linux-kernel - Re: [PATCH v2 0/2] Fix binfmt

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Date:   Wed, 14 Apr 2021 22:46:36 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Damien Le Moal <Damien.LeMoal@....com>, viro@...iv.linux.org.uk
CC:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        jcmvbkbc@...il.com, gerg@...ux-m68k.org,
        Anup Patel <Anup.Patel@....com>, Christoph Hellwig <hch@....de>
Subject:     Re: [PATCH v2 0/2] Fix binfmt_flat loader for RISC-V

On Wed, 14 Apr 2021 17:32:10 PDT (-0700), Damien Le Moal wrote:
>> On 2021/04/08 0:49, Damien Le Moal wrote:
>> RISC-V NOMMU flat binaries cannot tolerate a gap between the text and
>> data section as the toolchain fully resolves at compile time the PC
>> relative global pointer (__global_pointer$ value loaded in gp register).
>> Without a relocation entry provided, the flat bin loader cannot fix the
>> value if a gap is introduced and executables fail to run.
>> 
>> This series fixes this problem by allowing an architecture to request
>> the flat loader to suppress the gap between the text and data sections.
>> The first patch fixes binfmt_flat flat_load_file() using the new
>> configuration option CONFIG_BINFMT_FLAT_NO_TEXT_DATA_GAP. The second
>> patch enables this option for RISCV NOMMU builds.
>> 
>> These patches do not change the binfmt_flat loader behavior for other
>> architectures.
>> 
>> Changes from v1:
>> * Replace FLAT_TEXT_DATA_NO_GAP macro with
>>   CONFIG_BINFMT_FLAT_NO_TEXT_DATA_GAP config option (patch 1).
>> * Remove the addition of riscv/include/asm/flat.h and set
>>   CONFIG_BINFMT_FLAT_NO_TEXT_DATA_GAP for RISCV and !MMU
>> 
>> Damien Le Moal (2):
>>   binfmt_flat: allow not offsetting data start
>>   riscv: Disable text-data gap in flat binaries
>> 
>>  arch/riscv/Kconfig |  1 +
>>  fs/Kconfig.binfmt  |  3 +++
>>  fs/binfmt_flat.c   | 21 +++++++++++++++------
>>  3 files changed, 19 insertions(+), 6 deletions(-)
>> 
>
> Ping ?
>
> Any comment on these patches ?
>
> Without them, RISC-V NOMMU user space does not run... I would really like to get
> these in this cycle if possible.

This LGTM, but it's pretty far out of my area of expertise.  I'm happy 
to take them via my tree, but I'd prefer to get an Ack from someone.

Al, get_maintainer suggests you?

Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>