targets/stm32f730r8tx_arduino: Add linker script

Fork and combine the two arduino core linker scripts for the
stm32f730r8tx.

Change-Id: I5e38d5450f76c8f6c2d73a393cd45f0b22048051
Reviewed-on: https://pigweed-review.googlesource.com/c/gonk/+/188950
Commit-Queue: Anthony DiGirolamo <tonymd@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>
diff --git a/targets/stm32f730r8tx_arduino/BUILD.gn b/targets/stm32f730r8tx_arduino/BUILD.gn
index 2e33b31..cb9c5e2 100644
--- a/targets/stm32f730r8tx_arduino/BUILD.gn
+++ b/targets/stm32f730r8tx_arduino/BUILD.gn
@@ -27,6 +27,8 @@
 
   if (current_toolchain ==
       "//targets/stm32f730r8tx_arduino:arduino_size_optimized") {
+    _ldscript = "ldscript_variant.ld"
+
     config("arduino_build") {
       exec_script(arduino_builder_script,
                   filter_exclude(arduino_run_command_args,
@@ -53,21 +55,28 @@
       _ldflags = exec_script(arduino_builder_script,
                              arduino_show_command_args + [ "--ld-flags" ],
                              "list lines")
-      ldflags =
-          filter_exclude(_ldflags,
-                         [
-                           # Remove arguments ending in 'core.a', for example:
-                           # C:/Users/username/pigweed/out/core.a
-                           "*core.a\b",
+      ldflags = filter_exclude(
+              _ldflags,
+              [
+                # Remove arguments ending in 'core.a', for example:
+                # C:/Users/username/pigweed/out/core.a
+                "*core.a\b",
 
-                           # Remove .elf output file, for example:
-                           # -o C:/Users/username/pigweed/out/pigweed.elf
-                           "\b-o\b",
-                           "*.elf\b",
+                # Remove .elf output file, for example:
+                # -o C:/Users/username/pigweed/out/pigweed.elf
+                "\b-o\b",
+                "*.elf\b",
 
-                           # Remove the Arduino {object_files} variable
-                           "{object_files}",
-                         ])
+                # Remove the Arduino {object_files} variable
+                "{object_files}",
+
+                # Remove default STM32 F730R8T linker script args.
+                "-Wl,--default-script=*../../third_party/stm32duino/hardware/stm32/2.6.0/variants/STM32F7xx/F722R\(C-E\)T_F730R8T_F732RET/ldscript.ld",
+                "-Wl,--script=*../../third_party/stm32duino/hardware/stm32/2.6.0/system/ldscript.ld",
+              ])
+
+      # Add the replacement ldscript
+      ldflags += [ "-Wl,--script=" + rebase_path(_ldscript, root_build_dir) ]
 
       # Teensy4 core recipe uses: '-larm_cortexM7lfsp_math -lm -lstdc++'
       libs = filter_exclude(
@@ -86,6 +95,7 @@
     }
 
