int misaligned_fixup()

in kernel/unaligned.c [198:262]

• 47 lines of code
• 12 McCabe index (conditional complexity)

int misaligned_fixup(unsigned long address, struct pt_regs *regs,
		     struct callee_regs *cregs)
{
	struct disasm_state state;
	char buf[TASK_COMM_LEN];

	/* handle user mode only and only if enabled by sysadmin */
	if (!user_mode(regs) || !unaligned_enabled)
		return 1;

	if (no_unaligned_warning) {
		pr_warn_once("%s(%d) made unaligned access which was emulated"
			     " by kernel assist\n. This can degrade application"
			     " performance significantly\n. To enable further"
			     " logging of such instances, please \n"
			     " echo 0 > /proc/sys/kernel/ignore-unaligned-usertrap\n",
			     get_task_comm(buf, current), task_pid_nr(current));
	} else {
		/* Add rate limiting if it gets down to it */
		pr_warn("%s(%d): unaligned access to/from 0x%lx by PC: 0x%lx\n",
			get_task_comm(buf, current), task_pid_nr(current),
			address, regs->ret);

	}

	disasm_instr(regs->ret, &state, 1, regs, cregs);

	if (state.fault)
		goto fault;

	/* ldb/stb should not have unaligned exception */
	if ((state.zz == 1) || (state.di))
		goto fault;

	if (!state.write)
		fixup_load(&state, regs, cregs);
	else
		fixup_store(&state, regs, cregs);

	if (state.fault)
		goto fault;

	/* clear any remanants of delay slot */
	if (delay_mode(regs)) {
		regs->ret = regs->bta & ~1U;
		regs->status32 &= ~STATUS_DE_MASK;
	} else {
		regs->ret += state.instr_len;

		/* handle zero-overhead-loop */
		if ((regs->ret == regs->lp_end) && (regs->lp_count)) {
			regs->ret = regs->lp_start;
			regs->lp_count--;
		}
	}

	perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, address);
	return 0;

fault:
	pr_err("Alignment trap: fault in fix-up %08lx at [<%08lx>]\n",
		state.words[0], address);

	return 1;
}