doc: release-notes: document aarch32 cortex_a_r linker command file c…

…hanges

Document the changes implemented in #60368:
* Placement of the .bss and .noinit sections at the end of the binary
  so that large zero-/uninitialized data structures such as heaps,
  arrays etc. don't have to be padded in the resulting binary.
* Location of the z_mapped_start marker: prevents the assignment
  of the single 4k-page wide .vectors section right at the RAM
  base address as dynamic memory by the MMU at run-time. Instead
  of pointing to the start of the subsequent .text section, the
  z_mapped_start marker now covers all the data contained within
  the binary that ends up in RAM.

(cherry picked from commit eb731ab)

Original-Signed-off-by: Immo Birnbaum <mail@birnbaum.immo>
GitOrigin-RevId: eb731ab
Change-Id: I0889eff81a9677358e245577fd29ab711252ea03
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/4766826
Commit-Queue: Keith Short <keithshort@chromium.org>
Tested-by: Fabio Baltieri <fabiobaltieri@google.com>
Reviewed-by: Fabio Baltieri <fabiobaltieri@google.com>
Tested-by: Keith Short <keithshort@chromium.org>
Tested-by: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>
Reviewed-by: Keith Short <keithshort@chromium.org>

doc/releases/release-notes-3.5.rst

@@ -58,10 +58,33 @@ Kernel
 Architectures
 *************
 
-* ARM
+* ARC
 
 * ARM
 
+  * Fixed the Cortex-A/-R linker command file:
+
+    * The sections for zero-initialized (.bss) and uninitialized (.noinit) data
+      are now the last sections within the binary. This allows the linker to just
+      account for the required memory, but not having to actually include large
+      empty spaces within the binary. With the .bss and .noinit sections placed
+      somewhere in the middle of the resulting binary, as was the case with
+      previous releases, the linker had to pad the space for zero-/uninitialized
+      data due to subsequent sections containing initialized data. The inclusion
+      of large zero-initialized arrays or statically defined heaps reflected
+      directly in the size of the resulting binary, resulting in unnecessarily
+      large binaries, even when stripped.
+    * Fixed the location of the z_mapped_start address marker to point to the
+      base of RAM instead of to the start of the .text section. Therefore, the
+      single 4k page .vectors section, which is located right at the base of RAM
+      before the .text section and which was previously not included in the
+      mapped memory range, is now considered mapped and unavailable for dynamic
+      memory mapping via the MMU at run-time. This prevents the 4k page containing
+      the exception vectors data being mapped as regular memory at run-time, with
+      any subsequently mapped pages being located beyond the permanently mapped
+      memory regions (beyond z_mapped_end), resulting in non-contiguous memory
+      allocation for any first memory request greater than 4k.
+
 * ARM64
 
 * RISC-V