The main memory region of the GDB simulator ends at address 0xFFBF,
but the simulator linker scripts do not make full use of this available
memory.
>From 61f3d212741acee583e21ff2c2808775584ecad6 Mon Sep 17 00:00:00 2001
From: Jozef Lawrynowicz <jozef.l@mittosystems.com>
Date: Mon, 3 Aug 2020 19:38:23 +0100
Subject: [PATCH 2/2] MSP430: Increase the amount of main memory available in
sim ld scripts
The main memory region of the GDB simulator ends at address 0xFFBF,
but the simulator linker scripts do not make full use of this available
memory.
__{preinit,init,fini}_array_start symbols must be word aligned in
linker scripts. If the section preceding the __*_array_start symbol
has an odd size, then a NULL byte will be present between the start
symbol and the .*_array section itself, when the section gets
automatically word-aligned.
This results in a branch to an invalid address when the CRT startup
code tries to run through the functions listed in the array sections.
>From de115144d05ecbaa82c9c737cc261715ca4b7d67 Mon Sep 17 00:00:00 2001
From: Jozef Lawrynowicz <jozef.l@mittosystems.com>
Date: Mon, 3 Aug 2020 19:09:46 +0100
Subject: [PATCH 1/2] MSP430: Word align __*_array_start symbols in sim linker
scripts
__{preinit,init,fini}_array_start symbols must be word aligned in
linker scripts. If the section preceding the __*_array_start symbol
has an odd size, then a NULL byte will be present between the start
symbol and the .*_array section itself, when the section gets
automatically word-aligned.
This results in a branch to an invalid address when the CRT startup
code tries to run through the functions listed in the array sections.
The .init/.fini sections are not required for msp430-elf, and add unnecessary
code bloat to the CRT library. These sections are specified as "unused" by
the MSP430 EABI.
.init existed to call __crt0_run_{init,preinit}_array which run through
the functions in .{init,preinit}_array.
__crt0_run_{init,preinit}_array are already dynamically included like the
other crt0 functions, so these can be placed before the call to main,
which ensures they are still called if needed.
With these functions moved, .init has no purpose and can be removed.
.fini existed to call __crt0_run_fini_array.
However, the "__msp430_fini" symbol which marks the start of .fini has
never been used, so no termination routines have ever been run for
msp430. On returning from main(), _exit() is called which just loops
forever.
So there is no current expectation that __crt0_run_fini_array will
get called by the CRT code. Further work is to ensure functions
registered with atexit can be optionally called during program termination,
and then __crt0_run_fini_array can be registered with atexit during
program initialization.
The mechanisms for supporting the "-minrt" option have also been removed.
"-minrt" enabled a "minimum runtime environment" by removing calls to
functions which run global static initializers and constructors. Since
this behaviour is now dynamic, and these functions are only included
when needed, the minrt versions of the CRT object files are no longer
required.
Many of the MSP430 crt functions (e.g. to initialize bss) are linked
"dynamically", based on symbols defined in the program.
The GNU assembler defines the symbols corresponding to the crt
functions by examining the section names in the input file.
If GCC has been configured with --enable-initfini-array, then
.init_array and .fini_array will hold pointers to global
constructors/destructors. These sections can also hold functions that
need to be executed for other purposes.
The attached patch puts the __crt0_run_{preinit,init,fini}_array and
__crt0_run_array functions in their own object files, so they will
only be linked when needed.
Successfully regtested the DejaGNU GCC testsuite using the binutils and
newlib changes together with GCC trunk configured with
--enable-initfini-array.
The MSP430 debuggers support I/O on hardware through CIO, so
we can use a CIO-enabled library as the "nosys" library (in
addition to the libsim library, which talks to our simulator)
* configure.in: Don't build default libnosys for msp430
* configure: Regenerate.
* msp430/Makefile: Rename libcio to libnosys.
* msp430/msp430-sim.ld (.stack): Add an assertion to make sure
that the data area does not overrun the stack. PROVIDE a new
symbol __stack_size to allow the user to set the limit.
* msp430/msp430xl-sim.ld (.stack): Likewise.
* rl78/rl78-sim.ld (.stack): Likewise.
* rl78/rl78.ld (.stack): Likewise.
* rx/rx-sim.ld (.stack): Likewise.
* rx/rx.ld (.stack): Likewise.
* msp430/msp430.ld: Delete.
* msp430/msp430F5438A-l.ld: Delete.
* msp430/msp430F5438A-s.ld: Delete.
* msp430/crt_movedata.S: Delete.
* msp430/Makefile.in (SCRIPTS): Remove msp430.ld.
(CRT_OBJS): Add crt_move_highdata.o.
* msp430/memmodel.h (START_CRT_FUNC): New macro.
(END_CRT_FUNC): New macro.
(WEAK_DEF): New macro.
* msp430/crt0.S: Use new macros.
(move_highdata): New code to initialise the .data section if it is
held in high memory.
* msp430/msp430-sim.ld (.data): Add .either.data.
(.rodata2): Move some read-only data sections here.
(.text): Add .either.text.
(.rodata): Add .either.rodata.
(.bss): Add .either.bss.
* msp430/msp430xl-sim.ld (MEMORY): Add HIROM.
(.rodata2): Move some read-only data sections here.
(.upper.data): New section. Include notes about how to initialise
it.
* msp430/crt0.S (high_bss): Add.
* msp430/msp430-sim.ld: Add error message if .upper sections are
detected.
* msp430/msp430xl-sim.ld (MEMORY): Adjust to better mimic real
life MCUs. Add support for upper and lower sections.
from crt0.S with -DMINRT.
(CRT_OBJS): Expand.
(crt_%.o): New rule pattern. Build multiple objects from crt0.S.
* msp430/crt0.S: Further break out functionality. Support -DMINRT
that omits all init/fini logic.
* msp430/crtn.S: Likewise.
* msp430/msp430-sim.ld: Wildcard all .crt_* sections, sorted.
* msp430/msp430.ld: Likewise.
* msp430/msp430xl-sim.ld: Likewise.
Jozef Lawrynowicz
Martin Young
Jozef Lawrynowicz
Nick Clifton
DJ Delorie