CLS, &obj,
&prog_fd);
if (CHECK_FAIL(err))
return;
@@ -296,6 +293,22 @@ out:
bpf_object__close(obj);
}
+/* test_tailcall_3 checks that the count value of the tail call limit
+ * enforcement matches with expectations. JIT uses direct jump.
+ */
+static void test_tailcall_3(void)
+{
+ test_tailcall_count("tailcall3.o");
+}
+
+/* test_tailcall_6 checks that the count value of the tail call limit
+ * enforcement matches with expectations. JIT uses indirect jump.
+ */
+static void test_tailcall_6(void)
+{
+ test_tailcall_count("tailcall6.o");
+}
+
/* test_tailcall_4 checks that the kernel properly selects indirect jump
* for the case where the key is not known. Latter is passed via global
* data to select different targets we can compare return value of.
@@ -822,6 +835,8 @@ void test_tailcalls(void)
test_tailcall_4();
if (test__start_subtest("tailcall_5"))
test_tailcall_5();
+ if (test__start_subtest("tailcall_6"))
+ test_tailcall_6();
if (test__start_subtest("tailcall_bpf2bpf_1"))
test_tailcall_bpf2bpf_1();
if (test__start_subtest("tailcall_bpf2bpf_2"))
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tailcall6.c
@@ -0,0 +1,34 @@
+// 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, 1);
+ __uint(key_size, sizeof(__u32));
+ __uint(value_size, sizeof(__u32));
+} jmp_table SEC(".maps");
+
+int count, which;
+
+SEC("classifier/0")
+int bpf_func_0(struct __sk_buff *skb)
+{
+ count++;
+ if (__builtin_constant_p(which))
+ __bpf_unreachable();
+ bpf_tail_call(skb, &jmp_table, which);
+ return 1;
+}
+
+SEC("classifier")
+int entry(struct __sk_buff *skb)
+{
+ if (__builtin_constant_p(which))
+ __bpf_unreachable();
+ bpf_tail_call(skb, &jmp_table, which);
+ return 0;
+}
+
+char __license[] SEC("license") = "GPL";