/*
 * Just-In-Time compiler for eBPF filters on MIPS
 *
 * Copyright (c) 2017 Cavium, Inc.
 *
 * Based on code from:
 *
 * Copyright (c) 2014 Imagination Technologies Ltd.
 * Author: Markos Chandras <markos.chandras@imgtec.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; version 2 of the License.
 */

#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/slab.h>
#include <asm/bitops.h>
#include <asm/byteorder.h>
#include <asm/cacheflush.h>
#include <asm/cpu-features.h>
#include <asm/uasm.h>

/* Registers used by JIT */
#define MIPS_R_ZERO	0
#define MIPS_R_AT	1
#define MIPS_R_V0	2	/* BPF_R0 */
#define MIPS_R_V1	3
#define MIPS_R_A0	4	/* BPF_R1 */
#define MIPS_R_A1	5	/* BPF_R2 */
#define MIPS_R_A2	6	/* BPF_R3 */
#define MIPS_R_A3	7	/* BPF_R4 */
#define MIPS_R_A4	8	/* BPF_R5 */
#define MIPS_R_T4	12	/* BPF_AX */
#define MIPS_R_T5	13
#define MIPS_R_T6	14
#define MIPS_R_T7	15
#define MIPS_R_S0	16	/* BPF_R6 */
#define MIPS_R_S1	17	/* BPF_R7 */
#define MIPS_R_S2	18	/* BPF_R8 */
#define MIPS_R_S3	19	/* BPF_R9 */
#define MIPS_R_S4	20	/* BPF_TCC */
#define MIPS_R_S5	21
#define MIPS_R_S6	22
#define MIPS_R_S7	23
#define MIPS_R_T8	24
#define MIPS_R_T9	25
#define MIPS_R_SP	29
#define MIPS_R_RA	31

/* eBPF flags */
#define EBPF_SAVE_S0	BIT(0)
#define EBPF_SAVE_S1	BIT(1)
#define EBPF_SAVE_S2	BIT(2)
#define EBPF_SAVE_S3	BIT(3)
#define EBPF_SAVE_S4	BIT(4)
#define EBPF_SAVE_RA	BIT(5)
#define EBPF_SEEN_FP	BIT(6)
#define EBPF_SEEN_TC	BIT(7)
#define EBPF_TCC_IN_V1	BIT(8)

/*
 * For the mips64 ISA, we need to track the value range or type for
 * each JIT register.  The BPF machine requires zero extended 32-bit
 * values, but the mips64 ISA requires sign extended 32-bit values.
 * At each point in the BPF program we track the state of every
 * register so that we can zero extend or sign extend as the BPF
 * semantics require.
 */
enum reg_val_type {
	/* uninitialized */
	REG_UNKNOWN,
	/* not known to be 32-bit compatible. */
	REG_64BIT,
	/* 32-bit compatible, no truncation needed for 64-bit ops. */
	REG_64BIT_32BIT,
	/* 32-bit compatible, need truncation for 64-bit ops. */
	REG_32BIT,
	/* 32-bit zero extended. */
	REG_32BIT_ZERO_EX,
	/* 32-bit no sign/zero extension needed. */
	REG_32BIT_POS
};

/*
 * high bit of offsets indicates if long branch conversion done at
 * this insn.
 */
#define OFFSETS_B_CONV	BIT(31)

/**
 * struct jit_ctx - JIT context
 * @skf:		The sk_filter
 * @stack_size:		eBPF stack size
 * @tmp_offset:		eBPF $sp offset to 8-byte temporary memory
 * @idx:		Instruction index
 * @flags:		JIT flags
 * @offsets:		Instruction offsets
 * @target:		Memory location for the compiled filter
 * @reg_val_types	Packed enum reg_val_type for each register.
 */
struct jit_ctx {
	const struct bpf_prog *skf;
	int stack_size;
	int tmp_offset;
	u32 idx;
	u32 flags;
	u32 *offsets;
	u32 *target;
	u64 *reg_val_types;
	unsigned int long_b_conversion:1;
	unsigned int gen_b_offsets:1;
	unsigned int use_bbit_insns:1;
};

static void set_reg_val_type(u64 *rvt, int reg, enum reg_val_type type)
{
	*rvt &= ~(7ull << (reg * 3));
	*rvt |= ((u64)type << (reg * 3));
}

static enum reg_val_type get_reg_val_type(const struct jit_ctx *ctx,
					  int index, int reg)
{
	return (ctx->reg_val_types[index] >> (reg * 3)) & 7;
}

/* Simply emit the instruction if the JIT memory space has been allocated */
#define emit_instr(ctx, func, ...)			\
do {							\
	if ((ctx)->target != NULL) {			\
		u32 *p = &(ctx)->target[ctx->idx];	\
		uasm_i_##func(&p, ##__VA_ARGS__);	\
	}						\
	(ctx)->idx++;					\
} while (0)

static unsigned int j_target(struct jit_ctx *ctx, int target_idx)
{
	unsigned long target_va, base_va;
	unsigned int r;

	if (!ctx->target)
		return 0;

	base_va = (unsigned long)ctx->target;
	target_va = base_va + (ctx->offsets[target_idx] & ~OFFSETS_B_CONV);

	if ((base_va & ~0x0ffffffful) != (target_va & ~0x0ffffffful))
		return (unsigned int)-1;
	r = target_va & 0x0ffffffful;
	return r;
}

/* Compute the immediate value for PC-relative branches. */
static u32 b_imm(unsigned int tgt, struct jit_ctx *ctx)
{
	if (!ctx->gen_b_offsets)
		return 0;

	/*
	 * We want a pc-relative branch.  tgt is the instruction offset
	 * we want to jump to.

	 * Branch on MIPS:
	 * I: target_offset <- sign_extend(offset)
	 * I+1: PC += target_offset (delay slot)
	 *
	 * ctx->idx currently points to the branch instruction
	 * but the offset is added to the delay slot so we need
	 * to subtract 4.
	 */
	return (ctx->offsets[tgt] & ~OFFSETS_B_CONV) -
		(ctx->idx * 4) - 4;
}

int bpf_jit_enable __read_mostly;

enum which_ebpf_reg {
	src_reg,
	src_reg_no_fp,
	dst_reg,
	dst_reg_fp_ok
};

