gint/fx9860g.ld
Lephe c9264a06d5
kernel: driver and world system overhaul
Changes in the driver and world system:

* Rewrite driver logic to include more advanced concepts. The notion of
  binding a driver to a device is introduced to formalize wait(); power
  management is now built-in instead of being handled by the drivers
  (for instance DMA). The new driver model is described in great detail
  in <gint/drivers.h>

* Formalized the concept of "world switch" where the hardware state is
  saved and later restored. As a tool, the world switch turns out to be
  very stable, and allows a lot of hardware manipulation that would be
  edgy at best when running in the OS world.

* Added a GINT_DRV_SHARED flag for drivers to specify that their state
  is shared between worlds and not saved/restored. This has a couple of
  uses.

* Exposed a lot more of the internal driver/world system as their is no
  particular downside to it. This includes stuff in <gint/drivers.h>
  and the driver's state structures in <gint/drivers/states.h>. This is
  useful for debugging and for cracked concepts, but there is no
  API stability guarantee.

* Added a more flexible driver level system that allows any 2-digit
  level to be used.

Feature changes:

* Added a CPU driver that provides the VBR change as its state save.
  Because the whole context switch relied on interrupts being disabled
  anyway, there is no longer an inversion of control when setting the
  VBR; this is just part of the CPU driver's configuration. The CPU
  driver may also support other features such as XYRAM block transfer
  in the future.

* Moved gint_inthandler() to the INTC driver under the name
  intc_handler(), pairing up again with intc_priority().

* Added a reentrant atomic lock based on the test-and-set primitive.
  Interrupts are disabled with IMASK=15 for the duration of atomic
  operations.

* Enabled the DMA driver on SH7305-based fx-9860G. The DMA provides
  little benefit on this platform because the RAM is generally faster
  and buffers are ultimately small. The DMA is still not available on
  SH3-based fx-9860G models.

* Solved an extremely obnoxious bug in timer_spin_wait() where the
  timer is not freed, causing the callback to be called when interrupts
  are re-enabled. This increments a random value on the stack. As a
  consequence of the change, removed the long delays in the USB driver
  since they are not actually needed.

Minor changes:

* Deprecated some of the elements in <gint/hardware.h>. There really is
  no good way to "enumerate" devices yet.

* Deprecated gint_switch() in favor of a new function
  gint_world_switch() which uses the GINT_CALL abstraction.

* Made the fx-9860G VRAM 32-aligned so that it can be used for tests
  with the DMA.

Some features of the driver and world systems have not been implemented
yet, but may be in the future:

* Some driver flags should be per-world in order to create multiple
  gint worlds. This would be useful in Yatis' hypervisor.
* A GINT_DRV_LAZY flag would be useful for drivers that don't want to
  be started up automatically during a world switch. This is relevant
  for drivers that have a slow start/stop sequence. However, this is
  tricky to do correctly as it requires dynamic start/stop and also
  tracking which world the current hardware state belongs to.
2021-04-23 20:44:08 +02:00

252 lines
5.8 KiB
Plaintext

/*
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
/* User RAM is mapped at 0x08100000 through MMU; usually 8k on SH3, 32k
on SH4. This script exposes only 6k to the user, reserving:
* 0x200 bytes for text accessed without the TLB when SR.BL=1, linked
into the rram region below, then loaded dynamically
* 0x600 bytes for the VBR space, also without MMU
On SH3, the VBR space consumes these 0x600 bytes. On SH4, it spans
0x1100 bytes near the end of the user RAM, which is larger; the 6k
left for the user are honored in both cases. Unused memory from the
exposed 6k and non-exposed memory is available through malloc(). */
ram (rw): o = 0x08100200, l = 6k
/* This region represents the first block of user RAM. Linker arranges
sections as if linked to address 0, then gint's runtime determines
the location and relocates references (which are manual) */
rram (rwx): o = 0x00000000, l = 512
/* 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 : {
_gint_drivers = . ;
KEEP(*(SORT_BY_NAME(.gint.drivers.*)));
_gint_drivers_end = . ;
} > 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"
- The SH3-only data section (.gint.data.sh3) */
.data ALIGN(4) : ALIGN(4) {
_ldata = LOADADDR(.data);
_rdata = . ;
_lreloc = . ;
*(.gint.mappedrel);
_sreloc = ABSOLUTE(. - _lreloc);
*(.data .data.*)
*(D)
*(.gint.data.sh3)
. = 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);
/* gint's uninitialized BSS section */
.gint.bss (NOLOAD) : {
/* Since it's uninitialized, the location doesn't matter */
*(.gint.bss .gint.bss.sh3)
. = ALIGN(16);
/* End of user RAM */
_euram = . ;
} > ram :NONE
_sgbss = SIZEOF(.gint.bss);
/* 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);
/*
** Relocated no-MMU RAM sections
*/
. = ORIGIN(rram);
/* Code that must remain permanently mapped (.gint.mapped); relocated
to start of user RAM at startup, accessed through P1 */
.gint.mapped ALIGN(4) : ALIGN(4) {
_lgmapped = LOADADDR(.gint.mapped);
*(.gint.mapped)
. = ALIGN(16);
} > rram AT> rom
_sgmapped = SIZEOF(.gint.mapped);
/*
** Unused sections
*/
/DISCARD/ : {
/* Debug sections (often from libgcc) */
*(.debug_info .debug_abbrev .debug_loc .debug_aranges
.debug_ranges .debug_line .debug_str)
/* Java class registration (why are they even here?!) */
*(.jcr)
/* Asynchronous unwind tables: no C++ exception handling */
*(.eh_frame_hdr)
*(.eh_frame)
/* Comments or anything the compiler might generate */
*(.comment)
}
}