[PATCH] bootchooser: Change name of kernel parameter

[PATCH] bootchooser: Change name of kernel parameter

[Christian Eggers]

When passing the target name as "bootchooser.active", Linux will not
pass the parameter as environment variable to the init process. The only
way to get the bootchooser result (e.g. in an initramfs), is to parse it
out of /proc/cmdline (requires mounting of /proc, sed, ...).

After renaming, the bootchooser result will be passed as environment
variable which can easily accessed from /init (e.g. for selecting the
associated root fs).

Signed-off-by: Christian Eggers <ceggers@arri.de>
---
 common/bootchooser.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/common/bootchooser.c b/common/bootchooser.c
index c08db03eb..f0e3294dc 100644
--- a/common/bootchooser.c
+++ b/common/bootchooser.c
@@ -817,7 +817,7 @@ static int bootchooser_boot_one(struct bootchooser *bc, int *tryagain)
 		goto out;
 	}
 
-	system = basprintf("bootchooser.active=%s", target->name);
+	system = basprintf("bootchooser_active=%s", target->name);
 	globalvar_add_simple("linux.bootargs.bootchooser", system);
 	free(system);
 
-- 
Christian Eggers
Embedded software developer

Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRA 57918
Persoenlich haftender Gesellschafter: Arnold & Richter Cine Technik GmbH
Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRB 54477
Geschaeftsfuehrer: Dr. Michael Neuhaeuser; Stephan Schenk; Walter Trauninger; Markus Zeiler


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Re: [PATCH] bootchooser: Change name of kernel parameter

[Ahmad Fatoum]

Hello Christian,

On 1/27/20 8:46 AM, Christian Eggers wrote:
> When passing the target name as "bootchooser.active", Linux will not
> pass the parameter as environment variable to the init process. The only
> way to get the bootchooser result (e.g. in an initramfs), is to parse it
> out of /proc/cmdline (requires mounting of /proc, sed, ...).
> 
> After renaming, the bootchooser result will be passed as environment
> variable which can easily accessed from /init (e.g. for selecting the
> associated root fs).

Existing userspace like RAUC[1] rely on this naming, so the default may
not be changed.

[1]: https://github.com/rauc/rauc/blob/f52978d9736f18794f7e277ca440e2e4e78c9703/src/context.c#L47

Cheers
Ahmad

> 
> Signed-off-by: Christian Eggers <ceggers@arri.de>
> ---
>  common/bootchooser.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/common/bootchooser.c b/common/bootchooser.c
> index c08db03eb..f0e3294dc 100644
> --- a/common/bootchooser.c
> +++ b/common/bootchooser.c
> @@ -817,7 +817,7 @@ static int bootchooser_boot_one(struct bootchooser *bc, int *tryagain)
>  		goto out;
>  	}
>  
> -	system = basprintf("bootchooser.active=%s", target->name);
> +	system = basprintf("bootchooser_active=%s", target->name);
>  	globalvar_add_simple("linux.bootargs.bootchooser", system);
>  	free(system);
>  
> 

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Re: [PATCH] bootchooser: Change name of kernel parameter

[Christian Eggers]

Hello Ahmad,

> Existing userspace like RAUC[1] rely on this naming, so the default may
> not be changed.
> 
> [1]: https://github.com/rauc/rauc/blob/f52978d9736f18794f7e277ca440e2e4e78c9703/src/context.c#L47
that is what I already suspected...

For my initramfs (klibc based), I need a very cheap solution for mounting the "right" root fs. Currently
I work only with standard utilities (sh, mount, cat, ...) and I avoid creating a own program for this.
I had just success with the following expression

read CMDLINE < /proc/cmdline
if [ "${CMDLINE#bootchooser.active=system1}" != "${CMDLINE}" ]; then
	root=ubi0:rootfs1
else
	root=ubi0:rootfs0
fi
mount -t ubifs $root /root

If the string "bootchooser.active=system1" appears on the command line, the expression will match.
This way I can distinguish between "system1" and "system0".

As the result, my previous patch should be dropped.

regards
Christian





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