linux-kernel - Re: [RFC PATCH 9/9] fs/binfmt_elf_fdpic: Reflect that PIE binaries also work in KConfig help

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Message-ID: <6a3e9877-fc48-40ad-99ab-fa7a6228477a@t-8ch.de>
Date: Sun, 1 Feb 2026 17:27:07 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Daniel Palmer <daniel@...ngy.jp>
Cc: w@....eu, kees@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 9/9] fs/binfmt_elf_fdpic: Reflect that PIE binaries
 also work in KConfig help

On 2026-01-31 16:44:40+0900, Daniel Palmer wrote:
> Since commit 1bde925d2354 ("fs/binfmt_elf_fdpic.c: provide NOMMU loader for regular ELF binaries")
> it has been possible to load some normal ELF binaries on nommu but it
> wasn't documented in the help.
> 
> Since nolibc can generate static-pie binaries that work with this loader
> document that normal ELFs can work as long as they are PIE and you have
> a linker and that nolibc can also generate static-PIE binaries that
> can load without any assitance.
> 
> Signed-off-by: Daniel Palmer <daniel@...ngy.jp>
> ---
>  fs/Kconfig.binfmt | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
> index 1949e25c7741..71573bfd32ac 100644
> --- a/fs/Kconfig.binfmt
> +++ b/fs/Kconfig.binfmt
> @@ -69,6 +69,16 @@ config BINFMT_ELF_FDPIC
>  
>  	  It is also possible to run FDPIC ELF binaries on MMU linux also.
>  
> +	  On nommu systems this can also load normal ELF binaries as long as
> +	  the binary is linked as PIE. If the binary is not static PIE, does not
> +	  include it's own relocation code, this requires a linker like uldso to
> +	  be present and set as the interpreter.

Something like this can be split out of this series and submitted standalone.

> +
> +	  nolibc included in the kernel source can create static-PIE binaries
> +	  by including relocation code and the resulting binaries run on MMU
> +	  systems with the normal ELF loader and on nommu systems with this
> +	  loader.

I don't think this paragraph should be here.
Maybe we can add the information to the nolibc documentation instead.

> +
>  config ELFCORE
>  	bool
>  	help
> -- 
> 2.51.0
>