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authorKees Cook <keescook@chromium.org>2013-10-10 17:18:15 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2013-10-13 03:12:12 -0700
commit5bfce5ef55cbe78ee2ee6e97f2e26a8a582008f3 (patch)
treeead4a5281554b6f2e0a334cc7e1d83dccf35e15c /arch/x86/boot
parent8ab3820fd5b2896d66da7bb2a906bc382e63e7bc (diff)
downloadop-kernel-dev-5bfce5ef55cbe78ee2ee6e97f2e26a8a582008f3.zip
op-kernel-dev-5bfce5ef55cbe78ee2ee6e97f2e26a8a582008f3.tar.gz
x86, kaslr: Provide randomness functions
Adds potential sources of randomness: RDRAND, RDTSC, or the i8254. This moves the pre-alternatives inline rdrand function into the header so both pieces of code can use it. Availability of RDRAND is then controlled by CONFIG_ARCH_RANDOM, if someone wants to disable it even for kASLR. Signed-off-by: Kees Cook <keescook@chromium.org> Link: http://lkml.kernel.org/r/1381450698-28710-4-git-send-email-keescook@chromium.org Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/boot')
-rw-r--r--arch/x86/boot/compressed/aslr.c53
-rw-r--r--arch/x86/boot/compressed/misc.h2
2 files changed, 55 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index b73cc66..14b24e0 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -1,6 +1,59 @@
#include "misc.h"
#ifdef CONFIG_RANDOMIZE_BASE
+#include <asm/msr.h>
+#include <asm/archrandom.h>
+
+#define I8254_PORT_CONTROL 0x43
+#define I8254_PORT_COUNTER0 0x40
+#define I8254_CMD_READBACK 0xC0
+#define I8254_SELECT_COUNTER0 0x02
+#define I8254_STATUS_NOTREADY 0x40
+static inline u16 i8254(void)
+{
+ u16 status, timer;
+
+ do {
+ outb(I8254_PORT_CONTROL,
+ I8254_CMD_READBACK | I8254_SELECT_COUNTER0);
+ status = inb(I8254_PORT_COUNTER0);
+ timer = inb(I8254_PORT_COUNTER0);
+ timer |= inb(I8254_PORT_COUNTER0) << 8;
+ } while (status & I8254_STATUS_NOTREADY);
+
+ return timer;
+}
+
+static unsigned long get_random_long(void)
+{
+ unsigned long random;
+
+ if (has_cpuflag(X86_FEATURE_RDRAND)) {
+ debug_putstr("KASLR using RDRAND...\n");
+ if (rdrand_long(&random))
+ return random;
+ }
+
+ if (has_cpuflag(X86_FEATURE_TSC)) {
+ uint32_t raw;
+
+ debug_putstr("KASLR using RDTSC...\n");
+ rdtscl(raw);
+
+ /* Only use the low bits of rdtsc. */
+ random = raw & 0xffff;
+ } else {
+ debug_putstr("KASLR using i8254...\n");
+ random = i8254();
+ }
+
+ /* Extend timer bits poorly... */
+ random |= (random << 16);
+#ifdef CONFIG_X86_64
+ random |= (random << 32);
+#endif
+ return random;
+}
unsigned char *choose_kernel_location(unsigned char *input,
unsigned long input_size,
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 9077af7..0782eb0 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -52,6 +52,8 @@ unsigned char *choose_kernel_location(unsigned char *input,
unsigned long input_size,
unsigned char *output,
unsigned long output_size);
+/* cpuflags.c */
+bool has_cpuflag(int flag);
#else
static inline
unsigned char *choose_kernel_location(unsigned char *input,
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