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From:   Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Date:   Thu, 6 Jun 2019 11:44:12 -0300
To:     Leo Yan <leo.yan@linaro.org>
Cc:     Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Mike Leach <mike.leach@linaro.org>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        bpf@vger.kernel.org
Subject: Re: [PATCH v2 3/4] perf augmented_raw_syscalls: Support arm64 raw
 syscalls
Message-ID: <20190606144412.GC21245@kernel.org>
References: <20190606094845.4800-1-leo.yan@linaro.org>
 <20190606094845.4800-4-leo.yan@linaro.org>
 <20190606133838.GC30166@kernel.org>
 <20190606141231.GC5970@leoy-ThinkPad-X240s>
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Em Thu, Jun 06, 2019 at 10:12:31PM +0800, Leo Yan escreveu:
> Hi Arnaldo,
> 
> On Thu, Jun 06, 2019 at 10:38:38AM -0300, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Jun 06, 2019 at 05:48:44PM +0800, Leo Yan escreveu:
> > > This patch adds support for arm64 raw syscall numbers so that we can use
> > > it on arm64 platform.
> > > 
> > > After applied this patch, we need to specify macro -D__aarch64__ or
> > > -D__x86_64__ in compilation option so Clang can use the corresponding
> > > syscall numbers for arm64 or x86_64 respectively, other architectures
> > > will report failure when compilation.
> > 
> > So, please check what I have in my perf/core branch, I've completely
> > removed arch specific stuff from augmented_raw_syscalls.c.
> > 
> > What is done now is use a map to specify what to copy, that same map
> > that is used to state which syscalls should be traced.
> > 
> > It uses that tools/perf/arch/arm64/entry/syscalls/mksyscalltbl to figure
> > out the mapping of syscall names to ids, just like is done for x86_64
> > and other arches, falling back to audit-libs when that syscalltbl thing
> > is not present.
> 
> Actually I have noticed mksyscalltbl has been enabled for arm64, and
> had to say your approach is much better :)
> 
> Thanks for the info and I will try your patch at my side.

That is excellent news! I'm eager to hear from you if this perf+BPF
integration experiment works for arm64.

I'm now trying to get past the verifier when checking if more than one
syscall arg is a filename, i.e. things like the rename* family, that
take two filenames.

An exercise in loop unrolling, providing the right hints to the
verifier, making sure clang don't trash those via explicit barriers, and
a lot of patience, limitless fun! ;-)

- Arnaldo