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Message-ID: <20200414030424.csky65wqjzxpklzx@ast-mbp.dhcp.thefacebook.com>
Date: Mon, 13 Apr 2020 20:04:24 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: "Daniel T. Lee" <danieltimlee@...il.com>
Cc: bpf <bpf@...r.kernel.org>, netdev <netdev@...r.kernel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
Andrii Nakryiko <andrii.nakryiko@...il.com>,
Martin KaFai Lau <kafai@...com>
Subject: Re: BPF program attached on BPF map function (read,write) is not
working?
On Thu, Apr 09, 2020 at 12:26:37PM +0900, Daniel T. Lee wrote:
>
> So, I think this 'unable to attach bpf program on BPF map function (read,write)'
> is a bug. Or is it desired action?
desired action.
> If it is a bug, bpf_{enable|disable}_instrumentation() should only
> cover stackmap
> as the upper commit intended. Not sure but adding another flag for
> lock might work?
>
> Or if this is an desired action, this should be covered at
> documentation with a limitation
> and tracex6 sample has to be removed.
Right. That test has to be fixed.
These two old commits:
commit 020a32d9581a ("bpf: add a test case for helper bpf_perf_event_read_value")
commit 41e9a8046c92 ("samples/bpf: add tests for more perf event types")
attached kprobe bpf to inner map accessors get_next and lookup.
That's safe only for a subset of map types and not allowed in general.
It works for hash and array because they don't take locks in these operations.
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