lots of work on determinism in the linux driver.

luprex/core/cpp/driver-linux.cpp

@@ -225,7 +225,25 @@ static int console_read(char *bytes, int nbytes) {
     return read(0, bytes, nbytes);
 }
 
-
+static std::string_view read_file(const char *fn, char *buf, int bufsize, UmmString &err) {
+    int nread;
+    int fd = open(fn, O_RDONLY);
+    if (fd < 0) goto error_errno;
+    nread = read(fd, buf, bufsize);
+    if (nread < 0) goto error_errno;
+    if (nread == bufsize) {
+        err = "file too large";
+        goto error;
+    }
+    buf[nread] = 0;
+    err = "";
+    return std::string_view(buf, nread);
+  error_errno:
+    err = strerror_str(errno);
+  error:
+    buf[0] = 0;
+    return std::string_view(buf, 0);
+}
 
 static void disable_randomization(int argc, char *argv[]) {
    const int old_personality = personality(ADDR_NO_RANDOMIZE);