netdev - RE: [RESEND PATCH v4 0/8] bpf powerpc: Add BPF_PROBE

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Message-ID: <8091e1294ad343a88aa399417ff91aee@AcuMS.aculab.com>
Date:   Thu, 14 Oct 2021 08:15:23 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Hari Bathini' <hbathini@...ux.ibm.com>,
        "naveen.n.rao@...ux.ibm.com" <naveen.n.rao@...ux.ibm.com>,
        "christophe.leroy@...roup.eu" <christophe.leroy@...roup.eu>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>
CC:     "paulus@...ba.org" <paulus@...ba.org>,
        "andrii@...nel.org" <andrii@...nel.org>,
        "kafai@...com" <kafai@...com>,
        "songliubraving@...com" <songliubraving@...com>,
        "yhs@...com" <yhs@...com>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "kpsingh@...nel.org" <kpsingh@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: RE: [RESEND PATCH v4 0/8] bpf powerpc: Add BPF_PROBE_MEM support in
 powerpc JIT compiler

From: Hari Bathini 
> Sent: 12 October 2021 13:31
> 
> Patch #1 & #2 are simple cleanup patches. Patch #3 refactors JIT
> compiler code with the aim to simplify adding BPF_PROBE_MEM support.
> Patch #4 introduces PPC_RAW_BRANCH() macro instead of open coding
> branch instruction. Patch #5 & #7 add BPF_PROBE_MEM support for PPC64
> & PPC32 JIT compilers respectively. Patch #6 & #8 handle bad userspace
> pointers for PPC64 & PPC32 cases respectively.

I thought that BPF was only allowed to do fairly restricted
memory accesses - so WTF does it need a BPF_PROBE_MEM instruction?

	David

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