Problems using EXPORT_SYMBOL with lib/flex_array

Problems using EXPORT_SYMBOL with lib/flex_array

[Alex Bennee]

Hi,

I want to be able to use the flex_array functions in my module so I
wanted to EXPORT_SYMBOL the API.

I added the appropriate EXPORT_SYMBOL runes into lib/flex_array.c and
added externs in the header files but after re-building there is still
no sign of them in Module.symvers.

I've done a make clean, reset the whole repo to ensure the tree is
clean from previous builds and I'm still seeing problems. Am I being a
little dim or is there some other magic foo that needs doing to add an
export to a library function?

-- 
Alex, homepage: http://www.bennee.com/~alex/
http://www.half-llama.co.uk

Re: Problems using EXPORT_SYMBOL with lib/flex_array

[Alex Bennee]

On 1 December 2010 12:05, Alex Bennee <kernel-hacker@bennee.com> wrote:
> Hi,
>
> I want to be able to use the flex_array functions in my module so I
> wanted to EXPORT_SYMBOL the API.
> <snip>
> Am I being a
> little dim or is there some other magic foo that needs doing to add an
> export to a library function?

It turns out for library code there is. If the .o is only included in
the lib-y section then it will never get scanned for exported kernel
symbols. Tweaking the lib/Makefile so obj-y included flex_array.o did
the trick.

I'm unsure if this behaviour is what is wanted?

-- 
Alex, homepage: http://www.bennee.com/~alex/
http://www.half-llama.co.uk

Re: Problems using EXPORT_SYMBOL with lib/flex_array

[Américo Wang]

On Wed, Dec 01, 2010 at 01:20:30PM +0000, Alex Bennee wrote:
>On 1 December 2010 12:05, Alex Bennee <kernel-hacker@bennee.com> wrote:
>> Hi,
>>
>> I want to be able to use the flex_array functions in my module so I
>> wanted to EXPORT_SYMBOL the API.
>> <snip>
>> Am I being a
>> little dim or is there some other magic foo that needs doing to add an
>> export to a library function?
>
>It turns out for library code there is. If the .o is only included in
>the lib-y section then it will never get scanned for exported kernel
>symbols. Tweaking the lib/Makefile so obj-y included flex_array.o did
>the trick.
>
>I'm unsure if this behaviour is what is wanted?
>

Yes, but not sure about flex_array.o.
Which functions in flex_array.c do you need in your module anyway?

-- 
Live like a child, think like the god.
 

Re: Problems using EXPORT_SYMBOL with lib/flex_array

[Alex Bennee]

On 1 December 2010 16:19, Américo Wang <xiyou.wangcong@gmail.com> wrote:
> On Wed, Dec 01, 2010 at 01:20:30PM +0000, Alex Bennee wrote:
>>On 1 December 2010 12:05, Alex Bennee <kernel-hacker@bennee.com>
wrote:
<snip>
>>Tweaking the lib/Makefile so obj-y included flex_array.o did
>>the trick.
>>
>>I'm unsure if this behaviour is what is wanted?
>
> Yes, but not sure about flex_array.o.
> Which functions in flex_array.c do you need in your module anyway?

I want to use it to store a sparse array of ATM cell re-assembly
buffers for my ATM over Ethernet driver. Using the per-vcc user_back
structure causes problems when stacked with things like br2684.

So I'm currently using flex_array_alloc/free/clear/put although I
exported them all. I would have thought using library functions was
preferable to rolling your own?

I'm open to other suggestions though.

-- 
Alex, homepage: http://www.bennee.com/~alex/
http://www.half-llama.co.uk

[patch] flex_array: export symbols to modules

[David Rientjes]

On Wed, 1 Dec 2010, Alex Bennee wrote:

> Hi,
> 
> I want to be able to use the flex_array functions in my module so I
> wanted to EXPORT_SYMBOL the API.
> 
> I added the appropriate EXPORT_SYMBOL runes into lib/flex_array.c and
> added externs in the header files but after re-building there is still
> no sign of them in Module.symvers.
> 

You shouldn't need to add any externs in include/linux/flex_array.h, they 
should already be publically declared.

