Ответ 1
Вы можете определенно создать модульную систему, если напишите свой собственный компоновщик script и скопируйте то, что было сделано для конструкторов и деструкторов (ctors и dtors). Компилятор script ниже был основан на avr5.x от AVR GCC, но я добавил к нему материал отправки.
Если вы посмотрите на вывод сборки script в сеансе оболочки ниже, вы увидите, что таблица отправки настроена правильно и имеет символы, указывающие на начало и конец. Сеанс оболочки включает все сценарии исходного кода и сборки, которые я использовал для компиляции этого примера.
$ ls
avr5-x-modules.ld build.sh kernel.c kernel.h module_foo.c
$ cat avr5-x-modules.ld
/* Default linker script, for normal executables */
/* Copyright (C) 2014 Free Software Foundation, Inc.
Copying and distribution of this script, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved. */
OUTPUT_FORMAT("elf32-avr","elf32-avr","elf32-avr")
OUTPUT_ARCH(avr:5)
MEMORY
{
text (rx) : ORIGIN = 0, LENGTH = 128K
data (rw!x) : ORIGIN = 0x800060, LENGTH = 0xffa0
eeprom (rw!x) : ORIGIN = 0x810000, LENGTH = 64K
fuse (rw!x) : ORIGIN = 0x820000, LENGTH = 1K
lock (rw!x) : ORIGIN = 0x830000, LENGTH = 1K
signature (rw!x) : ORIGIN = 0x840000, LENGTH = 1K
user_signatures (rw!x) : ORIGIN = 0x850000, LENGTH = 1K
}
SECTIONS
{
/* Read-only sections, merged into text segment: */
.hash : { *(.hash) }
.dynsym : { *(.dynsym) }
.dynstr : { *(.dynstr) }
.gnu.version : { *(.gnu.version) }
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }
.rel.init : { *(.rel.init) }
.rela.init : { *(.rela.init) }
.rel.text :
{
*(.rel.text)
*(.rel.text.*)
*(.rel.gnu.linkonce.t*)
}
.rela.text :
{
*(.rela.text)
*(.rela.text.*)
*(.rela.gnu.linkonce.t*)
}
.rel.fini : { *(.rel.fini) }
.rela.fini : { *(.rela.fini) }
.rel.rodata :
{
*(.rel.rodata)
*(.rel.rodata.*)
*(.rel.gnu.linkonce.r*)
}
.rela.rodata :
{
*(.rela.rodata)
*(.rela.rodata.*)
*(.rela.gnu.linkonce.r*)
}
.rel.data :
{
*(.rel.data)
*(.rel.data.*)
*(.rel.gnu.linkonce.d*)
}
.rela.data :
{
*(.rela.data)
*(.rela.data.*)
*(.rela.gnu.linkonce.d*)
}
.rel.ctors : { *(.rel.ctors) }
.rela.ctors : { *(.rela.ctors) }
.rel.dtors : { *(.rel.dtors) }
.rela.dtors : { *(.rela.dtors) }
.rel.got : { *(.rel.got) }
.rela.got : { *(.rela.got) }
.rel.bss : { *(.rel.bss) }
.rela.bss : { *(.rela.bss) }
.rel.plt : { *(.rel.plt) }
.rela.plt : { *(.rela.plt) }
/* Internal text space or external memory. */
.text :
{
*(.vectors)
KEEP(*(.vectors))
/* For data that needs to reside in the lower 64k of progmem. */
*(.progmem.gcc*)
/* PR 13812: Placing the trampolines here gives a better chance
that they will be in range of the code that uses them. */
. = ALIGN(2);
__trampolines_start = . ;
/* The jump trampolines for the 16-bit limited relocs will reside here. */
*(.trampolines)
*(.trampolines*)
__trampolines_end = . ;
*(.progmem*)
. = ALIGN(2);
/* For future tablejump instruction arrays for 3 byte pc devices.
