[PATCH] ppc64: noexec fixes

There were a few issues with the ppc64 noexec support:

The 64bit ABI has a non executable stack by default.  At the moment 64bit apps
require a PT_GNU_STACK section in order to have a non executable stack.

Disable the read implies exec workaround on the 64bit ABI.  The 64bit
toolchain has never had problems with incorrect mmap permissions (the 32bit
has, thats why we need to retain the workaround).

With these fixes as well as a gcc fix from Alan Modra (that was recently
committed) 64bit apps work as expected.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 12 insertions, 3 deletions

diff --git a/include/asm-ppc64/page.h b/include/asm-ppc64/page.h
index 20e0f19324e8..86219574c1a5 100644
--- a/include/asm-ppc64/page.h
+++ b/include/asm-ppc64/page.h
@@ -252,10 +252,19 @@ extern u64 ppc64_pft_size;		/* Log 2 of page table size */
 
 /*
  * This is the default if a program doesn't have a PT_GNU_STACK
- * program header entry.
+ * program header entry. The PPC64 ELF ABI has a non executable stack
+ * stack by default, so in the absense of a PT_GNU_STACK program header
+ * we turn execute permission off.
  */
-#define VM_STACK_DEFAULT_FLAGS  (VM_READ | VM_WRITE | VM_EXEC | \
-                                 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
+#define VM_STACK_DEFAULT_FLAGS32        (VM_READ | VM_WRITE | VM_EXEC | \
+                                         VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
+
+#define VM_STACK_DEFAULT_FLAGS64        (VM_READ | VM_WRITE | \
+                                         VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
+
+#define VM_STACK_DEFAULT_FLAGS \
+        (test_thread_flag(TIF_32BIT) ? \
+         VM_STACK_DEFAULT_FLAGS32 : VM_STACK_DEFAULT_FLAGS64)
 
 #endif /* __KERNEL__ */
 #endif /* _PPC64_PAGE_H */