Blackfin arch: fix bug libstdc++ calling writev with an iovec containing { NULL, 0 } fails on Blackfin

Fix a problem reported in the forums - libstdc++ can call writev with an
iovec containing { NULL, 0 }, which works fine on i686-linux, but fails on
Blackfin.  Fixed by allowing size 0 transfers to/from userspace regardless
of the address.

Signed-off-by: Bernd Schmidt <bernd.schmidt@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/blackfin/kernel/process.c b/arch/blackfin/kernel/process.c
index de7d048bd4ee..9124467651c4 100644
--- a/arch/blackfin/kernel/process.c
+++ b/arch/blackfin/kernel/process.c
@@ -395,7 +395,8 @@ void finish_atomic_sections (struct pt_regs *regs)
 #if defined(CONFIG_ACCESS_CHECK)
 int _access_ok(unsigned long addr, unsigned long size)
 {
-
+        if (size == 0)
+                return 1;
         if (addr > (addr + size))
                 return 0;
         if (segment_eq(get_fs(), KERNEL_DS))