arch/arc/kernel/unaligned.c

Source file repositories/reference/linux-study-clean/arch/arc/kernel/unaligned.c

File Facts

System
Linux kernel
Corpus path
arch/arc/kernel/unaligned.c
Extension
.c
Size
6348 bytes
Lines
263
Domain
Architecture Layer
Bucket
arch/arc
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

if (state->zz == 2) {
			set_reg(state->wb_reg, state->src2 + (state->src3 << 1),
				regs, cregs);
		} else if (!state->zz) {
			set_reg(state->wb_reg, state->src2 + (state->src3 << 2),
				regs, cregs);
		} else {
			goto fault;
		}
	}

	/* write fix-up */
	if (!state->zz)
		put32_unaligned_check(state->src1, state->src2 + state->src3);
	else
		put16_unaligned_check(state->src1, state->src2 + state->src3);

	return;

fault:	state->fault = 1;
}

/*
 * Handle an unaligned access
 * Returns 0 if successfully handled, 1 if some error happened
 */
int misaligned_fixup(unsigned long address, struct pt_regs *regs,
		     struct callee_regs *cregs)
{
	struct disasm_state state;

	/* 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",
			     current->comm, 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",
			current->comm, 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 remnants 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;
}

Annotation

Implementation Notes