/*
 * For eBPF, the register mapping naturally falls out of the
 * requirements of eBPF and the MIPS n64 ABI.  We don't maintain a
 * separate frame pointer, so BPF_REG_10 relative accesses are
 * adjusted to be $sp relative.
 */
int ebpf_to_mips_reg(struct jit_ctx *ctx, const struct bpf_insn *insn,
		     enum which_ebpf_reg w)
{
	int ebpf_reg = (w == src_reg || w == src_reg_no_fp) ?
		insn->src_reg : insn->dst_reg;

	switch (ebpf_reg) {
	case BPF_REG_0:
		return MIPS_R_V0;
	case BPF_REG_1:
		return MIPS_R_A0;
	case BPF_REG_2:
		return MIPS_R_A1;
	case BPF_REG_3:
		return MIPS_R_A2;
	case BPF_REG_4:
		return MIPS_R_A3;
	case BPF_REG_5:
		return MIPS_R_A4;
	case BPF_REG_6:
		ctx->flags |= EBPF_SAVE_S0;
		return MIPS_R_S0;
	case BPF_REG_7:
		ctx->flags |= EBPF_SAVE_S1;
		return MIPS_R_S1;
	case BPF_REG_8:
		ctx->flags |= EBPF_SAVE_S2;
		return MIPS_R_S2;
	case BPF_REG_9:
		ctx->flags |= EBPF_SAVE_S3;
		return MIPS_R_S3;
	case BPF_REG_10:
		if (w == dst_reg || w == src_reg_no_fp)
			goto bad_reg;
		ctx->flags |= EBPF_SEEN_FP;
		/*
		 * Needs special handling, return something that
		 * cannot be clobbered just in case.
		 */
		return MIPS_R_ZERO;
	case BPF_REG_AX:
		return MIPS_R_T4;
	default:
bad_reg:
		WARN(1, "Illegal bpf reg: %d\n", ebpf_reg);
		return -EINVAL;
	}
}
/*
 * eBPF stack frame will be something like:
 *
 *  Entry $sp ------>   +--------------------------------+
 *                      |   $ra  (optional)              |
 *                      +--------------------------------+
 *                      |   $s0  (optional)              |
 *                      +--------------------------------+
 *                      |   $s1  (optional)              |
 *                      +--------------------------------+
 *                      |   $s2  (optional)              |
 *                      +--------------------------------+
 *                      |   $s3  (optional)              |
 *                      +--------------------------------+
 *                      |   $s4  (optional)              |
 *                      +--------------------------------+
 *                      |   tmp-storage  (if $ra saved)  |
 * $sp + tmp_offset --> +--------------------------------+ <--BPF_REG_10
 *                      |   BPF_REG_10 relative storage  |
 *                      |    MAX_BPF_STACK (optional)    |
 *                      |      .                         |
 *                      |      .                         |
 *                      |      .                         |
 *     $sp -------->    +--------------------------------+
 *
 * If BPF_REG_10 is never referenced, then the MAX_BPF_STACK sized
 * area is not allocated.
 */
static int gen_int_prologue(struct jit_ctx *ctx)
{
	int stack_adjust = 0;
	int store_offset;
	int locals_size;

	if (ctx->flags & EBPF_SAVE_RA)
		/*
		 * If RA we are doing a function call and may need
		 * extra 8-byte tmp area.
		 */
		stack_adjust += 16;
	if (ctx->flags & EBPF_SAVE_S0)
		stack_adjust += 8;
	if (ctx->flags & EBPF_SAVE_S1)
		stack_adjust += 8;
	if (ctx->flags & EBPF_SAVE_S2)
		stack_adjust += 8;
	if (ctx->flags & EBPF_SAVE_S3)
		stack_adjust += 8;
	if (ctx->flags & EBPF_SAVE_S4)
		stack_adjust += 8;

	BUILD_BUG_ON(MAX_BPF_STACK & 7);
	locals_size = (ctx->flags & EBPF_SEEN_FP) ? MAX_BPF_STACK : 0;

	stack_adjust += locals_size;
	ctx->tmp_offset = locals_size;

	ctx->stack_size = stack_adjust;

	/*
	 * First instruction initializes the tail call count (TCC).
	 * On tail call we skip this instruction, and the TCC is
	 * passed in $v1 from the caller.
	 */
	emit_instr(ctx, daddiu, MIPS_R_V1, MIPS_R_ZERO, MAX_TAIL_CALL_CNT);
	if (stack_adjust)
		emit_instr(ctx, daddiu, MIPS_R_SP, MIPS_R_SP, -stack_adjust);
	else
		return 0;

	store_offset = stack_adjust - 8;

	if (ctx->flags & EBPF_SAVE_RA) {
		emit_instr(ctx, sd, MIPS_R_RA, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S0) {
		emit_instr(ctx, sd, MIPS_R_S0, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S1) {
		emit_instr(ctx, sd, MIPS_R_S1, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S2) {
		emit_instr(ctx, sd, MIPS_R_S2, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S3) {
		emit_instr(ctx, sd, MIPS_R_S3, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S4) {
		emit_instr(ctx, sd, MIPS_R_S4, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}

	if ((ctx->flags & EBPF_SEEN_TC) && !(ctx->flags & EBPF_TCC_IN_V1))
		emit_instr(ctx, daddu, MIPS_R_S4, MIPS_R_V1, MIPS_R_ZERO);

	return 0;
}

static int build_int_epilogue(struct jit_ctx *ctx, int dest_reg)
{
	const struct bpf_prog *prog = ctx->skf;
	int stack_adjust = ctx->stack_size;
	int store_offset = stack_adjust - 8;
	int r0 = MIPS_R_V0;

	if (dest_reg == MIPS_R_RA &&
	    get_reg_val_type(ctx, prog->len, BPF_REG_0) == REG_32BIT_ZERO_EX)
		/* Don't let zero extended value escape. */
		emit_instr(ctx, sll, r0, r0, 0);

	if (ctx->flags & EBPF_SAVE_RA) {
		emit_instr(ctx, ld, MIPS_R_RA, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S0) {
		emit_instr(ctx, ld, MIPS_R_S0, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S1) {
		emit_instr(ctx, ld, MIPS_R_S1, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S2) {
		emit_instr(ctx, ld, MIPS_R_S2, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S3) {
		emit_instr(ctx, ld, MIPS_R_S3, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	if (ctx->flags & EBPF_SAVE_S4) {
		emit_instr(ctx, ld, MIPS_R_S4, store_offset, MIPS_R_SP);
		store_offset -= 8;
	}
	emit_instr(ctx, jr, dest_reg);

	if (stack_adjust)
		emit_instr(ctx, daddiu, MIPS_R_SP, MIPS_R_SP, stack_adjust);
	else
		emit_instr(ctx, nop);

	return 0;
}

static void gen_imm_to_reg(const struct bpf_insn *insn, int reg,
			   struct jit_ctx *ctx)
{
	if (insn->imm >= S16_MIN && insn->imm <= S16_MAX) {
		emit_instr(ctx, addiu, reg, MIPS_R_ZERO, insn->imm);
	} else {
		int lower = (s16)(insn->imm & 0xffff);
		int upper = insn->imm - lower;

		emit_instr(ctx, lui, reg, upper >> 16);
		emit_instr(ctx, addiu, reg, reg, lower);
	}

}

static int gen_imm_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
			int idx)
{
	int upper_bound, lower_bound;
	int dst = ebpf_to_mips_reg(ctx, insn, dst_reg);

	if (dst < 0)
		return dst;

	switch (BPF_OP(insn->code)) {
	case BPF_MOV:
	case BPF_ADD:
		upper_bound = S16_MAX;
		lower_bound = S16_MIN;
		break;
	case BPF_SUB:
		upper_bound = -(int)S16_MIN;
		lower_bound = -(int)S16_MAX;
		break;
	case BPF_AND:
	case BPF_OR:
	case BPF_XOR:
		upper_bound = 0xffff;
		lower_bound = 0;
		break;
	case BPF_RSH:
	case BPF_LSH:
	case BPF_ARSH:
		/* Shift amounts are truncated, no need for bounds */
		upper_bound = S32_MAX;
		lower_bound = S32_MIN;
		break;
	default:
		return -EINVAL;
	}

