i440fx-test: generate temporary firmware blob

The blob is 64K in size and contains 0x00..0xFF repeatedly.

The client code added to main() wouldn't make much sense in the long term.
It helps with debugging and it silences gcc about create_blob_file() being
unused, and we'll replace it in the next patch anyway.
Signed-off-by: NLaszlo Ersek <lersek@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>

tests/i440fx-test.c

@@ -20,6 +20,11 @@
 
 #include <glib.h>
 #include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/mman.h>
+#include <stdlib.h>
 
 #define BROKEN 1
 
@@ -272,13 +277,68 @@ static void test_i440fx_pam(gconstpointer opaque)
     qtest_end();
 }
 
+#define BLOB_SIZE ((size_t)65536)
+
+/* Create a blob file, and return its absolute pathname as a dynamically
+ * allocated string.
+ * The file is closed before the function returns.
+ * In case of error, NULL is returned. The function prints the error message.
+ */
+static char *create_blob_file(void)
+{
+    int ret, fd;
+    char *pathname;
+    GError *error = NULL;
+
+    ret = -1;
+    fd = g_file_open_tmp("blob_XXXXXX", &pathname, &error);
+    if (fd == -1) {
+        fprintf(stderr, "unable to create blob file: %s\n", error->message);
+        g_error_free(error);
+    } else {
+        if (ftruncate(fd, BLOB_SIZE) == -1) {
+            fprintf(stderr, "ftruncate(\"%s\", %zu): %s\n", pathname,
+                    BLOB_SIZE, strerror(errno));
+        } else {
+            void *buf;
+
+            buf = mmap(NULL, BLOB_SIZE, PROT_WRITE, MAP_SHARED, fd, 0);
+            if (buf == MAP_FAILED) {
+                fprintf(stderr, "mmap(\"%s\", %zu): %s\n", pathname, BLOB_SIZE,
+                        strerror(errno));
+            } else {
+                size_t i;
+
+                for (i = 0; i < BLOB_SIZE; ++i) {
+                    ((uint8_t *)buf)[i] = i;
+                }
+                munmap(buf, BLOB_SIZE);
+                ret = 0;
+            }
+        }
+        close(fd);
+        if (ret == -1) {
+            unlink(pathname);
+            g_free(pathname);
+        }
+    }
+
+    return ret == -1 ? NULL : pathname;
+}
+
 int main(int argc, char **argv)
 {
+    char *fw_pathname;
     TestData data;
     int ret;
 
     g_test_init(&argc, &argv, NULL);
 
+    fw_pathname = create_blob_file();
+    g_assert(fw_pathname != NULL);
+    unlink(fw_pathname);
+    g_free(fw_pathname);
+
     data.num_cpus = 1;
 
     g_test_add_data_func("/i440fx/defaults", &data, test_i440fx_defaults);