[RFC/PATCH 00/14] split exception table content out of module.h into extable.h

[RFC/PATCH 00/14] split exception table content out of module.h into extable.h

[Paul Gortmaker]

[RFC: Not looking for detailed review given the merge window is open.
 As long as nobody thinks the general idea is horrible, I'll expand into
 more fringe arch and resend in 2wks and get it added then to linux-next.]

While doing an audit looking for unnecessary instances of module.h
inclusion across arch/x86/ I found a significant number of includes
of module.h were for things like search_exception_table and friends.

For historical reasons (i.e. pre-git) the exception table stuff was
buried in the middle of the module.h file.  So we have core kernel
files that are completely non-modular (both arch specific and arch
independent) that are just including module.h for this.

The converse is also true, in that conventional drivers, be they for
filesystems or actual hardware peripherals or similar, do not
normally care about the exception tables.

Here we fork the exception table content out of module.h into a new
extable.h file.  The gain here is that module.h gets a bit smaller;
a win for all modular drivers that we build for allmodconfig.  Also
most core files that only need exception table stuff get to shed an
include of module.h that brings in lots of extra stuff and just
looks generally out of place.  They use the tiny extable.h instead.

We temporarily include extable.h into the module.h itself.  Then we
will work our way across the arch independent and arch specific
files needing just exception table content, and move them off
module.h and onto extable.h

Once that is done, we can remove the extable.h from module.h and in
doing it like this, we avoid introducing build failures into the git
history.

We have the option of taking this final one line commit and pushing
it out a complete release if we want to open up a bigger window for
converting some of the more fringe archtectures.

I've converted about a dozen architectures here w/o issue; that
largely reflects what I currently have toolchains for.  Build
testing seems necessary in all instances, since the odds are high
that the module.h presence was hiding implicit use of other headers,
as was the case for s390.

Paul.
-- 

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-alpha at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-m68k at lists.linux-m68k.org
Cc: linux-mips at linux-mips.org
Cc: linux-parisc at vger.kernel.org
Cc: linuxppc-dev at lists.ozlabs.org
Cc: linux-s390 at vger.kernel.org
Cc: x86 at kernel.org
Cc: sparclinux at vger.kernel.org

Paul Gortmaker (14):
  exceptions: fork exception table content from module.h into extable.h
  x86: migrate exception table users off module.h and onto extable.h
  arm: migrate exception table users off module.h and onto extable.h
  arm64: migrate exception table users off module.h and onto extable.h
  mips: migrate exception table users off module.h and onto extable.h
  sparc: migrate exception table users off module.h and onto extable.h
  powerpc: migrate exception table users off module.h and onto extable.h
  m68k: migrate exception table users off module.h and onto extable.h
  s390: migrate exception table users off module.h and onto extable.h
  tile: migrate exception table users off module.h and onto extable.h
  alpha: migrate exception table users off module.h and onto extable.h
  parisc: migrate exception table users off module.h and onto extable.h
  core: migrate exception table users off module.h and onto extable.h
  module.h: remove extable.h include now users have migrated

 arch/alpha/kernel/traps.c          |  2 +-
 arch/alpha/mm/fault.c              |  2 +-
 arch/arm/mm/extable.c              |  2 +-
 arch/arm/mm/fault.c                |  2 +-
 arch/arm64/kernel/probes/kprobes.c |  2 +-
 arch/arm64/mm/extable.c            |  2 +-
 arch/arm64/mm/fault.c              |  2 +-
 arch/m68k/kernel/signal.c          |  2 +-
 arch/mips/kernel/module.c          |  1 +
 arch/mips/kernel/traps.c           |  2 +-
 arch/mips/mm/extable.c             |  2 +-
 arch/parisc/mm/fault.c             |  2 +-
 arch/powerpc/kernel/kprobes.c      |  2 +-
 arch/powerpc/mm/fault.c            |  2 +-
 arch/s390/kernel/early.c           |  2 +-
 arch/s390/kernel/kprobes.c         |  2 ++
 arch/s390/kernel/traps.c           |  3 ++-
 arch/s390/mm/fault.c               |  2 +-
 arch/sparc/kernel/kprobes.c        |  2 +-
 arch/sparc/kernel/traps_64.c       |  2 +-
 arch/sparc/kernel/unaligned_64.c   |  2 +-
 arch/sparc/mm/fault_64.c           |  2 +-
 arch/sparc/mm/init_64.c            |  2 +-
 arch/tile/kernel/unaligned.c       |  2 +-
 arch/tile/mm/extable.c             |  2 +-
 arch/tile/mm/fault.c               |  2 +-
 arch/x86/kernel/kprobes/core.c     |  2 +-
 arch/x86/kernel/kprobes/opt.c      |  2 +-
 arch/x86/mm/extable.c              |  2 +-
 arch/x86/mm/fault.c                |  2 +-
 include/linux/extable.h            | 30 ++++++++++++++++++++++++++++++
 include/linux/module.h             | 26 +-------------------------
 init/main.c                        |  1 +
 kernel/extable.c                   |  1 +
 kernel/module.c                    |  1 +
 35 files changed, 66 insertions(+), 53 deletions(-)
 create mode 100644 include/linux/extable.h