	/*
	 * Immediate move clobbers the register, so no sign/zero
	 * extension needed.
	 */
	if (BPF_CLASS(insn->code) == BPF_ALU64 &&
	    BPF_OP(insn->code) != BPF_MOV &&
	    get_reg_val_type(ctx, idx, insn->dst_reg) == REG_32BIT)
		emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
	/* BPF_ALU | BPF_LSH doesn't need separate sign extension */
	if (BPF_CLASS(insn->code) == BPF_ALU &&
	    BPF_OP(insn->code) != BPF_LSH &&
	    BPF_OP(insn->code) != BPF_MOV &&
	    get_reg_val_type(ctx, idx, insn->dst_reg) != REG_32BIT)
		emit_instr(ctx, sll, dst, dst, 0);

	if (insn->imm >= lower_bound && insn->imm <= upper_bound) {
		/* single insn immediate case */
		switch (BPF_OP(insn->code) | BPF_CLASS(insn->code)) {
		case BPF_ALU64 | BPF_MOV:
			emit_instr(ctx, daddiu, dst, MIPS_R_ZERO, insn->imm);
			break;
		case BPF_ALU64 | BPF_AND:
		case BPF_ALU | BPF_AND:
			emit_instr(ctx, andi, dst, dst, insn->imm);
			break;
		case BPF_ALU64 | BPF_OR:
		case BPF_ALU | BPF_OR:
			emit_instr(ctx, ori, dst, dst, insn->imm);
			break;
		case BPF_ALU64 | BPF_XOR:
		case BPF_ALU | BPF_XOR:
			emit_instr(ctx, xori, dst, dst, insn->imm);
			break;
		case BPF_ALU64 | BPF_ADD:
			emit_instr(ctx, daddiu, dst, dst, insn->imm);
			break;
		case BPF_ALU64 | BPF_SUB:
			emit_instr(ctx, daddiu, dst, dst, -insn->imm);
			break;
		case BPF_ALU64 | BPF_RSH:
			emit_instr(ctx, dsrl_safe, dst, dst, insn->imm & 0x3f);
			break;
		case BPF_ALU | BPF_RSH:
			emit_instr(ctx, srl, dst, dst, insn->imm & 0x1f);
			break;
		case BPF_ALU64 | BPF_LSH:
			emit_instr(ctx, dsll_safe, dst, dst, insn->imm & 0x3f);
			break;
		case BPF_ALU | BPF_LSH:
			emit_instr(ctx, sll, dst, dst, insn->imm & 0x1f);
			break;
		case BPF_ALU64 | BPF_ARSH:
			emit_instr(ctx, dsra_safe, dst, dst, insn->imm & 0x3f);
			break;
		case BPF_ALU | BPF_ARSH:
			emit_instr(ctx, sra, dst, dst, insn->imm & 0x1f);
			break;
		case BPF_ALU | BPF_MOV:
			emit_instr(ctx, addiu, dst, MIPS_R_ZERO, insn->imm);
			break;
		case BPF_ALU | BPF_ADD:
			emit_instr(ctx, addiu, dst, dst, insn->imm);
			break;
		case BPF_ALU | BPF_SUB:
			emit_instr(ctx, addiu, dst, dst, -insn->imm);
			break;
		default:
			return -EINVAL;
		}
	} else {
		/* multi insn immediate case */
		if (BPF_OP(insn->code) == BPF_MOV) {
			gen_imm_to_reg(insn, dst, ctx);
		} else {
			gen_imm_to_reg(insn, MIPS_R_AT, ctx);
			switch (BPF_OP(insn->code) | BPF_CLASS(insn->code)) {
			case BPF_ALU64 | BPF_AND:
			case BPF_ALU | BPF_AND:
				emit_instr(ctx, and, dst, dst, MIPS_R_AT);
				break;
			case BPF_ALU64 | BPF_OR:
			case BPF_ALU | BPF_OR:
				emit_instr(ctx, or, dst, dst, MIPS_R_AT);
				break;
			case BPF_ALU64 | BPF_XOR:
			case BPF_ALU | BPF_XOR:
				emit_instr(ctx, xor, dst, dst, MIPS_R_AT);
				break;
			case BPF_ALU64 | BPF_ADD:
				emit_instr(ctx, daddu, dst, dst, MIPS_R_AT);
				break;
			case BPF_ALU64 | BPF_SUB:
				emit_instr(ctx, dsubu, dst, dst, MIPS_R_AT);
				break;
			case BPF_ALU | BPF_ADD:
				emit_instr(ctx, addu, dst, dst, MIPS_R_AT);
				break;
			case BPF_ALU | BPF_SUB:
				emit_instr(ctx, subu, dst, dst, MIPS_R_AT);
				break;
			default:
				return -EINVAL;
			}
		}
	}

	return 0;
}

static void * __must_check
ool_skb_header_pointer(const struct sk_buff *skb, int offset,
		       int len, void *buffer)
{
	return skb_header_pointer(skb, offset, len, buffer);
}

static int size_to_len(const struct bpf_insn *insn)
{
	switch (BPF_SIZE(insn->code)) {
	case BPF_B:
		return 1;
	case BPF_H:
		return 2;
	case BPF_W:
		return 4;
	case BPF_DW:
		return 8;
	}
	return 0;
}

static void emit_const_to_reg(struct jit_ctx *ctx, int dst, u64 value)
{
	if (value >= 0xffffffffffff8000ull || value < 0x8000ull) {
		emit_instr(ctx, daddiu, dst, MIPS_R_ZERO, (int)value);
	} else if (value >= 0xffffffff80000000ull ||
		   (value < 0x80000000 && value > 0xffff)) {
		emit_instr(ctx, lui, dst, (s32)(s16)(value >> 16));
		emit_instr(ctx, ori, dst, dst, (unsigned int)(value & 0xffff));
	} else {
		int i;
		bool seen_part = false;
		int needed_shift = 0;

		for (i = 0; i < 4; i++) {
			u64 part = (value >> (16 * (3 - i))) & 0xffff;

			if (seen_part && needed_shift > 0 && (part || i == 3)) {
				emit_instr(ctx, dsll_safe, dst, dst, needed_shift);
				needed_shift = 0;
			}
			if (part) {
				if (i == 0 || (!seen_part && i < 3 && part < 0x8000)) {
					emit_instr(ctx, lui, dst, (s32)(s16)part);
					needed_shift = -16;
				} else {
					emit_instr(ctx, ori, dst,
						   seen_part ? dst : MIPS_R_ZERO,
						   (unsigned int)part);
				}
				seen_part = true;
			}
			if (seen_part)
				needed_shift += 16;
		}
	}
}

static int emit_bpf_tail_call(struct jit_ctx *ctx, int this_idx)
{
	int off, b_off;

