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From: Song Liu <song@kernel.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Song Liu <songliubraving@fb.com>,
	Ilya Leoshkevich <iii@linux.ibm.com>, bpf <bpf@vger.kernel.org>,
	Network Development <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Kernel Team <Kernel-team@fb.com>,
	Peter Zijlstra <peterz@infradead.org>, X86 ML <x86@kernel.org>
Subject: Re: [PATCH v6 bpf-next 6/7] bpf: introduce bpf_prog_pack allocator
Date: Tue, 25 Jan 2022 17:28:53 -0800	[thread overview]
Message-ID: <CAPhsuW5gVLZeKznY0U2ccYbSzDht5K4fz2-9ScT15WBBJXeUJw@mail.gmail.com> (raw)
In-Reply-To: <CAADnVQ+xiQx4SWuEqm+vCjXs-GCo_jsVcF9DB7JyoEP=C_=-QA@mail.gmail.com>

On Tue, Jan 25, 2022 at 5:20 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Tue, Jan 25, 2022 at 4:50 PM Song Liu <song@kernel.org> wrote:
> >
> > On Tue, Jan 25, 2022 at 4:38 PM Alexei Starovoitov
> > <alexei.starovoitov@gmail.com> wrote:
> > >
[...]
> > > >
> > > > In bpf_jit_binary_hdr(), we calculate header as image & PAGE_MASK.
> > > > If we want s/PAGE_MASK/63 for x86_64, we will have different versions
> > > > of bpf_jit_binary_hdr(). It is not on any hot path, so we can use __weak for
> > > > it. Other than this, I think the solution works fine.
> > >
> > > I think it can stay generic.
> > >
> > > The existing bpf_jit_binary_hdr() will do & PAGE_MASK
> > > while bpf_jit_binary_hdr_pack() will do & 63.
> >
> > The problem with this approach is that we need bpf_prog_ksym_set_addr
> > to be smart to pick bpf_jit_binary_hdr() or bpf_jit_binary_hdr_pack().
>
> We can probably add a true JIT image size to bpf_prog_aux.
> bpf_prog_ksym_set_addr() is approximating the end:
> prog->aux->ksym.end   = addr + hdr->pages * PAGE_SIZE
> which doesn't have to include all the 'int 3' padding after the end.
>
> Or add a flag to bpf_prog_aux.
> Ideally bpf_jit_free() would stay generic too.

Both ideas sound promising. Let me try to implement them and see
which is better (or maybe we get both).

Thanks for the suggestions!
Song

  reply	other threads:[~2022-01-26  1:29 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-21 19:49 [PATCH v6 bpf-next 0/7] bpf_prog_pack allocator Song Liu
2022-01-21 19:49 ` [PATCH v6 bpf-next 1/7] x86/Kconfig: select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP Song Liu
2022-01-21 19:49 ` [PATCH v6 bpf-next 2/7] bpf: use bytes instead of pages for bpf_jit_[charge|uncharge]_modmem Song Liu
2022-01-21 19:49 ` [PATCH v6 bpf-next 3/7] bpf: use size instead of pages in bpf_binary_header Song Liu
2022-01-21 19:49 ` [PATCH v6 bpf-next 4/7] bpf: add a pointer of bpf_binary_header to bpf_prog Song Liu
2022-01-21 19:49 ` [PATCH v6 bpf-next 5/7] x86/alternative: introduce text_poke_copy Song Liu
2022-01-21 19:49 ` [PATCH v6 bpf-next 6/7] bpf: introduce bpf_prog_pack allocator Song Liu
2022-01-21 23:55   ` Alexei Starovoitov
2022-01-22  0:23     ` Song Liu
2022-01-22  0:41       ` Alexei Starovoitov
2022-01-22  1:01         ` Song Liu
2022-01-22  1:12           ` Alexei Starovoitov
2022-01-22  1:30             ` Song Liu
2022-01-22  2:12               ` Alexei Starovoitov
2022-01-23  1:03                 ` Song Liu
2022-01-24 12:29                   ` Ilya Leoshkevich
2022-01-24 18:27                     ` Song Liu
2022-01-25  5:21                       ` Alexei Starovoitov
2022-01-25  7:21                         ` Song Liu
2022-01-25 19:59                           ` Alexei Starovoitov
2022-01-25 22:25                             ` Song Liu
2022-01-25 22:48                               ` Alexei Starovoitov
2022-01-25 23:09                                 ` Song Liu
2022-01-26  0:38                                   ` Alexei Starovoitov
2022-01-26  0:50                                     ` Song Liu
2022-01-26  1:20                                       ` Alexei Starovoitov
2022-01-26  1:28                                         ` Song Liu [this message]
2022-01-26  1:31                                           ` Song Liu
2022-01-26  1:34                                             ` Alexei Starovoitov
2022-01-24 12:45                   ` Peter Zijlstra
2022-01-21 19:49 ` [PATCH v6 bpf-next 7/7] bpf, x86_64: use " Song Liu

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