-- 
2.8.4

[PATCH 03/14] arm: migrate exception table users off module.h and onto extable.h

[Paul Gortmaker]

These files were only including module.h for exception table
related functions.  We've now separated that content out into its
own file "extable.h" so now move over to that and avoid all the
extra header content in module.h that we don't really need to compile
these files.

Cc: Russell King <linux@armlinux.org.uk>
Cc: linux-arm-kernel at lists.infradead.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 arch/arm/mm/extable.c | 2 +-
 arch/arm/mm/fault.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mm/extable.c b/arch/arm/mm/extable.c
index 312e15e6d00b..f436f7439e46 100644
--- a/arch/arm/mm/extable.c
+++ b/arch/arm/mm/extable.c
@@ -1,7 +1,7 @@
 /*
  *  linux/arch/arm/mm/extable.c
  */
-#include <linux/module.h>
+#include <linux/extable.h>
 #include <linux/uaccess.h>
 
 int fixup_exception(struct pt_regs *regs)
diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 3a2e678b8d30..94de590db99e 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -8,7 +8,7 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
-#include <linux/module.h>
+#include <linux/extable.h>
 #include <linux/signal.h>
 #include <linux/mm.h>
 #include <linux/hardirq.h>
-- 
2.8.4

[PATCH 04/14] arm64: migrate exception table users off module.h and onto extable.h

[Paul Gortmaker]

These files were only including module.h for exception table
related functions.  We've now separated that content out into its
own file "extable.h" so now move over to that and avoid all the
extra header content in module.h that we don't really need to compile
these files.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel at lists.infradead.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 arch/arm64/kernel/probes/kprobes.c | 2 +-
 arch/arm64/mm/extable.c            | 2 +-
 arch/arm64/mm/fault.c              | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index bf9768588288..9c1866ef3271 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -19,7 +19,7 @@
 #include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/kprobes.h>
-#include <linux/module.h>
+#include <linux/extable.h>
 #include <linux/slab.h>
 #include <linux/stop_machine.h>
 #include <linux/stringify.h>
diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
index 81acd4706878..c9f118cd812b 100644
--- a/arch/arm64/mm/extable.c
+++ b/arch/arm64/mm/extable.c
@@ -2,7 +2,7 @@
  * Based on arch/arm/mm/extable.c
  */
 
-#include <linux/module.h>
+#include <linux/extable.h>
 #include <linux/uaccess.h>
 
 int fixup_exception(struct pt_regs *regs)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index c8beaa0da7df..427f2fd49463 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -18,7 +18,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <linux/module.h>
+#include <linux/extable.h>
 #include <linux/signal.h>
 #include <linux/mm.h>
 #include <linux/hardirq.h>
-- 
2.8.4

[RFC/PATCH 00/14] split exception table content out of module.h into extable.h

[Linus Torvalds]

On Sun, Jul 24, 2016 at 8:42 PM, Paul Gortmaker
<paul.gortmaker@windriver.com> wrote:
>
> While doing an audit looking for unnecessary instances of module.h
> inclusion across arch/x86/ I found a significant number of includes
> of module.h were for things like search_exception_table and friends.
>
> For historical reasons (i.e. pre-git) the exception table stuff was
> buried in the middle of the module.h file.  So we have core kernel
> files that are completely non-modular (both arch specific and arch
> independent) that are just including module.h for this.
>
> The converse is also true, in that conventional drivers, be they for
> filesystems or actual hardware peripherals or similar, do not
> normally care about the exception tables.
>
> Here we fork the exception table content [...]

This looks to be the right thing to do as far as I can tell. I'm not
sure how big of a problem the extable stuff is (we definitely have
much bigger unnecessary include files that cause a lot more problems),
but it seems like a reasonable cleanup.

              Linus

[PATCH 04/14] arm64: migrate exception table users off module.h and onto extable.h

[Catalin Marinas]

On Sun, Jul 24, 2016 at 11:42:37PM -0400, Paul Gortmaker wrote:
> These files were only including module.h for exception table
> related functions.  We've now separated that content out into its
> own file "extable.h" so now move over to that and avoid all the
> extra header content in module.h that we don't really need to compile
> these files.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: linux-arm-kernel at lists.infradead.org
> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>