	ctx->flags |= EBPF_SEEN_TC;
	/*
	 * if (index >= array->map.max_entries)
	 *     goto out;
	 */
	off = offsetof(struct bpf_array, map.max_entries);
	emit_instr(ctx, lwu, MIPS_R_T5, off, MIPS_R_A1);
	emit_instr(ctx, sltu, MIPS_R_AT, MIPS_R_T5, MIPS_R_A2);
	b_off = b_imm(this_idx + 1, ctx);
	emit_instr(ctx, bne, MIPS_R_AT, MIPS_R_ZERO, b_off);
	/*
	 * if (--TCC < 0)
	 *     goto out;
	 */
	/* Delay slot */
	emit_instr(ctx, daddiu, MIPS_R_T5,
		   (ctx->flags & EBPF_TCC_IN_V1) ? MIPS_R_V1 : MIPS_R_S4, -1);
	b_off = b_imm(this_idx + 1, ctx);
	emit_instr(ctx, bltz, MIPS_R_T5, b_off);
	/*
	 * prog = array->ptrs[index];
	 * if (prog == NULL)
	 *     goto out;
	 */
	/* Delay slot */
	emit_instr(ctx, dsll, MIPS_R_T8, MIPS_R_A2, 3);
	emit_instr(ctx, daddu, MIPS_R_T8, MIPS_R_T8, MIPS_R_A1);
	off = offsetof(struct bpf_array, ptrs);
	emit_instr(ctx, ld, MIPS_R_AT, off, MIPS_R_T8);
	b_off = b_imm(this_idx + 1, ctx);
	emit_instr(ctx, beq, MIPS_R_AT, MIPS_R_ZERO, b_off);
	/* Delay slot */
	emit_instr(ctx, nop);

	/* goto *(prog->bpf_func + 4); */
	off = offsetof(struct bpf_prog, bpf_func);
	emit_instr(ctx, ld, MIPS_R_T9, off, MIPS_R_AT);
	/* All systems are go... propagate TCC */
	emit_instr(ctx, daddu, MIPS_R_V1, MIPS_R_T5, MIPS_R_ZERO);
	/* Skip first instruction (TCC initialization) */
	emit_instr(ctx, daddiu, MIPS_R_T9, MIPS_R_T9, 4);
	return build_int_epilogue(ctx, MIPS_R_T9);
}

static bool is_bad_offset(int b_off)
{
	return b_off > 0x1ffff || b_off < -0x20000;
}

/* Returns the number of insn slots consumed. */
static int build_one_insn(const struct bpf_insn *insn, struct jit_ctx *ctx,
			  int this_idx, int exit_idx)
{
	int src, dst, r, td, ts, mem_off, b_off;
	bool need_swap, did_move, cmp_eq;
	unsigned int target = 0;
	u64 t64;
	s64 t64s;
	int bpf_op = BPF_OP(insn->code);

	switch (insn->code) {
	case BPF_ALU64 | BPF_ADD | BPF_K: /* ALU64_IMM */
	case BPF_ALU64 | BPF_SUB | BPF_K: /* ALU64_IMM */
	case BPF_ALU64 | BPF_OR | BPF_K: /* ALU64_IMM */
	case BPF_ALU64 | BPF_AND | BPF_K: /* ALU64_IMM */
	case BPF_ALU64 | BPF_LSH | BPF_K: /* ALU64_IMM */
	case BPF_ALU64 | BPF_RSH | BPF_K: /* ALU64_IMM */
	case BPF_ALU64 | BPF_XOR | BPF_K: /* ALU64_IMM */
	case BPF_ALU64 | BPF_ARSH | BPF_K: /* ALU64_IMM */
	case BPF_ALU64 | BPF_MOV | BPF_K: /* ALU64_IMM */
	case BPF_ALU | BPF_MOV | BPF_K: /* ALU32_IMM */
	case BPF_ALU | BPF_ADD | BPF_K: /* ALU32_IMM */
	case BPF_ALU | BPF_SUB | BPF_K: /* ALU32_IMM */
	case BPF_ALU | BPF_OR | BPF_K: /* ALU64_IMM */
	case BPF_ALU | BPF_AND | BPF_K: /* ALU64_IMM */
	case BPF_ALU | BPF_LSH | BPF_K: /* ALU64_IMM */
	case BPF_ALU | BPF_RSH | BPF_K: /* ALU64_IMM */
	case BPF_ALU | BPF_XOR | BPF_K: /* ALU64_IMM */
	case BPF_ALU | BPF_ARSH | BPF_K: /* ALU64_IMM */
		r = gen_imm_insn(insn, ctx, this_idx);
		if (r < 0)
			return r;
		break;
	case BPF_ALU64 | BPF_MUL | BPF_K: /* ALU64_IMM */
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (dst < 0)
			return dst;
		if (get_reg_val_type(ctx, this_idx, insn->dst_reg) == REG_32BIT)
			emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
		if (insn->imm == 1) /* Mult by 1 is a nop */
			break;
		gen_imm_to_reg(insn, MIPS_R_AT, ctx);
		emit_instr(ctx, dmultu, MIPS_R_AT, dst);
		emit_instr(ctx, mflo, dst);
		break;
	case BPF_ALU64 | BPF_NEG | BPF_K: /* ALU64_IMM */
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (dst < 0)
			return dst;
		if (get_reg_val_type(ctx, this_idx, insn->dst_reg) == REG_32BIT)
			emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
		emit_instr(ctx, dsubu, dst, MIPS_R_ZERO, dst);
		break;
	case BPF_ALU | BPF_MUL | BPF_K: /* ALU_IMM */
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (dst < 0)
			return dst;
		td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
		if (td == REG_64BIT || td == REG_32BIT_ZERO_EX) {
			/* sign extend */
			emit_instr(ctx, sll, dst, dst, 0);
		}
		if (insn->imm == 1) /* Mult by 1 is a nop */
			break;
		gen_imm_to_reg(insn, MIPS_R_AT, ctx);
		emit_instr(ctx, multu, dst, MIPS_R_AT);
		emit_instr(ctx, mflo, dst);
		break;
	case BPF_ALU | BPF_NEG | BPF_K: /* ALU_IMM */
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (dst < 0)
			return dst;
		td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
		if (td == REG_64BIT || td == REG_32BIT_ZERO_EX) {
			/* sign extend */
			emit_instr(ctx, sll, dst, dst, 0);
		}
		emit_instr(ctx, subu, dst, MIPS_R_ZERO, dst);
		break;
	case BPF_ALU | BPF_DIV | BPF_K: /* ALU_IMM */
	case BPF_ALU | BPF_MOD | BPF_K: /* ALU_IMM */
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (dst < 0)
			return dst;
		if (insn->imm == 0) { /* Div by zero */
			b_off = b_imm(exit_idx, ctx);
			if (is_bad_offset(b_off))
				return -E2BIG;
			emit_instr(ctx, beq, MIPS_R_ZERO, MIPS_R_ZERO, b_off);
			emit_instr(ctx, addu, MIPS_R_V0, MIPS_R_ZERO, MIPS_R_ZERO);
		}
		td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
		if (td == REG_64BIT || td == REG_32BIT_ZERO_EX)
			/* sign extend */
			emit_instr(ctx, sll, dst, dst, 0);
		if (insn->imm == 1) {
			/* div by 1 is a nop, mod by 1 is zero */
			if (bpf_op == BPF_MOD)
				emit_instr(ctx, addu, dst, MIPS_R_ZERO, MIPS_R_ZERO);
			break;
		}
		gen_imm_to_reg(insn, MIPS_R_AT, ctx);
		emit_instr(ctx, divu, dst, MIPS_R_AT);
		if (bpf_op == BPF_DIV)
			emit_instr(ctx, mflo, dst);
		else
			emit_instr(ctx, mfhi, dst);
		break;
	case BPF_ALU64 | BPF_DIV | BPF_K: /* ALU_IMM */
	case BPF_ALU64 | BPF_MOD | BPF_K: /* ALU_IMM */
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (dst < 0)
			return dst;
		if (insn->imm == 0) { /* Div by zero */
			b_off = b_imm(exit_idx, ctx);
			if (is_bad_offset(b_off))
				return -E2BIG;
			emit_instr(ctx, beq, MIPS_R_ZERO, MIPS_R_ZERO, b_off);
			emit_instr(ctx, addu, MIPS_R_V0, MIPS_R_ZERO, MIPS_R_ZERO);
		}
		if (get_reg_val_type(ctx, this_idx, insn->dst_reg) == REG_32BIT)
			emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);

