core/sdcard: make allocating new SD card for emulator fast

core/embed/unix/sdcard.c

@@ -52,20 +52,18 @@ void sdcard_init(void) {
   // check whether the file exists and it has the correct size
   struct stat sb;
   int r = stat(SDCARD_FILE, &sb);
+  int should_clear = 0;
 
   // (re)create if non existant or wrong size
   if (r != 0 || sb.st_size != SDCARD_SIZE) {
     int fd = open(SDCARD_FILE, O_RDWR | O_CREAT | O_TRUNC, (mode_t)0600);
     ensure(sectrue * (fd >= 0), "open failed");
-    for (int i = 0; i < SDCARD_SIZE / 16; i++) {
+    r = ftruncate(fd, SDCARD_SIZE);
-      ssize_t s = write(
+    ensure(sectrue * (r == 0), "truncate failed");
-          fd,
-          "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF",
-          16);
-      ensure(sectrue * (s >= 0), "write failed");
-    }
     r = close(fd);
     ensure(sectrue * (r == 0), "close failed");
+
+    should_clear = 1;
   }
 
   // mmap file
@@ -77,6 +75,10 @@ void sdcard_init(void) {
 
   sdcard_buffer = (uint8_t *)map;
 
+  if (should_clear) {
+    for (int i = 0; i < SDCARD_SIZE; ++i) sdcard_buffer[i] = 0xFF;
+  }
+
   sdcard_powered = secfalse;
 
   atexit(sdcard_exit);

core/emu.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-import gzip
 import logging
 import os
 import platform
@@ -25,7 +24,6 @@ except Exception:
 HERE = Path(__file__).parent.resolve()
 MICROPYTHON = HERE / "build" / "unix" / "micropython"
 SRC_DIR = HERE / "src"
-SD_CARD_GZ = HERE / "trezor.sdcard.gz"
 
 PROFILING_WRAPPER = HERE / "prof" / "prof.py"
 
@@ -189,9 +187,6 @@ def cli(
     elif temporary_profile:
         tempdir = tempfile.TemporaryDirectory(prefix="trezor-emulator-")
         profile_dir = Path(tempdir.name)
-        # unpack empty SD card for faster start-up
-        with gzip.open(SD_CARD_GZ, "rb") as gz:
-            (profile_dir / "trezor.sdcard").write_bytes(gz.read())
 
     elif "TREZOR_PROFILE_DIR" in os.environ:
         profile_dir = Path(os.environ["TREZOR_PROFILE_DIR"])

tests/emulators.py

@@ -14,7 +14,6 @@
 # You should have received a copy of the License along with this library.
 # If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
 
-import gzip
 import tempfile
 from collections import defaultdict
 from pathlib import Path
@@ -30,7 +29,6 @@ LOCAL_BUILD_PATHS = {
 }
 
 CORE_SRC_DIR = ROOT / "core" / "src"
-SD_CARD_GZ = ROOT / "core" / "trezor.sdcard.gz"
 
 ENV = {"SDL_VIDEODRIVER": "dummy"}
 
@@ -88,13 +86,11 @@ class EmulatorWrapper:
                 executable, self.profile_dir.name, storage=storage, headless=True,
             )
         elif gen == "core":
-            with gzip.open(SD_CARD_GZ, "rb") as gz:
             self.emulator = CoreEmulator(
                 executable,
                 self.profile_dir.name,
                 storage=storage,
                 workdir=workdir,
-                    sdcard=gz.read(),
                 headless=True,
             )