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authorAnton Blanchard <anton@samba.org>2009-02-22 01:50:03 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2009-02-23 15:53:20 +1100
commitd839088caec6891a5070f0b1ce61031e458533a9 (patch)
treea0489611eb3edce545f7aed98764220e195ef941 /arch
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')
-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 2a4be19a92c..f612798e1c9 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,
#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);
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 8ede428e76c..69b9d2d3cb8 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -35,6 +35,8 @@
#include <linux/utsname.h>
#include <linux/ftrace.h>
#include <linux/kernel_stat.h>
+#include <linux/personality.h>
+#include <linux/random.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
@@ -1138,3 +1140,10 @@ void thread_info_cache_init(void)
}
#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;
+}