gint/fx9860g.ld
Lephe 2b1f408cb4
kernel: compact VBR scheme on SH3
I have recenty discovered that the so-called "rram" section used by gint
to store its VBR space and a couple memory structures gets overwritten
when returning to the main menu. It is thus necessary to get rid of it
and store that data somewhere else.

My current lead is to have it at the start of the static RAM by querying
its address in the TLB. However, the static RAM is very small on SH3
(8k) so the VBR must be made more compact.

This change elaborates the event code translation scheme used on SH3 to
emulate SH4 event codes. It is now used to translate the event codes to
a gint-specific VBR layout that leaves no gaps and thus reduces the size
of the VBR space. The gint_inthandler() method has to be modified for
every new SH3 interrupt to maintain this scheme.
2020-07-09 10:44:37 +02:00

254 lines
5.9 KiB
Text

/*
Linker script for the fx9860g platform. Most of the symbols defined
here are used in the initialization routine in core/start.c; others are
used in core/setup.c.
*/
/* fx9860g may mean SH3 or SH4 and we want full compatibility */
OUTPUT_ARCH(sh3)
/* ELF offers a lot of symbol/section/relocation insights */
OUTPUT_FORMAT(elf32-sh)
/* Located in core/start.c */
ENTRY(_start)
MEMORY
{
/* Userspace mapping of the add-in (G1A header takes 0x200 bytes) */
rom (rx): o = 0x00300200, l = 500k
/* This is mapped to RAM; 8k on SH3, apparently 32k on SH4 */
ram (rw): o = 0x08100000, l = 8k
/* gint's VBR space, mentioned here for completeness */
vbr (rwx): o = 0x8800e000, l = 5k
/* Some RAM region from P1 area; gint's data will reside here */
rram (rwx): o = 0x8800f400, l = 3k
/* On-chip IL memory */
ilram (rwx): o = 0xe5200000, l = 4k
/* On-chip X and Y memory */
xram (rwx): o = 0xe5007000, l = 8k
yram (rwx): o = 0xe5017000, l = 8k
}
SECTIONS
{
/*
** ROM sections
*/
/* First address to be mapped to ROM (including G1A header) */
_brom = 0x00300000;
/* Size of ROM mappings */
_srom = 0x200
+ SIZEOF(.text) + SIZEOF(.rodata)
+ SIZEOF(.gint.drivers) + SIZEOF(.gint.blocks);
/* Machine code going to ROM:
- Entry function (.text.entry)
- Compiler-provided constructors (.ctors) and destructors (.dtors)
- All text from .text and .text.* (including user code)
- Code sections from fxlib, named "C" and "P" */
.text : {
*(.text.entry)
_bctors = . ;
*(.ctors .ctors.*)
_ectors = . ;
_bdtors = . ;
*(.dtors .dtors.*)
_edtors = . ;
_gint_exch_start = . ;
*(.gint.exch)
_gint_exch_size = ABSOLUTE(. - _gint_exch_start);
_gint_tlbh_start = . ;
*(.gint.tlbh)
_gint_tlbh_size = ABSOLUTE(. - _gint_tlbh_start);
*(.text .text.*)
*(C P)
} > rom
/* Interrupt handlers going to ROM:
- gint's interrupt handler blocks (.gint.blocks)
Although gint's blocks end up in VBR space, they are selected and
installed on-the-fly by the library and the drivers, so we can't
just put them in the vbr region and wait for the copy */
.gint.blocks : {
KEEP(*(.gint.blocks));
} > rom
/* Driver data going to ROM:
- Exposed driver interfaces (.gint.drivers)
The driver information is required to start and configure the
driver, even if the symbols are not referenced */
.gint.drivers : {
_bdrv = . ;
KEEP(*(.gint.drivers.0));
KEEP(*(.gint.drivers.1));
