commit 9117fded476768b458253902a7d9c87e3663802a
author Fabio Utzig <utzig@apache.org> Thu Oct 17 11:11:46 2019 -0300
committer Fabio Utzig <utzig@utzig.org> Thu Oct 17 20:00:47 2019 -0300
tree 0604188e4f55573c674d8a531f1f81ee7ed3d017
parent f5c5dd0d90015a122188be5494076d2f241264dc

imgtool: add erased-val cli option

Add `-R`/`--erased-val` CLI option when creating images, which accepts
a value to be used for padding. This is useful when creating images
that run in devices that have flash erased to some value different
from 0xff (like STM32L0x and STM32L1x that have 0s).

Signed-off-by: Fabio Utzig <utzig@apache.org>

scripts/imgtool/image.py

diff --git a/scripts/imgtool/image.py b/scripts/imgtool/image.py
index 78600dd..e6ae581 100644
--- a/scripts/imgtool/image.py
+++ b/scripts/imgtool/image.py
@@ -113,7 +113,7 @@
     def __init__(self, version=None, header_size=IMAGE_HEADER_SIZE,
                  pad_header=False, pad=False, align=1, slot_size=0,
                  max_sectors=DEFAULT_MAX_SECTORS, overwrite_only=False,
-                 endian="little", load_addr=0):
+                 endian="little", load_addr=0, erased_val=0xff):
         self.version = version or versmod.decode_version("0")
         self.header_size = header_size
         self.pad_header = pad_header
@@ -125,6 +125,7 @@
         self.endian = endian
         self.base_addr = None
         self.load_addr = 0 if load_addr is None else load_addr
+        self.erased_val = 0xff if erased_val is None else int(erased_val)
         self.payload = []
         self.enckey = None
 
@@ -160,7 +161,8 @@
             if self.base_addr:
                 # Adjust base_addr for new header
                 self.base_addr -= self.header_size
-            self.payload = (b'\000' * self.header_size) + self.payload
+            self.payload = bytes([self.erased_val] * self.header_size) + \
+                self.payload
 
         self.check()
 
@@ -347,8 +349,8 @@
         tsize = self._trailer_size(self.align, self.max_sectors,
                                    self.overwrite_only, self.enckey)
         padding = size - (len(self.payload) + tsize)
-        pbytes = b'\xff' * padding
-        pbytes += b'\xff' * (tsize - len(boot_magic))
+        pbytes = bytes([self.erased_val] * padding)
+        pbytes += bytes([self.erased_val] * (tsize - len(boot_magic)))
         pbytes += boot_magic
         self.payload += pbytes