linux-kernel - Re: [perf-tools] Build-error in tools/perf/util/annotate.c with LLVM-14

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Date:   Sun, 3 Jul 2022 09:51:15 -0700
From:   Andres Freund <andres@...razel.de>
To:     Sedat Dilek <sedat.dilek@...il.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        Namhyung Kim <namhyung@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [perf-tools] Build-error in tools/perf/util/annotate.c with
 LLVM-14

Hi,

On 2022-07-03 13:54:41 +0200, Sedat Dilek wrote:
> Andres, you have some test-cases how you verified the built perf is OK?

I ran an intentionally expensive workload, monitored it with bpftrace, then
took a perf profile. Then annotated the bpf "function" and verified it looked
the same before / after, using a perf built in a container (and thus
compiling).

Similar with bpftool, I dumped a jited program with a bpftool built with /
without the patches (inside the container using nsenter for the version
without the patches, so I could build it, using nsenter -t $pid -m -p) and
compared both the json and non-json output before / after.

V=4; nsenter -t 847325 -m -p /usr/src/linux/tools/bpf/bpftool/bpftool -j -d prog dump jited id 22 > /tmp/22.jit.json.$V; nsenter -t 847325 -m -p /usr/src/linux/tools/bpf/bpftool/bpftool -d prog dump jited id 22 > /tmp/22.jit.txt.$V

and then diffed the results.

bpf_jit_disasm was harder, because bpf_jit_enable = 2 is broken currently. So
I gathered output in a VM from an older kernel, and used bpf_jit_disasm -f ...
before / after the patches.

Greetings,

Andres Freund