[sw] Fix flash_header section attributes

Moving the flash_header section from the linker script to an assembly file allows us to specify that section's attributes and ensure it's not writeable. This prevents the segment containing the code and other read-only data to also be flagged as writeable. Signed-off-by: Luís Marques <[email protected]>
tomeroberts · Aug 7, 2020 · 64c8973 · 64c8973
1 parent d4651a2
commit 64c8973
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Showing 2 changed files with 10 additions and 6 deletions.
diff --git a/sw/device/exts/common/flash_crt.S b/sw/device/exts/common/flash_crt.S
@@ -2,13 +2,21 @@
 // Licensed under the Apache License, Version 2.0, see LICENSE for details.
 // SPDX-License-Identifier: Apache-2.0
 
+/**
+ * Flash header.
+ *
+ * Contains the address of the entry point.
+ */
+  .section .flash_header, "a", @progbits
+  .4byte _start
+
 /**
  * Flash executable runtime initialization code.
  */
 
   // NOTE: The "ax" flag below is necessary to ensure that this section
   // is allocated space in ROM by the linker.
-  .section .crt, "ax"
+  .section .crt, "ax", @progbits
 
   .extern main
   .extern crt_interrupt_vector

diff --git a/sw/device/exts/common/flash_link.ld b/sw/device/exts/common/flash_link.ld
@@ -38,11 +38,7 @@ SECTIONS {
    * signature, but for now it's just the entry point at offset zero.
    */
   .flash_header ORIGIN(eflash) : ALIGN(4) {
-    /**
-     * NOTE:ld scripts do not provide a mechanism to refer to ENTRY,
-     * so we just harcode the _start symbol.
-     */
-    LONG(_start)
+    KEEP(*(.flash_header))
   } > eflash
 
   /**