		if (insn->imm == 1) {
			/* div by 1 is a nop, mod by 1 is zero */
			if (bpf_op == BPF_MOD)
				emit_instr(ctx, addu, dst, MIPS_R_ZERO, MIPS_R_ZERO);
			break;
		}
		gen_imm_to_reg(insn, MIPS_R_AT, ctx);
		emit_instr(ctx, ddivu, dst, MIPS_R_AT);
		if (bpf_op == BPF_DIV)
			emit_instr(ctx, mflo, dst);
		else
			emit_instr(ctx, mfhi, dst);
		break;
	case BPF_ALU64 | BPF_MOV | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_ADD | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_SUB | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_XOR | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_OR | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_AND | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_MUL | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_DIV | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_MOD | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_LSH | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_RSH | BPF_X: /* ALU64_REG */
	case BPF_ALU64 | BPF_ARSH | BPF_X: /* ALU64_REG */
		src = ebpf_to_mips_reg(ctx, insn, src_reg);
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (src < 0 || dst < 0)
			return -EINVAL;
		if (get_reg_val_type(ctx, this_idx, insn->dst_reg) == REG_32BIT)
			emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);
		did_move = false;
		if (insn->src_reg == BPF_REG_10) {
			if (bpf_op == BPF_MOV) {
				emit_instr(ctx, daddiu, dst, MIPS_R_SP, MAX_BPF_STACK);
				did_move = true;
			} else {
				emit_instr(ctx, daddiu, MIPS_R_AT, MIPS_R_SP, MAX_BPF_STACK);
				src = MIPS_R_AT;
			}
		} else if (get_reg_val_type(ctx, this_idx, insn->src_reg) == REG_32BIT) {
			int tmp_reg = MIPS_R_AT;

			if (bpf_op == BPF_MOV) {
				tmp_reg = dst;
				did_move = true;
			}
			emit_instr(ctx, daddu, tmp_reg, src, MIPS_R_ZERO);
			emit_instr(ctx, dinsu, tmp_reg, MIPS_R_ZERO, 32, 32);
			src = MIPS_R_AT;
		}
		switch (bpf_op) {
		case BPF_MOV:
			if (!did_move)
				emit_instr(ctx, daddu, dst, src, MIPS_R_ZERO);
			break;
		case BPF_ADD:
			emit_instr(ctx, daddu, dst, dst, src);
			break;
		case BPF_SUB:
			emit_instr(ctx, dsubu, dst, dst, src);
			break;
		case BPF_XOR:
			emit_instr(ctx, xor, dst, dst, src);
			break;
		case BPF_OR:
			emit_instr(ctx, or, dst, dst, src);
			break;
		case BPF_AND:
			emit_instr(ctx, and, dst, dst, src);
			break;
		case BPF_MUL:
			emit_instr(ctx, dmultu, dst, src);
			emit_instr(ctx, mflo, dst);
			break;
		case BPF_DIV:
		case BPF_MOD:
			b_off = b_imm(exit_idx, ctx);
			if (is_bad_offset(b_off))
				return -E2BIG;
			emit_instr(ctx, beq, src, MIPS_R_ZERO, b_off);
			emit_instr(ctx, movz, MIPS_R_V0, MIPS_R_ZERO, src);
			emit_instr(ctx, ddivu, dst, src);
			if (bpf_op == BPF_DIV)
				emit_instr(ctx, mflo, dst);
			else
				emit_instr(ctx, mfhi, dst);
			break;
		case BPF_LSH:
			emit_instr(ctx, dsllv, dst, dst, src);
			break;
		case BPF_RSH:
			emit_instr(ctx, dsrlv, dst, dst, src);
			break;
		case BPF_ARSH:
			emit_instr(ctx, dsrav, dst, dst, src);
			break;
		default:
			pr_err("ALU64_REG NOT HANDLED\n");
			return -EINVAL;
		}
		break;
	case BPF_ALU | BPF_MOV | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_ADD | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_SUB | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_XOR | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_OR | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_AND | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_MUL | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_DIV | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_MOD | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_LSH | BPF_X: /* ALU_REG */
	case BPF_ALU | BPF_RSH | BPF_X: /* ALU_REG */
		src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (src < 0 || dst < 0)
			return -EINVAL;
		td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
		if (td == REG_64BIT || td == REG_32BIT_ZERO_EX) {
			/* sign extend */
			emit_instr(ctx, sll, dst, dst, 0);
		}
		did_move = false;
		ts = get_reg_val_type(ctx, this_idx, insn->src_reg);
		if (ts == REG_64BIT || ts == REG_32BIT_ZERO_EX) {
			int tmp_reg = MIPS_R_AT;

