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SubjectRe: [PATCH] Show version information for built-in modules in sysfs
On Tue, Dec 21, 2010 at 05:02:40PM -0800, Rusty Russell wrote:
> On Thu, 16 Dec 2010 08:30:19 am Dmitry Torokhov wrote:
> > Currently only drivers that are built as modules have their versions
> > shown in /sys/module/<module_name>/version, but this information might
> > also be useful for built-in drivers as well. This especially important
> > for drivers that do not define any parameters - such drivers, if
> > built-in, are completely invisible from userspace.
> >
> > This patch changes MODULE_VERSION() macro so that in case when we are
> > compiling built-in module, version information is stored in a separate
> > section. Kernel then uses this data to create 'version' sysfs attribute
> > in the same fashion it creates attributes for module parameters.
> >
> > Signed-off-by: Dmitry Torokhov <dtor@vmware.com>
> > ---
> >
> > This change is driven by our desire to detect whether vmw_balloon driver
> > is built-in into the kernel when we installing our tool package in the
> > guest and avoid installing our own version of the driver.
> >
> > Since vmw_balloon does not have any module parameter nor registers any
> > driver core devices, without this patch it is completely invisible from
> > userspace when built into the kernel.
> >
> > Thanks,
> > Dmitry
> >
> > include/asm-generic/vmlinux.lds.h | 7 ++++
> > include/linux/module.h | 27 +++++++++++++++
> > kernel/params.c | 65 ++++++++++++++++++++++++++++++------
> > 3 files changed, 88 insertions(+), 11 deletions(-)
> >
> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> > index bd69d79..0d83dd1 100644
> > --- a/include/asm-generic/vmlinux.lds.h
> > +++ b/include/asm-generic/vmlinux.lds.h
> > @@ -355,6 +355,13 @@
> > VMLINUX_SYMBOL(__start___param) = .; \
> > *(__param) \
> > VMLINUX_SYMBOL(__stop___param) = .; \
> > + } \
> > + \
> > + /* Built-in module versions. */ \
> > + __modver : AT(ADDR(__modver) - LOAD_OFFSET) { \
> > + VMLINUX_SYMBOL(__start___modver) = .; \
> > + *(__modver) \
> > + VMLINUX_SYMBOL(__stop___modver) = .; \
> > . = ALIGN((align)); \
> > VMLINUX_SYMBOL(__end_rodata) = .; \
> > } \
> > diff --git a/include/linux/module.h b/include/linux/module.h
> > index 7575bbb..f74ddda 100644
> > --- a/include/linux/module.h
> > +++ b/include/linux/module.h
> > @@ -58,6 +58,12 @@ struct module_attribute {
> > void (*free)(struct module *);
> > };
> >
> > +struct module_version_attribute {
> > + struct module_attribute mattr;
> > + const char *module_name;
> > + const char *version;
> > +};
> > +
> > struct module_kobject
> > {
> > struct kobject kobj;
> > @@ -161,7 +167,28 @@ extern struct module __this_module;
> > Using this automatically adds a checksum of the .c files and the
> > local headers in "srcversion".
> > */
> > +
> > +#ifdef MODULE
> > #define MODULE_VERSION(_version) MODULE_INFO(version, _version)
> > +#else
> > +#define MODULE_VERSION(_version) \
> > + extern ssize_t __modver_version_show(struct module_attribute *, \
> > + struct module *, char *); \
> > + static struct module_version_attribute __modver_version_attr \
> > + __used \
> > + __attribute__ ((unused,__section__ ("__modver"),aligned(sizeof(void *)))) \
>
> __used and unused seems overkill, and confused.
>

Must admit that I copied used/unused verbatim from linux/moduleparam.h:

/* This is the fundamental function for registering boot/module
parameters. */
#define __module_param_call(prefix, name, ops, arg, isbool, perm) \
/* Default value instead of permissions? */ \
static int __param_perm_check_##name __attribute__((unused)) = \
BUILD_BUG_ON_ZERO((perm) < 0 || (perm) > 0777 || ((perm) & 2)) \
+ BUILD_BUG_ON_ZERO(sizeof(""prefix) > MAX_PARAM_PREFIX_LEN); \
static const char __param_str_##name[] = prefix #name; \
static struct kernel_param __moduleparam_const __param_##name \
__used \
__attribute__ ((unused,__section__ ("__param"),aligned(sizeof(void *)))) \
= { __param_str_##name, ops, perm, isbool ? KPARAM_ISBOOL : 0, \
{ arg } }


So should it be removed from here as well?

Thanks,

Dmitry



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