backport binfmt_misc: pass binfmt_misc flags to the interpreter

backport binfmt_misc: pass binfmt_misc flags to the interpreter

[YunQiang Su]

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.12-rc1&id=2347961b11d4079deace3c81dceed460c08a8fc1
This patch can be apply to 5.10 and 5.11 directly.

binfmt_misc: pass binfmt_misc flags to the interpreter

It can be useful to the interpreter to know which flags are in use.

For instance, knowing if the preserve-argv[0] is in use would allow to
skip the pathname argument.

This patch uses an unused auxiliary vector, AT_FLAGS, to add a flag to
inform interpreter if the preserve-argv[0] is enabled.

Note by Helge Deller:
The real-world user of this patch is qemu-user, which needs to know if
it has to preserve the argv[0]. See Debian bug #970460.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: YunQiang Su <ysu@wavecomp.com>
URL: http://bugs.debian.org/970460
Signed-off-by: Helge Deller <deller@gmx.de>

Re: backport binfmt_misc: pass binfmt_misc flags to the interpreter

[Greg KH]

On Tue, Mar 02, 2021 at 04:02:22PM +0800, YunQiang Su wrote:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.12-rc1&id=2347961b11d4079deace3c81dceed460c08a8fc1
> This patch can be apply to 5.10 and 5.11 directly.
> 
> binfmt_misc: pass binfmt_misc flags to the interpreter
> 
> It can be useful to the interpreter to know which flags are in use.
> 
> For instance, knowing if the preserve-argv[0] is in use would allow to
> skip the pathname argument.
> 
> This patch uses an unused auxiliary vector, AT_FLAGS, to add a flag to
> inform interpreter if the preserve-argv[0] is enabled.
> 
> Note by Helge Deller:
> The real-world user of this patch is qemu-user, which needs to know if
> it has to preserve the argv[0]. See Debian bug #970460.
> 
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> Reviewed-by: YunQiang Su <ysu@wavecomp.com>
> URL: http://bugs.debian.org/970460
> Signed-off-by: Helge Deller <deller@gmx.de>

This feels like a new feature, how does it fit with the stable kernel
rules?

thanks,

greg k-h