     pw_source_set("pre_init") {
+      inputs = [ _ldscript ]
       sources = [ "init.cc" ]
       public_deps = [
         "$dir_pw_sys_io_arduino",
diff --git a/targets/stm32f730r8tx_arduino/ldscript_variant.ld b/targets/stm32f730r8tx_arduino/ldscript_variant.ld
new file mode 100644
index 0000000..b5b0eb5
--- /dev/null
+++ b/targets/stm32f730r8tx_arduino/ldscript_variant.ld
@@ -0,0 +1,168 @@
+/* Entry Point */
+ENTRY(Reset_Handler)
+
+/* Highest address of the user mode stack */
+_estack = ORIGIN(RAM) + LENGTH(RAM); /* end of "RAM" Ram type memory */
+
+_Min_Heap_Size = 0x200; /* required amount of heap */
+_Min_Stack_Size = 0x400; /* required amount of stack */
+
+/* Memories definition */
+MEMORY
+{
+  RAM    (xrw)    : ORIGIN = 0x20000000,   LENGTH = LD_MAX_DATA_SIZE
+  FLASH    (rx)    : ORIGIN = 0x8000000 + LD_FLASH_OFFSET, LENGTH = LD_MAX_SIZE - LD_FLASH_OFFSET
+}
+
+/* Sections */
+SECTIONS
+{
+  /* The startup code into "FLASH" Rom type memory */
+  .isr_vector :
+  {
+    . = ALIGN(4);
+    KEEP(*(.isr_vector)) /* Startup code */
+    . = ALIGN(4);
+  } >FLASH
+
+  /* The program code and other data into "FLASH" Rom type memory */
+  .text :
+  {
+    . = ALIGN(4);
+    *(.text)           /* .text sections (code) */
+    *(.text*)          /* .text* sections (code) */
+    *(.glue_7)         /* glue arm to thumb code */
+    *(.glue_7t)        /* glue thumb to arm code */
+    *(.eh_frame)
+
+    KEEP (*(.init))
+    KEEP (*(.fini))
+
+    . = ALIGN(4);
+    _etext = .;        /* define a global symbols at end of code */
+  } >FLASH
+
+  /* Constant data into "FLASH" Rom type memory */
+  .rodata :
+  {
+    . = ALIGN(4);
+    *(.rodata)         /* .rodata sections (constants, strings, etc.) */
+    *(.rodata*)        /* .rodata* sections (constants, strings, etc.) */
+    . = ALIGN(4);
+  } >FLASH
+
+  .ARM.extab   : {
+    . = ALIGN(4);
+    *(.ARM.extab* .gnu.linkonce.armextab.*)
+    . = ALIGN(4);
+  } >FLASH
+
+  .ARM : {
+    . = ALIGN(4);
+    __exidx_start = .;
+    *(.ARM.exidx*)
+    __exidx_end = .;
+    . = ALIGN(4);
+  } >FLASH
+
+  .preinit_array     :
+  {
+    . = ALIGN(4);
+    PROVIDE_HIDDEN (__preinit_array_start = .);
+    KEEP (*(.preinit_array*))
+    PROVIDE_HIDDEN (__preinit_array_end = .);
+    . = ALIGN(4);
+  } >FLASH
+
+  .init_array :
+  {
+    . = ALIGN(4);
+    PROVIDE_HIDDEN (__init_array_start = .);
+    KEEP (*(SORT(.init_array.*)))
+    KEEP (*(.init_array*))
+    PROVIDE_HIDDEN (__init_array_end = .);
+    . = ALIGN(4);
+  } >FLASH
+
+  .fini_array :
+  {
+    . = ALIGN(4);
+    PROVIDE_HIDDEN (__fini_array_start = .);
+    KEEP (*(SORT(.fini_array.*)))
+    KEEP (*(.fini_array*))
+    PROVIDE_HIDDEN (__fini_array_end = .);
+    . = ALIGN(4);
+  } >FLASH
+
+  /* Used by the startup to initialize data */
+  _sidata = LOADADDR(.data);
+
+  /* Initialized data sections into "RAM" Ram type memory */
+  .data :
+  {
+    . = ALIGN(4);
+    _sdata = .;        /* create a global symbol at data start */
+    *(.data)           /* .data sections */
+    *(.data*)          /* .data* sections */
+    *(.RamFunc)        /* .RamFunc sections */
+    *(.RamFunc*)       /* .RamFunc* sections */
+
+    . = ALIGN(4);
+    _edata = .;        /* define a global symbol at data end */
+
+  } >RAM AT> FLASH
+
+  /* Uninitialized data section into "RAM" Ram type memory */
+  . = ALIGN(4);
+  .bss :
+  {
+    /* This is used by the startup in order to initialize the .bss section */
+    _sbss = .;         /* define a global symbol at bss start */
+    __bss_start__ = _sbss;
+    *(.bss)
+    *(.bss*)
+    *(COMMON)
+
+    . = ALIGN(4);
+    _ebss = .;         /* define a global symbol at bss end */
+    __bss_end__ = _ebss;
+  } >RAM
+
+  /* Define a noinit output section and mark it as NOLOAD to prevent
+   * putting its contents into the resulting .bin file (which is the
+   * default). */
+  .noinit (NOLOAD) :
+  {
+    /* Ensure output is aligned */
+    . = ALIGN(4);
+    /* Define a global _snoinit (and _enoinit below) symbol just in case
+     * code wants to iterate over all noinit variables for some reason */
+    _snoinit = .;
+    /* Actually import the .noinit and .noinit* import sections */
+    *(.noinit)
+    *(.noinit*)
+    . = ALIGN(4);
+    _enoinit = .;
+  }
+
+  /* User_heap_stack section, used to check that there is enough "RAM" Ram  type memory left */
+  ._user_heap_stack :
+  {
+    . = ALIGN(8);
+    PROVIDE ( end = . );
+    PROVIDE ( _end = . );
+    . = . + _Min_Heap_Size;
+    . = . + _Min_Stack_Size;
+    . = ALIGN(8);
+  } >RAM
+
+  /* Remove information from the compiler libraries */
+  /DISCARD/ :
+  {
+    libc.a ( * )
+    libm.a ( * )
+    libgcc.a ( * )
+  }
+
+  .ARM.attributes 0 : { *(.ARM.attributes) }
+}