Kconfig: consolidate CONFIG_DEBUG_STRICT_USER_COPY_CHECKS

The help text for this config is duplicated across the x86, parisc, and
s390 Kconfig.debug files.  Arnd Bergman noted that the help text was
slightly misleading and should be fixed to state that enabling this
option isn't a problem when using pre 4.4 gcc.

To simplify the rewording, consolidate the text into lib/Kconfig.debug
and modify it there to be more explicit about when you should say N to
this config.

Also, make the text a bit more generic by stating that this option
enables compile time checks so we can cover architectures which emit
warnings vs.  ones which emit errors.  The details of how an
architecture decided to implement the checks isn't as important as the
concept of compile time checking of copy_from_user() calls.

While we're doing this, remove all the copy_from_user_overflow() code
that's duplicated many times and place it into lib/ so that any
architecture supporting this option can get the function for free.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Helge Deller <deller@gmx.de>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 1 insertions, 23 deletions

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index bda6ba6..ce640af 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -91,6 +91,7 @@ config S390
 	select ARCH_INLINE_WRITE_UNLOCK_BH
 	select ARCH_INLINE_WRITE_UNLOCK_IRQ
 	select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
+	select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
 	select ARCH_SAVE_PAGE_KEYS if HIBERNATION
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_EXTABLE_SORT
diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug
index fc32a2d..c56878e 100644
--- a/arch/s390/Kconfig.debug
+++ b/arch/s390/Kconfig.debug
@@ -17,20 +17,6 @@ config STRICT_DEVMEM
 
 	  If you are unsure, say Y.
 
-config DEBUG_STRICT_USER_COPY_CHECKS
-	def_bool n
-	prompt "Strict user copy size checks"
-	---help---
-	  Enabling this option turns a certain set of sanity checks for user
-	  copy operations into compile time warnings.
-
-	  The copy_from_user() etc checks are there to help test if there
-	  are sufficient security checks on the length argument of
-	  the copy operation, by having gcc prove that the argument is
-	  within bounds.
-
-	  If unsure, or if you run an older (pre 4.4) gcc, say N.
-
 config S390_PTDUMP
 	bool "Export kernel pagetable layout to userspace via debugfs"
 	depends on DEBUG_KERNEL
diff --git a/arch/s390/lib/Makefile b/arch/s390/lib/Makefile
index 6ab0d0b..20b0e97 100644
--- a/arch/s390/lib/Makefile
+++ b/arch/s390/lib/Makefile
@@ -3,7 +3,6 @@
 #
 
 lib-y += delay.o string.o uaccess_std.o uaccess_pt.o
-obj-y += usercopy.o
 obj-$(CONFIG_32BIT) += div64.o qrnnd.o ucmpdi2.o mem32.o
 obj-$(CONFIG_64BIT) += mem64.o
 lib-$(CONFIG_64BIT) += uaccess_mvcos.o
diff --git a/arch/s390/lib/usercopy.c b/arch/s390/lib/usercopy.c
deleted file mode 100644
index 14b363f..0000000
--- a/arch/s390/lib/usercopy.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <linux/module.h>
-#include <linux/bug.h>
-
-void copy_from_user_overflow(void)
-{
-	WARN(1, "Buffer overflow detected!\n");
-}
-EXPORT_SYMBOL(copy_from_user_overflow);