Enable previously added CONFIG_STACK_PROTECTOR feature for ARM
platform. We initialize stack protector very early, in head.S using
boot_stack_chk_guard_setup. This ensures that all C code from the very
beginning can use stack protector.

Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>

---
In v4:
 - setup.c does not call boot_stack_chk_guard_setup() anymore, because
   the original implementation was removed and
   boot_stack_chk_guard_setup_early was renamed to boot_stack_chk_guard_setup
In v3:
 - Call boot_stack_chk_guard_setup_early from head.S to ensure
   that stack is protected from early boot stages
 - Call boot_stack_chk_guard_setup() later, when time subsystem is
   sufficiently initialized to provide values for the random number
   generator.
In v2:
 - Reordered Kconfig entry
---
 xen/arch/arm/Kconfig      | 1 +
 xen/arch/arm/arm64/head.S | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index a26d3e1182..8f1a3c7d74 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -16,6 +16,7 @@ config ARM
 	select GENERIC_UART_INIT
 	select HAS_ALTERNATIVE if HAS_VMAP
 	select HAS_DEVICE_TREE
+	select HAS_STACK_PROTECTOR
 	select HAS_UBSAN
 
 config ARCH_DEFCONFIG
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 72c7b24498..5cbd62af86 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -250,6 +250,9 @@ real_start_efi:
 #endif
         PRINT("- Boot CPU booting -\r\n")
 
+#ifdef CONFIG_STACK_PROTECTOR
+        bl    boot_stack_chk_guard_setup
+#endif
         bl    check_cpu_mode
         bl    cpu_init
 
-- 
2.47.1