[PATCH] distro_boot: Fix bootfile env after calling boot_extlinux

[Tom Rini]

On Tue, Oct 12, 2021 at 02:31:18PM -0600, Simon Glass wrote:
> Hi Tom,
> 
> On Tue, 12 Oct 2021 at 13:44, Tom Rini <trini at konsulko.com> wrote:
> >
> > 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>
> 
> IMO a better approach will be the bootflow implementation. I hope to
> get v2 out early next week.

I'm not sure if the bootflow way of going here would or would not have
the same problem, or perhaps a slightly different problem.  At heart
here, "sysboot" calls env_set(...) and then calls in to the pxe code
which does env_get(...).  So now I wonder how this would be fixed in
bootflow, since we aren't dealing with the environment directly.

-- 
Tom
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