To avoid excessive usage of EXPORT_SYMBOL_NS(sym, MY_NAMESPACE), where
MY_NAMESPACE will always be the namespace we are exporting to, allow
exporting all definitions of EXPORT_SYMBOL() and friends by defining
DEFAULT_SYMBOL_NAMESPACE.
For example, to export all symbols defined in usb-common into the
namespace USB_COMMON, add a line like this to drivers/usb/common/Makefile:
ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=USB_COMMON
That is equivalent to changing all EXPORT_SYMBOL(sym) definitions to
EXPORT_SYMBOL_NS(sym, USB_COMMON). Subsequently all symbol namespaces
functionality will apply.
Another way of making use of this feature is to define the namespace
within source or header files similar to how TRACE_SYSTEM defines are
used:
#undef DEFAULT_SYMBOL_NAMESPACE
#define DEFAULT_SYMBOL_NAMESPACE USB_COMMON
Please note that, as opposed to TRACE_SYSTEM, DEFAULT_SYMBOL_NAMESPACE
has to be defined before including include/linux/export.h.
If DEFAULT_SYMBOL_NAMESPACE is defined, a symbol can still be exported
to another namespace by using EXPORT_SYMBOL_NS() and friends with
explicitly specifying the namespace.
Suggested-by: Arnd Bergmann <[email protected]>
Reviewed-by: Martijn Coenen <[email protected]>
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Matthias Maennich <[email protected]>
---
include/linux/export.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/include/linux/export.h b/include/linux/export.h
index 8e12e05444d1..1fb243abdbc4 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -166,6 +166,12 @@ struct kernel_symbol {
#define __EXPORT_SYMBOL ___EXPORT_SYMBOL
#endif
+#ifdef DEFAULT_SYMBOL_NAMESPACE
+#undef __EXPORT_SYMBOL
+#define __EXPORT_SYMBOL(sym, sec) \
+ __EXPORT_SYMBOL_NS(sym, sec, DEFAULT_SYMBOL_NAMESPACE)
+#endif
+
#define EXPORT_SYMBOL(sym) __EXPORT_SYMBOL(sym, "")
#define EXPORT_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_gpl")
#define EXPORT_SYMBOL_GPL_FUTURE(sym) __EXPORT_SYMBOL(sym, "_gpl_future")
--
2.23.0.rc1.153.gdeed80330f-goog
+++ Matthias Maennich [21/08/19 12:49 +0100]:
>To avoid excessive usage of EXPORT_SYMBOL_NS(sym, MY_NAMESPACE), where
>MY_NAMESPACE will always be the namespace we are exporting to, allow
>exporting all definitions of EXPORT_SYMBOL() and friends by defining
>DEFAULT_SYMBOL_NAMESPACE.
>
>For example, to export all symbols defined in usb-common into the
>namespace USB_COMMON, add a line like this to drivers/usb/common/Makefile:
>
> ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=USB_COMMON
>
>That is equivalent to changing all EXPORT_SYMBOL(sym) definitions to
>EXPORT_SYMBOL_NS(sym, USB_COMMON). Subsequently all symbol namespaces
>functionality will apply.
>
>Another way of making use of this feature is to define the namespace
>within source or header files similar to how TRACE_SYSTEM defines are
>used:
> #undef DEFAULT_SYMBOL_NAMESPACE
> #define DEFAULT_SYMBOL_NAMESPACE USB_COMMON
>
>Please note that, as opposed to TRACE_SYSTEM, DEFAULT_SYMBOL_NAMESPACE
>has to be defined before including include/linux/export.h.
>
>If DEFAULT_SYMBOL_NAMESPACE is defined, a symbol can still be exported
>to another namespace by using EXPORT_SYMBOL_NS() and friends with
>explicitly specifying the namespace.
This changelog provides a good summary of how to use
DEFAULT_SYMBOL_NAMESPACE, I wonder if we should explicitly document
its proper usage somewhere? (along with EXPORT_SYMBOL_NS*)
The EXPORT_SYMBOL API is briefly documented in
Documentation/kernel-hacking/hacking.rst - it might be slightly dated,
but perhaps it'd fit there best?
