Hello Wally application now running, can print in spike and wsim via UART. Verilator simulation is broken

examples/C/common/syscalls.c

@@ -15,6 +15,44 @@
 extern volatile uint64_t tohost;
 extern volatile uint64_t fromhost;
 
+/////////////////////////////
+// Start of code added for Wally
+//   Use UART rather than syscall host interface for printing
+//////////////////////////////
+
+#include <stdint.h>
+
+void uartInit(void) {
+  volatile uint8_t *UART_LCR = (uint8_t*)0x10000003;
+	*UART_LCR = 0b0000011; // 8-bit characters, 1 stop bit, no parity
+}
+
+void uartSend(char c) {
+  volatile uint8_t *UART_THR = (uint8_t*)0x10000000;
+  volatile uint8_t *UART_LSR = (uint8_t*)0x10000005;
+
+	while (!(*UART_LSR & (1<<5))); // wait for THRE (trans hold reg empty)
+	*UART_THR = c;
+}
+
+char uartReceive(void) {
+  volatile uint8_t *UART_RBR = (uint8_t*)0x10000000;
+  volatile uint8_t *UART_LSR = (uint8_t*)0x10000005;
+
+	while (!(*UART_LSR & (1<<0))); // wait for DR (Data Ready)
+	return *UART_RBR;
+}
+
+char uartPutStr(const char *str) {
+    while (*str) {
+        uartSend(*str++);
+    }
+}
+
+/////////////////////////////
+// End of code added for Wally
+//////////////////////////////
+
 static uintptr_t syscall(uintptr_t which, uint64_t arg0, uint64_t arg1, uint64_t arg2)
 {
   volatile uint64_t magic_mem[8] __attribute__((aligned(64)));
@@ -76,7 +114,19 @@ void abort()
 
 void printstr(const char* s)
 {
-  syscall(SYS_write, 1, (uintptr_t)s, strlen(s));
+  // david_harris@hmc.edu 11/30/24 switch to printing via UART rather than syscall
+  // This works on both Spike and Wally simulations
+  //syscall(SYS_write, 1, (uintptr_t)s, strlen(s));
+  uartPutStr(s);
+}
+
+// Added 30 November 2024 David_Harris@hmc.edu
+// The compiler encountering printf with a pure string argument tries to invoke puts
+// rather than the usual printf, so puts must be defined.
+int puts(const char* s)
+{
+  printstr(s);
+  return 0;
 }
 
 void __attribute__((weak)) thread_entry(int cid, int nc)
@@ -107,6 +157,7 @@ void _init(int cid, int nc)
 {
   init_tls();
   thread_entry(cid, nc);
+  uartInit(); // added 11/30/2024 David_Harris@hmc.edu for printing via UART
 
   // only single-threaded programs should ever get here.
   int ret = main(0, 0);
@@ -125,6 +176,11 @@ void _init(int cid, int nc)
 #undef putchar
 int putchar(int ch)
 {
+  // David_Harris@hmc.edu 11/30/2024
+  // Replaced syscall with uartSend
+  uartSend(ch);
+ 
+  /*
   static __thread char buf[64] __attribute__((aligned(64)));
   static __thread int buflen = 0;
 
@@ -134,7 +190,7 @@ int putchar(int ch)
   {
     syscall(SYS_write, 1, (uintptr_t)buf, buflen);
     buflen = 0;
-  }
+  } */
 
   return 0;
 }

examples/C/hello/Makefile

@@ -0,0 +1,33 @@
+TARGET = hello
+
+$(TARGET).objdump: $(TARGET)
+	riscv64-unknown-elf-objdump -S -D $(TARGET) > $(TARGET).objdump
+	cp $(TARGET) $(TARGET).elf
+    
+$(TARGET): $(TARGET).c Makefile
+	riscv64-unknown-elf-gcc -o $(TARGET) -gdwarf-2 -O\
+	  -march=rv64gc -mabi=lp64d -mcmodel=medany \
+	  -nostdlib -static -lm -fno-tree-loop-distribute-patterns \
+	  -T../common/test.ld -I../common \
+	  $(TARGET).c ../common/crt.S ../common/syscalls.c
+# Compiler flags:
+#  -o $(TARGET) defines the name of the output file
+#  -g generates debugging symbols for gdb
+#  -O turns on basic optimization; -O3 turns on heavy optimization; omit for no optimization
+#  -march=rv64gc -mabi=lp64d =mcmodel=medany generates code for RV64GC with doubles and long/ptrs = 64 bits
+#  -static forces static linking (no dynamic shared libraries on bare metal)
+#  -lm links the math library if necessary (when #include math.h)
+#  -nostdlib avoids inserting standard startup files and default libraries 
+#     because we are using crt.s on bare metal
+#  -fno-tree-loop-distribute-patterns turns replacing loops with memcpy/memset in the std library 
+#  -T specifies the linker file
+#  -I specifies the include path (e.g. for util.h)
+#  The last line defines the C files to compile.  
+#    crt.S is needed as our startup file to initialize the processor
+#    syscalls.c implements printf through the HTIF for Spike
+# other flags from riscv-tests makefiles that don't seem to be important
+#	  -ffast-math -DPREALLOCATE=1 -std=gnu99  \
+#     -fno-common -fno-builtin-printf -nostartfiles -lgcc \
+
+clean:
+	rm -f $(TARGET) $(TARGET).objdump

examples/C/hello/hello.c

@@ -0,0 +1,23 @@
+// hello.c
+// David_Harris@hmc.edu 30 November 2024
+
+// Hello World program illustrating compiled C code printing via the UART
+// The Wally team has modified the Berkeley syscalls.c (in examples/C/common)
+// to print via UART rather than the syscall interface.  This is supported
+// on both Spike and Wally.  It assumes the PC16550-compatible UART is at 
+// the default SiFive address of 0x10000000.
+// Note that there seem to be some discrepancies between the UART and Spike
+// such that using \n\r for new lines works best.
+
+// compile with make
+// simulate with: wsim rv64gc hello.elf --sim verilator
+
+#include <stdio.h>  
+
+int main(void) {
+    printf("Hello Wally!\n\r");
+    for (int i = 0; i < 10; i++) {
+        printf("%d ", i);
+    }
+    printf("\n\r");
+}