asmlinkage void handle_unaligned_c()

in kernel/misaligned.c [66:202]

• 108 lines of code
• 17 McCabe index (conditional complexity)

asmlinkage void handle_unaligned_c(struct pt_regs *fp, int cause)
{
	u32 isn, addr, val;
	int in_kernel;
	u8 a, b, d0, d1, d2, d3;
	s16 imm16;
	unsigned int fault;

	/* back up one instruction */
	fp->ea -= 4;

	if (fixup_exception(fp)) {
		return;
	}

	in_kernel = !user_mode(fp);

	isn = *(unsigned long *)(fp->ea);

	fault = 0;

	/* do fixup if in kernel or mode turned on */
	if (in_kernel || (ma_usermode & UM_FIXUP)) {
		/* decompose instruction */
		a = (isn >> 27) & 0x1f;
		b = (isn >> 22) & 0x1f;
		imm16 = (isn >> 6) & 0xffff;
		addr = get_reg_val(fp, a) + imm16;

		/* do fixup to saved registers */
		switch (isn & 0x3f) {
		case INST_LDHU:
			fault |= __get_user(d0, (u8 *)(addr+0));
			fault |= __get_user(d1, (u8 *)(addr+1));
			val = (d1 << 8) | d0;
			put_reg_val(fp, b, val);
			break;
		case INST_STH:
			val = get_reg_val(fp, b);
			d1 = val >> 8;
			d0 = val >> 0;
			if (in_kernel) {
				*(u8 *)(addr+0) = d0;
				*(u8 *)(addr+1) = d1;
			} else {
				fault |= __put_user(d0, (u8 *)(addr+0));
				fault |= __put_user(d1, (u8 *)(addr+1));
			}
			break;
		case INST_LDH:
			fault |= __get_user(d0, (u8 *)(addr+0));
			fault |= __get_user(d1, (u8 *)(addr+1));
			val = (short)((d1 << 8) | d0);
			put_reg_val(fp, b, val);
			break;
		case INST_STW:
			val = get_reg_val(fp, b);
			d3 = val >> 24;
			d2 = val >> 16;
			d1 = val >> 8;
			d0 = val >> 0;
			if (in_kernel) {
				*(u8 *)(addr+0) = d0;
				*(u8 *)(addr+1) = d1;
				*(u8 *)(addr+2) = d2;
				*(u8 *)(addr+3) = d3;
			} else {
				fault |= __put_user(d0, (u8 *)(addr+0));
				fault |= __put_user(d1, (u8 *)(addr+1));
				fault |= __put_user(d2, (u8 *)(addr+2));
				fault |= __put_user(d3, (u8 *)(addr+3));
			}
			break;
		case INST_LDW:
			fault |= __get_user(d0, (u8 *)(addr+0));
			fault |= __get_user(d1, (u8 *)(addr+1));
			fault |= __get_user(d2, (u8 *)(addr+2));
			fault |= __get_user(d3, (u8 *)(addr+3));
			val = (d3 << 24) | (d2 << 16) | (d1 << 8) | d0;
			put_reg_val(fp, b, val);
			break;
		}
	}

	addr = RDCTL(CTL_BADADDR);
	cause >>= 2;

	if (fault) {
		if (in_kernel) {
			pr_err("fault during kernel misaligned fixup @ %#lx; addr 0x%08x; isn=0x%08x\n",
				fp->ea, (unsigned int)addr,
				(unsigned int)isn);
		} else {
			pr_err("fault during user misaligned fixup @ %#lx; isn=%08x addr=0x%08x sp=0x%08lx pid=%d\n",
				fp->ea,
				(unsigned int)isn, addr, fp->sp,
				current->pid);

			_exception(SIGSEGV, fp, SEGV_MAPERR, fp->ea);
			return;
		}
	}

	/*
	 * kernel mode -
	 *  note exception and skip bad instruction (return)
	 */
	if (in_kernel) {
		fp->ea += 4;

		if (ma_usermode & KM_WARN) {
			pr_err("kernel unaligned access @ %#lx; BADADDR 0x%08x; cause=%d, isn=0x%08x\n",
				fp->ea,
				(unsigned int)addr, cause,
				(unsigned int)isn);
			/* show_regs(fp); */
		}

		return;
	}

	/*
	 * user mode -
	 *  possibly warn,
	 *  possibly send SIGBUS signal to process
	 */
	if (ma_usermode & UM_WARN) {
		pr_err("user unaligned access @ %#lx; isn=0x%08lx ea=0x%08lx ra=0x%08lx sp=0x%08lx\n",
			(unsigned long)addr, (unsigned long)isn,
			fp->ea, fp->ra, fp->sp);
	}

	if (ma_usermode & UM_SIGNAL)
		_exception(SIGBUS, fp, BUS_ADRALN, fp->ea);
	else
		fp->ea += 4;	/* else advance */
}