From: illusionist.neo@gmail.com (Shubham Bansal)
To: linux-arm-kernel@lists.infradead.org
Subject: arch: arm: bpf: Converting cBPF to eBPF for arm 32 bit
Date: Mon, 30 Jan 2017 16:08:54 +0530 [thread overview]
Message-ID: <20170130103853.GA34633@in3o.xyz> (raw)
Hi all,
Please ignore last copy of this mail. Kernel mailing lists bounced my
last mail back because of HTML content.
Just starting a new thread with proper heading on the main kernel
hardening and net-dev mailing list so that other people can be involved
in this. Please don't take this as a personal mail.
I am working on conversion of arm32 cBPF into eBPF JIT. I wanted some
help, regarding understanding of kernel code, from the dev available on
the mailing list. If you look at the ./arch/arm/net/bpf_jit_32.c code,
you will see jit_ctx structure. If anybody could help me understand what
each fields of this structure represent then it would be great.
Also, currently I am mapping the eBPF registers to arm 32 bit registers
in the following way.
> static const int bpf2a32[] = {
>
> /* return value from in-kernel function, and exit value from
> eBPF
> */
> [BPF_REG_0] = ARM_R0,
>
> /* arguments from eBPF program to in-kernel function */
>
> [BPF_REG_1] = ARM_R1,
>
> [BPF_REG_2] = ARM_R2,
>
> [BPF_REG_3] = ARM_R3,
>
> [BPF_REG_4] = ARM_R4,
>
> [BPF_REG_5] = ARM_R5,
>
> /* callee saved registers that in-kernel function will
> preserve */
>
> [BPF_REG_6] = ARM_R6,
>
> [BPF_REG_7] = ARM_R7,
>
> [BPF_REG_8] = ARM_R8,
>
> [BPF_REG_9] = ARM_R9,
>
> /* Read only Frame Pointer to access Stack */
>
> [BPF_REG_FP] = ARM_FP,
>
> /* Temperory Register for internal BPF JIT */
>
> [TMP_REG_1] = ARM_R11,
>
> /* temporary register for blinding constants */
>
> [BPF_REG_AX] = ARM_R10,
>
> };
But I have some question if anybody could help with those.
1.) Currently, as eBPF uses 64 bit registers, I am mapping 64 bit eBPF
registers with 32 bit arm registers which looks wrong to me. Do anybody
have some idea about how to map eBPF->arm 32 bit registers ?
2.) Also, is my current mapping good enough to make the JIT fast enough ?
because as you might know, eBPF JIT mostly depends on 1-to-1 mapping of
its instructions with native instructions.
Appreciate the help from anybody from the mailing list.
Best,
Shubham Bansal
next reply other threads:[~2017-01-30 10:38 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-30 10:38 Shubham Bansal [this message]
2017-01-30 21:57 ` arch: arm: bpf: Converting cBPF to eBPF for arm 32 bit Kees Cook
[not found] ` <CAHgaXd+nj69n-Xf46N=4M-j-0hKHVrrLfsvRZCG=2CCAtVF6ZA@mail.gmail.com>
[not found] ` <CAGXu5j+NSLomuSgD40kys+pWc+J9aB6Bbk_gSP9Lp_ScimQn_w@mail.gmail.com>
2017-02-01 13:01 ` Shubham Bansal
[not found] ` <76621BFF-B30B-4417-AB2B-DB21CA6092D9@netronome.com>
2017-02-03 7:04 ` Shubham Bansal
2017-02-03 8:25 ` nick viljoen
2017-02-08 7:29 ` Shubham Bansal
2017-02-08 19:41 ` Kees Cook
2017-03-15 12:13 ` Shubham Bansal
2017-03-15 21:55 ` David Miller
2017-03-28 20:49 ` Shubham Bansal
2017-03-29 0:00 ` Daniel Borkmann
2017-03-30 14:04 ` Shubham Bansal
2017-04-06 11:05 ` Shubham Bansal
2017-04-06 12:51 ` Daniel Borkmann
2017-05-06 16:48 ` Shubham Bansal
2017-05-06 18:38 ` David Miller
2017-05-06 20:27 ` Shubham Bansal
2017-05-06 22:17 ` Shubham Bansal
2017-05-09 20:12 ` Shubham Bansal
2017-05-09 20:19 ` David Miller
2017-05-09 20:25 ` Daniel Borkmann
[not found] <CAHgaXdKsO2xoKYp7g91g+n+d_1KHSSByLjzBB-WjVXSjhB7qxw@mail.gmail.com>
[not found] ` <20170510.212952.1440495072777358778.davem@davemloft.net>
[not found] ` <CAHgaXdK8LEEUPm4jTRRzCnjwdWAauHmmB=caZsSFY8MmStH89Q@mail.gmail.com>
[not found] ` <20170510.215218.2185526627014393313.davem@davemloft.net>
[not found] ` <CAHgaXdKZ_v+iO7uqEDx7PA7D+xcp1FngGvJ1SRSsGXNQ-iWWDQ@mail.gmail.com>
2017-05-11 9:32 ` Shubham Bansal
2017-05-11 15:30 ` Kees Cook
2017-05-13 21:38 ` Shubham Bansal
2017-05-15 17:44 ` Kees Cook
2017-05-15 19:55 ` Daniel Borkmann
2017-05-20 20:01 ` Shubham Bansal
2017-05-22 13:01 ` Daniel Borkmann
2017-05-22 17:04 ` Shubham Bansal
2017-05-22 20:05 ` Kees Cook
2017-05-23 2:58 ` Shubham Bansal
2017-05-23 4:27 ` Kees Cook
2017-05-22 18:58 ` Kees Cook
2017-05-22 19:08 ` Florian Fainelli
2017-05-23 3:34 ` Shubham Bansal
2017-05-23 4:22 ` Kees Cook
2017-05-23 5:03 ` Shubham Bansal
2017-05-23 5:35 ` Kees Cook
[not found] ` <CAHgaXdJa9uJYO3bODuzDRaqOas0i=zMk0jioWFXKm_=UJRtVrw@mail.gmail.com>
2017-05-23 19:32 ` Kees Cook
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