arc: enable thread local storage

This adds the necessary bits to support thread local storage
in ARC.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

arch/Kconfig

@@ -21,6 +21,7 @@ config ARC
 	select ARCH_IS_SET
 	select HAS_DTS
 	imply XIP
+	select ARCH_HAS_THREAD_LOCAL_STORAGE
 	help
 	  ARC architecture
 

arch/arc/CMakeLists.txt

@@ -12,4 +12,8 @@ zephyr_cc_option(-fno-delete-null-pointer-checks)
 
 zephyr_cc_option_ifdef(CONFIG_ARC_USE_UNALIGNED_MEM_ACCESS -munaligned-access)
 
+# Instruct compiler to use register R26 as thread pointer
+# for thread local storage.
+zephyr_cc_option_ifdef(CONFIG_THREAD_LOCAL_STORAGE -mtp-regno=26)
+
 add_subdirectory(core)

arch/arc/core/CMakeLists.txt

@@ -32,6 +32,8 @@ zephyr_library_sources_ifdef(CONFIG_USERSPACE userspace.S)
 zephyr_library_sources_ifdef(CONFIG_ARC_CONNECT arc_connect.c)
 zephyr_library_sources_ifdef(CONFIG_ARC_CONNECT arc_smp.c)
 
+zephyr_library_sources_ifdef(CONFIG_THREAD_LOCAL_STORAGE tls.c)
+
 add_subdirectory_ifdef(CONFIG_ARC_CORE_MPU mpu)
 add_subdirectory_ifdef(CONFIG_ARC_SECURE_FIRMWARE secureshield)
 

arch/arc/core/thread.c

@@ -108,6 +108,25 @@ static struct init_stack_frame *get_iframe(struct k_thread *thread,
 	return Z_STACK_PTR_TO_FRAME(struct init_stack_frame, stack_ptr);
 }
 
+/*
+ * Pre-populate values in the registers inside _callee_saved_stack struct
+ * so these registers have pre-defined values when new thread begins
+ * execution. For example, setting up the thread pointer for thread local
+ * storage here so the thread starts with thread pointer already set up.
+ */
+static inline void arch_setup_callee_saved_regs(struct k_thread *thread,
+						uintptr_t stack_ptr)
+{
+	_callee_saved_stack_t *regs = UINT_TO_POINTER(stack_ptr);
+
+	ARG_UNUSED(regs);
+
+#ifdef CONFIG_THREAD_LOCAL_STORAGE
+	/* R26 is used for thread pointer */
+	regs->r26 = thread->tls;
+#endif
+}
+
 /*
  * The initial context is a basic stack frame that contains arguments for
  * z_thread_entry() return address, that points at z_thread_entry()
@@ -164,6 +183,9 @@ void arch_new_thread(struct k_thread *thread, k_thread_stack_t *stack,
 	thread->arch.relinquish_cause = _CAUSE_COOP;
 	thread->callee_saved.sp =
 		(uint32_t)iframe - ___callee_saved_stack_t_SIZEOF;
+
+	arch_setup_callee_saved_regs(thread, thread->callee_saved.sp);
+
 	/* initial values in all other regs/k_thread entries are irrelevant */
 }
 

arch/arc/core/tls.c

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2020 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <kernel.h>
+#include <kernel_structs.h>
+#include <kernel_internal.h>
+#include <kernel_tls.h>
+#include <sys/util.h>
+
+size_t arch_tls_stack_setup(struct k_thread *new_thread, char *stack_ptr)
+{
+	/*
+	 * TLS area for ARC has some data fields following by
+	 * thread data and bss. These fields are supposed to be
+	 * used by toolchain and OS TLS code to aid in locating
+	 * the TLS data/bss. Zephyr currently has no use for
+	 * this so we can simply skip these. However, since GCC
+	 * is generating code assuming these fields are there,
+	 * we simply skip them when setting the TLS pointer.
+	 */
+
+	/*
+	 * Since we are populating things backwards,
+	 * setup the TLS data/bss area first.
+	 */
+	stack_ptr -= z_tls_data_size();
+	z_tls_copy(stack_ptr);
+
+	/* Skip two pointers due to toolchain */
+	stack_ptr -= sizeof(uintptr_t) * 2;
+
+	/*
+	 * Set thread TLS pointer which is used in
+	 * context switch to point to TLS area.
+	 */
+	new_thread->tls = POINTER_TO_UINT(stack_ptr);
+
+	return (z_tls_data_size() + (sizeof(uintptr_t) * 2));
+}

include/arch/arc/v2/linker.ld

@@ -98,6 +98,7 @@ SECTIONS {
 	_image_rodata_start = .;
 
 #include <linker/common-rom.ld>
+#include <linker/thread-local-storage.ld>
 
 	SECTION_PROLOGUE(_RODATA_SECTION_NAME,,) {
 		KEEP(*(.openocd_dbg))
@@ -220,5 +221,11 @@ SECTIONS {
 		KEEP(*(.gnu.attributes))
 	}
 
-	/DISCARD/ : { *(.note.GNU-stack) }
+	/DISCARD/ : {
+		*(.note.GNU-stack)
+		*(.got.plt)
+		*(.igot.plt)
+		*(.got)
+		*(.igot)
+	}
 }