We don't relax jump/call instructions within these sections. */
*(.jumptables)
*(.jumptables*)
/* For code that needs to reside in the lower 128k progmem. */
*(.lowtext)
*(.lowtext*)
__ctors_start = . ;
*(.ctors)
__ctors_end = . ;
__dtors_start = . ;
*(.dtors)
__dtors_end = . ;
KEEP(SORT(*)(.ctors))
KEEP(SORT(*)(.dtors))
__dispatch_start = . ;
*(.dispatch)
__dispatch_end = . ;
KEEP(SORT(*)(.dispatch))
/* From this point on, we don't bother about wether the insns are
below or above the 16 bits boundary. */
*(.init0) /* Start here after reset. */
KEEP (*(.init0))
*(.init1)
KEEP (*(.init1))
*(.init2) /* Clear __zero_reg__, set up stack pointer. */
KEEP (*(.init2))
*(.init3)
KEEP (*(.init3))
*(.init4) /* Initialize data and BSS. */
KEEP (*(.init4))
*(.init5)
KEEP (*(.init5))
*(.init6) /* C++ constructors. */
KEEP (*(.init6))
*(.init7)
KEEP (*(.init7))
*(.init8)
KEEP (*(.init8))
*(.init9) /* Call main(). */
KEEP (*(.init9))
*(.text)
. = ALIGN(2);
*(.text.*)
. = ALIGN(2);
*(.fini9) /* _exit() starts here. */
KEEP (*(.fini9))
*(.fini8)
KEEP (*(.fini8))
*(.fini7)
KEEP (*(.fini7))
*(.fini6) /* C++ destructors. */
KEEP (*(.fini6))
*(.fini5)
KEEP (*(.fini5))
*(.fini4)
KEEP (*(.fini4))
*(.fini3)
KEEP (*(.fini3))
*(.fini2)
KEEP (*(.fini2))
*(.fini1)
KEEP (*(.fini1))
*(.fini0) /* Infinite loop after program termination. */
KEEP (*(.fini0))
_etext = . ;
} > text
.data :
{
PROVIDE (__data_start = .) ;
*(.data)
*(.data*)
*(.rodata) /* We need to include .rodata here if gcc is used */
*(.rodata*) /* with -fdata-sections. */
*(.gnu.linkonce.d*)
. = ALIGN(2);
_edata = . ;
PROVIDE (__data_end = .) ;
} > data AT> text
.bss ADDR(.data) + SIZEOF (.data) : AT (ADDR (.bss))
{
PROVIDE (__bss_start = .) ;
*(.bss)
*(.bss*)
*(COMMON)
PROVIDE (__bss_end = .) ;
} > data
__data_load_start = LOADADDR(.data);
__data_load_end = __data_load_start + SIZEOF(.data);
/* Global data not cleared after reset. */
.noinit ADDR(.bss) + SIZEOF (.bss) : AT (ADDR (.noinit))
{
PROVIDE (__noinit_start = .) ;
*(.noinit*)
PROVIDE (__noinit_end = .) ;
_end = . ;
PROVIDE (__heap_start = .) ;
} > data
.eeprom :
{
/* See .data above... */
KEEP(*(.eeprom*))
__eeprom_end = . ;
} > eeprom
.fuse :
{
KEEP(*(.fuse))
KEEP(*(.lfuse))
KEEP(*(.hfuse))
KEEP(*(.efuse))
} > fuse
.lock :
{
KEEP(*(.lock*))
} > lock
.signature :
{
KEEP(*(.signature*))
} > signature
.user_signatures :
{
KEEP(*(.user_signatures*))
} > user_signatures
/* Stabs debugging sections. */
.stab 0 : { *(.stab) }
.stabstr 0 : { *(.stabstr) }
.stab.excl 0 : { *(.stab.excl) }
.stab.exclstr 0 : { *(.stab.exclstr) }
.stab.index 0 : { *(.stab.index) }
.stab.indexstr 0 : { *(.stab.indexstr) }
.comment 0 : { *(.comment) }
.note.gnu.build-id : { *(.note.gnu.build-id) }
/* DWARF debug sections.