Perhaps you forgot to include linux/module.h in lib/flex_array.c?



flex_array: export symbols to modules

Add EXPORT_SYMBOL() for all publically accessible flex array functions.

Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 lib/flex_array.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/lib/flex_array.c b/lib/flex_array.c
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -23,6 +23,7 @@
 #include <linux/flex_array.h>
 #include <linux/slab.h>
 #include <linux/stddef.h>
+#include <linux/module.h>
 
 struct flex_array_part {
 	char elements[FLEX_ARRAY_PART_SIZE];
@@ -103,6 +104,7 @@ struct flex_array *flex_array_alloc(int element_size, unsigned int total,
 						FLEX_ARRAY_BASE_BYTES_LEFT);
 	return ret;
 }
+EXPORT_SYMBOL(flex_array_alloc);
 
 static int fa_element_to_part_nr(struct flex_array *fa,
 					unsigned int element_nr)
@@ -126,12 +128,14 @@ void flex_array_free_parts(struct flex_array *fa)
 	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++)
 		kfree(fa->parts[part_nr]);
 }
+EXPORT_SYMBOL(flex_array_free_parts);
 
 void flex_array_free(struct flex_array *fa)
 {
 	flex_array_free_parts(fa);
 	kfree(fa);
 }
+EXPORT_SYMBOL(flex_array_free);
 
 static unsigned int index_inside_part(struct flex_array *fa,
 					unsigned int element_nr)
@@ -196,6 +200,7 @@ int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
 	memcpy(dst, src, fa->element_size);
 	return 0;
 }
+EXPORT_SYMBOL(flex_array_put);
 
 /**
  * flex_array_clear - clear element in array at @element_nr
@@ -223,6 +228,7 @@ int flex_array_clear(struct flex_array *fa, unsigned int element_nr)
 	memset(dst, FLEX_ARRAY_FREE, fa->element_size);
 	return 0;
 }
+EXPORT_SYMBOL(flex_array_clear);
 
 /**
  * flex_array_prealloc - guarantee that array space exists
@@ -259,6 +265,7 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
 	}
 	return 0;
 }
+EXPORT_SYMBOL(flex_array_prealloc);
 
 /**
  * flex_array_get - pull data back out of the array
@@ -288,6 +295,7 @@ void *flex_array_get(struct flex_array *fa, unsigned int element_nr)
 	}
 	return &part->elements[index_inside_part(fa, element_nr)];
 }
+EXPORT_SYMBOL(flex_array_get);
 
 /**
  * flex_array_get_ptr - pull a ptr back out of the array
@@ -308,6 +316,7 @@ void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr)
 
 	return *tmp;
 }
+EXPORT_SYMBOL(flex_array_get_ptr);
 
 static int part_is_free(struct flex_array_part *part)
 {
@@ -348,3 +357,4 @@ int flex_array_shrink(struct flex_array *fa)
 	}
 	return ret;
 }
+EXPORT_SYMBOL(flex_array_shrink);

Re: [patch] flex_array: export symbols to modules

[Paul Mundt]

On Wed, Dec 01, 2010 at 05:16:05PM -0800, David Rientjes wrote:
> On Wed, 1 Dec 2010, Alex Bennee wrote:
> > I want to be able to use the flex_array functions in my module so I
> > wanted to EXPORT_SYMBOL the API.
> > 
> > I added the appropriate EXPORT_SYMBOL runes into lib/flex_array.c and
> > added externs in the header files but after re-building there is still
> > no sign of them in Module.symvers.
> 
> You shouldn't need to add any externs in include/linux/flex_array.h, they 
> should already be publically declared.
> 
> Perhaps you forgot to include linux/module.h in lib/flex_array.c?
> 
> flex_array: export symbols to modules
> 
> Add EXPORT_SYMBOL() for all publically accessible flex array functions.
> 
> Cc: Dave Hansen <dave@linux.vnet.ibm.com>
> Signed-off-by: David Rientjes <rientjes@google.com>
> ---
>  lib/flex_array.c |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)
> 
This will be ineffective so long as flex_array.o remains lib-y. It will
need to be moved to obj-y if modules are to also make use of it.

