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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sW8yb4Cg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="sW8yb4Cg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7DBCCC4CEC3; Tue, 22 Oct 2024 23:52:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729641138; bh=rFVlsj1qHn0/duDf7jKx17I7NGXKofb8ULGbc4GE0XI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sW8yb4CgXjRyuzn3MRhtnszS8mdpFspNU2huCIPazc07bCEAKZORjJxPKbw17eAqF 7qFgowQUCXRLpTpqzKodv6Jp4U0vlnrKOtw9S+bjBPKzQbcP1kKGYjRGQ2/On7A7p8 4xHzZY21eBgWXyNZOdFIjX83AaMXJuL9E/AT53fGpcbqIRdx5rrNHP4Uxos1saHkd9 Z8vnbovbGHlfD2IsjTjLCYfUMJA6+eVg4LO9htSthcJAHW8WhGjNpJGkZuADn5yQ33 fxcP/oWVhxquaNa6g5z7Abcoq2S8QEciQGpoWgewfmKCWhCfZ7CKw0pdj3GADQcYCr libLGrNRrEa7A== Date: Tue, 22 Oct 2024 16:52:16 -0700 From: Namhyung Kim To: Arnaldo Carvalho de Melo Cc: Song Liu , Howard Chu , Andrea Righi , peterz@infradead.org, mingo@redhat.com, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, james.clark@linaro.org, alan.maguire@oracle.com Subject: Re: [PATCH v2 0/2] perf trace: Fix support for the new BPF feature in clang 12 Message-ID: References: <20241011021403.4089793-1-howardchu95@gmail.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Oct 22, 2024 at 03:33:00PM -0300, Arnaldo Carvalho de Melo wrote: > On Tue, Oct 22, 2024 at 10:04:52AM -0700, Namhyung Kim wrote: > > Hi Arnaldo, > > > > On Wed, Oct 16, 2024 at 11:22:15AM -0300, Arnaldo Carvalho de Melo wrote: > > > On Tue, Oct 15, 2024 at 07:06:35PM -0700, Namhyung Kim wrote: > > > > Hi Arnaldo, > > > > > > > > On Tue, Oct 15, 2024 at 05:37:38PM -0300, Arnaldo Carvalho de Melo wrote: > > > > > On Tue, Oct 15, 2024 at 04:58:56PM -0300, Arnaldo Carvalho de Melo wrote: > > > > > > So I'm trying adding extra bounds checking, marking the index as > > > > > > volatile, adding compiler barriers, etc, all the fun with the verifier, > > > > > > but got distracted with other stuff, coming back to this now. > > > > > > > > > > > Ok, the following seems to do the trick: > > > > > > > > > > > [acme@dell-per740-01 perf-tools]$ git diff > > > > > > diff --git a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c > > > > > > index 3b30aa74a3ae..ef87a04ff8d0 100644 > > > > > > --- a/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c > > > > > > +++ b/tools/perf/util/bpf_skel/augmented_raw_syscalls.bpf.c > > > > > > @@ -486,6 +486,7 @@ static int augment_sys_enter(void *ctx, struct syscall_enter_args *args) > > > > > > augmented = true; > > > > > > } else if (size < 0 && size >= -6) { /* buffer */ > > > > > > index = -(size + 1); > > > > > > + index &= 7; // To satisfy the bounds checking with the verifier in some kernels > > > > > > aug_size = args->args[index]; > > > > > > > > > > > > if (aug_size > TRACE_AUG_MAX_BUF) > > > > > > > > > > > > I'll now test it without Howard's patch to see if it fixes the RHEL8 + > > > > > > clang 17 case. > > > > > > > > > > It works with this one-liner + the simplified patch from Howard and also > > > > > on this other system (RHEL9), as well as with Fedora 40, it would be > > > > > nice if someone could test with clang 16 and report back the version of > > > > > the kernel tested as well as the distro name/release, that way I can try > > > > > to get my hands on such as system and test there as well. > > > > > > > > > > Its all at: > > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools.git tmp.perf-tools > > > > > > > > > > This is the current set of patches that when further tested will go to > > > > > Linus for v6.12: > > > > > > > > > > ⬢[acme@toolbox perf-tools]$ git log --oneline torvalds/master.. > > > > > ff14baa7a290bf42 (HEAD -> perf-tools, x1/perf-tools, perf-tools/tmp.perf-tools) perf trace augmented_raw_syscalls: Add more checks to pass the verifier > > > > > 46180bec048aad85 perf trace augmented_raw_syscalls: Add extra array index bounds checking to satisfy some BPF verifiers > > > > > 45d1aadac64869a2 perf build: Change the clang check back to 12.0.1 > > > > > > > > Wouldn't it be better to have this change after fixing the verifier > > > > issues in the later commits? > > > > > > I'm still testing it, this is a one-liner, so I think that the order in > > > which the patches are applied isn't important. Also Howard's patch (the > > > simplified one) doesn't clash with it. > > > > I'm afraid if it'd break git bisect by allowing old clang versions > > before the fix. > > I can reorder the patches if you think it is interesting, but from the > extended set of tests I'm performing on different kernel and clang > version and in x86_64 and arm 64-bit, 32-bit and various distros, I'm > not sure bisection is an option for BPF programs at this stage 8-) Maybe. But at least we can try our best. :) > > There, did it now it looks like this: > > ⬢ [acme@toolbox perf-tools]$ git log --oneline torvalds/master.. > 5d3a1b9ca3b1a059 (HEAD -> perf-tools) perf trace arm32: Fix iteration of syscall ids in syscalltbl->entries > 34d2358a24fb5963 perf trace augmented_raw_syscalls: Add more checks to pass the verifier > cdb84c31bd2813de perf trace augmented_raw_syscalls: Add extra array index bounds checking to satisfy some BPF verifiers > e5c1811c590c4312 perf build: Change the clang check back to 12.0.1 > 39c6a356201ebbd7 perf trace: The return from 'write' isn't a pid > ab8aaab874c4aa37 tools headers UAPI: Sync linux/const.h with the kernel headers > ⬢ [acme@toolbox perf-tools]$ > > Is that what you meant? Nope, I'd like to have e5c1811c590c4312 after the verifier fixes: 34d2358a24fb5963 perf trace augmented_raw_syscalls: Add more checks to pass the verifier cdb84c31bd2813de perf trace augmented_raw_syscalls: Add extra array index bounds checking to satisfy some BPF verifiers Thanks, Namhyung