			if (bpf_op == BPF_MOV) {
				tmp_reg = dst;
				did_move = true;
			}
			/* sign extend */
			emit_instr(ctx, sll, tmp_reg, src, 0);
			src = MIPS_R_AT;
		}
		switch (bpf_op) {
		case BPF_MOV:
			if (!did_move)
				emit_instr(ctx, addu, dst, src, MIPS_R_ZERO);
			break;
		case BPF_ADD:
			emit_instr(ctx, addu, dst, dst, src);
			break;
		case BPF_SUB:
			emit_instr(ctx, subu, dst, dst, src);
			break;
		case BPF_XOR:
			emit_instr(ctx, xor, dst, dst, src);
			break;
		case BPF_OR:
			emit_instr(ctx, or, dst, dst, src);
			break;
		case BPF_AND:
			emit_instr(ctx, and, dst, dst, src);
			break;
		case BPF_MUL:
			emit_instr(ctx, mul, dst, dst, src);
			break;
		case BPF_DIV:
		case BPF_MOD:
			b_off = b_imm(exit_idx, ctx);
			if (is_bad_offset(b_off))
				return -E2BIG;
			emit_instr(ctx, beq, src, MIPS_R_ZERO, b_off);
			emit_instr(ctx, movz, MIPS_R_V0, MIPS_R_ZERO, src);
			emit_instr(ctx, divu, dst, src);
			if (bpf_op == BPF_DIV)
				emit_instr(ctx, mflo, dst);
			else
				emit_instr(ctx, mfhi, dst);
			break;
		case BPF_LSH:
			emit_instr(ctx, sllv, dst, dst, src);
			break;
		case BPF_RSH:
			emit_instr(ctx, srlv, dst, dst, src);
			break;
		default:
			pr_err("ALU_REG NOT HANDLED\n");
			return -EINVAL;
		}
		break;
	case BPF_JMP | BPF_EXIT:
		if (this_idx + 1 < exit_idx) {
			b_off = b_imm(exit_idx, ctx);
			if (is_bad_offset(b_off))
				return -E2BIG;
			emit_instr(ctx, beq, MIPS_R_ZERO, MIPS_R_ZERO, b_off);
			emit_instr(ctx, nop);
		}
		break;
	case BPF_JMP | BPF_JEQ | BPF_K: /* JMP_IMM */
	case BPF_JMP | BPF_JNE | BPF_K: /* JMP_IMM */
		cmp_eq = (bpf_op == BPF_JEQ);
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg_fp_ok);
		if (dst < 0)
			return dst;
		if (insn->imm == 0) {
			src = MIPS_R_ZERO;
		} else {
			gen_imm_to_reg(insn, MIPS_R_AT, ctx);
			src = MIPS_R_AT;
		}
		goto jeq_common;
	case BPF_JMP | BPF_JEQ | BPF_X: /* JMP_REG */
	case BPF_JMP | BPF_JNE | BPF_X:
	case BPF_JMP | BPF_JSLT | BPF_X:
	case BPF_JMP | BPF_JSLE | BPF_X:
	case BPF_JMP | BPF_JSGT | BPF_X:
	case BPF_JMP | BPF_JSGE | BPF_X:
	case BPF_JMP | BPF_JLT | BPF_X:
	case BPF_JMP | BPF_JLE | BPF_X:
	case BPF_JMP | BPF_JGT | BPF_X:
	case BPF_JMP | BPF_JGE | BPF_X:
	case BPF_JMP | BPF_JSET | BPF_X:
		src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (src < 0 || dst < 0)
			return -EINVAL;
		td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
		ts = get_reg_val_type(ctx, this_idx, insn->src_reg);
		if (td == REG_32BIT && ts != REG_32BIT) {
			emit_instr(ctx, sll, MIPS_R_AT, src, 0);
			src = MIPS_R_AT;
		} else if (ts == REG_32BIT && td != REG_32BIT) {
			emit_instr(ctx, sll, MIPS_R_AT, dst, 0);
			dst = MIPS_R_AT;
		}
		if (bpf_op == BPF_JSET) {
			emit_instr(ctx, and, MIPS_R_AT, dst, src);
			cmp_eq = false;
			dst = MIPS_R_AT;
			src = MIPS_R_ZERO;
		} else if (bpf_op == BPF_JSGT || bpf_op == BPF_JSLE) {
			emit_instr(ctx, dsubu, MIPS_R_AT, dst, src);
			if ((insn + 1)->code == (BPF_JMP | BPF_EXIT) && insn->off == 1) {
				b_off = b_imm(exit_idx, ctx);
				if (is_bad_offset(b_off))
					return -E2BIG;
				if (bpf_op == BPF_JSGT)
					emit_instr(ctx, blez, MIPS_R_AT, b_off);
				else
					emit_instr(ctx, bgtz, MIPS_R_AT, b_off);
				emit_instr(ctx, nop);
				return 2; /* We consumed the exit. */
			}
			b_off = b_imm(this_idx + insn->off + 1, ctx);
			if (is_bad_offset(b_off))
				return -E2BIG;
			if (bpf_op == BPF_JSGT)
				emit_instr(ctx, bgtz, MIPS_R_AT, b_off);
			else
				emit_instr(ctx, blez, MIPS_R_AT, b_off);
			emit_instr(ctx, nop);
			break;
		} else if (bpf_op == BPF_JSGE || bpf_op == BPF_JSLT) {
			emit_instr(ctx, slt, MIPS_R_AT, dst, src);
			cmp_eq = bpf_op == BPF_JSGE;
			dst = MIPS_R_AT;
			src = MIPS_R_ZERO;
		} else if (bpf_op == BPF_JGT || bpf_op == BPF_JLE) {
			/* dst or src could be AT */
			emit_instr(ctx, dsubu, MIPS_R_T8, dst, src);
			emit_instr(ctx, sltu, MIPS_R_AT, dst, src);
			/* SP known to be non-zero, movz becomes boolean not */
			emit_instr(ctx, movz, MIPS_R_T9, MIPS_R_SP, MIPS_R_T8);
			emit_instr(ctx, movn, MIPS_R_T9, MIPS_R_ZERO, MIPS_R_T8);
			emit_instr(ctx, or, MIPS_R_AT, MIPS_R_T9, MIPS_R_AT);
			cmp_eq = bpf_op == BPF_JGT;
			dst = MIPS_R_AT;
			src = MIPS_R_ZERO;
		} else if (bpf_op == BPF_JGE || bpf_op == BPF_JLT) {
			emit_instr(ctx, sltu, MIPS_R_AT, dst, src);
			cmp_eq = bpf_op == BPF_JGE;
			dst = MIPS_R_AT;
			src = MIPS_R_ZERO;
		} else { /* JNE/JEQ case */
			cmp_eq = (bpf_op == BPF_JEQ);
		}
jeq_common:
		/*
		 * If the next insn is EXIT and we are jumping arround
		 * only it, invert the sense of the compare and
		 * conditionally jump to the exit.  Poor man's branch
		 * chaining.
		 */
		if ((insn + 1)->code == (BPF_JMP | BPF_EXIT) && insn->off == 1) {
			b_off = b_imm(exit_idx, ctx);
			if (is_bad_offset(b_off)) {
				target = j_target(ctx, exit_idx);
				if (target == (unsigned int)-1)
					return -E2BIG;
				cmp_eq = !cmp_eq;
				b_off = 4 * 3;
				if (!(ctx->offsets[this_idx] & OFFSETS_B_CONV)) {
					ctx->offsets[this_idx] |= OFFSETS_B_CONV;
					ctx->long_b_conversion = 1;
				}
			}

			if (cmp_eq)
				emit_instr(ctx, bne, dst, src, b_off);
			else
				emit_instr(ctx, beq, dst, src, b_off);
			emit_instr(ctx, nop);
			if (ctx->offsets[this_idx] & OFFSETS_B_CONV) {
				emit_instr(ctx, j, target);
				emit_instr(ctx, nop);
			}
			return 2; /* We consumed the exit. */
		}
		b_off = b_imm(this_idx + insn->off + 1, ctx);
		if (is_bad_offset(b_off)) {
			target = j_target(ctx, this_idx + insn->off + 1);
			if (target == (unsigned int)-1)
				return -E2BIG;
			cmp_eq = !cmp_eq;
			b_off = 4 * 3;
			if (!(ctx->offsets[this_idx] & OFFSETS_B_CONV)) {
				ctx->offsets[this_idx] |= OFFSETS_B_CONV;
				ctx->long_b_conversion = 1;
			}
		}

		if (cmp_eq)
			emit_instr(ctx, beq, dst, src, b_off);
		else
			emit_instr(ctx, bne, dst, src, b_off);
		emit_instr(ctx, nop);
		if (ctx->offsets[this_idx] & OFFSETS_B_CONV) {
			emit_instr(ctx, j, target);
			emit_instr(ctx, nop);
		}
		break;
	case BPF_JMP | BPF_JSGT | BPF_K: /* JMP_IMM */
	case BPF_JMP | BPF_JSGE | BPF_K: /* JMP_IMM */
	case BPF_JMP | BPF_JSLT | BPF_K: /* JMP_IMM */
	case BPF_JMP | BPF_JSLE | BPF_K: /* JMP_IMM */
		cmp_eq = (bpf_op == BPF_JSGE);
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg_fp_ok);
		if (dst < 0)
			return dst;

