On 2026/1/28 23:01 Leon Hwang <[email protected]> write: > fsession programs can currently be loaded on architectures that do not > implement fsession support, which leads to runtime errors instead of a > clean verifier rejection. > > For example, running fsession selftests on arm64 before fsession support > is added results in: > > test_fsession_basic:PASS:fsession_test__open_and_load 0 nsec > test_fsession_basic:PASS:fsession_attach 0 nsec > check_result:FAIL:test_run_opts err unexpected error: -14 (errno 14) > > Introduce bpf_arch_supports_fsession() to explicitly gate fsession usage > based on architecture support. Architectures without fsession support > will now fail program load with -EOPNOTSUPP, allowing selftests to skip > cleanly instead of errors at runtime. > > x86 declares fsession support, while the default implementation returns > false. > > Fixes: 2d419c44658f ("bpf: add fsession support")
I were wondering how this problem happen, as I remember that I added such checking. When I look back, I found that the checking is lost during v3->v4. I recalled that the AI warned me about this part, but I thought that checking exists in my mind :/ It seems that we can't ignore the AI's warning easily. It mostly make sense. > Signed-off-by: Leon Hwang <[email protected]> > --- > arch/x86/net/bpf_jit_comp.c | 5 +++ > include/linux/filter.h | 1 + > kernel/bpf/core.c | 5 +++ > kernel/bpf/verifier.c | 3 ++ > .../selftests/bpf/prog_tests/fsession_test.c | 32 ++++++++++++++----- > 5 files changed, 38 insertions(+), 8 deletions(-) > > diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c > index 5a075e06cf45..070ba80e39d7 100644 > --- a/arch/x86/net/bpf_jit_comp.c > +++ b/arch/x86/net/bpf_jit_comp.c > @@ -4112,3 +4112,8 @@ bool bpf_jit_supports_timed_may_goto(void) > { > return true; > } > + > +bool bpf_jit_supports_fsession(void) > +{ > + return true; > +} > diff --git a/include/linux/filter.h b/include/linux/filter.h > index fd54fed8f95f..4e1cb4f91f49 100644 > --- a/include/linux/filter.h > +++ b/include/linux/filter.h > @@ -1167,6 +1167,7 @@ bool bpf_jit_supports_arena(void); > bool bpf_jit_supports_insn(struct bpf_insn *insn, bool in_arena); > bool bpf_jit_supports_private_stack(void); > bool bpf_jit_supports_timed_may_goto(void); > +bool bpf_jit_supports_fsession(void); > u64 bpf_arch_uaddress_limit(void); > void arch_bpf_stack_walk(bool (*consume_fn)(void *cookie, u64 ip, u64 sp, > u64 bp), void *cookie); > u64 arch_bpf_timed_may_goto(void); > diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > index e0b8a8a5aaa9..3b1eb632bf7c 100644 > --- a/kernel/bpf/core.c > +++ b/kernel/bpf/core.c > @@ -3142,6 +3142,11 @@ bool __weak bpf_jit_supports_insn(struct bpf_insn > *insn, bool in_arena) > return false; > } > > +bool __weak bpf_jit_supports_fsession(void) > +{ > + return false; > +} > + > u64 __weak bpf_arch_uaddress_limit(void) > { > #if defined(CONFIG_64BIT) && > defined(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index c2f2650db9fd..6f867ebf78d1 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -24872,6 +24872,9 @@ int bpf_check_attach_target(struct bpf_verifier_log > *log, > case BPF_TRACE_FENTRY: > case BPF_TRACE_FEXIT: > case BPF_TRACE_FSESSION: > + if (prog->expected_attach_type == BPF_TRACE_FSESSION && > + !bpf_jit_supports_fsession()) > + return -EOPNOTSUPP; > if (!btf_type_is_func(t)) { > bpf_log(log, "attach_btf_id %u is not a function\n", > btf_id); > diff --git a/tools/testing/selftests/bpf/prog_tests/fsession_test.c > b/tools/testing/selftests/bpf/prog_tests/fsession_test.c > index 0c4b428e1cee..a299aeb8cc2e 100644 > --- a/tools/testing/selftests/bpf/prog_tests/fsession_test.c > +++ b/tools/testing/selftests/bpf/prog_tests/fsession_test.c > @@ -29,8 +29,16 @@ static void test_fsession_basic(void) > struct fsession_test *skel = NULL; > int err; > > - skel = fsession_test__open_and_load(); > - if (!ASSERT_OK_PTR(skel, "fsession_test__open_and_load")) > + skel = fsession_test__open(); > + if (!ASSERT_OK_PTR(skel, "fsession_test__open")) > + return; > + > + err = fsession_test__load(skel); > + if (err == -EOPNOTSUPP) { > + test__skip(); > + goto cleanup; > + } > + if (!ASSERT_OK(err, "fsession_test__load")) > goto cleanup; > > err = fsession_test__attach(skel); > @@ -47,8 +55,16 @@ static void test_fsession_reattach(void) > struct fsession_test *skel = NULL; > int err; > > - skel = fsession_test__open_and_load(); > - if (!ASSERT_OK_PTR(skel, "fsession_test__open_and_load")) > + skel = fsession_test__open(); > + if (!ASSERT_OK_PTR(skel, "fsession_test__open")) > + return; > + > + err = fsession_test__load(skel); > + if (err == -EOPNOTSUPP) { > + test__skip(); > + goto cleanup; > + } > + if (!ASSERT_OK(err, "fsession_test__load")) > goto cleanup; > > /* first attach */ > @@ -94,6 +110,10 @@ static void test_fsession_cookie(void) > bpf_program__set_autoload(skel->progs.test6, false); > > err = fsession_test__load(skel); > + if (err == -EOPNOTSUPP) { > + test__skip(); > + goto cleanup; > + } > if (!ASSERT_OK(err, "fsession_test__load")) > goto cleanup; > > @@ -111,10 +131,6 @@ static void test_fsession_cookie(void) > > void test_fsession_test(void) > { > -#if !defined(__x86_64__) > - test__skip(); > - return; > -#endif Ah, I see you enabled the testing for arm64 in this patch. Maybe we can move this part to the 3rd patch, or split it out to another patch? TBH, I prefer the previous implement. In this way, the CI can still pass if x86_64 or arm64 return -EOPNOTSUPP, right? Maybe you can test the not-supported case stand alone, such as: #if !defined(__x86_64__) test__fsession_not_support(); return; #endif wdyt? Thanks! Menglong Dong > if (test__start_subtest("fsession_test")) > test_fsession_basic(); > if (test__start_subtest("fsession_reattach")) > -- > 2.52.0 > > >
