From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta1.migadu.com (out-189.mta1.migadu.com [95.215.58.189]) (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 07D4F1DE2A7 for ; Wed, 18 Jun 2025 04:36:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750221393; cv=none; b=oAJeGV8lqatBasEpsW6PwU25q8/0fOZ/SFEefX4qsfN5cwU1fuIOWmm9HAN6hKq4lU/3rwnXS38tCfBG+FqH+WHRr7eta9O11nDuTrNtaqCmpEd6gt+L0oRWBOnwg+v94L5Ow1KdBCivRCMwrui1LPSEHrTNmni2JSIFVHj8vL8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750221393; c=relaxed/simple; bh=w4pcOt+ScaAM5Jfr0CS430TwrL8pDBZeEekyT57w/QM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=fY4BQpq4G2Y5l+1wmcrIwto3JOHACn4NfHNCWSMfQ9aYW3zZooVDaLJqkfc4G017K7/QAaC4w7BgAe5xPg4rJPnwrG28Hb1I7g/rrfNDaapub+aqTFgmzun9IUVGMe/rR2yIkx7PRzDgvUZ/7xJH+pZ0aiQsTRagc1fHgxXI33M= 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=WuGvWiEo; arc=none smtp.client-ip=95.215.58.189 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="WuGvWiEo" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1750221387; 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=vMiBGwJIFsuwKorQA5fQy1QVopHhwCl6+KnXqj2rbSc=; b=WuGvWiEoIpWes/X3aCpDaHrlKnkMllDPN3RjE0i5YkO4ips96xJtiY3lLkgZQk3blVa+IB 8JMArdIWra9aqciu6IMHPrRcJNPP1JwoCi76KXO7SI/uTo8CYzoQ/e/csc/Evm41szivCT QnM8Mnj2dEK6XoKIT47AWsJ6D1Nr34Y= Date: Tue, 17 Jun 2025 21:36:15 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v2 1/3] selftests/bpf: Refactor the failed assertion to another subtest Content-Language: en-GB To: Andrii Nakryiko Cc: bpf@vger.kernel.org, Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com, Martin KaFai Lau References: <20250615185345.2756663-1-yonghong.song@linux.dev> <20250615185351.2757391-1-yonghong.song@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT On 6/16/25 3:00 PM, Andrii Nakryiko wrote: > On Sun, Jun 15, 2025 at 11:54 AM Yonghong Song wrote: >> When building the selftest with arm64/clang20, the following test failed: >> ... >> ubtest_multispec_usdt:PASS:usdt_100_called 0 nsec >> subtest_multispec_usdt:PASS:usdt_100_sum 0 nsec >> subtest_multispec_usdt:FAIL:usdt_300_bad_attach unexpected pointer: 0xaaaad82a2a80 >> #469/2 usdt/multispec:FAIL >> #469 usdt:FAIL >> >> The failed assertion >> subtest_multispec_usdt:FAIL:usdt_300_bad_attach unexpected pointer: 0xaaaad82a2a80 >> is caused by bpf_program__attach_usdt() which is expected to fail. But >> with arm64/clang20 bpf_program__attach_usdt() actually succeeded. > I think I missed that it's unexpected *success* that is causing > issues. If that's so, then I think it might be more straightforward to > just ensure that test is expectedly failing regardless of compiler > code generation logic. Maybe something along the following lines: > > diff --git a/tools/testing/selftests/bpf/prog_tests/usdt.c > b/tools/testing/selftests/bpf/prog_tests/usdt.c > index 495d66414b57..fdd8642cfdff 100644 > --- a/tools/testing/selftests/bpf/prog_tests/usdt.c > +++ b/tools/testing/selftests/bpf/prog_tests/usdt.c > @@ -190,11 +190,21 @@ static void __always_inline f300(int x) > STAP_PROBE1(test, usdt_300, x); > } > > +#define RP10(F, X) F(*(X+0)); F(*(X+1));F(*(X+2)); F(*(X+3)); F(*(X+4)); \ > + F(*(X+5)); F(*(X+6)); F(*(X+7)); F(*(X+8)); F(*(X+9)); > +#define RP100(F, X) RP10(F,X+ > 0);RP10(F,X+10);RP10(F,X+20);RP10(F,X+30);RP10(F,X+40); \ > + > RP10(F,X+50);RP10(F,X+60);RP10(F,X+70);RP10(F,X+80);RP10(F,X+90); > + > __weak void trigger_300_usdts(void) > { > - R100(f300, 0); > - R100(f300, 100); > - R100(f300, 200); > + volatile int arr[300], i; > + > + for (i = 0; i < 300; i++) > + arr[i] = 300; > + > + RP100(f300, arr + 0); > + RP100(f300, arr + 100); > + RP100(f300, arr + 200); > } > > > So basically force the compiler to use 300 different locations for > each of 300 USDT instantiations? I didn't check how that will look > like on arm64, but on x86 gcc it seems to generate what is expected of > it. > > Can you please try it on arm64 and see if that works? I tried the above on arm64 and it does not work. It has the same usdt arguments as without this patch: stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors) Provider: test Name: usdt_300 Location: 0x00000000000009e0, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 Arguments: -4@[x9] stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors) Provider: test Name: usdt_300 Location: 0x00000000000009f8, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 Arguments: -4@[x9] ... But I found if we build usdt.c file with -O2 (RELEASE=1) on arm64, the test will be successful: stapsdt 0x0000002b NT_STAPSDT (SystemTap probe descriptors) Provider: test Name: usdt_300 Location: 0x00000000000001a4, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 Arguments: -4@0 stapsdt 0x0000002b NT_STAPSDT (SystemTap probe descriptors) Provider: test Name: usdt_300 Location: 0x00000000000001a8, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 Arguments: -4@1 ... But usdt.c with -O2 will have a problem with gcc14 on x86: stapsdt 0x00000087 NT_STAPSDT (SystemTap probe descriptors) Provider: test Name: usdt12 Location: 0x000000000000258f, Base: 0x0000000000000000, Semaphore: 0x0000000000000006 Arguments: -4@$2 -4@$3 -8@$42 -8@$44 -4@$5 -8@$6 8@%rdx 8@%rsi -4@$-9 -2@%cx -2@nums(%rax,%rax) -1@t1+4(%rip) ... You can see the above last two arguments which are not supported by libbpf. So let us say usdt.c is compiled with -O2: x86: gcc14 built kernel/selftests: failed, see the above clang built kernel/selftests: good arm64: both gcc14/clang built kernel/selftrests: good arm64 has more reigsters so it is likely to have better argument representation, e.g., for arm64/gcc with -O2, we have stapsdt 0x00000071 NT_STAPSDT (SystemTap probe descriptors) Provider: test Name: usdt12 Location: 0x0000000000002e74, Base: 0x0000000000000000, Semaphore: 0x000000000000000a Arguments: -4@2 -4@3 -8@42 -8@44 -4@5 -8@6 8@x1 8@x3 -4@-9 -2@x2 -2@[x0, 8] -1@[x3, 28] Eduard helped me to figure out how to compile prog_tests/usdt.c with -O2 alone. The following patch resolved the issue and usdt test will be happy for both x86 and arm64: diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index 97013c49920b..05fc9149bc4f 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -760,6 +760,14 @@ TRUNNER_BPF_BUILD_RULE := $$(error no BPF objects should be built) TRUNNER_BPF_CFLAGS := $(eval $(call DEFINE_TEST_RUNNER,test_maps)) +# Compiler prog_tests/usdt.c with -O2 with clang compiler. +# Otherwise, with -O0 on arm64, the usdt test will fail. +ifneq ($(LLVM),) +$(OUTPUT)/usdt.test.o: CFLAGS:=$(subst O0,O2,$(CFLAGS)) +$(OUTPUT)/cpuv4/usdt.test.o: CFLAGS:=$(subst O0,O2,$(CFLAGS)) +$(OUTPUT)/no_alu32/usdt.test.o: CFLAGS:=$(subst O0,O2,$(CFLAGS)) +endif + # Define test_verifier test runner. # It is much simpler than test_maps/test_progs and sufficiently different from # them (e.g., test.h is using completely pattern), that it's worth just Another choice is to support argument like `-2@nums(%rax,%rax)` and `-1@t1+4(%rip)`. But I am not sure whether we should do it or not as typically a usdt probe probably won't have lots of diverse arguments. WDYT? > >> Checking usdt probes with usdt.test.o, >> >> with gcc11 build binary: >> stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x00000000000054f8, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[sp] >> stapsdt 0x00000031 NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x0000000000005510, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[sp, 4] >> ... >> stapsdt 0x00000032 NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x0000000000005660, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[sp, 60] >> ... >> stapsdt 0x00000034 NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x00000000000070e8, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[sp, 1192] >> stapsdt 0x00000034 NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x0000000000007100, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[sp, 1196] >> ... >> stapsdt 0x00000032 NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x0000000000009ec4, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[sp, 60] >> >> with clang20 build binary: >> stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x00000000000009a0, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[x9] >> stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x00000000000009b8, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[x9] >> ... >> stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x0000000000002590, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[x9] >> stapsdt 0x0000002e NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x00000000000025a8, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[x8] >> ... >> stapsdt 0x0000002f NT_STAPSDT (SystemTap probe descriptors) >> Provider: test >> Name: usdt_300 >> Location: 0x0000000000007fdc, Base: 0x0000000000000000, Semaphore: 0x0000000000000008 >> Arguments: -4@[x10] >> >> There are total 301 locations for usdt_300. For gcc11 built binary, there are >> 300 spec's. But for clang20 built binary, there are 3 spec's. The libbpf default >> BPF_USDT_MAX_SPEC_CNT is 256. So for gcc11, the above bpf_program__attach_usdt() will >> fail, but the function will succeed for clang20. >> >> Note that we cannot just change BPF_USDT_MAX_SPEC_CNT from 256 to 2 (through overwriting >> BPF_USDT_MAX_SPEC_CNT before usdt.bpf.h) since it will cause other test failures. >> We cannot just set BPF_USDT_MAX_SPEC_CNT to 2 for test_usdt_multispec.c since we >> have below in the Makefile: >> test_usdt.skel.h-deps := test_usdt.bpf.o test_usdt_multispec.bpf.o >> and the linker will enforce that BPF_USDT_MAX_SPEC_CNT values for both progs must >> be the same. >> >> The refactoring does not change existing test result. But the future change will >> allow to set BPF_USDT_MAX_SPEC_CNT to be 2 for arm64/clang20 case, which will have >> the same attachment failure as in gcc11. >> >> Signed-off-by: Yonghong Song >> --- >> tools/testing/selftests/bpf/prog_tests/usdt.c | 35 +++++++++++++------ >> 1 file changed, 25 insertions(+), 10 deletions(-) >> >> diff --git a/tools/testing/selftests/bpf/prog_tests/usdt.c b/tools/testing/selftests/bpf/prog_tests/usdt.c >> index 495d66414b57..dc29ef94312a 100644 >> --- a/tools/testing/selftests/bpf/prog_tests/usdt.c >> +++ b/tools/testing/selftests/bpf/prog_tests/usdt.c >> @@ -270,18 +270,8 @@ static void subtest_multispec_usdt(void) >> */ >> trigger_300_usdts(); >> >> - /* we'll reuse usdt_100 BPF program for usdt_300 test */ >> bpf_link__destroy(skel->links.usdt_100); >> - skel->links.usdt_100 = bpf_program__attach_usdt(skel->progs.usdt_100, -1, "/proc/self/exe", >> - "test", "usdt_300", NULL); >> - err = -errno; >> - if (!ASSERT_ERR_PTR(skel->links.usdt_100, "usdt_300_bad_attach")) >> - goto cleanup; >> - ASSERT_EQ(err, -E2BIG, "usdt_300_attach_err"); >> >> - /* let's check that there are no "dangling" BPF programs attached due >> - * to partial success of the above test:usdt_300 attachment >> - */ >> bss->usdt_100_called = 0; >> bss->usdt_100_sum = 0; >> >> @@ -312,6 +302,29 @@ static void subtest_multispec_usdt(void) >> test_usdt__destroy(skel); >> } >> >> +static void subtest_multispec_fail_usdt(void) >> +{ >> + LIBBPF_OPTS(bpf_usdt_opts, opts); >> + struct test_usdt *skel; >> + int err; >> + >> + skel = test_usdt__open_and_load(); >> + if (!ASSERT_OK_PTR(skel, "skel_open")) >> + return; >> + >> + skel->bss->my_pid = getpid(); >> + >> + skel->links.usdt_100 = bpf_program__attach_usdt(skel->progs.usdt_100, -1, "/proc/self/exe", >> + "test", "usdt_300", NULL); >> + err = -errno; >> + if (!ASSERT_ERR_PTR(skel->links.usdt_100, "usdt_300_bad_attach")) >> + goto cleanup; >> + ASSERT_EQ(err, -E2BIG, "usdt_300_attach_err"); >> + >> +cleanup: >> + test_usdt__destroy(skel); >> +} >> + >> static FILE *urand_spawn(int *pid) >> { >> FILE *f; >> @@ -422,6 +435,8 @@ void test_usdt(void) >> subtest_basic_usdt(); >> if (test__start_subtest("multispec")) >> subtest_multispec_usdt(); >> + if (test__start_subtest("multispec_fail")) >> + subtest_multispec_fail_usdt(); >> if (test__start_subtest("urand_auto_attach")) >> subtest_urandom_usdt(true /* auto_attach */); >> if (test__start_subtest("urand_pid_attach")) >> -- >> 2.47.1 >>