From caf9a6f4f7a40f725dc57a3f675434aaa265e1b8 Mon Sep 17 00:00:00 2001
From: Brendan Haines <brendan.haines@gmail.com>
Date: Tue, 10 Nov 2020 00:19:42 -0700
Subject: [PATCH] separate .text and .data for instruction and data memory

---
 hdl/tb/core_tb.v | 24 ++++++++++++++++++------
 test/Makefile    | 12 +++++++++---
 test/test.S      | 33 +++++++++++++++++++++++++++++++++
 test/test.ld     | 15 ++++++++++++++-
 4 files changed, 74 insertions(+), 10 deletions(-)

diff --git a/hdl/tb/core_tb.v b/hdl/tb/core_tb.v
index d60b06a..d2417d8 100644
--- a/hdl/tb/core_tb.v
+++ b/hdl/tb/core_tb.v
@@ -4,27 +4,31 @@ module core_tb();
 
 initial $timeformat(-9, 2, " ns", 20);
 
-localparam  MEM_INST_LENGTH = 256;
-localparam  MEM_DATA_LENGTH = 256;
+wire dummy_out;
 
-localparam  INST_NOP = 32'h00000013;  // nop
+localparam  MEM_INST_LENGTH = 256;  // words
+localparam  MEM_DATA_LENGTH = 256;  // words
+
+localparam  INST_NOP        = 32'h00000013;  // nop
+localparam  DATA_DEFAULT    = 32'hdeadbeef;
 
 reg clk, reset;
+
+// Instruction memory
 reg [31:0] mem_inst [0:MEM_INST_LENGTH-1];
 wire [31:0] mem_inst_addr;
 wire [31:0] mem_inst_idx = mem_inst_addr >> 2;
 wire [31:0] mem_inst_data = mem_inst_idx < MEM_INST_LENGTH ? mem_inst[mem_inst_idx] : INST_NOP;
 
-wire dummy_out;
-
 initial begin: mem_inst_init
     integer i;
     for (i=0; i<MEM_INST_LENGTH; i=i+1) begin
         mem_inst[i] = INST_NOP;
     end
-    $readmemh("../test/test.hex", mem_inst);
+    $readmemh("../test/text.hex", mem_inst);
 end
 
+// Data memory
 reg [31:0] mem_data [0:MEM_DATA_LENGTH-1];
 wire [31:0] mem_data_waddr;
 wire [31:0] mem_data_wdata;
@@ -34,6 +38,14 @@ wire [31:0] mem_data_raddr;
 reg [31:0] mem_data_rdata;
 wire [3:0] mem_data_rmask;
 
+initial begin: mem_data_init
+    integer i;
+    for (i=0; i<MEM_DATA_LENGTH; i=i+1) begin
+        mem_data[i] = DATA_DEFAULT;
+    end
+    $readmemh("../test/data.hex", mem_data);
+end
+
 initial begin
     #0
     clk = 0;
diff --git a/test/Makefile b/test/Makefile
index 02f2775..fb01f9c 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -1,4 +1,4 @@
-all: test.hex
+all: text.hex data.hex
 
 CC = riscv64-linux-gnu-gcc
 # CFLAGS = -march=rv32i -mabi=ilp32
@@ -19,5 +19,11 @@ LDFLAGS = -T test.ld
 %.elf: %.o
 	$(LD) $(LDFLAGS) $^ -o $@
 
-test.hex: test.elf
-	riscv64-linux-gnu-objdump -s $^ | sed -n '/0000/,$$p' | cut -f3-6 -d ' ' | sed -e 's/ /\n/g' | sed 's/^\(..\)\(..\)\(..\)\(..\)/\4\3\2\1/' > $@
+text.hex: test.elf
+	riscv64-linux-gnu-objdump -s $^ | sed -n '/.text/,$$p' | tail -n+2 | sed -n '/.data/,$$!p' | cut -f3-6 -d ' ' | sed -e 's/ /\n/g' | sed 's/^\(..\)\(..\)\(..\)\(..\)/\4\3\2\1/' > $@
+
+data.hex: test.elf
+	riscv64-linux-gnu-objdump -s $^ | sed -n '/.data/,$$p' | tail -n+2 | sed -n '/.bss/,$$!p' | cut -f3-6 -d ' ' | sed -e 's/ /\n/g' | sed 's/^\(..\)\(..\)\(..\)\(..\)/\4\3\2\1/' > $@
+
+clean:
+	rm test.elf text.hex data.hex
\ No newline at end of file
diff --git a/test/test.S b/test/test.S
index 18716ad..67372ba 100644
--- a/test/test.S
+++ b/test/test.S
@@ -1,4 +1,7 @@
+# NOTE: .text .data .bss must occur in that order
+
 .global _start
+
 .text
 _start:
 
@@ -206,8 +209,31 @@ test9:
     j       fail
 
 test10:
+    # now for some memory stuff
+#     # sw
+#     la      x9, someint         # x9  = start of .bss
+#     li      x10, 0x12345678     # x10 = 0x12345678
+#     nop
+#     nop
+#     nop
+#     nop
+#     nop
+#     sw      x10, 0(x9)          # someint = 0x12345678
+#     nop
+#     nop
+#     nop
+#     nop
+#     nop
+#     lw      x11, 0(x9)          # x11 = 0x12345678
+#     nop
+#     nop
+#     nop
+#     nop
+#     nop
 
 
+done:
+
     # set registers to known values before loop
     addi     x2, x0, 1         # x1 = 1
     addi     x3, x0, 1         # x1 = 1
@@ -257,4 +283,11 @@ fail:
     nop
     nop
 
+
 .data
+someint:
+    .word 0xfedcba98
+
+.bss
+anotherint:
+    .word
\ No newline at end of file
diff --git a/test/test.ld b/test/test.ld
index 4ede032..13d874c 100644
--- a/test/test.ld
+++ b/test/test.ld
@@ -2,16 +2,29 @@ ENTRY(_start)
 
 MEMORY
 {
-    ROM (rx) : ORIGIN = 0x00000000, LENGTH = 1024
+    ROM (rx)    : ORIGIN = 0x00000000, LENGTH = 1024
+    RAM (rwx)   : ORIGIN = 0x10000000, LENGTH = 512
+    /* FLASH (rx) : ORIGIN = 0x00200000, LENGTH = 512 */
 }
 
 SECTIONS
 {
     .text :
     {
+        . = ALIGN(4);
         _text = .;
         *(.text*)
         *(.rodata*)
         _etext = .;
+        . = ALIGN(4);
     } > ROM
+
+    .data :
+    {
+        . = ALIGN(4);
+        _data = .;
+        *(.data*)
+        _edata = .;
+        . = ALIGN(4);
+    } > RAM /*AT> FLASH*/
 }
\ No newline at end of file