From: Anton Blanchard <anton@samba•org>
To: linuxppc-dev@ozlabs•org
Subject: [patch 06/10] powerpc: Randomise lower bits of stack address
Date: Sun, 22 Feb 2009 22:50:03 +1100 [thread overview]
Message-ID: <20090222115332.404685001@samba.org> (raw)
In-Reply-To: 20090222114957.213647384@samba.org
Randomise the lower bits of the stack address. More randomisation is good for
security but the scatter can also help with SMT threads that share an L1. A
quick test case shows this working:
int main()
{
int sp;
printf("%x\n", (unsigned long)&sp & 4095);
}
before:
80
80
80
80
80
after:
610
490
300
6b0
d80
Signed-off-by: Anton Blanchard <anton@samba•org>
---
Index: linux-2.6/arch/powerpc/include/asm/system.h
===================================================================
--- linux-2.6.orig/arch/powerpc/include/asm/system.h 2009-02-20 13:39:05.000000000 +1100
+++ linux-2.6/arch/powerpc/include/asm/system.h 2009-02-20 13:51:39.000000000 +1100
@@ -531,7 +531,7 @@
#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
#endif
-#define arch_align_stack(x) (x)
+extern unsigned long arch_align_stack(unsigned long sp);
/* Used in very early kernel initialization. */
extern unsigned long reloc_offset(void);
Index: linux-2.6/arch/powerpc/kernel/process.c
===================================================================
--- linux-2.6.orig/arch/powerpc/kernel/process.c 2009-02-20 13:39:05.000000000 +1100
+++ linux-2.6/arch/powerpc/kernel/process.c 2009-02-20 13:51:39.000000000 +1100
@@ -34,6 +34,8 @@
#include <linux/hardirq.h>
#include <linux/utsname.h>
#include <linux/kernel_stat.h>
+#include <linux/personality.h>
+#include <linux/random.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
@@ -1122,3 +1124,10 @@
}
#endif /* THREAD_SHIFT < PAGE_SHIFT */
+
+unsigned long arch_align_stack(unsigned long sp)
+{
+ if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
+ sp -= get_random_int() & ~PAGE_MASK;
+ return sp & ~0xf;
+}
--
next prev parent reply other threads:[~2009-02-22 11:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-22 11:49 [patch 00/10] PowerPC address space randomisation Anton Blanchard
2009-02-22 11:49 ` [patch 01/10] powerpc: Move is_32bit_task Anton Blanchard
2009-02-22 11:49 ` [patch 02/10] powerpc: Use new layout for 64bit binaries Anton Blanchard
2009-02-22 11:50 ` [patch 03/10] powerpc: Rearrange mmap.c Anton Blanchard
2009-02-22 11:50 ` [patch 04/10] powerpc: Randomise mmap start address Anton Blanchard
2009-02-22 11:50 ` [patch 05/10] powerpc: More stack randomisation for 64bit binaries Anton Blanchard
2009-02-22 11:50 ` Anton Blanchard [this message]
2009-02-22 11:50 ` [patch 07/10] powerpc: Randomise the brk region Anton Blanchard
2009-02-22 11:50 ` [patch 08/10] powerpc: Ensure random space between stack and mmaps Anton Blanchard
2009-02-22 11:50 ` [patch 09/10] powerpc: Increase stack gap on 64bit binaries Anton Blanchard
2009-02-22 11:50 ` [patch 10/10] powerpc: Randomise PIEs Anton Blanchard
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