arm: Placing the functions which holds __ramfunc into '.ramfunc'

Using __ramfunc to places a function in RAM instead of Flash.
Code that for example reprograms flash at runtime can't execute
from flash, in that case must placing code into RAM.

This commit create a new section named '.ramfunc' in link scripts,
all functions has __ramfunc keyword saved in thats sections and
will load from flash to sram after the system booted.

Fixes: #10253

Signed-off-by: qianfan Zhao <qianfanguijin@163.com>

arch/arm/core/cortex_m/mpu/arm_core_mpu.c

@@ -77,8 +77,15 @@ void _arch_configure_static_mpu_regions(void)
 		.start = (u32_t)&_nocache_ram_start,
 		.size = (u32_t)&_nocache_ram_size,
 		.attr = K_MEM_PARTITION_P_RW_U_NA_NOCACHE,
-		}
+		},
 #endif /* CONFIG_NOCACHE_MEMORY */
+#if defined(CONFIG_RAM_FUNCTION)
+		{
+		.start = (u32_t)&_ramfunc_ram_start,
+		.size = (u32_t)&_ramfunc_ram_start - (u32_t)&_ramfunc_ram_end,
+		.attr = K_MEM_PARTITION_P_RX_U_RX,
+		}
+#endif /* CONFIG_RAM_FUNCTION */
 	};
 
 	/* Configure the static MPU regions within firmware SRAM boundaries.

include/arch/arm/cortex_m/scripts/linker.ld

@@ -368,6 +368,20 @@ SECTIONS
 	_nocache_ram_size = _nocache_ram_end - _nocache_ram_start;
 #endif /* CONFIG_NOCACHE_MEMORY */
 
+#if defined(CONFIG_RAM_FUNCTION)
+	SECTION_DATA_PROLOGUE(.ramfunc,,)
+	{
+		MPU_ALIGN(_ramfunc_ram_size);
+		_ramfunc_ram_start = .;
+		*(.ramfunc)
+		*(".ramfunc.*")
+		MPU_ALIGN(_ramfunc_ram_size);
+		_ramfunc_ram_end = .;
+	} GROUP_DATA_LINK_IN(RAMABLE_REGION, ROMABLE_REGION)
+	_ramfunc_ram_size = _ramfunc_ram_end - _ramfunc_ram_start;
+	_ramfunc_rom_start = LOADADDR(.ramfunc);
+#endif /* CONFIG_RAM_FUNCTION */
+
 #if defined(CONFIG_APP_SHARED_MEM)
 #define APP_SHARED_ALIGN . = ALIGN(_region_min_align);
 #define SMEM_PARTITION_ALIGN MPU_ALIGN

include/linker/linker-defs.h

@@ -239,6 +239,16 @@ extern char _nocache_ram_end[];
 extern char _nocache_ram_size[];
 #endif /* CONFIG_NOCACHE_MEMORY */
 
+/* Memory owned by the kernel. Start and end will be aligned for memory
+ * management/protection hardware for the target architecture.
+ *
+ * All the functions with '__ramfunc' keyword will be placed into this
+ * sections.
+ */
+extern char _ramfunc_ram_start[];
+extern char _ramfunc_ram_end[];
+extern char _ramfunc_rom_start[];
+
 #endif /* ! _ASMLANGUAGE */
 
 #endif /* ZEPHYR_INCLUDE_LINKER_LINKER_DEFS_H_ */

include/toolchain/gcc.h

@@ -115,6 +115,16 @@ do {                                                                    \
 
 #define __in_section_unique(seg) ___in_section(seg, __FILE__, __COUNTER__)
 
+#ifdef CONFIG_RAM_FUNCTION
+/* Using this places a function into RAM instead of FLASH.
+ * Make sure '__ramfunc' are defined only when CONFIG_RAM_FUNCTION,
+ * so the compiler can report error if used '__ramfunc' but hadn't
+ * enable CONFIG_RAM_FUNCTION in Kconfig.
+ */
+#define __ramfunc	__attribute__((noinline))			\
+			__attribute__((long_call, section(".ramfunc")))
+#endif
+
 #ifndef __packed
 #define __packed        __attribute__((__packed__))
 #endif

kernel/Kconfig

@@ -207,6 +207,13 @@ config ERRNO
 	  symbol. The C library must access the per-thread errno via the
 	  _get_errno() symbol.
 
+config RAM_FUNCTION
+	bool "Enable __ramfunc support"
+	help
+	  Using '__ramfunc' places a function into RAM instead of Flash.
+	  Code that for example reprograms flash at runtime can't execute
+	  from flash, in that case must placing code into RAM.
+
 choice SCHED_ALGORITHM
 	prompt "Scheduler priority queue algorithm"
 	default SCHED_DUMB

kernel/init.c

@@ -173,6 +173,10 @@ void _data_copy(void)
 {
 	(void)memcpy(&__data_ram_start, &__data_rom_start,
 		 ((u32_t) &__data_ram_end - (u32_t) &__data_ram_start));
+#ifdef CONFIG_RAM_FUNCTION
+	(void)memcpy(&_ramfunc_ram_start, &_ramfunc_rom_start,
+		 ((u32_t) &_ramfunc_ram_end - (u32_t) &_ramfunc_ram_start));
+#endif
 #ifdef DT_CCM_BASE_ADDRESS
 	(void)memcpy(&__ccm_data_start, &__ccm_data_rom_start,
 		 ((u32_t) &__ccm_data_end - (u32_t) &__ccm_data_start));