1 files changed, 38 insertions, 0 deletions

diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h
new file mode 100644
index 000000000000..36a700acaf2b
--- /dev/null
+++ b/arch/x86/include/asm/stackprotector.h
@@ -0,0 +1,38 @@
+#ifndef _ASM_STACKPROTECTOR_H
+#define _ASM_STACKPROTECTOR_H 1
+
+#include <asm/tsc.h>
+#include <asm/processor.h>
+
+/*
+ * Initialize the stackprotector canary value.
+ *
+ * NOTE: this must only be called from functions that never return,
+ * and it must always be inlined.
+ */
+static __always_inline void boot_init_stack_canary(void)
+{
+        u64 canary;
+        u64 tsc;
+
+        /*
+         * Build time only check to make sure the stack_canary is at
+         * offset 40 in the pda; this is a gcc ABI requirement
+         */
+        BUILD_BUG_ON(offsetof(union irq_stack_union, stack_canary) != 40);
+
+        /*
+         * We both use the random pool and the current TSC as a source
+         * of randomness. The TSC only matters for very early init,
+         * there it already has some randomness on most systems. Later
+         * on during the bootup the random pool has true entropy too.
+         */
+        get_random_bytes(&canary, sizeof(canary));
+        tsc = __native_read_tsc();
+        canary += tsc + (tsc << 32UL);
+
+        current->stack_canary = canary;
+        percpu_write(irq_stack_union.stack_canary, canary);
+}
+
+#endif