[RFC PATCH] kexec-tools: Fix option/argument parsing

[Simon Horman]

On Thu, May 13, 2010 at 06:14:32PM +1000, Matt Evans wrote:
> Hi,
> 
> 
> In playing with kexec-tools I've noticed various problems with the argument
> passing, meaning one has to be careful to use certain forms of arguments
> and present them in a certain order.
> 
> The arguments end up being parsed three times, each getting more specific
> than the last.  main() looks for general args, arch_process_options() looks
> for options common to all loaders for the arch, and then finally many 
> file_type load() methods check for options specific to that filetype.
> 
> As GNU getopt works, it re-orders the argv[] pushing any args it doesn't
> recognise to the end.  This includes arguments to valid options which
> are simply not recognised the first time around.
> 
> For example, this does not work:
>   # ./kexec -l --append "init=/bin/foo" /boot/vmlinux
>   Cannot open `init=/bin/foo': No such file or directory
> 
> but this does:
>   # ./kexec -l --append="init=/bin/foo" /boot/vmlinux
>   <joy>
> 
> Using the --opt<space>arg variant results in the first non-option argument
> in main() being "init=/bin/foo" which is then used as the kernel filename,
> failing.  Also, the order affects things in unintuitive ways:
> 
>   # ./kexec -l /boot/vmlinux --append "init=/bin/foo" 
> <appears to load correctly, but command line appended with "/boot/vmlinux"!>
> 
> This behaviour is avoided by using the --opt= forms, but getopt does allow
> both and hence the user can have a fairly frustrating experience.  (Doing
> something unexpected (ex. 3) is more annoying than an error exit (ex. 1)
> in many cases.)
> 
> The fix presented here is to create a new #define to encapsulate all possible
> options for an architecture build.  The intention is that this set includes
> all possible loaders' all possible options.  
> 
> main() walks through the options and silently ignores any non-general
> options (BUT respects that "--arg foo" should remain together, as 
> getopt_long() does now recognise it).  arch_process_options() walks through
> them again and responds to any arch-specific options, again ignoring but 
> respecting any non-arch options.  Finally the loader may look for its
> options, and find them in-order and present.  Any outside of this combined
> set are complained-about as usual.
> 
> So, comments please.  Is this a reasonable way to do it or is there an
> obvious better way I've missed? :-)  So far I have been able to test on
> x86(32,64) and ppc(32,64) but none of the others. :(

This seems reasonable to me.

I've compiled tested the code on all architectures except cris (I don't
have my build environment at the moment). I found a minor problem on arm
which I have noted below.

[snip]

> diff --git a/kexec/arch/arm/include/arch/options.h b/kexec/arch/arm/include/arch/options.h
> index 248230b..a76539e 100644
> --- a/kexec/arch/arm/include/arch/options.h
> +++ b/kexec/arch/arm/include/arch/options.h
> @@ -3,9 +3,38 @@
>  
>  #define OPT_ARCH_MAX   (OPT_MAX+0)
>  
> +#define OPT_APPEND	'a'
> +#define OPT_RAMDISK	'r'
> +
> +/* Options relevant to the architecture (excluding loader-specific ones),
> + * in this case none:
> + */
>  #define KEXEC_ARCH_OPTIONS \
>  	KEXEC_OPTIONS \
>  
>  #define KEXEC_ARCH_OPT_STR KEXEC_OPT_STR ""
>  
> +/* The following two #defines list ALL of the options added by all of the
> + * architecture's loaders.
> + * o	main() uses this complete list to scan for its options, ignoring
> + *	arch-specific/loader-specific ones.
> + * o	Then, arch_process_options() uses this complete list to scan for its
> + *	options, ignoring general/loader-specific ones.
> + * o	Then, the file_type[n].load re-scans for options, using
> + *	KEXEC_ARCH_OPTIONS plus its loader-specific options subset.
> + *	Any unrecognised options cause an error here.
> + *
> + * This is done so that main()'s/arch_process_options()'s getopt_long() calls
> + * don't choose a kernel filename from random arguments to options they don't
> + * recognise -- as they now recognise (if not act upon) all possible options.
> + */
> +#define KEXEC_ALL_OPTIONS \
> +	KEXEC_ARCH_OPTIONS
> +	{ "command-line",	1, 0, OPT_APPEND },
> +	{ "append",		1, 0, OPT_APPEND },
> +	{ "initrd",		1, 0, OPT_RAMDISK },

The above 4 lines seem to be missing a trailing '\'

> +	{ "ramdisk",		1, 0, OPT_RAMDISK },
> +
> +#define KEXEC_ALL_OPT_STR KEXEC_ARCH_OPT_STR "a:r:"
> +
>  #endif /* KEXEC_ARCH_ARM_OPTIONS_H */

[snip]