Add feature to preserve cmsis-pack metadata in output elf

.cargo/config

@@ -2,7 +2,7 @@
 
 rustflags = [
   "-C", "link-arg=--nmagic",
-  "-C", "link-arg=-Tlink.x",
+  "-C", "link-arg=-Tlink_generated.x",
 
   # Code-size optimizations.
   "-C", "inline-threshold=5",

Cargo.toml

@@ -11,6 +11,11 @@ flash-algorithm = { version = "0.4.0", default-features = false, features = [
     "panic-handler",
 ] }
 
+[features]
+# Keep extra metadata in the final binary that probe-rs doesn't strictly need.
+# Other tools use of these datastructures: probe-rs' target-gen, pyocd, jlink
+cmsis-pack-compat = []
+
 # this lets you use `cargo fix`!
 [[bin]]
 name = "flash-algo"

build.rs

@@ -1,21 +1,41 @@
 use std::env;
 use std::fs::File;
 use std::io::Write;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 fn main() {
     // Put `link.x` in our output directory and ensure it's
     // on the linker search path.
     let out = &PathBuf::from(env::var_os("OUT_DIR").unwrap());
-    File::create(out.join("link.x"))
+
+    println!("cargo:rustc-link-search={}", out.display());
+
+    // Call another function to copy the linker script into the output directory.
+    // This allows us to use a different linker script based on whether the
+    // cmsis-pack-compat feature is enabled or not
+    setup_linker_script(out);
+}
+
+#[cfg(not(feature = "cmsis-pack-compat"))]
+fn setup_linker_script(out: &Path) {
+    // rename the linker output to ensure we use the one in the
+    // build output instead of the one in the project root
+    File::create(out.join("link_generated.x"))
         .unwrap()
         .write_all(include_bytes!("link.x"))
         .unwrap();
-    println!("cargo:rustc-link-search={}", out.display());
-
     // By default, Cargo will re-run a build script whenever
     // any file in the project changes. By specifying `link.x`
     // here, we ensure the build script is only re-run when
     // `link.x` is changed.
     println!("cargo:rerun-if-changed=link.x");
 }
+
+#[cfg(feature = "cmsis-pack-compat")]
+fn setup_linker_script(out: &Path) {
+    File::create(out.join("link_generated.x"))
+        .unwrap()
+        .write_all(include_bytes!("link_metadata.x"))
+        .unwrap();
+    println!("cargo:rerun-if-changed=link_metadata.x");
+}

build_w_metadata.sh

@@ -0,0 +1,33 @@
+#!/bin/bash
+
+set -euo pipefail
+
+# macOS base64 doesn't take -w argument and defaults to a single line.
+if [[ $(uname) = "Darwin" ]]; then
+    BASE64_FLAGS=""
+else
+    BASE64_FLAGS="-w0"
+fi
+
+cargo build --release --features cmsis-pack-compat
+ELF=target/thumbv6m-none-eabi/release/flash-algo
+
+rust-objdump --disassemble $ELF > target/disassembly.s
+rust-objdump -x $ELF > target/dump.txt
+rust-nm $ELF -n > target/nm.txt
+
+function bin {
+    rust-objcopy $ELF -O binary - | base64 $BASE64_FLAGS
+}
+
+function sym {
+    echo $((0x$(rust-nm $ELF | grep -w $1 | cut -d ' ' -f 1) + 1))
+}
+
+cat <<EOF
+    instructions: $(bin)
+    pc_init: $(sym Init)
+    pc_uninit: $(sym UnInit)
+    pc_program_page: $(sym ProgramPage)
+    pc_erase_sector: $(sym EraseSector)
+EOF

link_metadata.x

@@ -0,0 +1,70 @@
+SECTIONS {
+    . = 0x0;
+
+    /*
+     * The PrgCode output section name comes from the CMSIS-Pack flash algo
+     * templates and armlink. It is used here because several tools that work
+     * with these flash algos expect this section name.
+     *
+     * All input sections are combined into PrgCode because RWPI using R9 is not
+     * currently stable in Rust, thus having separate PrgData sections that the
+     * debug host might locate at a different offset from PrgCode is not safe.
+     */
+    PrgCode : {
+        KEEP(*(.entry))
+        KEEP(*(.entry.*))
+
+        *(.text)
+        *(.text.*)
+
+        *(.rodata)
+        *(.rodata.*)
+
+        *(.data)
+        *(.data.*)
+
+        *(.sdata)
+        *(.sdata.*)
+
+        *(.bss)
+        *(.bss.*)
+
+        *(.uninit)
+        *(.uninit.*)
+
+        . = ALIGN(4);
+    }
+
+    /* Section for data, specified by flashloader standard. */
+    PrgData : {
+      /*
+       * We're explicitly putting a single object here (PRGDATA_Start in main.c) as this is required by some tools.
+       * It is not used by this algorithm
+       *
+       * The KEEP statement ensures it's not removed by accident.
+       */
+        KEEP(*(PrgData))
+
+        . = ALIGN(4);
+    }
+
+    /* Description of the flash algorithm */
+    DevDscr . : {
+        /* The device data content is only for external tools,
+         * and usually not referenced by the code.
+         * All rules have exceptions: device data is used by this flash algo.
+         *
+         * The KEEP statement ensures it's not removed by accident.
+         */
+        KEEP(*(DeviceData))
+
+        . = ALIGN(4);
+    }
+
+    /DISCARD/ : {
+        /* Unused exception related info that only wastes space */
+        *(.ARM.exidx);
+        *(.ARM.exidx.*);
+        *(.ARM.extab.*);
+    }
+}

src/main.rs

@@ -100,3 +100,14 @@ impl Drop for RP2040Algo {
         (self.funcs.flash_enter_cmd_xip)();
     }
 }
+
+/// Some tools (eg Segger's debugger) require the PrgData section to exist in the target binary
+///
+/// They scan the flashloader binary for this symbol to determine the section location
+/// If they cannot find it, the tool exits. This variable serves no other purpose
+#[allow(non_upper_case_globals)]
+#[no_mangle]
+#[used]
+#[link_section = "PrgData"]
+#[cfg(feature = "cmsis-pack-compat")]
+pub static mut PRGDATA_Start: usize = 0;