Merge pull request #61 from mmicko/linker-script

Created lds file (section mapping) and init for data and bss sections

picosoc/Makefile

@@ -39,10 +39,10 @@ firmware.elf: sections.lds start.s firmware.c
 	riscv32-unknown-elf-gcc -march=rv32imc -Wl,-Bstatic,-T,sections.lds,--strip-debug -ffreestanding -nostdlib -o firmware.elf start.s firmware.c
 
 firmware.hex: firmware.elf
-	riscv32-unknown-elf-objcopy -O verilog firmware.elf /dev/stdout | sed -e '1 s/@00000000/@00100000/; 2,65537 d;' > firmware.hex
+	riscv32-unknown-elf-objcopy -O verilog firmware.elf > firmware.hex
 
 firmware.bin: firmware.elf
-	riscv32-unknown-elf-objcopy -O binary firmware.elf /dev/stdout | tail -c +1048577 > firmware.bin
+	riscv32-unknown-elf-objcopy -O binary firmware.elf > firmware.bin
 
 # ---- Testbench for SPI Flash Model ----
 

picosoc/firmware.c

@@ -340,8 +340,19 @@ void cmd_benchmark_all()
 
 // --------------------------------------------------------
 
+extern uint32_t _sidata, _sdata, _edata, _sbss, _ebss;
+
 void main()
 {	
+	// copy data section
+	for (uint32_t *src = &_sidata, *dest = &_sdata; dest < &_edata;) {
+        *dest++ = *src++;
+	}
+    // zero out .bss section
+    for (uint32_t *dest = &_sbss; dest < &_ebss;) {
+        *dest++ = 0;
+    }
+
 	reg_uart_clkdiv = 104;
 	set_flash_qspi_flag();
 

picosoc/sections.lds

@@ -1,11 +1,62 @@
-SECTIONS {
-	.memory : {
-		sram = 0;
-		*(.data);
-		*(.bss);
-		. = 0x100000;
-		start*(.text);
-		*(.text);
-		*(*);
-	}
+MEMORY
+{
+    FLASH (rx)      : ORIGIN = 0x00100000, LENGTH = 0x400000 /* entire flash, 4 MiB */
+    RAM (xrw)       : ORIGIN = 0x00000000, LENGTH = 0x000400 /* 1 KB */
+}
+
+SECTIONS {
+    /* The program code and other data goes into FLASH */
+    .text :
+    {
+        . = ALIGN(4);
+        *(.text)           /* .text sections (code) */
+        *(.text*)          /* .text* sections (code) */
+        *(.rodata)         /* .rodata sections (constants, strings, etc.) */
+        *(.rodata*)        /* .rodata* sections (constants, strings, etc.) */
+        *(.srodata)        /* .rodata sections (constants, strings, etc.) */
+        *(.srodata*)       /* .rodata* sections (constants, strings, etc.) */
+        _etext = .;        /* define a global symbol at end of code */
+        _sidata = _etext;  /* This is used by the startup in order to initialize the .data secion */
+    } >FLASH
+
+
+    /* This is the initialized data section
+    The program executes knowing that the data is in the RAM
+    but the loader puts the initial values in the FLASH (inidata).
+    It is one task of the startup to copy the initial values from FLASH to RAM. */
+    .data : AT ( _sidata )
+    {
+        . = ALIGN(4);
+        _sdata = .;        /* create a global symbol at data start; used by startup code in order to initialise the .data section in RAM */
+        _ram_start = .;    /* create a global symbol at ram start for garbage collector */
+        . = ALIGN(4);
+        *(.data)           /* .data sections */
+        *(.data*)          /* .data* sections */
+        *(.sdata)           /* .sdata sections */
+        *(.sdata*)          /* .sdata* sections */
+        . = ALIGN(4);
+        _edata = .;        /* define a global symbol at data end; used by startup code in order to initialise the .data section in RAM */
+    } >RAM
+
+    /* Uninitialized data section */
+    .bss :
+    {
+        . = ALIGN(4);
+        _sbss = .;         /* define a global symbol at bss start; used by startup code */
+        *(.bss)
+        *(.bss*)
+        *(.sbss)
+        *(.sbss*)
+        *(COMMON)
+
+        . = ALIGN(4);
+        _ebss = .;         /* define a global symbol at bss end; used by startup code */
+    } >RAM
+
+    /* this is to define the start of the heap, and make sure we have a minimum size */
+    .heap :
+    {
+        . = ALIGN(4);
+        _heap_start = .;    /* define a global symbol at heap start */
+    } >RAM
 }