[PATCH] module: add modinfo support for all built-in modules

[rae l]

On Jan 16, 2008 8:25 PM, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
> I'd love to see patches.  module_parm showed it's possible, if messy.
>
> Thanks!
> Rusty.

here's the patch, I added .modinfo section to the vmlinux, to collect
built-in module information.

I have just define __MODULE_INFO to another meaning while
CONFIG_MODULES undefined
(modules compiled built-in), instead of nothing; and so the
MODULE_LICENSE, MODULE_AUTHOR,
MODULE_DESCRIPTION's meaning also changed, each macro would define one
struct kernel_modinfo
entry in the .modinfo section of vmlinux; and one __initcall converts
all these information to read-only
files under /sys/modules/<module-name>/...

but the MODULE_PARM_DESC macro is still different:
it generates entries with the same tag, that would confuse
sys_create_group, so I skipped them in the __initcall,
since the parameters had been in /sys/modules/<>/parameters/(with perm
non-zero) or didn't appear(with perm 0);
I think the parameter description might be only useful for external
module files, not needed in memory(under /sys/module/),
so a better solution is define MODULE_PARM_DESC to nothing while
CONFIG_MODULES undefined.

Another possible defect is that it compares two modname with
(km->modname != modname),
that depends on a gcc feature: keep same constant string only one copy
in the image,
this did work on my test machines, but I'm not sure it's standard or
not; and if not, I would change it to strcmp.

Apperantly this approach will increase the kernel image size. on a
moderate system(with 1.8MB bzImage),
this patch would increase vmlinux 46KB and after compression increase
bzImage 9.2KB.
and in the increment of vmlinux, the .modinfo section occupied 5.3KB
and others are constant strings.

However, the iscsid can now work well when scsi_transport_iscsi module
built-in without the problem refered in my former email.

please give comments.