add atari8-stdcart target (#92)

* add atari8-stdcart target

* cleanup/fix atari8-stdcart target

* atari8-stdcart typo

* atari8-stdcart fix crt0 and .*data copies

* atari8-stdcart avoid duplicate symbols, expose _cart_init

tweak to avoid duplicate symbols (tested with --whole-archive)

allow override of _cart_init; this won't be used most of the time but
is useful in cases where you want to taint memory in order to test
that the data copy functions are working

* reference copy-data.c from mos-common

mos-platform/CMakeLists.txt

@@ -46,6 +46,7 @@ endif()
 
 add_subdirectory(common)
 add_subdirectory(atari8)
+add_subdirectory(atari8-stdcart)
 add_subdirectory(commodore)
 add_subdirectory(c64)
 add_subdirectory(cpm65)

mos-platform/atari8-stdcart/CMakeLists.txt

@@ -0,0 +1,16 @@
+# TODO; refactor atari8, remove copy-data.c
+platform(atari8-stdcart COMPLETE PARENT atari8)
+
+if(NOT CMAKE_CROSSCOMPILING)
+  return()
+endif()
+
+install(FILES
+  cart-rom-fixed.ld
+  link.ld
+  stdcart.ld
+TYPE LIB)
+
+# ../common/crt0/copy-data; see above
+add_platform_library(atari8-stdcart-crt0 syms.s ../common/crt0/copy-data.c)
+target_compile_options(atari8-stdcart-crt0 PRIVATE -fno-lto)

mos-platform/atari8-stdcart/cart-rom-fixed.ld

@@ -0,0 +1,20 @@
+ASSERT(__cart_rom_size == 8 || __cart_rom_size == 16,
+       "ATARI 800 STDCART: Only 8 KiB and 16 KiB ROM supported")
+
+MEMORY {
+  cart_rom_vma (rx) : ORIGIN = __cart_rom_size == 16 ? 0x8000 : 0xA000,
+                     LENGTH = __cart_rom_size * 1024
+}
+
+REGION_ALIAS("c_rom_vma", cart_rom_vma)
+REGION_ALIAS("c_rom_lma", cart_rom)
+
+SECTIONS {
+  .cart_rom_fixed : { *(.cart_rom_fixed .cart_rom_fixed.*) } >cart_rom
+  .vector 0xbffa - ORIGIN(cart_rom_vma) + ORIGIN(cart_rom) : {
+    SHORT(_start)      /* START entrypoint (after OS setup)   */
+    BYTE(0x0)          /* "Inserted"                          */
+    BYTE(0x04)         /* Bits: 7=diag, 2=start, 0=Enable_DOS */
+    SHORT(_cart_init)  /* INIT entrpoint (before OS setup)    */
+  } >cart_rom
+}

mos-platform/atari8-stdcart/link.ld

@@ -0,0 +1,8 @@
+/* Atari800 cartridge linker scripts. */
+
+INCLUDE stdcart.ld
+INCLUDE cart-rom-fixed.ld
+
+OUTPUT_FORMAT {
+  FULL(cart_rom)
+}

mos-platform/atari8-stdcart/stdcart.ld

@@ -0,0 +1,41 @@
+/* Provide imaginary (zero page) registers. */
+__rc0 = 0x80;
+INCLUDE imag-regs.ld
+ASSERT(__rc31 == 0x9f, "Inconsistent zero page map.")
+
+ASSERT(__cart_rom_size == 1 << LOG2CEIL(__cart_rom_size),
+       "ATARI 800 STDCART: ROM size must be a power of 2.")
+
+MEMORY {
+  zp : ORIGIN = __rc31 + 1, LENGTH = 0x100 - (__rc31 + 1)
+
+  /* 0x700 works w/o DOS. */
+  ram : ORIGIN = 0x700, LENGTH = 0x2000 - 0x700
+
+  /* CART-ROM LMA. */
+  cart_rom : ORIGIN = 0x01000000, LENGTH = __cart_rom_size * 1024
+}
+
+SECTIONS {
+  .text : {
+       INCLUDE text-sections.ld
+  } >c_rom_vma AT>c_rom_lma
+  .rodata : { INCLUDE rodata-sections.ld } >c_rom_vma AT>c_rom_lma
+  .data : { INCLUDE data-sections.ld } >ram AT>c_rom_lma
+  __data_load_start = LOADADDR(.data) - LOADADDR(.rodata) + ADDR(.rodata);
+  __data_size = SIZEOF(.data);
+  .zp.data : { INCLUDE zp-data-sections.ld } >zp AT>c_rom_lma
+  __zp_data_load_start = LOADADDR(.zp.data) - LOADADDR(.rodata) + ADDR(.rodata);
+  __zp_data_size = SIZEOF(.zp.data);
+  /* The data initializers take up space at the C_ROM_VMA too, not just in RAM. */
+  .data_initializers ADDR(.rodata) + SIZEOF(.rodata) + __data_size +
+                   __zp_data_size : {} >c_rom_vma
+  .zp.bss (NOLOAD) : {
+    INCLUDE zp-bss-sections.ld
+  } >zp
+  INCLUDE zp-bss-symbols.ld
+  INCLUDE zp-noinit.ld
+  .bss (NOLOAD) : { INCLUDE bss-sections.ld } >ram AT>ram
+  INCLUDE bss-symbols.ld
+  .noinit (NOLOAD) : { INCLUDE noinit-sections.ld } >ram AT>ram
+}

mos-platform/atari8-stdcart/syms.s

@@ -0,0 +1,10 @@
+; defaults
+
+; ROM size, only 8 and 16 KiB are supported
+.weak __cart_rom_size
+__cart_rom_size = 8
+
+; INIT typically isn't used but allow override
+.weak _cart_init
+_cart_init:
+	rts