Fixed SP and add new lds and soubroutine test

firmware.c

@@ -1,7 +1,36 @@
-volatile int * const outreg = (int*)0x02000000;
+/*
+ *  PicoRV -- A Small and Extensible RISC-V Processor
+ *
+ *  Copyright (C) 2019  Claire Wolf <claire@symbioticeda.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+void putc(int c)
+{
+	volatile char *p = (void*)0x02000000;
+	*p = c;
+}
+
+void puts(char *s)
+{
+	while (*s) putc(*(s++));
+}
 
 int main()
 {
-	*outreg = 42;
+	puts("Hello World!\n");
+	putc(0);
 	return 0;
 }

firmware.s

@@ -52,7 +52,37 @@ addi x28, zero, 0
 addi x29, zero, 0
 addi x30, zero, 0
 addi x31, zero, 0
-li sp, 0x00100000
+
+# place SP at the end of RAM
+li sp, 0x00010000
+
+# copy data section
+la a0, _sidata
+la a1, _sdata
+la a2, _edata
+bge a1, a2, end_init_data
+loop_init_data:
+lw a3, 0(a0)
+sw a3, 0(a1)
+addi a0, a0, 4
+addi a1, a1, 4
+blt a1, a2, loop_init_data
+end_init_data:
+
+# zero-init bss section
+la a0, _sbss
+la a1, _ebss
+bge a0, a1, end_init_bss
+loop_init_bss:
+sw zero, 0(a0)
+addi a0, a0, 4
+blt a0, a1, loop_init_bss
+end_init_bss:
+
+# call main
 call main
 end:
 j end
+
+
+

sections.lds

@@ -1,14 +1,64 @@
-MEMORY {
+MEMORY
+{
 	/* the memory in the testbench is 64k in size;
 	 * set LENGTH=48k and leave at least 16k for stack */
-	mem : ORIGIN = 0x00000000, LENGTH = 0x0000c000
+    RAM (xrw)       : ORIGIN = 0x00000000, LENGTH = 0x00c000
 }
+
 SECTIONS {
-	.memory : {
-		. = 0x000000;
-		start*(.text);
-		*(.text);
-		*(*);
-		end = .;
-	} > mem
+    /* 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.) */
+        . = ALIGN(4);
+        _etext = .;        /* define a global symbol at end of code */
+        _sidata = _etext;  /* This is used by the startup in order to initialize the .data secion */
+    } >RAM
+
+
+    /* 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
 }

stupidrv_tb.sv

@@ -2,7 +2,7 @@ module stupidrv_tb (
 
 );
 
-localparam MEM_ADDR_WIDTH = 14;
+localparam MEM_ADDR_WIDTH = 16;
 localparam TIMEOUT = (1<<10);
 
 reg clock;