>Suggested-by: Arnd Bergmann <[email protected]>
>Reviewed-by: Martijn Coenen <[email protected]>
>Reviewed-by: Greg Kroah-Hartman <[email protected]>
>Signed-off-by: Matthias Maennich <[email protected]>
>---
> include/linux/export.h | 6 ++++++
> 1 file changed, 6 insertions(+)
>
>diff --git a/include/linux/export.h b/include/linux/export.h
>index 8e12e05444d1..1fb243abdbc4 100644
>--- a/include/linux/export.h
>+++ b/include/linux/export.h
>@@ -166,6 +166,12 @@ struct kernel_symbol {
> #define __EXPORT_SYMBOL ___EXPORT_SYMBOL
> #endif
>
>+#ifdef DEFAULT_SYMBOL_NAMESPACE
>+#undef __EXPORT_SYMBOL
>+#define __EXPORT_SYMBOL(sym, sec) \
>+ __EXPORT_SYMBOL_NS(sym, sec, DEFAULT_SYMBOL_NAMESPACE)
>+#endif
>+
> #define EXPORT_SYMBOL(sym) __EXPORT_SYMBOL(sym, "")
> #define EXPORT_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_gpl")
> #define EXPORT_SYMBOL_GPL_FUTURE(sym) __EXPORT_SYMBOL(sym, "_gpl_future")
>--
>2.23.0.rc1.153.gdeed80330f-goog
>
On Wed, Aug 28, 2019 at 12:49:51PM +0200, Jessica Yu wrote:
>+++ Matthias Maennich [21/08/19 12:49 +0100]:
>>To avoid excessive usage of EXPORT_SYMBOL_NS(sym, MY_NAMESPACE), where
>>MY_NAMESPACE will always be the namespace we are exporting to, allow
>>exporting all definitions of EXPORT_SYMBOL() and friends by defining
>>DEFAULT_SYMBOL_NAMESPACE.
>>
>>For example, to export all symbols defined in usb-common into the
>>namespace USB_COMMON, add a line like this to drivers/usb/common/Makefile:
>>
>> ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=USB_COMMON
>>
>>That is equivalent to changing all EXPORT_SYMBOL(sym) definitions to
>>EXPORT_SYMBOL_NS(sym, USB_COMMON). Subsequently all symbol namespaces
>>functionality will apply.
>>
>>Another way of making use of this feature is to define the namespace
>>within source or header files similar to how TRACE_SYSTEM defines are
>>used:
>> #undef DEFAULT_SYMBOL_NAMESPACE
>> #define DEFAULT_SYMBOL_NAMESPACE USB_COMMON
>>
>>Please note that, as opposed to TRACE_SYSTEM, DEFAULT_SYMBOL_NAMESPACE
>>has to be defined before including include/linux/export.h.
>>
>>If DEFAULT_SYMBOL_NAMESPACE is defined, a symbol can still be exported
>>to another namespace by using EXPORT_SYMBOL_NS() and friends with
>>explicitly specifying the namespace.
>
>This changelog provides a good summary of how to use
>DEFAULT_SYMBOL_NAMESPACE, I wonder if we should explicitly document
>its proper usage somewhere? (along with EXPORT_SYMBOL_NS*)
>The EXPORT_SYMBOL API is briefly documented in
>Documentation/kernel-hacking/hacking.rst - it might be slightly dated,
>but perhaps it'd fit there best?
I will add documentation along with the commits. Not only for the
macros, but in general to describe the feature.
>>Suggested-by: Arnd Bergmann <[email protected]>
>>Reviewed-by: Martijn Coenen <[email protected]>
>>Reviewed-by: Greg Kroah-Hartman <[email protected]>
>>Signed-off-by: Matthias Maennich <[email protected]>
>>---
>>include/linux/export.h | 6 ++++++
>>1 file changed, 6 insertions(+)
>>
>>diff --git a/include/linux/export.h b/include/linux/export.h
>>index 8e12e05444d1..1fb243abdbc4 100644
>>--- a/include/linux/export.h
>>+++ b/include/linux/export.h
>>@@ -166,6 +166,12 @@ struct kernel_symbol {
>>#define __EXPORT_SYMBOL ___EXPORT_SYMBOL
>>#endif
>>
>>+#ifdef DEFAULT_SYMBOL_NAMESPACE
>>+#undef __EXPORT_SYMBOL
>>+#define __EXPORT_SYMBOL(sym, sec) \
>>+ __EXPORT_SYMBOL_NS(sym, sec, DEFAULT_SYMBOL_NAMESPACE)
>>+#endif
>>+
>>#define EXPORT_SYMBOL(sym) __EXPORT_SYMBOL(sym, "")
>>#define EXPORT_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_gpl")
>>#define EXPORT_SYMBOL_GPL_FUTURE(sym) __EXPORT_SYMBOL(sym, "_gpl_future")
>>--
>>2.23.0.rc1.153.gdeed80330f-goog
>>