[PATCH] distro_boot: Fix bootfile env after calling boot_extlinux

[Tom Rini]

On Tue, Oct 12, 2021 at 04:55:44PM +0800, Artem Lapkin wrote:

> Problem
> 
> PXE cannot boot normally after Sysboot changed the bootfile env (called
> from boot_extlinux) from the default "boot.scr.uimg" to
> "/boot/extlinux/extlinux.conf".
> 
> In addition, an unbootable extlinux configuration will also make the PXE
> boot unbootable, because it will use the incorrect path "/boot/extlinux/"
> from the bootfile env.
> 
> Solution
> 
> Save and restore default bootfile env value when boot_extlinux is used.
> 
> Example
> ================================================================
> Hit SPACE in 2 seconds to stop autoboot
> ... is now current device
> Found /boot/extlinux/extlinux.conf
> Retrieving file: /boot/extlinux/extlinux.conf
> 413 bytes read in 2 ms (201.2 KiB/s)
> Skipping Krescue for failure retrieving kernel
> SCRIPT FAILED: continuing...
> ...
> Speed: 1000, full duplex
> BOOTP broadcast 1
> DHCP client bound to address 192.168.11.151 (8 ms)
> Using ethernet at ff3f0000 device
> TFTP from server 192.168.11.1; our IP address is 192.168.11.151
> Filename '/boot/extlinux/pxelinux.cfg/default'.
> Not retrying...
> ================================================================
> 
> Signed-off-by: Artem Lapkin <art at khadas.com>
> ---
>  include/config_distro_bootcmd.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/config_distro_bootcmd.h b/include/config_distro_bootcmd.h
> index 3f724aa10f..db3d1b2362 100644
> --- a/include/config_distro_bootcmd.h
> +++ b/include/config_distro_bootcmd.h
> @@ -445,7 +445,9 @@
>  				"${devnum}:${distro_bootpart} "           \
>  				"${prefix}${boot_syslinux_conf}; then "   \
>  			"echo Found ${prefix}${boot_syslinux_conf}; "     \
> +			"bootfile_bak=${bootfile}; "                      \
>  			"run boot_extlinux; "                             \
> +			"setenv bootfile ${bootfile_bak}; "               \
>  			"echo SCRIPT FAILED: continuing...; "             \
>  		"fi\0"                                                    \
>  	\

We've had this kind of problem before, and the answer is that variables
should be local, not global in scope.  In this case, I see that the way
the pxe/sysboot code works is that we have to env_set("..") in one place
to env_get("..") in another, so I don't see a way around this.

Reviewed-by: Tom Rini <trini at konsulko.com>

-- 
Tom
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