Linker Script

Overview

The linker script defines how code and data are organized in memory for gint applications. It specifies memory regions, sections, and the layout of the final binary.

Memory Regions

The linker script defines five memory regions:

ram (Main RAM)

Origin: 0x8c052800
Size: 337920 bytes (330 KB)
Purpose: VRAM backup area, main fixed area to load code
Attributes: Read, Write, Execute (rwx)

eram (End-of-RAM)

Origin: 0x8cff0000
Size: 61184 bytes (64 KB - 0x1100)
Purpose: Space after HollyHock loader
Attributes: Read, Write, Execute (rwx)

HollyHock itself loads at 0x8cfd0000 (128 KB before the application). This region fits after it.

vbr (Vector Base Register)

Origin: 0x8cffef00
Size: 4352 bytes (0x1100)
Purpose: Space for interrupt vectors
Attributes: Read, Write, Execute (rwx)

ilram (On-chip IL Memory)

Origin: 0xe5200000
Size: 4 KB
Purpose: Fast on-chip instruction local memory
Attributes: Read, Write, Execute (rwx)

xyram (On-chip X and Y Memory)

Origin: 0xe500e000
Size: 16 KB
Purpose: Fast on-chip data memory for DSP operations
Attributes: Read, Write, Execute (rwx)

Sections

ROM Sections

These sections contain code and read-only data:

.hh3 Section

Contains machine code for entry functions and compiler constructors/destructors.

.hh3 : {
    *(.hh3*)
    *(.eram*)
} > eram

.text Section

Contains executable code including:

Entry function (.text.entry)
Constructors (.ctors)
Destructors (.dtors)
Exchange handlers (.gint.exch)
TLB handlers (.gint.tlbh)
User code (.text, .text.*)

.text : {
    *(.text.entry)
    _bctors = . ;
    KEEP(*(.ctors .ctors.*))
    _ectors = . ;

    _bdtors = . ;
    KEEP(*(.dtors .dtors.*))
    _edtors = . ;

    *(.gint.exch)
    *(.gint.tlbh)
    *(.text .text.*)
} > ram

.gint.blocks Section

Contains gint’s interrupt handler blocks. These are relocated at startup by the library/drivers.

.gint.blocks ALIGN(4) : ALIGN(4) {
    KEEP(*(.gint.blocks));
} > ram

.gint.drivers Section

Contains exposed driver interfaces. Required to start and configure drivers even if symbols are not referenced.

.gint.drivers ALIGN(4) : ALIGN(4) {
    _gint_drivers = . ;
    KEEP(*(SORT_BY_NAME(.gint.drivers.*)));
    _gint_drivers_end = . ;
} > ram

.rodata Section

Contains read-only data:

Resources from fxconv converters
Compiler-marked read-only data

.rodata ALIGN(4) : ALIGN(4) SUBALIGN(4) {
    *(.rodata.4)
    *(.rodata .rodata.*)
} > ram

RAM Sections

These sections contain read-write data:

.data Section

Contains initialized read-write data and mapped code.

.data ALIGN(4) : ALIGN(4) {
    _ldata = LOADADDR(.data);
    _rdata = . ;

    *(.data .data.*)
    *(.gint.mapped)
    *(.gint.mappedrel)
} > ram

.ilram Section

Contains code for on-chip IL memory.

.ilram ALIGN(4) : ALIGN(4) {
    _lilram = ABSOLUTE(LOADADDR(.ilram) + ORIGIN(ram));
    _rilram = . ;
    *(.ilram)
} > ilram

.xyram Section

Contains code for on-chip X and Y memory.

.xyram ALIGN(4) : ALIGN(4) {
    _lxyram = ABSOLUTE(LOADADDR(.xyram) + ORIGIN(ram));
    _rxyram = . ;
    *(.xram .yram .xyram)
} > xyram

.bss Section

Contains uninitialized data. Wiped by the loader at startup.

.bss : {
    _rbss = . ;
    *(.bss .bss.* COMMON)
} > ram

.gint.bss Section

Contains gint’s uninitialized BSS section for large data arrays.

.gint.bss : {
    *(.gint.bss)
    _euram = . ;  /* End of user RAM */
} > ram

Discarded Sections

These sections are removed from the final binary:

/DISCARD/ : {
    *(.gint.rodata.sh3 .gint.data.sh3 .gint.bss.sh3)  /* SH3-only data */
    *(.jcr)  /* Java class registration */
    *(.eh_frame_hdr) *(.eh_frame)  /* Exception handling tables */
    *(.comment)  /* Compiler comments */
}

Key Symbols

The linker script defines several important symbols:

Symbol	Description
`_brom`	Start of ROM mappings
`_srom`	Size of ROM mappings
`_bctors`, `_ectors`	Constructor table bounds
`_bdtors`, `_edtors`	Destructor table bounds
`_gint_exch_start`, `_gint_exch_end`	Exchange handler bounds
`_gint_tlbh_start`, `_gint_tlbh_end`	TLB handler bounds
`_gint_drivers`, `_gint_drivers_end`	Driver info bounds
`_ldata`, `_rdata`	Data load/runtime addresses
`_sdata`	Size of data sections
`_lilram`, `_rilram`	ILRAM addresses
`_silram`	Size of ILRAM
`_lxyram`, `_rxyram`	XYRAM addresses
`_sxyram`	Size of XYRAM
`_rbss`	BSS start
`_sbss`	BSS size
`_sgbss`	gint BSS size
`_euram`	End of user RAM
`_gint_region_vbr`	VBR region origin

Implementation

Source file: fxcp_hh3.ld.c