linker script: throw away .discard section

x86 throws away .discard section but no other archs do.  Also,
.discard is not thrown away while linking modules.  Make every arch
and module linking throw it away.  This will be used to define dummy
variables for percpu declarations and definitions.

This patch is based on Ivan Kokshaysky's alpha percpu patch.

[ Impact: always throw away everything in .discard ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Bryan Wu <cooloney@kernel.org>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>

arch/sparc/kernel/vmlinux.lds.S

@@ -175,6 +175,7 @@ SECTIONS
 		EXIT_TEXT
 		EXIT_DATA
 		*(.exitcall.exit)
+		*(.discard)
 	}
 
 	STABS_DEBUG

arch/um/kernel/dyn.lds.S

@@ -156,4 +156,6 @@ SECTIONS
   STABS_DEBUG
 
   DWARF_DEBUG
+
+  /DISCARD/	: { *(.discard) }
 }

arch/um/kernel/uml.lds.S

@@ -100,4 +100,6 @@ SECTIONS
   STABS_DEBUG
 
   DWARF_DEBUG
+
+  /DISCARD/	: { *(.discard) }
 }

arch/xtensa/kernel/vmlinux.lds.S

@@ -287,6 +287,7 @@ SECTIONS
 	EXIT_TEXT
 	EXIT_DATA
         *(.exitcall.exit)
+	*(.discard)
   }
 
   .xt.lit : { *(.xt.lit) }

include/asm-generic/vmlinux.lds.h

@@ -628,6 +628,14 @@
 #define INITRAMFS
 #endif
 
+#define DISCARDS							\
+	/DISCARD/ : {							\
+	EXIT_TEXT							\
+	EXIT_DATA							\
+	*(.exitcall.exit)						\
+	*(.discard)							\
+	}
+
 /**
  * PERCPU_VADDR - define output section for percpu area
  * @vaddr: explicit base address (optional)

scripts/module-common.lds

+/*
+ * Common module linker script, always used when linking a module.
+ * Archs are free to supply their own linker scripts.  ld will
+ * combine them automatically.
+ */
+SECTIONS {
+	/DISCARD/ : { *(.discard) }
+}