		if (insn->imm == 0) {
			if ((insn + 1)->code == (BPF_JMP | BPF_EXIT) && insn->off == 1) {
				b_off = b_imm(exit_idx, ctx);
				if (is_bad_offset(b_off))
					return -E2BIG;
				switch (bpf_op) {
				case BPF_JSGT:
					emit_instr(ctx, blez, dst, b_off);
					break;
				case BPF_JSGE:
					emit_instr(ctx, bltz, dst, b_off);
					break;
				case BPF_JSLT:
					emit_instr(ctx, bgez, dst, b_off);
					break;
				case BPF_JSLE:
					emit_instr(ctx, bgtz, dst, b_off);
					break;
				}
				emit_instr(ctx, nop);
				return 2; /* We consumed the exit. */
			}
			b_off = b_imm(this_idx + insn->off + 1, ctx);
			if (is_bad_offset(b_off))
				return -E2BIG;
			switch (bpf_op) {
			case BPF_JSGT:
				emit_instr(ctx, bgtz, dst, b_off);
				break;
			case BPF_JSGE:
				emit_instr(ctx, bgez, dst, b_off);
				break;
			case BPF_JSLT:
				emit_instr(ctx, bltz, dst, b_off);
				break;
			case BPF_JSLE:
				emit_instr(ctx, blez, dst, b_off);
				break;
			}
			emit_instr(ctx, nop);
			break;
		}
		/*
		 * only "LT" compare available, so we must use imm + 1
		 * to generate "GT" and imm -1 to generate LE
		 */
		if (bpf_op == BPF_JSGT)
			t64s = insn->imm + 1;
		else if (bpf_op == BPF_JSLE)
			t64s = insn->imm + 1;
		else
			t64s = insn->imm;

		cmp_eq = bpf_op == BPF_JSGT || bpf_op == BPF_JSGE;
		if (t64s >= S16_MIN && t64s <= S16_MAX) {
			emit_instr(ctx, slti, MIPS_R_AT, dst, (int)t64s);
			src = MIPS_R_AT;
			dst = MIPS_R_ZERO;
			goto jeq_common;
		}
		emit_const_to_reg(ctx, MIPS_R_AT, (u64)t64s);
		emit_instr(ctx, slt, MIPS_R_AT, dst, MIPS_R_AT);
		src = MIPS_R_AT;
		dst = MIPS_R_ZERO;
		goto jeq_common;

	case BPF_JMP | BPF_JGT | BPF_K:
	case BPF_JMP | BPF_JGE | BPF_K:
	case BPF_JMP | BPF_JLT | BPF_K:
	case BPF_JMP | BPF_JLE | BPF_K:
		cmp_eq = (bpf_op == BPF_JGE);
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg_fp_ok);
		if (dst < 0)
			return dst;
		/*
		 * only "LT" compare available, so we must use imm + 1
		 * to generate "GT" and imm -1 to generate LE
		 */
		if (bpf_op == BPF_JGT)
			t64s = (u64)(u32)(insn->imm) + 1;
		else if (bpf_op == BPF_JLE)
			t64s = (u64)(u32)(insn->imm) + 1;
		else
			t64s = (u64)(u32)(insn->imm);

		cmp_eq = bpf_op == BPF_JGT || bpf_op == BPF_JGE;

		emit_const_to_reg(ctx, MIPS_R_AT, (u64)t64s);
		emit_instr(ctx, sltu, MIPS_R_AT, dst, MIPS_R_AT);
		src = MIPS_R_AT;
		dst = MIPS_R_ZERO;
		goto jeq_common;

	case BPF_JMP | BPF_JSET | BPF_K: /* JMP_IMM */
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg_fp_ok);
		if (dst < 0)
			return dst;

		if (ctx->use_bbit_insns && hweight32((u32)insn->imm) == 1) {
			if ((insn + 1)->code == (BPF_JMP | BPF_EXIT) && insn->off == 1) {
				b_off = b_imm(exit_idx, ctx);
				if (is_bad_offset(b_off))
					return -E2BIG;
				emit_instr(ctx, bbit0, dst, ffs((u32)insn->imm) - 1, b_off);
				emit_instr(ctx, nop);
				return 2; /* We consumed the exit. */
			}
			b_off = b_imm(this_idx + insn->off + 1, ctx);
			if (is_bad_offset(b_off))
				return -E2BIG;
			emit_instr(ctx, bbit1, dst, ffs((u32)insn->imm) - 1, b_off);
			emit_instr(ctx, nop);
			break;
		}
		t64 = (u32)insn->imm;
		emit_const_to_reg(ctx, MIPS_R_AT, t64);
		emit_instr(ctx, and, MIPS_R_AT, dst, MIPS_R_AT);
		src = MIPS_R_AT;
		dst = MIPS_R_ZERO;
		cmp_eq = false;
		goto jeq_common;

	case BPF_JMP | BPF_JA:
		/*
		 * Prefer relative branch for easier debugging, but
		 * fall back if needed.
		 */
		b_off = b_imm(this_idx + insn->off + 1, ctx);
		if (is_bad_offset(b_off)) {
			target = j_target(ctx, this_idx + insn->off + 1);
			if (target == (unsigned int)-1)
				return -E2BIG;
			emit_instr(ctx, j, target);
		} else {
			emit_instr(ctx, b, b_off);
		}
		emit_instr(ctx, nop);
		break;
	case BPF_LD | BPF_DW | BPF_IMM:
		if (insn->src_reg != 0)
			return -EINVAL;
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (dst < 0)
			return dst;
		t64 = ((u64)(u32)insn->imm) | ((u64)(insn + 1)->imm << 32);
		emit_const_to_reg(ctx, dst, t64);
		return 2; /* Double slot insn */

	case BPF_JMP | BPF_CALL:
		ctx->flags |= EBPF_SAVE_RA;
		t64s = (s64)insn->imm + (s64)__bpf_call_base;
		emit_const_to_reg(ctx, MIPS_R_T9, (u64)t64s);
		emit_instr(ctx, jalr, MIPS_R_RA, MIPS_R_T9);
		/* delay slot */
		emit_instr(ctx, nop);
		break;

	case BPF_JMP | BPF_TAIL_CALL:
		if (emit_bpf_tail_call(ctx, this_idx))
			return -EINVAL;
		break;

	case BPF_LD | BPF_B | BPF_ABS:
	case BPF_LD | BPF_H | BPF_ABS:
	case BPF_LD | BPF_W | BPF_ABS:
	case BPF_LD | BPF_DW | BPF_ABS:
		ctx->flags |= EBPF_SAVE_RA;

		gen_imm_to_reg(insn, MIPS_R_A1, ctx);
		emit_instr(ctx, addiu, MIPS_R_A2, MIPS_R_ZERO, size_to_len(insn));

