[U-Boot-Users] [PATCH] new CONFIG_RETURN_FROM_BOOTM
Jerry Van Baren
gerald.vanbaren at smiths-aerospace.com
Fri Jul 20 16:22:52 CEST 2007
Wilson Callan wrote:
> Hi,
>
> I've added an option similar to the netretry=no environment option
> which allows a script to control the retry operation for networking.
> This option controls a retry operation for bootm. Here is the README
> entry:
>
> +- CONFIG_RETURN_FROM_BOOTM
> +
> + Return from the bootm command instead of rebooting. This
> + is useful for setting up multiple boot image options in a
> + script. It allows the script to control the retry
> + operation. For example, these scripts setup a system that
> + will attempt a primary flash image, then a backup image
> + location, then resort to TFTP:
> + "boot_tftp=dhcp 3c0;bootm 3c0;reset\0" /* if fails, reset */ \
> + "boot_flash=bootm ff050000 3c0;bootm ffc00000 3c0;run
> boot_tftp;reset\0"
>
>
> CHANGELOG:
>
> Added CONFIG_RETURN_FROM_BOOTM to control retry operation of bootm command.
>
> Signed-off-by: Wilson Callan <wcallan at savantav.com>
NAK
This is a *BAD* idea as is. See the comment in cmd_bootm.c line 298:
<http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot.git;a=blob;f=common/cmd_bootm.c;h=ba286f1e636c1f6d36ea41b0366b6e192ef03d0f;hb=HEAD#l298>
298 /*
299 * We have reached the point of no return: we are going to
300 * overwrite all exception vector code, so we cannot easily
301 * recover from any failures any more...
302 */
If you return, one of four things will happen:
a) U-boot will continue to work.
b) It may work by pure luck.
c) It may work for a while and then go goofy and crash.
d) It may simply crash.
Unless you can guarantee (a), this is not an acceptable patch. Note
that the current code does *NOT* guarantee (a). My experience is that
it is (c) or (b), in that order (DAMHIKT).
Trivia: I have some pending reorganization and other improvements in my
u-boot-fdt repo that fix some erroneous returns. One Of These Days they
will be pulled into the mainline repo.
<http://www.denx.de/cgi-bin/gitweb.cgi?p=u-boot/u-boot-fdt.git;a=blob;f=common/cmd_bootm.c;h=ba286f1e636c1f6d36ea41b0366b6e192ef03d0f;hb=HEAD>
One thought is to copy the interrupt vectors to a set-aside area so
that, if something fails after line 298, you can restore the interrupt
vectors and _then_ return. Note that you have to guarantee your u-boot
(static) variables are not overwritten by the aborted bootm command as
well. This /shouldn't/ be an issue, but it could be since stupid^W
ignorant users can load in poorly chosen memory locations.
Good luck,
gvb
More information about the U-Boot
mailing list