Symbols in the DWARF debugging sections are relative to the beginning
of the section so we begin them at 0. */
/* DWARF 1 */
.debug 0 : { *(.debug) }
.line 0 : { *(.line) }
/* GNU DWARF 1 extensions */
.debug_srcinfo 0 : { *(.debug_srcinfo) }
.debug_sfnames 0 : { *(.debug_sfnames) }
/* DWARF 1.1 and DWARF 2 */
.debug_aranges 0 : { *(.debug_aranges) }
.debug_pubnames 0 : { *(.debug_pubnames) }
/* DWARF 2 */
.debug_info 0 : { *(.debug_info .gnu.linkonce.wi.*) }
.debug_abbrev 0 : { *(.debug_abbrev) }
.debug_line 0 : { *(.debug_line .debug_line.* .debug_line_end ) }
.debug_frame 0 : { *(.debug_frame) }
.debug_str 0 : { *(.debug_str) }
.debug_loc 0 : { *(.debug_loc) }
.debug_macinfo 0 : { *(.debug_macinfo) }
/* SGI/MIPS DWARF 2 extensions */
.debug_weaknames 0 : { *(.debug_weaknames) }
.debug_funcnames 0 : { *(.debug_funcnames) }
.debug_typenames 0 : { *(.debug_typenames) }
.debug_varnames 0 : { *(.debug_varnames) }
/* DWARF 3 */
.debug_pubtypes 0 : { *(.debug_pubtypes) }
.debug_ranges 0 : { *(.debug_ranges) }
/* DWARF Extension. */
.debug_macro 0 : { *(.debug_macro) }
}
$ cat build.sh
CFLAGS="-std=gnu11 -mmcu=atmega328p"
set -uex
avr-gcc $CFLAGS -c module_foo.c -o module_foo.o
avr-gcc $CFLAGS -c kernel.c -o kernel.o
avr-gcc -T avr5-x-modules.ld kernel.o module_foo.o \
-o program.elf -Wl,-Map=program.map
grep dispatch program.map
$ cat kernel.c
#include "kernel.h"
#include <avr/pgmspace.h>
extern dispatch_item * __dispatch_start;
extern dispatch_item * __dispatch_end;
int main()
{
while (1)
{
for (dispatch_item * item = __dispatch_start; item < __dispatch_end; item++)
{
// TODO: Insert code here for reading the contents of the
// dispatch item from program space and using it. You
// probably have to use pgm_read_word avr avr/pgmspace.h,
// but with GCC 5 you could probably use the new named
// memory space feature to just access the dispatch item
// the same way you would access any other struct:
// https://gcc.gnu.org/onlinedocs/gcc/Named-Address-Spaces.html
}
}
}
$ cat kernel.h
#pragma once
#include <stdint.h>
typedef struct dispatch_item {
uint16_t func_id;
void (*func)(void);
} dispatch_item;
#define DISPATCH_ITEM dispatch_item const __attribute__((section (".dispatch")))
$ cat module_foo.c
#include "kernel.h"
#include <avr/io.h>
// This gets called before main.
void __attribute__((constructor)) foo_init()
{
PINB = 0;
}
// There is a pointer to this in the dispatch table.
void foo()
{
PINB = 1;
}
// DISPATHCH_TABLE_ENTRY(0x12, &foo);
DISPATCH_ITEM foo_dispatch = { 0x12, &foo };
DISPATCH_ITEM foo_dispatch2 = { 0x13, &foo };
$ ./build.sh
++ avr-gcc -std=gnu11 -mmcu=atmega328p -c module_foo.c -o module_foo.o
++ avr-gcc -std=gnu11 -mmcu=atmega328p -c kernel.c -o kernel.o
++ avr-gcc -T avr5-x-modules.ld kernel.o module_foo.o -o program.elf -Wl,-Map=program.map
++ grep dispatch program.map
0x00000002 __dispatch_start = .
*(.dispatch)
.dispatch 0x00000002 0x8 module_foo.o
0x00000002 foo_dispatch
0x00000006 foo_dispatch2
0x0000000a __dispatch_end = .
SORT(*)(.dispatch)