linux-kernel - Re: [PATCH] x86 bpf: Fix extable offset calculation

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Message-ID: <CAADnVQL7BdReSgw++Eh+MvS4+_uqnFFvp+7N4cGO2MWMTWaqcQ@mail.gmail.com>
Date:   Fri, 25 Jun 2021 08:07:11 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Subject: Re: [PATCH] x86 bpf: Fix extable offset calculation

On Thu, Jun 24, 2021 at 11:22 PM Ravi Bangoria
<ravi.bangoria@...ux.ibm.com> wrote:
> > Could you send a followup patch with a selftest, so I don't make
> > the same mistake again ? ;)
>
> Unfortunately extable gets involved only for bad kernel pointers and
> ideally there should not be any bad pointer in kernel. So there is no
> easy way to create a proper selftest for this.

Right. We have lib/test_bpf.c kernel module for such cases.