[PATCH] x86_64: Increase the variability of the process stack on 64bit architectures

8MB is not really very random, use 1GB (or more with larger page sizes)
instead.

Also use the low bits of the random generator output now instead of
throwing them away.

Only enabled on x86-64 right now. Other architectures need to add
a suitable STACK_RND_MASK

Cc: mingo@elte.hu
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/asm-x86_64/elf.h b/include/asm-x86_64/elf.h
index 43862cd6a569..c98633af07d2 100644
--- a/include/asm-x86_64/elf.h
+++ b/include/asm-x86_64/elf.h
@@ -8,6 +8,7 @@
 #include <asm/ptrace.h>
 #include <asm/user.h>
 #include <asm/processor.h>
+#include <asm/compat.h>
 
 /* x86-64 relocation types */
 #define R_X86_64_NONE           0       /* No reloc */
@@ -157,6 +158,9 @@ extern int dump_task_fpu (struct task_struct *, elf_fpregset_t *);
 #define ELF_CORE_COPY_TASK_REGS(tsk, elf_regs) dump_task_regs(tsk, elf_regs)
 #define ELF_CORE_COPY_FPREGS(tsk, elf_fpregs) dump_task_fpu(tsk, elf_fpregs)
 
+/* 1GB for 64bit, 8MB for 32bit */
+#define STACK_RND_MASK (is_compat_task() ? 0x7ff : 0x3fffff)
+
 #endif
 
 #endif