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@xxxxxxxxxxxxx> Cc: Johan Almbladh <johan.almbladh@xxxxxxxxxxxxxxxxx> Cc: Paul Chaignon <paul@xxxxxxxxx> Cc: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx> Link: https://lore.kernel.org/bpf/CAM1=_QRyRVCODcXo_Y6qOm1iT163HoiSj8U2pZ8Rj3hzMTT=HQ@xxxxxxxxxxxxxx --- [ Cooked up proper patch for it after manual inspection as I think it's useful in any case to have the coverage for both JIT code generation cases. ] .../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 diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c index b5940e6ca67c..7bf3a7a97d7b 100644 --- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c +++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c @@ -219,10 +219,7 @@ static void test_tailcall_2(void) 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 @@ static void test_tailcall_3(void) 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")) diff --git a/tools/testing/selftests/bpf/progs/tailcall6.c b/tools/testing/selftests/bpf/progs/tailcall6.c new file mode 100644 index 000000000000..0f4a811cc028 --- /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"; -- 2.27.0
