[U-Boot-Users] PATCH: fix parser problem with whitespace command line

[Andrew Dyer]

On 6/13/05, Wolfgang Denk <wd at denx.de> wrote:
> In message <c166aa9f05061220474bc0d039 at mail.gmail.com> you wrote:
> > I noticed on my board that if I enter a space and then return at the
> > u-boot command line I get an exception.  I using u-boot from cvs and
> > the standard (not hush) parser on a mips platform.
> > Does anybody else see this behaviour?
> 
> You should see a "Unknown command '<NULL>' - try 'help'" error message.

Did you try it?

I dug a bit more and what I found was that in run_command() the parse_line()
function eats the leading whitespace then doesn't see anything it recognizes,
so sets argv[0] to NULL and returns a zero.  The null pointer gets passed to
find_cmd() which happily dereferences it and the cpu throws an exception.

Below is the output of main with DEBUG_PARSER turned on (and a printf
of argc and *argv I added before the call to find_cmd():


AMR boot#
[RUN_COMMAND] cmd[83ff8bc0]=" "
[PROCESS_SEPARATORS]
token: " "
[PROCESS_MACROS] INPUT len 1: " "
[PROCESS_MACROS] OUTPUT len 1: " "
parse_line: " "
parse_line: nargs=0
argc 0
*argv 0
Unhandled exception

$ 0   : 00000000 b1100000 00000000 00000004
$ 4   : 83ff2748 83eefb78 0000000a fffffffb
$ 8   : ffffffff 83eefb7e 00000002 00000000
$12   : 00000000 00000000 83ff6d10 00000020
$16   : 83eefcb8 00000000 83eefcb9 83eefdb8
$20   : 00000000 00000000 83eefeb8 00000001
$24   : 3afe5cff 83feff2c
$28   : 83ff8050 83eefca0 281925aa 83fdb130
Hi    : 00000001
Lo    : 00000000
epc   : 83fdb144 ra    : 83fdb130 Status: 00400002    KERNEL EXL
Cause : 00800008
BadVA : 00000000
PrId  : 03030200


Attached is a fix which checks if the value of argc is zero before
calling find_cmd()
and continues.


CHANGELOG:
* Patch by Andrew Dyer, 13 June2005:
add test to see if no valid commands were found in input string before
passing string
to find_cmd()

-- 
Hardware, n.:
        The parts of a computer system that can be kicked.
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