netdev - Re: bloat-o-meter +32832 (was: Re: bpf: add prog_digest and expose it via fdinfo/netlink)

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Date:   Tue, 13 Dec 2016 11:06:49 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: bloat-o-meter +32832 (was: Re: bpf: add prog_digest and expose
 it via fdinfo/netlink)

On 12/13/2016 10:29 AM, Geert Uytterhoeven wrote:
> Hi Daniel,
>
> On Mon, Dec 12, 2016 at 6:08 PM, Linux Kernel Mailing List
> <linux-kernel@...r.kernel.org> wrote:
>> Web:        https://git.kernel.org/torvalds/c/7bd509e311f408f7a5132fcdde2069af65fa05ae
>> Commit:     7bd509e311f408f7a5132fcdde2069af65fa05ae
>> Parent:     8d829bdb97dc3a0c9c8090b9b168ca46ea99c8d8
>> Refname:    refs/heads/master
>> Author:     Daniel Borkmann <daniel@...earbox.net>
>> AuthorDate: Sun Dec 4 23:19:41 2016 +0100
>> Committer:  David S. Miller <davem@...emloft.net>
>> CommitDate: Mon Dec 5 15:33:11 2016 -0500
>>
>>      bpf: add prog_digest and expose it via fdinfo/netlink
>>
>>      When loading a BPF program via bpf(2), calculate the digest over
>>      the program's instruction stream and store it in struct bpf_prog's
>>      digest member. This is done at a point in time before any instructions
>>      are rewritten by the verifier. Any unstable map file descriptor
>>      number part of the imm field will be zeroed for the hash.
>>
>>      fdinfo example output for progs:
>>
>>        # cat /proc/1590/fdinfo/5
>>        pos:          0
>>        flags:        02000002
>>        mnt_id:       11
>>        prog_type:    1
>>        prog_jited:   1
>>        prog_digest:  b27e8b06da22707513aa97363dfb11c7c3675d28
>>        memlock:      4096
>>
>>      When programs are pinned and retrieved by an ELF loader, the loader
>>      can check the program's digest through fdinfo and compare it against
>>      one that was generated over the ELF file's program section to see
>>      if the program needs to be reloaded. Furthermore, this can also be
>>      exposed through other means such as netlink in case of a tc cls/act
>>      dump (or xdp in future), but also through tracepoints or other
>>      facilities to identify the program. Other than that, the digest can
>>      also serve as a base name for the work in progress kallsyms support
>>      of programs. The digest doesn't depend/select the crypto layer, since
>>      we need to keep dependencies to a minimum. iproute2 will get support
>>      for this facility.
>>
>>      Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
>>      Acked-by: Alexei Starovoitov <ast@...nel.org>
>>      Signed-off-by: David S. Miller <davem@...emloft.net>
>
>> --- a/kernel/bpf/core.c
>> +++ b/kernel/bpf/core.c
>> @@ -136,6 +136,71 @@ void __bpf_prog_free(struct bpf_prog *fp)
>>          vfree(fp);
>>   }
>>
>> +#define SHA_BPF_RAW_SIZE                                               \
>> +       round_up(MAX_BPF_SIZE + sizeof(__be64) + 1, SHA_MESSAGE_BYTES)
>> +
>> +/* Called under verifier mutex. */
>> +void bpf_prog_calc_digest(struct bpf_prog *fp)
>> +{
>> +       const u32 bits_offset = SHA_MESSAGE_BYTES - sizeof(__be64);
>> +       static u32 ws[SHA_WORKSPACE_WORDS];
>> +       static u8 raw[SHA_BPF_RAW_SIZE];
>
> function                                     old     new   delta
> raw                                            -   32832  +32832
>
> Congratulations!
> We've found the first nominee for the v4.10-rc1 bloat-o-meter contest! :-(
>
> Can this please be allocated dynamically? Thanks!

Sure, should be okay since mostly slow-path. Will send a patch.