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authorAnton Blanchard <anton@samba.org>2009-02-21 20:50:03 -0500
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-02-22 23:53:20 -0500
commitd839088caec6891a5070f0b1ce61031e458533a9 (patch)
treea0489611eb3edce545f7aed98764220e195ef941 /arch/powerpc
parent2dadb987e09995b2910c419cdfe2307e66537649 (diff)
powerpc: Randomise lower bits of stack address
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> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/include/asm/system.h2
-rw-r--r--arch/powerpc/kernel/process.c9
2 files changed, 10 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/system.h b/arch/powerpc/include/asm/system.h
index 2a4be19a92c4..f612798e1c93 100644
--- a/arch/powerpc/include/asm/system.h
+++ b/arch/powerpc/include/asm/system.h
@@ -531,7 +531,7 @@ __cmpxchg_local(volatile void *ptr, unsigned long old, unsigned long new,
531#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n)) 531#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
532#endif 532#endif
533 533
534#define arch_align_stack(x) (x) 534extern unsigned long arch_align_stack(unsigned long sp);
535 535
536/* Used in very early kernel initialization. */ 536/* Used in very early kernel initialization. */
537extern unsigned long reloc_offset(void); 537extern unsigned long reloc_offset(void);
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 8ede428e76c0..69b9d2d3cb84 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -35,6 +35,8 @@
35#include <linux/utsname.h> 35#include <linux/utsname.h>
36#include <linux/ftrace.h> 36#include <linux/ftrace.h>
37#include <linux/kernel_stat.h> 37#include <linux/kernel_stat.h>
38#include <linux/personality.h>
39#include <linux/random.h>
38 40
39#include <asm/pgtable.h> 41#include <asm/pgtable.h>
40#include <asm/uaccess.h> 42#include <asm/uaccess.h>
@@ -1138,3 +1140,10 @@ void thread_info_cache_init(void)
1138} 1140}
1139 1141
1140#endif /* THREAD_SHIFT < PAGE_SHIFT */ 1142#endif /* THREAD_SHIFT < PAGE_SHIFT */
1143
1144unsigned long arch_align_stack(unsigned long sp)
1145{
1146 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
1147 sp -= get_random_int() & ~PAGE_MASK;
1148 return sp & ~0xf;
1149}