/*
 * Copyright (c) 2020 Stephanos Ioannidis <root@stephanos.io>
 * Copyright (c) 2018 Lexmark International, Inc.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <zephyr/kernel.h>
#include <kernel_internal.h>
#include <zephyr/exc_handle.h>
#include <zephyr/logging/log.h>
LOG_MODULE_DECLARE(os, CONFIG_KERNEL_LOG_LEVEL);

#define FAULT_DUMP_VERBOSE	(CONFIG_FAULT_DUMP == 2)

#if FAULT_DUMP_VERBOSE
static const char *get_dbgdscr_moe_string(uint32_t moe)
{
	switch (moe) {
	case DBGDSCR_MOE_HALT_REQUEST:
		return "Halt Request";
	case DBGDSCR_MOE_BREAKPOINT:
		return "Breakpoint";
	case DBGDSCR_MOE_ASYNC_WATCHPOINT:
		return "Asynchronous Watchpoint";
	case DBGDSCR_MOE_BKPT_INSTRUCTION:
		return "BKPT Instruction";
	case DBGDSCR_MOE_EXT_DEBUG_REQUEST:
		return "External Debug Request";
	case DBGDSCR_MOE_VECTOR_CATCH:
		return "Vector Catch";
	case DBGDSCR_MOE_OS_UNLOCK_CATCH:
		return "OS Unlock Catch";
	case DBGDSCR_MOE_SYNC_WATCHPOINT:
		return "Synchronous Watchpoint";
	default:
		return "Unknown";
	}
}

static void dump_debug_event(void)
{
	/* Read and parse debug mode of entry */
	uint32_t dbgdscr = __get_DBGDSCR();
	uint32_t moe = (dbgdscr & DBGDSCR_MOE_Msk) >> DBGDSCR_MOE_Pos;

	/* Print debug event information */
	LOG_ERR("Debug Event (%s)", get_dbgdscr_moe_string(moe));
}

static uint32_t dump_fault(uint32_t status, uint32_t addr)
{
	uint32_t reason = K_ERR_CPU_EXCEPTION;
	/*
	 * Dump fault status and, if applicable, tatus-specific information.
	 * Note that the fault address is only displayed for the synchronous
	 * faults because it is unpredictable for asynchronous faults.
	 */
	switch (status) {
	case FSR_FS_ALIGNMENT_FAULT:
		reason = K_ERR_ARM_ALIGNMENT_FAULT;
		LOG_ERR("Alignment Fault @ 0x%08x", addr);
		break;
	case FSR_FS_BACKGROUND_FAULT:
		reason = K_ERR_ARM_BACKGROUND_FAULT;
		LOG_ERR("Background Fault @ 0x%08x", addr);
		break;
	case FSR_FS_PERMISSION_FAULT:
		reason = K_ERR_ARM_PERMISSION_FAULT;
		LOG_ERR("Permission Fault @ 0x%08x", addr);
		break;
	case FSR_FS_SYNC_EXTERNAL_ABORT:
		reason = K_ERR_ARM_SYNC_EXTERNAL_ABORT;
		LOG_ERR("Synchronous External Abort @ 0x%08x", addr);
		break;
	case FSR_FS_ASYNC_EXTERNAL_ABORT:
		reason = K_ERR_ARM_ASYNC_EXTERNAL_ABORT;
		LOG_ERR("Asynchronous External Abort");
		break;
	case FSR_FS_SYNC_PARITY_ERROR:
		reason = K_ERR_ARM_SYNC_PARITY_ERROR;
		LOG_ERR("Synchronous Parity/ECC Error @ 0x%08x", addr);
		break;
	case FSR_FS_ASYNC_PARITY_ERROR:
		reason = K_ERR_ARM_ASYNC_PARITY_ERROR;
		LOG_ERR("Asynchronous Parity/ECC Error");
		break;
	case FSR_FS_DEBUG_EVENT:
		reason = K_ERR_ARM_DEBUG_EVENT;
		dump_debug_event();
		break;
	default:
		LOG_ERR("Unknown (%u)", status);
	}
	return reason;
}
#endif

#if defined(CONFIG_FPU_SHARING)
/**
 * @brief FPU undefined instruction fault handler
 *
 * @return Returns true if the FPU is already enabled
 *           implying a true undefined instruction
 *         Returns false if the FPU was disabled
 */
bool z_arm_fault_undef_instruction_fp(void)
{
	/*
	 * Assume this is a floating point instruction that faulted because
	 * the FP unit was disabled.  Enable the FP unit and try again.  If
	 * the FP was already enabled then this was an actual undefined
	 * instruction.
	 */
	if (__get_FPEXC() & FPEXC_EN)
		return true;

	__set_FPEXC(FPEXC_EN);

	if (_kernel.cpus[0].nested > 1) {
		/*
		 * If the nested count is greater than 1, the undefined
		 * instruction exception came from an irq/svc context.  (The
		 * irq/svc handler would have the nested count at 1 and then
		 * the undef exception would increment it to 2).
		 */
		struct __fpu_sf *spill_esf =
			(struct __fpu_sf *)_kernel.cpus[0].fp_ctx;

		if (spill_esf == NULL)
			return false;

		_kernel.cpus[0].fp_ctx = NULL;

