riscv: add support for thread local storage

Adds the necessary bits to initialize TLS in the stack
area and sets up CPU registers during context switch.

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

arch/Kconfig

@@ -65,6 +65,7 @@ config RISCV
 	bool
 	select ARCH_IS_SET
 	select HAS_DTS
+	select ARCH_HAS_THREAD_LOCAL_STORAGE
 	imply XIP
 	help
 	  RISCV architecture

arch/riscv/core/CMakeLists.txt

@@ -14,3 +14,4 @@ zephyr_library_sources(
 )
 
 zephyr_library_sources_ifdef(CONFIG_IRQ_OFFLOAD irq_offload.c)
+zephyr_library_sources_ifdef(CONFIG_THREAD_LOCAL_STORAGE tls.c)

arch/riscv/core/thread.c

@@ -30,6 +30,11 @@ void arch_new_thread(struct k_thread *thread, k_thread_stack_t *stack,
 	stack_init->a1 = (ulong_t)p1;
 	stack_init->a2 = (ulong_t)p2;
 	stack_init->a3 = (ulong_t)p3;
+
+#ifdef CONFIG_THREAD_LOCAL_STORAGE
+	stack_init->tp = (ulong_t)thread->tls;
+#endif
+
 	/*
 	 * Following the RISC-V architecture,
 	 * the MSTATUS register (used to globally enable/disable interrupt),

arch/riscv/core/tls.c

@@ -0,0 +1,35 @@
+/*
+ * 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 <app_memory/app_memdomain.h>
+#include <sys/util.h>
+
+size_t arch_tls_stack_setup(struct k_thread *new_thread, char *stack_ptr)
+{
+	/*
+	 * TLS area for RISC-V is simple without any extra
+	 * data.
+	 */
+
+	/*
+	 * Since we are populating things backwards,
+	 * setup the TLS data/bss area first.
+	 */
+	stack_ptr -= z_tls_data_size();
+	z_tls_copy(stack_ptr);
+
+	/*
+	 * 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();
+}

include/arch/riscv/common/linker.ld

@@ -111,6 +111,7 @@ SECTIONS
     _image_text_end = .;
 
 #include <linker/common-rom.ld>
+#include <linker/thread-local-storage.ld>
 
     SECTION_PROLOGUE(_RODATA_SECTION_NAME,,)
 	{

soc/riscv/openisa_rv32m1/linker.ld

@@ -122,6 +122,7 @@ SECTIONS
     _image_rodata_start = .;
 
 #include <linker/common-rom.ld>
+#include <linker/thread-local-storage.ld>
 
     SECTION_PROLOGUE(_RODATA_SECTION_NAME,,)
 	{