From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-186.mta0.migadu.com (out-186.mta0.migadu.com [91.218.175.186]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF26F422545 for ; Fri, 10 Jul 2026 15:44:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.186 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783698252; cv=none; b=kLANhMdf6yREHwloaizrkkKZAaXkRcURVD8P304C7CpkyNObdcAwwKqzqlZGf2kwjeAS0U2v+yP7tzs3aou3t8RJ4oF/L46C/lkHjvZCB06oxRh6WyFeUbWOaiwF5CXvNl37hP7uXPYxZPKrRb/rEqwvAs+wOZ/3PGod/HBY+5Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783698252; c=relaxed/simple; bh=TCjdOlVN5VsiVS5G9/zcGIlOX2Mrnnty8wmg/bxHoes=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NfPF5QvVy9szPC4jTEhtk3YvJYUv5iqmiwW2J7MT4AxOkGGCLRMNSS64BT3W4C3S5d7HahL6hQb/y+ckitVmBkBsKvi9N6QrkFCEExY8lxvDrvaq9BsvYLCcu0Pg5GjgQ8YRsYQjKyE5RWE/eQhF5QqlKE2CI2VC7dVOETwLK1s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=b0GhkuCD; arc=none smtp.client-ip=91.218.175.186 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="b0GhkuCD" Message-ID: <8a01331a-8296-4860-a8f0-cdf3cfcfe19a@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1783698236; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GPGeJudEf6et3fiACcWKhIe5Vz9K7dJmFGcd3lJV1/0=; b=b0GhkuCDsJEXZhnUAC0ATR9h47by6XDiwIcAYguNALAbc+Wi/P119LqgpL7e4ps5QNvtKL sBEKJbP7xIc3RekBDWlEAZtEWeH0fcYCBoVDqX2MpV/vVYFAnyq2mm4ubmv4j1b/09Spwp y99cjoqs2u573I55KSrkAz5rgNIE2xU= Date: Fri, 10 Jul 2026 08:43:51 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf 2/2] selftests/bpf: Add test for >8 byte return value on fexit attach Content-Language: en-GB To: Leon Hwang , bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , kernel-team@fb.com References: <20260710144404.2579671-1-yonghong.song@linux.dev> <20260710144409.2580215-1-yonghong.song@linux.dev> <9401462c-ea70-4541-acb0-78cf2e6c34dc@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <9401462c-ea70-4541-acb0-78cf2e6c34dc@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 7/10/26 8:29 AM, Leon Hwang wrote: > On 2026/7/10 22:44, Yonghong Song wrote: >> The BPF trampoline preserves only 8 bytes of the target's return value >> (R0), so attaching an fexit/fmod_ret/fsession program to a function that >> returns a >8 byte value is now rejected by the verifier. >> >> Add a bpf_testmod function returning __int128 and an fexit program that >> targets it. The program is expected to fail to load with the >> "with a >8 byte return value is not supported for this attach type" >> message. >> >> __int128 is only available on 64-bit targets (where the compiler defines >> __SIZEOF_INT128__). Guard the testmod function and the test with >> __SIZEOF_INT128__ so a 32-bit build still compiles; on such builds >> the subtest is simply not run. >> >> Signed-off-by: Yonghong Song >> --- >> .../selftests/bpf/prog_tests/tracing_failure.c | 12 ++++++++++++ >> tools/testing/selftests/bpf/progs/tracing_failure.c | 6 ++++++ >> .../testing/selftests/bpf/test_kmods/bpf_testmod.c | 13 +++++++++++++ >> 3 files changed, 31 insertions(+) >> >> diff --git a/tools/testing/selftests/bpf/prog_tests/tracing_failure.c b/tools/testing/selftests/bpf/prog_tests/tracing_failure.c >> index f9f9e1cb87bf..6c199f5ff4db 100644 >> --- a/tools/testing/selftests/bpf/prog_tests/tracing_failure.c >> +++ b/tools/testing/selftests/bpf/prog_tests/tracing_failure.c >> @@ -76,6 +76,14 @@ static void test_fexit_noreturns(void) >> "Attaching fexit/fsession/fmod_ret to __noreturn function 'do_exit' is rejected."); >> } >> >> +#ifdef __SIZEOF_INT128__ >> +static void test_fexit_int128_ret(void) >> +{ >> + test_tracing_fail_prog("fexit_int128_ret", >> + "with a >8 byte return value is not supported for this attach type"); >> +} > > Seems that this subtest can be simplified to > > static void test_fexit_int128_ret(void) > { > #ifdef __SIZEOF_INT128__ > test_tracing_fail_prog("fexit_int128_ret", > "with a >8 byte return value is not supported for this attach > type"); > #else > test__skip(); > #endif > } > > Then, no '#ifdef' below. Thanks. Let me test this. > > Thanks, > Leon > >> +#endif >> + >> void test_tracing_failure(void) >> { >> if (test__start_subtest("bpf_spin_lock")) >> @@ -86,4 +94,8 @@ void test_tracing_failure(void) >> test_tracing_deny(); >> if (test__start_subtest("fexit_noreturns")) >> test_fexit_noreturns(); >> +#ifdef __SIZEOF_INT128__ >> + if (test__start_subtest("fexit_int128_ret")) >> + test_fexit_int128_ret(); >> +#endif >> } >> diff --git a/tools/testing/selftests/bpf/progs/tracing_failure.c b/tools/testing/selftests/bpf/progs/tracing_failure.c >> index 65e485c4468c..f7a095767679 100644 >> --- a/tools/testing/selftests/bpf/progs/tracing_failure.c >> +++ b/tools/testing/selftests/bpf/progs/tracing_failure.c >> @@ -30,3 +30,9 @@ int BPF_PROG(fexit_noreturns) >> { >> return 0; >> } >> + >> +SEC("?fexit/bpf_testmod_test_int128_ret") >> +int BPF_PROG(fexit_int128_ret) >> +{ >> + return 0; >> +} >> diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c >> index 30f1cd23093c..902dbf658250 100644 >> --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c >> +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c >> @@ -161,6 +161,15 @@ bpf_testmod_test_arg_ptr_to_struct(struct bpf_testmod_struct_arg_1 *a) { >> return bpf_testmod_test_struct_arg_result; >> } >> >> +#ifdef __SIZEOF_INT128__ >> +noinline __int128 >> +bpf_testmod_test_int128_ret(int a) >> +{ >> + bpf_testmod_test_struct_arg_result = a; >> + return (__int128)a; >> +} >> +#endif >> + >> __weak noinline void bpf_testmod_looooooooooooooooooooooooooooooong_name(void) >> { >> } >> @@ -514,6 +523,10 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj, >> >> (void)bpf_testmod_test_arg_ptr_to_struct(&struct_arg1_2); >> >> +#ifdef __SIZEOF_INT128__ >> + (void)bpf_testmod_test_int128_ret(i); >> +#endif >> + >> (void)trace_bpf_testmod_test_raw_tp_null_tp(NULL); >> >> bpf_testmod_test_struct_ops3();