commit 3abc94480225677ea08af817d56edfb0df9e9b80
author Vineet Gupta <vgupta@synopsys.com> Wed Jun 05 17:49:14 2013 +0530
committer Vineet Gupta <vgupta@synopsys.com> Sat Jun 22 19:23:20 2013 +0530
tree 364c3c03f33d3934f53621669aba62023d5a5633
parent 2ed21dae021db1f9f988494ceee519290217520d

ARC: [mm] Make stack/heap Non-executable by default

1. For VM_EXEC based delayed dcache/icache flush, reduces the number of
   flushes.

2. Makes this security feature ON by default rather than OFF before.

3. Applications can use mprotect() to selectively override this.

4. ELF binaries have a GNU_STACK segment which can easily override the
   kernel default permissions.
   For nested-functions/trampolines, gcc already auto-enables executable
   stack in elf. Others needing this can use -Wl,-z,execstack option.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/page.h

diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
index ab84bf1..9c8aa41 100644
--- a/arch/arc/include/asm/page.h
+++ b/arch/arc/include/asm/page.h
@@ -96,13 +96,8 @@
 
 #define virt_addr_valid(kaddr)  pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
 
-/* Default Permissions for page, used in mmap.c */
-#ifdef CONFIG_ARC_STACK_NONEXEC
+/* Default Permissions for stack/heaps pages (Non Executable) */
 #define VM_DATA_DEFAULT_FLAGS   (VM_READ | VM_WRITE | VM_MAYREAD | VM_MAYWRITE)
-#else
-#define VM_DATA_DEFAULT_FLAGS   (VM_READ | VM_WRITE | VM_EXEC | \
-				 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
-#endif
 
 #define WANT_PAGE_VIRTUAL   1