1 files changed, 56 insertions, 0 deletions
diff --git a/MdePkg/Library/DynamicStackCookieEntryPointLib/AArch64/DynamicCookieGcc.S b/MdePkg/Library/DynamicStackCookieEntryPointLib/AArch64/DynamicCookieGcc.S
new file mode 100644
index 0000000000..d33c02a7c4
--- /dev/null
+++ b/MdePkg/Library/DynamicStackCookieEntryPointLib/AArch64/DynamicCookieGcc.S
@@ -0,0 +1,56 @@
+#------------------------------------------------------------------------------
+#
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: BSD-2-Clause-Patent
+#
+# Module Name:
+#
+#   DynamicCookie.S
+#
+# Abstract:
+#
+#   Generates random number through the RNDR instruction on a 64-bit AARCH64 platform
+#   to store a random value in the GCC __stack_check_guard stack cookie.
+#   The first byte is 0'd to prevent string copy functions from clobbering
+#   the stack cookie.
+#
+# Notes:
+#
+# If RNDR fails, the build time static stack cookie value will be used instead.
+#
+#------------------------------------------------------------------------------
+
+#include <AArch64/AArch64.h>
+
+.text
+.p2align 2
+
+GCC_ASM_IMPORT(__stack_chk_guard)
+GCC_ASM_IMPORT(_CModuleEntryPoint)
+GCC_ASM_EXPORT(_ModuleEntryPoint)
+
+#------------------------------------------------------------------------------
+# VOID
+# EFIAPI
+# _ModuleEntryPoint (
+#   Parameters are passed through.
+# )
+#------------------------------------------------------------------------------
+ASM_PFX(_ModuleEntryPoint):
+  AARCH64_BTI(c)
+
+  mrs x9, ID_AA64ISAR0_EL1          // Read the AArch64 Instruction Set Attribute Register 0
+  ubfx x9, x9, #60, #4              // Extract the RNDR bit field (bits 60-63)
+  cbz x9, c_entry                   // If RNDR is not supported, jump to c_entry
+
+  mrs x9, RNDR                      // Generate a random number
+  b.eq c_entry                      // RNDR sets NZCV to 0b0100 on failure
+                                    // So if the zero flag is set, use the static stack guard
+
+  and x9, x9, #0xFFFFFFFFFFFFFF00   // Zero the first byte of the random value
+
+  adrp x8, ASM_PFX(__stack_chk_guard)             // Load the page address of __stack_chk_guard
+  str x9, [x8, :lo12:ASM_PFX(__stack_chk_guard)]  // Store the random value in __stack_chk_guard
+
+c_entry:
+  b ASM_PFX(_CModuleEntryPoint)     // Jump to the C module entry point