linux-kernel - Re: [PATCH v4 2/2] riscv: Disable data start offset in flat binaries

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Date:   Sat, 17 Apr 2021 14:56:41 +1000
From:   Greg Ungerer <gerg@...ux-m68k.org>
To:     Damien Le Moal <damien.lemoal@....com>, uclinux-dev@...inux.org,
        Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, Anup Patel <anup.patel@....com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v4 2/2] riscv: Disable data start offset in flat binaries


On 17/4/21 11:10 am, Damien Le Moal wrote:
> uclibc/gcc combined with elf2flt riscv linker file fully resolve the
> PC relative __global_pointer$ value at compile time and do not generate
> a relocation entry to set a correct value of the gp register at runtime.
> As a result, if the flatbin loader offsets the start of the data
> section, the relative position change between the text and data sections
> compared to the compile time positions results in an incorrect gp value
> being used. This causes flatbin executables to crash.
> 
> Avoid this problem by enabling CONFIG_BINFMT_FLAT_NO_DATA_START_OFFSET
> automatically when CONFIG_RISCV is enabled and CONFIG_MMU is disabled.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@....com>
> Acked-by: Palmer Dabbelt <palmerdabbelt@...gle.com>

Acked-by: Greg Ungerer <gerg@...ux-m68k.org>

Palmer do you want me to take this via my tree with 1/2 in the series,
or are you going to pick it up?

Regards
Greg


> ---
>   arch/riscv/Kconfig | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 4515a10c5d22..add528eb9235 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -33,6 +33,7 @@ config RISCV
>   	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
>   	select ARCH_WANT_FRAME_POINTERS
>   	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
> +	select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU
>   	select CLONE_BACKWARDS
>   	select CLINT_TIMER if !MMU
>   	select COMMON_CLK
>