		/*
		 * If the nested count is 2 and the current thread has used the
		 * VFP (whether or not it was actually using the VFP before the
		 * current exception) OR if the nested count is greater than 2
		 * and the VFP was enabled on the irq/svc entrance for the
		 * saved exception stack frame, then save the floating point
		 * context because it is about to be overwritten.
		 */
		if (((_kernel.cpus[0].nested == 2)
				&& (_current->base.user_options & K_FP_REGS))
			|| ((_kernel.cpus[0].nested > 2)
				&& (spill_esf->undefined & FPEXC_EN))) {
			/*
			 * Spill VFP registers to specified exception stack
			 * frame
			 */
			spill_esf->undefined |= FPEXC_EN;
			spill_esf->fpscr = __get_FPSCR();
			__asm__ volatile (
				"vstmia %0, {s0-s15};\n"
				: : "r" (&spill_esf->s[0])
				: "memory"
				);
		}
	} else {
		/*
		 * If the nested count is one, a thread was the faulting
		 * context.  Just flag that this thread uses the VFP.  This
		 * means that a thread that uses the VFP does not have to,
		 * but should, set K_FP_REGS on thread creation.
		 */
		_current->base.user_options |= K_FP_REGS;
	}

	return false;
}
#endif

/**
 * @brief Undefined instruction fault handler
 *
 * @return Returns true if the fault is fatal
 */
bool z_arm_fault_undef_instruction(z_arch_esf_t *esf)
{
#if defined(CONFIG_FPU_SHARING)
	/*
	 * This is a true undefined instruction and we will be crashing
	 * so save away the VFP registers.
	 */
	esf->fpu.undefined = __get_FPEXC();
	esf->fpu.fpscr = __get_FPSCR();
	__asm__ volatile (
		"vstmia %0, {s0-s15};\n"
		: : "r" (&esf->fpu.s[0])
		: "memory"
		);
#endif

	/* Print fault information */
	LOG_ERR("***** UNDEFINED INSTRUCTION ABORT *****");

	uint32_t reason = IS_ENABLED(CONFIG_SIMPLIFIED_EXCEPTION_CODES) ?
			  K_ERR_CPU_EXCEPTION :
			  K_ERR_ARM_UNDEFINED_INSTRUCTION;

	/* Invoke kernel fatal exception handler */
	z_arm_fatal_error(reason, esf);

	/* All undefined instructions are treated as fatal for now */
	return true;
}

/**
 * @brief Prefetch abort fault handler
 *
 * @return Returns true if the fault is fatal
 */
bool z_arm_fault_prefetch(z_arch_esf_t *esf)
{
	uint32_t reason = K_ERR_CPU_EXCEPTION;

	/* Read and parse Instruction Fault Status Register (IFSR) */
	uint32_t ifsr = __get_IFSR();
	uint32_t fs = ((ifsr & IFSR_FS1_Msk) >> 6) | (ifsr & IFSR_FS0_Msk);

	/* Read Instruction Fault Address Register (IFAR) */
	uint32_t ifar = __get_IFAR();

	/* Print fault information*/
	LOG_ERR("***** PREFETCH ABORT *****");
	if (FAULT_DUMP_VERBOSE) {
		reason = dump_fault(fs, ifar);
	}

	/* Simplify exception codes if requested */
	if (IS_ENABLED(CONFIG_SIMPLIFIED_EXCEPTION_CODES) && (reason >= K_ERR_ARCH_START)) {
		reason = K_ERR_CPU_EXCEPTION;
	}

	/* Invoke kernel fatal exception handler */
	z_arm_fatal_error(reason, esf);

	/* All prefetch aborts are treated as fatal for now */
	return true;
}

#ifdef CONFIG_USERSPACE
Z_EXC_DECLARE(z_arm_user_string_nlen);

static const struct z_exc_handle exceptions[] = {
	Z_EXC_HANDLE(z_arm_user_string_nlen)
};

/* Perform an assessment whether an MPU fault shall be
 * treated as recoverable.
 *
 * @return true if error is recoverable, otherwise return false.
 */
static bool memory_fault_recoverable(z_arch_esf_t *esf)
{
	for (int i = 0; i < ARRAY_SIZE(exceptions); i++) {
		/* Mask out instruction mode */
		uint32_t start = (uint32_t)exceptions[i].start & ~0x1U;
		uint32_t end = (uint32_t)exceptions[i].end & ~0x1U;

		if (esf->basic.pc >= start && esf->basic.pc < end) {
			esf->basic.pc = (uint32_t)(exceptions[i].fixup);
			return true;
		}
	}

	return false;
}
#endif

/**
 * @brief Data abort fault handler
 *
 * @return Returns true if the fault is fatal
 */
bool z_arm_fault_data(z_arch_esf_t *esf)
{
	uint32_t reason = K_ERR_CPU_EXCEPTION;

	/* Read and parse Data Fault Status Register (DFSR) */
	uint32_t dfsr = __get_DFSR();
	uint32_t fs = ((dfsr & DFSR_FS1_Msk) >> 6) | (dfsr & DFSR_FS0_Msk);

	/* Read Data Fault Address Register (DFAR) */
	uint32_t dfar = __get_DFAR();

#if defined(CONFIG_USERSPACE)
	if ((fs == FSR_FS_BACKGROUND_FAULT)
			|| (fs == FSR_FS_PERMISSION_FAULT)) {
		if (memory_fault_recoverable(esf)) {
			return false;
		}
	}
#endif

	/* Print fault information*/
	LOG_ERR("***** DATA ABORT *****");
	if (FAULT_DUMP_VERBOSE) {
		reason = dump_fault(fs, dfar);
	}

	/* Simplify exception codes if requested */
	if (IS_ENABLED(CONFIG_SIMPLIFIED_EXCEPTION_CODES) && (reason >= K_ERR_ARCH_START)) {
		reason = K_ERR_CPU_EXCEPTION;
	}

	/* Invoke kernel fatal exception handler */
	z_arm_fatal_error(reason, esf);

	/* All data aborts are treated as fatal for now */
	return true;
}

/**
 * @brief Initialisation of fault handling
 */
void z_arm_fault_init(void)
{
	/* Nothing to do for now */
}