Add cmdline option to stop the emulator after a number of cycles

For performance testing

Author: onnokort

README.md

@@ -69,13 +69,14 @@ You can exit the emulator using: \<Ctrl-a x\>. (press Ctrl+A, leave it, afterwar
 ## Usage
 
 ```shell
-./semu -k linux-image [-b dtb-file] [-i initrd-image] [-d disk-image]
+./semu -k linux-image [-b dtb-file] [-i initrd-image] [-d disk-image] [-c max_cycles]
 ```
 
 * `linux-image` is the path to the Linux kernel `Image`.
 * `dtb-file` is optional, as it specifies the user-specified device tree blob.
 * `initrd-image` is optional, as it specifies the user-specified initial RAM disk image.
 * `disk-image` is optional, as it specifies the path of a disk image in ext4 file system for the virtio-blk device.
+* `max_cycles` allows to set a limit of cycles the emulator should run for - for testing performance
 
 ## Build Linux kernel image and root file system
 

main.c

@@ -293,7 +293,8 @@ static void usage(const char *execpath)
 {
     fprintf(
         stderr,
-        "Usage: %s -k linux-image [-b dtb] [-i initrd-image] [-d disk-image]\n",
+        "Usage: %s -k linux-image [-b dtb] [-i initrd-image] "
+        "[-d disk-image] [-c max_cycles]\n",
         execpath);
 }
 
@@ -302,19 +303,21 @@ static void handle_options(int argc,
                            char **kernel_file,
                            char **dtb_file,
                            char **initrd_file,
-                           char **disk_file)
+                           char **disk_file,
+                           uint32_t *cycle_limit)
 {
     *kernel_file = *dtb_file = *initrd_file = *disk_file = NULL;
 
     int optidx = 0;
     struct option opts[] = {
         {"kernel", 1, NULL, 'k'}, {"dtb", 1, NULL, 'b'},
         {"initrd", 1, NULL, 'i'}, {"disk", 1, NULL, 'd'},
+        {"max_cycles", 1, NULL, 'c'},
         {"help", 0, NULL, 'h'},
     };
 
     int c;
-    while ((c = getopt_long(argc, argv, "k:b:i:d:h", opts, &optidx)) != -1) {
+    while ((c = getopt_long(argc, argv, "k:b:i:d:c:h", opts, &optidx)) != -1) {
         switch (c) {
         case 'k':
             *kernel_file = optarg;
@@ -328,6 +331,14 @@ static void handle_options(int argc,
         case 'd':
             *disk_file = optarg;
             break;
+        case 'c':
+            if (sscanf(optarg, "%u", cycle_limit) != 1) {
+                fprintf(stderr, "Cannot parse -c max_cycles argument '%s'.\n",
+                        optarg);
+                usage(argv[0]);
+                exit(2);
+            }
+            break;
         case 'h':
             usage(argv[0]);
             exit(0);
@@ -354,8 +365,9 @@ static int semu_start(int argc, char **argv)
     char *dtb_file;
     char *initrd_file;
     char *disk_file;
+    uint32_t cycle_limit = 0;
     handle_options(argc, argv, &kernel_file, &dtb_file, &initrd_file,
-                   &disk_file);
+                   &disk_file, &cycle_limit);
 
     /* Initialize the emulator */
     emu_state_t emu;
@@ -442,6 +454,7 @@ static int semu_start(int argc, char **argv)
             if (emu.vblk.InterruptStatus)
                 emu_update_vblk_interrupts(&vm);
 #endif
+            if (cycle_limit && vm.insn_count >= cycle_limit) exit(0);
         }
 
         if (vm.insn_count_hi > emu.timer_hi ||