Update cortex-m-rt to 0.7.5HEADmain

There's an unreleased commit upstream to support stack painting with
custom memory layouts, like ours. I eagerly defined the _stack_end
symbol. Tested on hardware.

3 files changed, 24 insertions, 2 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0ae56f7..70c7376 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,24 @@ true if you only specify the count, or if you make no choice. However, if you
 specify the layout, the builder guarantees that the FlexRAM banks will match
 that layout.
 
+### cortex-m-rt 0.7.5
+
+Update to cortex-m-rt 0.7.5. The new runtime introduces additional build-time
+features. You could enable these features yourself by depending on the same
+`cortex-m-rt` package and selecting features. Here's how this runtime supports
+each `cortex-m-rt` feature.
+
+The `paint-stack` feature is not supported. Do not enable this feature.
+(Upstream commits suggest that we should be able to support stack painting in a
+future release.)
+
+The `zero-init-ram` feature will zero the VMA region of `.data` before copying
+contents from the load region. This isn't particularly useful, but it's safe to
+enable.
+
+This package still enables `set-vtor` and `set-sp` features by default. For
+convenience, this package still forwards the `device` feature.
+
 ## [0.1.7] 2025-06-14
 
 Introduce `RuntimeBuilder::in_flash` for creating images that can be launched
diff --git a/Cargo.toml b/Cargo.toml
index bb93245..daf59d0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,7 +18,7 @@ device = ["cortex-m-rt/device"]
 cfg-if = "1.0"
 
 [target.'cfg(all(target_arch = "arm", target_os = "none"))'.dependencies]
-cortex-m-rt = { version = "=0.7.3", features = ["set-vtor", "set-sp"] }
+cortex-m-rt = { version = "=0.7.5", features = ["set-vtor", "set-sp"] }
 
 [target.'cfg(all(target_arch = "arm", target_os = "none"))'.dev-dependencies]
 board = { path = "board" }
diff --git a/src/host/imxrt-link.x b/src/host/imxrt-link.x
index 7fcd76c..2a5deff 100644
--- a/src/host/imxrt-link.x
+++ b/src/host/imxrt-link.x
@@ -42,8 +42,9 @@ SECTIONS
     __estack = .;
     . += ALIGN(__stack_size, 8);
     __sstack = .;
-    /* Symbol expected by cortex-m-rt */
+    /* Symbols expected by cortex-m-rt */
     _stack_start = __sstack;
+    _stack_end   = __estack;
   } > REGION_STACK
 
   .vector_table : ALIGN(1024)
@@ -118,6 +119,9 @@ SECTIONS
   } > REGION_DATA AT> REGION_LOAD_DATA
   __sidata = LOADADDR(.data);
 
+  _ram_start = __sdata;
+  _ram_end = __edata;
+
   .bss (NOLOAD) : ALIGN(4)
   {
     . = ALIGN(4);