MSP430 irq handlers and vectors with gcc

The linker scripts do not define a single section that covers all interrupt vectors (there's a single section for each vector).

However, it would be possible to change the linker script: remove all the *VECT* memory definitions and the __interrupt_vector* sections, and replace them with a single definition:

MEMORY {
  ...
  ALLVECTORS       : ORIGIN = 0xFF80, LENGTH = 0x0080  /* or whatever your model uses */
}

SECTIONS
{
  __interrupt_vectors    : { KEEP (*(__interrupt_vectors )) } > ALLVECTORS

  ...
}

You also have to change your code so that none of the old sections are used, i.e., don't use __attribute__(interrupt(number)), and change the start-up code not to place a pointer into the reset vector.

This is a minimal program that is executed directly from the reset vector and replaces the normal startup code.

Compile with something like: msp430-gcc -Os -mmcu=msp430... -nostartfiles -o minimal.elf minimal.c

#include <msp430.h>

// defined by the linker script
extern char __stack;

__attribute__((naked))
static void my_program(void)
{
	// no stack yet; cannot have local variables

	_set_SP_register(&__stack);

	WDTCTL = WDTPW | WDTHOLD;

	P1DIR |= BIT0;
	for (;;)
		P1OUT ^= BIT0;
}

__attribute__((section(".resetvec"), used))
static void (*reset_vector)(void) = my_program; 

"Minimal" means that it does not even initialize global variables. This could be done with code like this (some sections are not used on all architectures, or might be empty), after setting SP:

extern char __bssstart, __bsssize;
extern char __high_bssstart, __high_bsssize;
extern char __datastart, __romdatastart, __romdatacopysize;
extern int __upper_data_init;
extern char __high_datastart, __rom_highdatastart, __rom_highdatacopysize;
...

	// initialize .bss
	memset(&__bssstart, 0, (uintptr_t)&__bsssize);
	// initialize .upper.bss
	memset(&__high_bssstart, 0, (uintptr_t)&__high_bsssize);
	// initialize .data
	memmove(&__datastart, &__romdatastart, (uintptr_t)&__romdatacopysize);
	// initialize .upper.data
	if (&__rom_highdatacopysize != 0) {
		if (__upper_data_init == 0) {
			__upper_data_init = 1;
			memmove(&__rom_highdatastart, &__high_datastart, (uintptr_t)&__rom_highdatacopysize);
		} else {
			memmove(&__high_datastart, &__rom_highdatastart, (uintptr_t)&__rom_highdatacopysize);
		}
	}

This still uses the original .resetvec section. To make the interrupt vectors an array, I've put the following into the file vec.ld (this is for the F2013; others have more entries):

MEMORY {
  ALLVECTORS       : ORIGIN = 0xFFE0, LENGTH = 0x0020
}

SECTIONS
{
  __interrupt_vectors    : { KEEP (*(__interrupt_vectors )) } > ALLVECTORS
}

And the vectors are put into that section (this replaces the reset_vector pointer in the first program):

static void __attribute((interrupt)) some_interrupt(void)
{
	...
}

__attribute__((section("__interrupt_vectors"), used))
static void (*vectors[16])(void) = {
	0,               // unused
	0,               // unused
	some_interrupt,  // P1
	0,               // P2
	0,               // USI
	0,               // ADC10/SD16_A
	0,               // unused
	0,               // unused
	0,               // Timer_A2
	0,               // Timer_A2 CCR0
	0,               // WDT+
	0,               // Comp_A+
	0,               // unused
	0,               // unused
	0,               // NMI
	my_program       // reset
};

Compile with something like:
msp430-gcc -Os -mmcu=msp430f2013 -nostartfiles -Xlinker "-Tvec.ld" -o whatever.elf whatever.c