fix(read_flash): add flash size arg to enable reading past 2MB without stub

docs/en/esptool/basic-commands.rst

@@ -113,6 +113,11 @@ It is also possible to autodetect flash size by using ``ALL`` as size. The above
     esptool.py -p PORT -b 460800 read_flash 0 ALL flash_contents.bin
 
 
+.. note::
+
+    When using the ``read_flash`` command in combination with the ``--no-stub`` argument, it may be necessary to also set the ``--flash_size`` argument to ensure proper reading of the flash contents by the ROM.
+
+
 .. note::
 
     If ``write_flash`` updated the boot image's :ref:`flash mode and flash size <flash-modes>` during flashing then these bytes may be different when read back.

esptool/__init__.py

@@ -217,7 +217,12 @@ def main(argv=None, esp=None):
         default="0xFFFFFFFF",
     )
 
-    def add_spi_flash_subparsers(parent, allow_keep, auto_detect):
+    def add_spi_flash_subparsers(
+        parent: argparse.ArgumentParser,
+        allow_keep: bool,
+        auto_detect: bool,
+        size_only: bool = False,
+    ):
         """Add common parser arguments for SPI flash properties"""
         extra_keep_args = ["keep"] if allow_keep else []
 
@@ -234,33 +239,35 @@ def main(argv=None, esp=None):
             extra_fs_message = ""
             flash_sizes = []
 
-        parent.add_argument(
-            "--flash_freq",
-            "-ff",
-            help="SPI Flash frequency",
-            choices=extra_keep_args
-            + [
-                "80m",
-                "60m",
-                "48m",
-                "40m",
-                "30m",
-                "26m",
-                "24m",
-                "20m",
-                "16m",
-                "15m",
-                "12m",
-            ],
-            default=os.environ.get("ESPTOOL_FF", "keep" if allow_keep else None),
-        )
-        parent.add_argument(
-            "--flash_mode",
-            "-fm",
-            help="SPI Flash mode",
-            choices=extra_keep_args + ["qio", "qout", "dio", "dout"],
-            default=os.environ.get("ESPTOOL_FM", "keep" if allow_keep else "qio"),
-        )
+        if not size_only:
+            parent.add_argument(
+                "--flash_freq",
+                "-ff",
+                help="SPI Flash frequency",
+                choices=extra_keep_args
+                + [
+                    "80m",
+                    "60m",
+                    "48m",
+                    "40m",
+                    "30m",
+                    "26m",
+                    "24m",
+                    "20m",
+                    "16m",
+                    "15m",
+                    "12m",
+                ],
+                default=os.environ.get("ESPTOOL_FF", "keep" if allow_keep else None),
+            )
+            parent.add_argument(
+                "--flash_mode",
+                "-fm",
+                help="SPI Flash mode",
+                choices=extra_keep_args + ["qio", "qout", "dio", "dout"],
+                default=os.environ.get("ESPTOOL_FM", "keep" if allow_keep else "qio"),
+            )
+
         parent.add_argument(
             "--flash_size",
             "-fs",
@@ -540,7 +547,9 @@ def main(argv=None, esp=None):
     parser_read_flash = subparsers.add_parser(
         "read_flash", help="Read SPI flash content"
     )
-    add_spi_connection_arg(parser_read_flash)
+    add_spi_flash_subparsers(
+        parser_read_flash, allow_keep=True, auto_detect=True, size_only=True
+    )
     parser_read_flash.add_argument("address", help="Start address", type=arg_auto_int)
     parser_read_flash.add_argument(
         "size",

esptool/targets/esp32.py

@@ -329,11 +329,17 @@ class ESP32ROM(ESPLoader):
         data = b""
         while len(data) < length:
             block_len = min(BLOCK_LEN, length - len(data))
-            r = self.check_command(
-                "read flash block",
-                self.ESP_READ_FLASH_SLOW,
-                struct.pack("<II", offset + len(data), block_len),
-            )
+            try:
+                r = self.check_command(
+                    "read flash block",
+                    self.ESP_READ_FLASH_SLOW,
+                    struct.pack("<II", offset + len(data), block_len),
+                )
+            except FatalError:
+                print(
+                    "Hint: Consider specifying flash size using '--flash_size' argument"
+                )
+                raise
             if len(r) < block_len:
                 raise FatalError(
                     "Expected %d byte block, got %d bytes. Serial errors?"

test/test_esptool.py

@@ -251,6 +251,12 @@ class EsptoolTestCase:
             dump_file.close()
             os.unlink(dump_file.name)
 
+    def diff(self, readback, compare_to):
+        for rb_b, ct_b, offs in zip(readback, compare_to, range(len(readback))):
+            assert (
+                rb_b == ct_b
+            ), f"First difference at offset {offs:#x} Expected {ct_b} got {rb_b}"
+
     def verify_readback(
         self, offset, length, compare_to, is_bootloader=False, spi_connection=None
     ):
@@ -268,10 +274,7 @@ class EsptoolTestCase:
             assert ct[0] == rb[0], "First bytes should be identical"
             rb = rb[8:]
             ct = ct[8:]
-        for rb_b, ct_b, offs in zip(rb, ct, range(len(rb))):
-            assert (
-                rb_b == ct_b
-            ), f"First difference at offset {offs:#x} Expected {ct_b} got {rb_b}"
+        self.diff(rb, ct)
 
 
 @pytest.mark.skipif(arg_chip != "esp32", reason="ESP32 only")
@@ -735,6 +738,32 @@ class TestFlashSizes(EsptoolTestCase):
         # header should be the same as in the .bin file
         self.verify_readback(offset, image_len, image)
 
+    @pytest.mark.skipif(
+        arg_chip == "esp8266", reason="ESP8266 does not support read_flash_slow"
+    )
+    def test_read_nostub_high_offset(self):
+        offset = 0x300000
+        length = 1024
+        self.run_esptool(f"write_flash -fs detect {offset} images/one_kb.bin")
+        dump_file = tempfile.NamedTemporaryFile(delete=False)
+        # readback with no-stub and flash-size set
+        try:
+            self.run_esptool(
+                f"--no-stub read_flash -fs detect {offset} 1024 {dump_file.name}"
+            )
+            with open(dump_file.name, "rb") as f:
+                rb = f.read()
+            assert length == len(
+                rb
+            ), f"read_flash length {length} offset {offset:#x} yielded {len(rb)} bytes!"
+        finally:
+            dump_file.close()
+            os.unlink(dump_file.name)
+        # compare files
+        with open("images/one_kb.bin", "rb") as f:
+            ct = f.read()
+        self.diff(rb, ct)
+
 
 class TestFlashDetection(EsptoolTestCase):
     @pytest.mark.quick_test
@@ -1337,10 +1366,7 @@ class TestMakeImage(EsptoolTestCase):
                 f"WARNING: Expected length {len(ct)} doesn't match comparison {len(rb)}"
             )
         print(f"Readback {len(rb)} bytes")
-        for rb_b, ct_b, offs in zip(rb, ct, range(len(rb))):
-            assert (
-                rb_b == ct_b
-            ), f"First difference at offset {offs:#x} Expected {ct_b} got {rb_b}"
+        self.diff(rb, ct)
 
     def test_make_image(self):
         output = self.run_esptool(