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>

3 files changed, 7 insertions, 16 deletions

diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 25877ae..0f712f4e 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -19,6 +19,7 @@ config TILE
 	select HAVE_SYSCALL_WRAPPERS if TILEGX
 	select VIRT_TO_BUS
 	select SYS_HYPERVISOR
+	select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select GENERIC_CLOCKEVENTS
 	select MODULES_USE_ELF_RELA
@@ -114,13 +115,6 @@ config STRICT_DEVMEM
 config SMP
 	def_bool y
 
-# Allow checking for compile-time determined overflow errors in
-# copy_from_user().  There are still unprovable places in the
-# generic code as of 2.6.34, so this option is not really compatible
-# with -Werror, which is more useful in general.
-config DEBUG_COPY_FROM_USER
-	def_bool n
-
 config HVC_TILE
 	depends on TTY
 	select HVC_DRIVER
diff --git a/arch/tile/include/asm/uaccess.h b/arch/tile/include/asm/uaccess.h
index 9ab078a..8a082bc 100644
--- a/arch/tile/include/asm/uaccess.h
+++ b/arch/tile/include/asm/uaccess.h
@@ -395,7 +395,12 @@ _copy_from_user(void *to, const void __user *from, unsigned long n)
 	return n;
 }
 
-#ifdef CONFIG_DEBUG_COPY_FROM_USER
+#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
+/*
+ * There are still unprovable places in the generic code as of 2.6.34, so this
+ * option is not really compatible with -Werror, which is more useful in
+ * general.
+ */
 extern void copy_from_user_overflow(void)
 	__compiletime_warning("copy_from_user() size is not provably correct");
 
diff --git a/arch/tile/lib/uaccess.c b/arch/tile/lib/uaccess.c
index f8d398c..030abe3 100644
--- a/arch/tile/lib/uaccess.c
+++ b/arch/tile/lib/uaccess.c
@@ -22,11 +22,3 @@ int __range_ok(unsigned long addr, unsigned long size)
 		 is_arch_mappable_range(addr, size));
 }
 EXPORT_SYMBOL(__range_ok);
-
-#ifdef CONFIG_DEBUG_COPY_FROM_USER
-void copy_from_user_overflow(void)
-{
-       WARN(1, "Buffer overflow detected!\n");
-}
-EXPORT_SYMBOL(copy_from_user_overflow);
-#endif