added TextIO module for outputting text

Makefile

@@ -11,12 +11,15 @@ GCC_PREF=riscv32-unknown-elf-
 
 CC=$(GCC_PREF)gcc
 OBJDUMP=$(GCC_PREF)objdump
-CFLAGS=-I$(KLIBDIR) -O3 -MD -mcmodel=medany -Wall -Wextra -pedantic-errors
+CFLAGS=-I$(KLIBDIR) -MD -mcmodel=medany -Wall -Wextra -pedantic-errors
 KERNEL_CFLAGS=-nostdlib -T linker.ld
 ARCH = rv32im							# here you 
 
 ### Build configuration:
 
+# comment out if you don't have any text IO device memory mapped
+CFLAGS += -DTEXT_IO_ADDR=0xff0000 -DTEXT_IO_BUFLEN=64
+
 # uncomment these to build with only the rv32i standard
 #CFLAGS += -D__risc_no_ext=1
 #ARCH = rv32i
@@ -30,10 +33,10 @@ ARCH = rv32im							# here you
 CFLAGS += -march=$(ARCH)
 
 # dependencies that need to be built:
-_DEPS = ecall.c csr.c sched.c
+_DEPS = ecall.c csr.c sched.c io.o
 
 # dependencies as object files:
-_OBJ = ecall.o sched.o boot.o csr.o
+_OBJ = ecall.o sched.o boot.o csr.o io.o
 
 
 DEPS  = $(patsubst %,$(KLIBDIR)/%,$(_DEPS))

kernel.c

@@ -1,6 +1,7 @@
 #include "kernel.h"
 #include "ecall.h"
 #include "sched.h"
+#include "io.h"
 
 void create_processes_from_bin_table();
 
@@ -8,10 +9,14 @@ extern ProcessControlBlock processes[PROCESS_COUNT];
 
 loaded_binary binary_table[NUM_BINARIES] __attribute__ ((section (".data")));
 
+extern void memset(unsigned int, void*, void*);
+
 extern void init()
 {
     init_ecall_table();
 
+    dbgln("Kernel started!", 15);
+
     create_processes_from_bin_table();
 
     scheduler_run_next();   

kernel.h

@@ -20,7 +20,7 @@
 typedef struct loaded_binary {
     int binid;
     int entrypoint;
-    int bounds[2];
+    void* bounds[2];
 } loaded_binary;
 
 // create a global table holding all loaded binaries.

kinclude/boot.S

@@ -106,18 +106,21 @@ trap_vector:
             jal     trap_handle
 
 
+// make memset global
+.global     memset
+.type       memset, @function
 #ifdef __risc_no_ext
 // "dumb" memset, if RV32M is not present on the target
 // since memset is currently only used at startup, the performance implications
 // should be minimal.
 memset:
-    bge     a1, a2, 2f
+            bge     a1, a2, 2f
 1:
-    sw      a0, 0(a1)
+            sw      a0, 0(a1)
-    addi    a1, a1, 4
+            addi    a1, a1, 4
-    blt     a1, a2, 1b
+            blt     a1, a2, 1b
 2:
-    ret
+            ret
 
 #else
 

kinclude/ecall.c

@@ -1,6 +1,7 @@
 #include "ecall.h"
 #include "sched.h"
 #include "csr.h"
+#include "io.h"
 
 typedef int (*ecall_handler)(int*,ProcessControlBlock*);
 
@@ -44,6 +45,13 @@ int ecall_handle_exit(int* args, ProcessControlBlock* pcb)
     pcb->status = PROC_DEAD;
     pcb->exit_code = *args;
 
+    char msg[34] = "process    exited with code   ";
+
+    itoa(pcb->pid, &msg[8], 10);
+    itoa(*args % 10, &msg[28], 10);
+
+    dbgln(msg, 34);
+
     return 0;
 }
 
@@ -54,7 +62,7 @@ void trap_handle_ecall() {
     };
     ProcessControlBlock* pcb = get_current_process();
     int *regs = pcb->regs;
-    int code = regs[16];
+    int code = regs[16];    // code is inside a7
 
     // check if the code is too large/small or if the handler is zero
     if (code < 0 || code > ECALL_TABLE_LEN || ecall_table[code] == 0) {
@@ -129,5 +137,6 @@ void init_ecall_table()
 
 void handle_exception(int ecode, int mtval) 
 {
-
+    dbgln("Trap encountered!", 17);
+    __asm__("ebreak");
 }

kinclude/ecall.h

@@ -17,7 +17,7 @@ enum ecall_codes {
 
 #define ECALL_TABLE_LEN 16
 
-enum ecall_errors {
+enum error_code {
     ENOCODE = -1,   // invalid syscall code
     EINVAL  = -2,   // invalid argument value
     ENOMEM  = -3,   // not enough memory

kinclude/io.c

@@ -0,0 +1,63 @@
+#include "io.h"
+
+#ifdef TEXT_IO_ADDR
+
+#ifndef TEXT_IO_BUFLEN
+#error "When defining TEXT_IO_ADDR, please also provide TEXT_IO_BUFLEN, otherwise textIO won't work!"
+#endif
+
+void dbgln(char* text, int len)
+{
+    while (len > TEXT_IO_BUFLEN) {
+        dbgln(text, TEXT_IO_BUFLEN);
+        text += TEXT_IO_BUFLEN;
+        len -= TEXT_IO_BUFLEN;
+    }
+
+    char* ioaddr = (char*) TEXT_IO_ADDR + 4;
+
+    for (int i = 0; i < len; i++) {
+        if (*text == 0)
+            break;
+        *ioaddr++ = *text++;
+    }
+
+    if (len < TEXT_IO_BUFLEN)
+        *ioaddr = '\n';
+
+    // write a 1 to the start of the textIO to signal a buffer flush
+    *((char*) TEXT_IO_ADDR) = 1;
+}
+
+#else
+
+/* if no textIO module loaded, dbgln is a noop :( */
+void dbgln(char*, int){}
+
+#endif
+
+
+/* alphabet for itoa */
+char alpha[16] = "0123456789abcdef";
+char* itoa (int value, char* str, int base)
+{
+    if (base > 16 || base < 2) {
+        *str++ = '?';
+        return str;
+    }
+
+    if (value < 0) {
+        *str++ = '-';
+        value *= -1;
+    }
+
+    int num;
+    do {
+        num = value % base;
+        value = value / base;
+        *str++ = alpha[num];
+    }
+    while (value > 0);
+
+    return str;
+}

kinclude/io.h

@@ -0,0 +1,10 @@
+#ifndef H_IO
+#define H_IO
+
+/* print a line to the debug textIO module */
+void dbgln(char* text, int len);
+
+/* alphabet for itoa */
+char* itoa (int value, char* str, int base);
+
+#endif