csim: Allow redirecting trace output to a file using command line flag

This is useful when booting an operating system with tracing enabled
as it allows showing the printed messages on the terminal and storing
the trace log to a separate file.

Example usage:
`./c_emulator/riscv_sim_RV64 -b os-boot/rv64-64mb.dtb -t /dev/stderr os-boot/linux-rv64-64mb.bbl --trace-output /tmp/linux.log`

c_emulator/riscv_platform_impl.h

@@ -2,6 +2,7 @@
 
 #include <stdbool.h>
 #include <stdint.h>
+#include <stdio.h>
 
 /* Settings of the platform implementation. */
 
@@ -32,5 +33,6 @@ extern uint64_t rv_clint_size;
 extern uint64_t rv_htif_tohost;
 extern uint64_t rv_insns_per_tick;
 
+extern FILE *trace_log;
 extern int term_fd;
 void plat_term_write_impl(char c);

c_emulator/riscv_prelude.c

@@ -1,37 +1,38 @@
 #include "riscv_prelude.h"
 #include "riscv_config.h"
+#include "riscv_platform_impl.h"
 
 unit print_string(sail_string prefix, sail_string msg)
 {
-  printf("%s%s\n", prefix, msg);
+  fprintf(trace_log, "%s%s\n", prefix, msg);
   return UNIT;
 }
 
 unit print_instr(sail_string s)
 {
   if (config_print_instr)
-    printf("%s\n", s);
+    fprintf(trace_log, "%s\n", s);
   return UNIT;
 }
 
 unit print_reg(sail_string s)
 {
   if (config_print_reg)
-    printf("%s\n", s);
+    fprintf(trace_log, "%s\n", s);
   return UNIT;
 }
 
 unit print_mem_access(sail_string s)
 {
   if (config_print_mem_access)
-    printf("%s\n", s);
+    fprintf(trace_log, "%s\n", s);
   return UNIT;
 }
 
 unit print_platform(sail_string s)
 {
   if (config_print_platform)
-    printf("%s\n", s);
+    fprintf(trace_log, "%s\n", s);
   return UNIT;
 }
 

c_emulator/riscv_sim.c

@@ -48,10 +48,14 @@ const char *RV32ISA = "RV32IMAC";
 #define CSR_MTVAL 0x343
 #define CSR_MIP 0x344
 
+#define OPT_TRACE_OUTPUT 1000
+
 static bool do_dump_dts = false;
 static bool do_show_times = false;
 struct tv_spike_t *s = NULL;
 char *term_log = NULL;
+static const char *trace_log_path = NULL;
+FILE *trace_log = NULL;
 char *dtb_file = NULL;
 unsigned char *dtb = NULL;
 size_t dtb_len = 0;
@@ -111,33 +115,34 @@ char *sailcov_file = NULL;
 #endif
 
 static struct option options[] = {
-    {"enable-dirty-update",         no_argument,       0, 'd'},
-    {"enable-misaligned",           no_argument,       0, 'm'},
-    {"enable-pmp",                  no_argument,       0, 'P'},
-    {"enable-next",                 no_argument,       0, 'N'},
-    {"ram-size",                    required_argument, 0, 'z'},
-    {"disable-compressed",          no_argument,       0, 'C'},
-    {"disable-writable-misa",       no_argument,       0, 'I'},
-    {"disable-fdext",               no_argument,       0, 'F'},
-    {"mtval-has-illegal-inst-bits", no_argument,       0, 'i'},
-    {"device-tree-blob",            required_argument, 0, 'b'},
-    {"terminal-log",                required_argument, 0, 't'},
-    {"show-times",                  required_argument, 0, 'p'},
-    {"report-arch",                 no_argument,       0, 'a'},
-    {"test-signature",              required_argument, 0, 'T'},
-    {"signature-granularity",       required_argument, 0, 'g'},
+    {"enable-dirty-update",         no_argument,       0, 'd'             },
+    {"enable-misaligned",           no_argument,       0, 'm'             },
+    {"enable-pmp",                  no_argument,       0, 'P'             },
+    {"enable-next",                 no_argument,       0, 'N'             },
+    {"ram-size",                    required_argument, 0, 'z'             },
+    {"disable-compressed",          no_argument,       0, 'C'             },
+    {"disable-writable-misa",       no_argument,       0, 'I'             },
+    {"disable-fdext",               no_argument,       0, 'F'             },
+    {"mtval-has-illegal-inst-bits", no_argument,       0, 'i'             },
+    {"device-tree-blob",            required_argument, 0, 'b'             },
+    {"terminal-log",                required_argument, 0, 't'             },
+    {"show-times",                  required_argument, 0, 'p'             },
+    {"report-arch",                 no_argument,       0, 'a'             },
+    {"test-signature",              required_argument, 0, 'T'             },
+    {"signature-granularity",       required_argument, 0, 'g'             },
 #ifdef RVFI_DII
-    {"rvfi-dii",                    required_argument, 0, 'r'},
+    {"rvfi-dii",                    required_argument, 0, 'r'             },
 #endif
-    {"help",                        no_argument,       0, 'h'},
-    {"trace",                       optional_argument, 0, 'v'},
-    {"no-trace",                    optional_argument, 0, 'V'},
-    {"inst-limit",                  required_argument, 0, 'l'},
-    {"enable-zfinx",                no_argument,       0, 'x'},
+    {"help",                        no_argument,       0, 'h'             },
+    {"trace",                       optional_argument, 0, 'v'             },
+    {"no-trace",                    optional_argument, 0, 'V'             },
+    {"trace-output",                required_argument, 0, OPT_TRACE_OUTPUT},
+    {"inst-limit",                  required_argument, 0, 'l'             },
+    {"enable-zfinx",                no_argument,       0, 'x'             },
 #ifdef SAILCOV
-    {"sailcov-file",                required_argument, 0, 'c'},
+    {"sailcov-file",                required_argument, 0, 'c'             },
 #endif
-    {0,                             0,                 0, 0  }
+    {0,                             0,                 0, 0               }
 };
 
 static void print_usage(const char *argv0, int ec)
@@ -352,6 +357,10 @@ char *process_args(int argc, char **argv)
       sailcov_file = strdup(optarg);
       break;
 #endif
+    case OPT_TRACE_OUTPUT:
+      trace_log_path = optarg;
+      fprintf(stderr, "using %s for trace output.\n", trace_log_path);
+      break;
     case '?':
       print_usage(argv[0], 1);
       break;
@@ -626,6 +635,9 @@ void close_logs(void)
     exit(EXIT_FAILURE);
   }
 #endif
+  if (trace_log != stdout) {
+    fclose(trace_log);
+  }
 }
 
 void finish(int ec)
@@ -724,10 +736,8 @@ int compare_states(struct tv_spike_t *s)
 void flush_logs(void)
 {
   if (config_print_instr) {
-    fprintf(stderr, "\n");
     fflush(stderr);
-    fprintf(stdout, "\n");
-    fflush(stdout);
+    fflush(trace_log);
   }
 }
 
@@ -1010,6 +1020,14 @@ void init_logs()
     exit(1);
   }
 
+  if (trace_log_path == NULL) {
+    trace_log = stdout;
+  } else if ((trace_log = fopen(trace_log_path, "w+")) < 0) {
+    fprintf(stderr, "Cannot create trace log '%s': %s\n", trace_log,
+            strerror(errno));
+    exit(1);
+  }
+
 #ifdef SAILCOV
   if (sailcov_file != NULL) {
     sail_set_coverage_file(sailcov_file);