Re: [patch] flex_array: export symbols to modules

[Américo Wang]

On Thu, Dec 02, 2010 at 03:30:55PM +0900, Paul Mundt wrote:
>On Wed, Dec 01, 2010 at 05:16:05PM -0800, David Rientjes wrote:
>> On Wed, 1 Dec 2010, Alex Bennee wrote:
>> > I want to be able to use the flex_array functions in my module so I
>> > wanted to EXPORT_SYMBOL the API.
>> > 
>> > I added the appropriate EXPORT_SYMBOL runes into lib/flex_array.c and
>> > added externs in the header files but after re-building there is still
>> > no sign of them in Module.symvers.
>> 
>> You shouldn't need to add any externs in include/linux/flex_array.h, they 
>> should already be publically declared.
>> 
>> Perhaps you forgot to include linux/module.h in lib/flex_array.c?
>> 
>> flex_array: export symbols to modules
>> 
>> Add EXPORT_SYMBOL() for all publically accessible flex array functions.
>> 
>> Cc: Dave Hansen <dave@linux.vnet.ibm.com>
>> Signed-off-by: David Rientjes <rientjes@google.com>
>> ---
>>  lib/flex_array.c |   10 ++++++++++
>>  1 files changed, 10 insertions(+), 0 deletions(-)
>> 
>This will be ineffective so long as flex_array.o remains lib-y. It will
>need to be moved to obj-y if modules are to also make use of it.

Not moved, it needs to be added to obj-y.

Re: [patch] flex_array: export symbols to modules

[Paul Mundt]

On Thu, Dec 02, 2010 at 02:57:35PM +0800, Am??rico Wang wrote:
> On Thu, Dec 02, 2010 at 03:30:55PM +0900, Paul Mundt wrote:
> >On Wed, Dec 01, 2010 at 05:16:05PM -0800, David Rientjes wrote:
> >> On Wed, 1 Dec 2010, Alex Bennee wrote:
> >> > I want to be able to use the flex_array functions in my module so I
> >> > wanted to EXPORT_SYMBOL the API.
> >> > 
> >> > I added the appropriate EXPORT_SYMBOL runes into lib/flex_array.c and
> >> > added externs in the header files but after re-building there is still
> >> > no sign of them in Module.symvers.
> >> 
> >> You shouldn't need to add any externs in include/linux/flex_array.h, they 
> >> should already be publically declared.
> >> 
> >> Perhaps you forgot to include linux/module.h in lib/flex_array.c?
> >> 
> >> flex_array: export symbols to modules
> >> 
> >> Add EXPORT_SYMBOL() for all publically accessible flex array functions.
> >> 
> >> Cc: Dave Hansen <dave@linux.vnet.ibm.com>
> >> Signed-off-by: David Rientjes <rientjes@google.com>
> >> ---
> >>  lib/flex_array.c |   10 ++++++++++
> >>  1 files changed, 10 insertions(+), 0 deletions(-)
> >> 
> >This will be ineffective so long as flex_array.o remains lib-y. It will
> >need to be moved to obj-y if modules are to also make use of it.
> 
> Not moved, it needs to be added to obj-y.

Wrong, try again. Unless something has recently changed, an object can
not be both lib-y and obj-y. The object needs to be moved for modules to
make use of it, period.

[patch v2] flex_array: export symbols to modules

[David Rientjes]

Add EXPORT_SYMBOL() for all publically accessible flex array functions
and move to obj-y so that modules may use this library.

Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 v2: moved to obj-y per Paul Mundt's feedback, thanks!

 lib/Makefile     |    4 ++--
 lib/flex_array.c |   10 ++++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/lib/Makefile b/lib/Makefile
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -12,7 +12,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 idr.o int_sqrt.o extable.o prio_tree.o \
 	 sha1.o irq_regs.o reciprocal_div.o argv_split.o \
 	 proportions.o prio_heap.o ratelimit.o show_mem.o \
-	 is_single_threaded.o plist.o decompress.o flex_array.o
+	 is_single_threaded.o plist.o decompress.o
 
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
@@ -21,7 +21,7 @@ lib-y	+= kobject.o kref.o klist.o
 
 obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
 	 bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \
-	 string_helpers.o gcd.o lcm.o list_sort.o uuid.o
+	 string_helpers.o gcd.o lcm.o list_sort.o uuid.o flex_array.o
 
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG
diff --git a/lib/flex_array.c b/lib/flex_array.c
--- a/lib/flex_array.c
+++ b/lib/flex_array.c
@@ -23,6 +23,7 @@
 #include <linux/flex_array.h>
 #include <linux/slab.h>
 #include <linux/stddef.h>
+#include <linux/module.h>
 
 struct flex_array_part {
 	char elements[FLEX_ARRAY_PART_SIZE];
@@ -103,6 +104,7 @@ struct flex_array *flex_array_alloc(int element_size, unsigned int total,
 						FLEX_ARRAY_BASE_BYTES_LEFT);
 	return ret;
 }
+EXPORT_SYMBOL(flex_array_alloc);
 
 static int fa_element_to_part_nr(struct flex_array *fa,
 					unsigned int element_nr)
@@ -126,12 +128,14 @@ void flex_array_free_parts(struct flex_array *fa)
 	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++)
 		kfree(fa->parts[part_nr]);
 }
+EXPORT_SYMBOL(flex_array_free_parts);
 
 void flex_array_free(struct flex_array *fa)
 {
 	flex_array_free_parts(fa);
 	kfree(fa);
 }
+EXPORT_SYMBOL(flex_array_free);
 
 static unsigned int index_inside_part(struct flex_array *fa,
 					unsigned int element_nr)
@@ -196,6 +200,7 @@ int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
 	memcpy(dst, src, fa->element_size);
 	return 0;
 }
+EXPORT_SYMBOL(flex_array_put);
 
 /**
  * flex_array_clear - clear element in array at @element_nr
@@ -223,6 +228,7 @@ int flex_array_clear(struct flex_array *fa, unsigned int element_nr)
 	memset(dst, FLEX_ARRAY_FREE, fa->element_size);
 	return 0;
 }
+EXPORT_SYMBOL(flex_array_clear);
 
 /**
  * flex_array_prealloc - guarantee that array space exists
@@ -259,6 +265,7 @@ int flex_array_prealloc(struct flex_array *fa, unsigned int start,
 	}
 	return 0;
 }
+EXPORT_SYMBOL(flex_array_prealloc);
 
 /**
  * flex_array_get - pull data back out of the array
@@ -288,6 +295,7 @@ void *flex_array_get(struct flex_array *fa, unsigned int element_nr)
 	}
 	return &part->elements[index_inside_part(fa, element_nr)];
 }
+EXPORT_SYMBOL(flex_array_get);
 
 /**
  * flex_array_get_ptr - pull a ptr back out of the array
@@ -308,6 +316,7 @@ void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr)
 
 	return *tmp;
 }
+EXPORT_SYMBOL(flex_array_get_ptr);
 
 static int part_is_free(struct flex_array_part *part)
 {
@@ -348,3 +357,4 @@ int flex_array_shrink(struct flex_array *fa)
 	}
 	return ret;
 }
+EXPORT_SYMBOL(flex_array_shrink);