arch/risc-v: Add support for S-mode flat build

There is no need to use kernel build for S-mode all the time. As cpu
scratch is supported for non kernel mode build, it is possible to use
flat build for S-mode.

Add flat build support for risc-v S mode.

Signed-off-by: Inochi Amaoto <inochiama@outlook.com>

arch/risc-v/Kconfig

@@ -516,9 +516,9 @@ config RISCV_PERCPU_SCRATCH
 #
 
 config ARCH_USE_S_MODE
-	bool "Run the NuttX kernel in S-mode"
+	bool "Run NuttX in S-mode"
 	default n
-	depends on ARCH_HAVE_S_MODE && BUILD_KERNEL && ARCH_USE_MMU
+	depends on ARCH_HAVE_S_MODE
 	select RISCV_PERCPU_SCRATCH
 	---help---
 		Most of the RISC-V implementations run in M-mode (flat addressing)

arch/risc-v/src/common/CMakeLists.txt

@@ -109,7 +109,7 @@ if(CONFIG_RISCV_PERCPU_SCRATCH)
   list(APPEND SRCS riscv_percpu.c)
 endif()
 
-if(CONFIG_BUILD_KERNEL)
+if(CONFIG_ARCH_USE_S_MODE)
   add_subdirectory(supervisor)
 endif()
 

arch/risc-v/src/common/supervisor/CMakeLists.txt

@@ -18,8 +18,7 @@
 #
 # ##############################################################################
 
-if(CONFIG_BUILD_KERNEL)
-
+if(CONFIG_ARCH_USE_S_MODE)
   set(SRCS)
 
   list(APPEND SRCS riscv_syscall.S riscv_perform_syscall.c riscv_sbi.c)

arch/risc-v/src/k230/k230_head.S

@@ -59,7 +59,7 @@ __start:
 
   /* Preserve a1 by not using it here as it contains DTB */
 
-#ifndef CONFIG_BUILD_KERNEL
+#ifndef CONFIG_ARCH_USE_S_MODE
   /* Load mhartid (cpuid) */
 
   csrr a0, CSR_MHARTID

arch/risc-v/src/k230/k230_start.c

@@ -122,7 +122,7 @@ void k230_start(int mhartid, const char *dtb)
 #endif
     }
 
-#ifndef CONFIG_BUILD_KERNEL
+#ifndef CONFIG_ARCH_USE_S_MODE
     k230_hart_init();
 #endif
 

arch/risc-v/src/qemu-rv/qemu_rv_head.S

@@ -45,7 +45,7 @@ __start:
   /* Preserve a1 as it contains the pointer to DTB */
   /* Load mhartid (cpuid) */
 
-#ifndef CONFIG_BUILD_KERNEL
+#ifndef CONFIG_ARCH_USE_S_MODE
   csrr a0, CSR_MHARTID
 #endif
 

arch/risc-v/src/qemu-rv/qemu_rv_start.c

@@ -58,7 +58,7 @@
  * Extern Function Declarations
  ****************************************************************************/
 
-#ifdef CONFIG_BUILD_KERNEL
+#ifdef CONFIG_ARCH_USE_S_MODE
 extern void __start(void);
 #endif
 
@@ -80,7 +80,7 @@ static void qemu_rv_clear_bss(void)
     }
 }
 
-#ifdef CONFIG_BUILD_KERNEL
+#ifdef CONFIG_ARCH_USE_S_MODE
 static void qemu_boot_secondary(int mhartid, uintptr_t dtb)
 {
   int i;
@@ -101,7 +101,7 @@ static void qemu_boot_secondary(int mhartid, uintptr_t dtb)
  * Private Data
  ****************************************************************************/
 
-#ifdef CONFIG_BUILD_KERNEL
+#ifdef CONFIG_ARCH_USE_S_MODE
 static bool boot_secondary = false;
 #endif
 
@@ -119,7 +119,7 @@ static bool boot_secondary = false;
 
 void qemu_rv_start(int mhartid, const char *dtb)
 {
-#ifdef CONFIG_BUILD_KERNEL
+#ifdef CONFIG_ARCH_USE_S_MODE
   /* Boot other cores */
 
   if (!boot_secondary)

boards/risc-v/qemu-rv/rv-virt/scripts/ld.script

@@ -18,9 +18,17 @@
  *
  ****************************************************************************/
 
+#include <nuttx/config.h>
+
+#ifdef CONFIG_ARCH_USE_S_MODE
+#define TEXT_ADDR     0x80200000
+#else
+#define TEXT_ADDR     0x80000000
+#endif
+
 SECTIONS
 {
-  . = 0x80000000;
+  . = TEXT_ADDR;
 
   /* where the global variable out-of-bounds detection information located */
 #ifdef CONFIG_MM_KASAN_GLOBAL