KEEP(*(.gint.drivers.2));
KEEP(*(.gint.drivers.3));
KEEP(*(.gint.drivers.4));
KEEP(*(.gint.drivers.5));
KEEP(*(.gint.drivers.6));
_edrv = . ;
} > rom
/* Read-only data going to ROM:
- Resources or assets from fxconv or similar converters
- Data marked read-only by the compiler (.rodata and .rodata.*) */
.rodata : SUBALIGN(4) {
/* Put these first, they need to be 4-aligned */
*(.rodata.4)
*(.rodata .rodata.*)
} > rom
/*
** RAM sections
*/
. = ORIGIN(ram);
/* BSS stuff going to RAM:
- Data marked BSS by the compiler
- BSS sections from fxlib, namely "B" and "R"
The BSS section is to be stripped from the ELF file later, and wiped
at startup. */
.bss (NOLOAD) : {
_rbss = . ;
*(.bss COMMON)
*(B R)
. = ALIGN(16);
} > ram :NONE
_sbss = SIZEOF(.bss);
/* Read-write data going to RAM:
- Data sections generated by the compiler (.data and .data.*)
- Data sections from fxlib, "D" */
.data ALIGN(4) : ALIGN(4) {
_ldata = LOADADDR(.data);
_rdata = . ;
*(.data .data.*)
*(D)
. = ALIGN(16);
} > ram AT> rom
/* Read-write data sub-aligned to 4 bytes (mainly from fxconv) */
.data.4 : SUBALIGN(4) {
*(.data.4)
. = ALIGN(16);
} > ram AT> rom
_sdata = SIZEOF(.data) + SIZEOF(.data.4);
/* On-chip memory sections: IL, X and Y memory */
. = ORIGIN(ilram);
.ilram ALIGN(4) : ALIGN(4) {
_lilram = LOADADDR(.ilram);
_rilram = . ;
*(.ilram)
. = ALIGN(16);
} > ilram AT> rom
. = ORIGIN(xram);
.xram ALIGN(4) : ALIGN(4) {
_lxram = LOADADDR(.xram);
_rxram = . ;
*(.xram)
. = ALIGN(16);
} > xram AT> rom
. = ORIGIN(yram);
.yram ALIGN(4) : ALIGN(4) {
_lyram = LOADADDR(.yram);
_ryram = . ;
*(.yram)
. = ALIGN(16);
} > yram AT> rom
_silram = SIZEOF(.ilram);
_sxram = SIZEOF(.xram);
_syram = SIZEOF(.yram);
/*
** RRAM sections
** 8800e000:5k VBR space
** 8800f400:3k .gint.data and .gint.bss
*/
/* VBR address: let's just start at the beginning of the RRAM area.
There's an unused 0x100-byte gap at the start of the VBR space.
The VBR space is already a large block (> 2 kiB), so I'm cutting off
the gap to spare some memory */
_gint_vbr_fx9860g = ORIGIN(vbr) - 0x100;
. = ORIGIN(rram);
/* gint's data section, going to Real RAM. This section contains many
small objects from the library (static/global variables, etc) */
.gint.data ALIGN(4) : ALIGN(4) {
_lgdata = LOADADDR(.gint.data);
_rgdata = . ;
*(.gint.data .gint.data.*)
/* Also code that must remain permanently mapped! */
*(.gint.mapped)
. = ALIGN(16);
} > rram AT> rom
_sgdata = SIZEOF(.gint.data);
/* gint's uninitialized BSS section, going to Real RAM. All the large
data arrays will be located here */
.gint.bss (NOLOAD) : {
/* Since it's uninitialized, the location doesn't matter */
*(.gint.bss .gint.bss.*)
. = ALIGN(16);
} > rram :NONE
_sgbss = SIZEOF(.gint.bss);
/*
** Other sections
*/
/* Unwanted sections going to meet Dave Null:
- Debug sections, often come out of libgcc
- Java classes registration (why is there any of this here?)
- Asynchronous unwind tables: no C++ exception handling for now ^^
- Comments or anything the compiler might put in its assembler
- A stack section sometimes generated for build/version.o */
/DISCARD/ : {
*(.debug_info .debug_abbrev .debug_loc .debug_aranges
.debug_ranges .debug_line .debug_str)
*(.jcr)
*(.eh_frame_hdr)
*(.eh_frame)
*(.comment)
}
}