Fix duplicate atomic_t typedef conflicting with types.h

local/recipes/gpu/amdgpu-source/include/linux/randomize_kstack.h

@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _LINUX_RANDOMIZE_KSTACK_H
+#define _LINUX_RANDOMIZE_KSTACK_H
+
+#ifdef CONFIG_RANDOMIZE_KSTACK_OFFSET
+#include <linux/kernel.h>
+#include <linux/jump_label.h>
+#include <linux/percpu-defs.h>
+#include <linux/prandom.h>
+
+DECLARE_STATIC_KEY_MAYBE(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT,
+			 randomize_kstack_offset);
+
+/*
+ * Do not use this anywhere else in the kernel. This is used here because
+ * it provides an arch-agnostic way to grow the stack with correct
+ * alignment. Also, since this use is being explicitly masked to a max of
+ * 10 bits, stack-clash style attacks are unlikely. For more details see
+ * "VLAs" in Documentation/process/deprecated.rst
+ *
+ * The normal __builtin_alloca() is initialized with INIT_STACK_ALL (currently
+ * only with Clang and not GCC). Initializing the unused area on each syscall
+ * entry is expensive, and generating an implicit call to memset() may also be
+ * problematic (such as in noinstr functions). Therefore, if the compiler
+ * supports it (which it should if it initializes allocas), always use the
+ * "uninitialized" variant of the builtin.
+ */
+#if __has_builtin(__builtin_alloca_uninitialized)
+#define __kstack_alloca __builtin_alloca_uninitialized
+#else
+#define __kstack_alloca __builtin_alloca
+#endif
+
+/*
+ * Use, at most, 6 bits of entropy (on 64-bit; 8 on 32-bit). This cap is
+ * to keep the "VLA" from being unbounded (see above). Additionally clear
+ * the bottom 4 bits (on 64-bit systems, 2 for 32-bit), since stack
+ * alignment will always be at least word size. This makes the compiler
+ * code gen better when it is applying the actual per-arch alignment to
+ * the final offset. The resulting randomness is reasonable without overly
+ * constraining usable stack space.
+ */
+#ifdef CONFIG_64BIT
+#define KSTACK_OFFSET_MAX(x)	((x) & 0b1111110000)
+#else
+#define KSTACK_OFFSET_MAX(x)	((x) & 0b1111111100)
+#endif
+
+DECLARE_PER_CPU(struct rnd_state, kstack_rnd_state);
+
+static __always_inline u32 get_kstack_offset(void)
+{
+	struct rnd_state *state;
+	u32 rnd;
+
+	state = &get_cpu_var(kstack_rnd_state);
+	rnd = prandom_u32_state(state);
+	put_cpu_var(kstack_rnd_state);
+
+	return rnd;
+}
+
+/**
+ * add_random_kstack_offset - Increase stack utilization by a random offset.
+ *
+ * This should be used in the syscall entry path after user registers have been
+ * stored to the stack. Preemption may be enabled. For testing the resulting
+ * entropy, please see: tools/testing/selftests/lkdtm/stack-entropy.sh
+ */
+#define add_random_kstack_offset() do {					\
+	if (static_branch_maybe(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT,	\
+				&randomize_kstack_offset)) {		\
+		u32 offset = get_kstack_offset();			\
+		u8 *ptr = __kstack_alloca(KSTACK_OFFSET_MAX(offset));	\
+		/* Keep allocation even after "ptr" loses scope. */	\
+		asm volatile("" :: "r"(ptr) : "memory");		\
+	}								\
+} while (0)
+
+#else /* CONFIG_RANDOMIZE_KSTACK_OFFSET */
+#define add_random_kstack_offset()		do { } while (0)
+#endif /* CONFIG_RANDOMIZE_KSTACK_OFFSET */
+
+#endif