		if (insn->imm < 0) {
			emit_const_to_reg(ctx, MIPS_R_T9, (u64)bpf_internal_load_pointer_neg_helper);
		} else {
			emit_const_to_reg(ctx, MIPS_R_T9, (u64)ool_skb_header_pointer);
			emit_instr(ctx, daddiu, MIPS_R_A3, MIPS_R_SP, ctx->tmp_offset);
		}
		goto ld_skb_common;

	case BPF_LD | BPF_B | BPF_IND:
	case BPF_LD | BPF_H | BPF_IND:
	case BPF_LD | BPF_W | BPF_IND:
	case BPF_LD | BPF_DW | BPF_IND:
		ctx->flags |= EBPF_SAVE_RA;
		src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
		if (src < 0)
			return src;
		ts = get_reg_val_type(ctx, this_idx, insn->src_reg);
		if (ts == REG_32BIT_ZERO_EX) {
			/* sign extend */
			emit_instr(ctx, sll, MIPS_R_A1, src, 0);
			src = MIPS_R_A1;
		}
		if (insn->imm >= S16_MIN && insn->imm <= S16_MAX) {
			emit_instr(ctx, daddiu, MIPS_R_A1, src, insn->imm);
		} else {
			gen_imm_to_reg(insn, MIPS_R_AT, ctx);
			emit_instr(ctx, daddu, MIPS_R_A1, MIPS_R_AT, src);
		}
		/* truncate to 32-bit int */
		emit_instr(ctx, sll, MIPS_R_A1, MIPS_R_A1, 0);
		emit_instr(ctx, daddiu, MIPS_R_A3, MIPS_R_SP, ctx->tmp_offset);
		emit_instr(ctx, slt, MIPS_R_AT, MIPS_R_A1, MIPS_R_ZERO);

		emit_const_to_reg(ctx, MIPS_R_T8, (u64)bpf_internal_load_pointer_neg_helper);
		emit_const_to_reg(ctx, MIPS_R_T9, (u64)ool_skb_header_pointer);
		emit_instr(ctx, addiu, MIPS_R_A2, MIPS_R_ZERO, size_to_len(insn));
		emit_instr(ctx, movn, MIPS_R_T9, MIPS_R_T8, MIPS_R_AT);

ld_skb_common:
		emit_instr(ctx, jalr, MIPS_R_RA, MIPS_R_T9);
		/* delay slot move */
		emit_instr(ctx, daddu, MIPS_R_A0, MIPS_R_S0, MIPS_R_ZERO);

		/* Check the error value */
		b_off = b_imm(exit_idx, ctx);
		if (is_bad_offset(b_off)) {
			target = j_target(ctx, exit_idx);
			if (target == (unsigned int)-1)
				return -E2BIG;

			if (!(ctx->offsets[this_idx] & OFFSETS_B_CONV)) {
				ctx->offsets[this_idx] |= OFFSETS_B_CONV;
				ctx->long_b_conversion = 1;
			}
			emit_instr(ctx, bne, MIPS_R_V0, MIPS_R_ZERO, 4 * 3);
			emit_instr(ctx, nop);
			emit_instr(ctx, j, target);
			emit_instr(ctx, nop);
		} else {
			emit_instr(ctx, beq, MIPS_R_V0, MIPS_R_ZERO, b_off);
			emit_instr(ctx, nop);
		}

#ifdef __BIG_ENDIAN
		need_swap = false;
#else
		need_swap = true;
#endif
		dst = MIPS_R_V0;
		switch (BPF_SIZE(insn->code)) {
		case BPF_B:
			emit_instr(ctx, lbu, dst, 0, MIPS_R_V0);
			break;
		case BPF_H:
			emit_instr(ctx, lhu, dst, 0, MIPS_R_V0);
			if (need_swap)
				emit_instr(ctx, wsbh, dst, dst);
			break;
		case BPF_W:
			emit_instr(ctx, lw, dst, 0, MIPS_R_V0);
			if (need_swap) {
				emit_instr(ctx, wsbh, dst, dst);
				emit_instr(ctx, rotr, dst, dst, 16);
			}
			break;
		case BPF_DW:
			emit_instr(ctx, ld, dst, 0, MIPS_R_V0);
			if (need_swap) {
				emit_instr(ctx, dsbh, dst, dst);
				emit_instr(ctx, dshd, dst, dst);
			}
			break;
		}

		break;
	case BPF_ALU | BPF_END | BPF_FROM_BE:
	case BPF_ALU | BPF_END | BPF_FROM_LE:
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (dst < 0)
			return dst;
		td = get_reg_val_type(ctx, this_idx, insn->dst_reg);
		if (insn->imm == 64 && td == REG_32BIT)
			emit_instr(ctx, dinsu, dst, MIPS_R_ZERO, 32, 32);

		if (insn->imm != 64 &&
		    (td == REG_64BIT || td == REG_32BIT_ZERO_EX)) {
			/* sign extend */
			emit_instr(ctx, sll, dst, dst, 0);
		}

#ifdef __BIG_ENDIAN
		need_swap = (BPF_SRC(insn->code) == BPF_FROM_LE);
#else
		need_swap = (BPF_SRC(insn->code) == BPF_FROM_BE);
#endif
		if (insn->imm == 16) {
			if (need_swap)
				emit_instr(ctx, wsbh, dst, dst);
			emit_instr(ctx, andi, dst, dst, 0xffff);
		} else if (insn->imm == 32) {
			if (need_swap) {
				emit_instr(ctx, wsbh, dst, dst);
				emit_instr(ctx, rotr, dst, dst, 16);
			}
		} else { /* 64-bit*/
			if (need_swap) {
				emit_instr(ctx, dsbh, dst, dst);
				emit_instr(ctx, dshd, dst, dst);
			}
		}
		break;

	case BPF_ST | BPF_B | BPF_MEM:
	case BPF_ST | BPF_H | BPF_MEM:
	case BPF_ST | BPF_W | BPF_MEM:
	case BPF_ST | BPF_DW | BPF_MEM:
		if (insn->dst_reg == BPF_REG_10) {
			ctx->flags |= EBPF_SEEN_FP;
			dst = MIPS_R_SP;
			mem_off = insn->off + MAX_BPF_STACK;
		} else {
			dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
			if (dst < 0)
				return dst;
			mem_off = insn->off;
		}
		gen_imm_to_reg(insn, MIPS_R_AT, ctx);
		switch (BPF_SIZE(insn->code)) {
		case BPF_B:
			emit_instr(ctx, sb, MIPS_R_AT, mem_off, dst);
			break;
		case BPF_H:
			emit_instr(ctx, sh, MIPS_R_AT, mem_off, dst);
			break;
		case BPF_W:
			emit_instr(ctx, sw, MIPS_R_AT, mem_off, dst);
			break;
		case BPF_DW:
			emit_instr(ctx, sd, MIPS_R_AT, mem_off, dst);
			break;
		}
		break;

	case BPF_LDX | BPF_B | BPF_MEM:
	case BPF_LDX | BPF_H | BPF_MEM:
	case BPF_LDX | BPF_W | BPF_MEM:
	case BPF_LDX | BPF_DW | BPF_MEM:
		if (insn->src_reg == BPF_REG_10) {
			ctx->flags |= EBPF_SEEN_FP;
			src = MIPS_R_SP;
			mem_off = insn->off + MAX_BPF_STACK;
		} else {
			src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
			if (src < 0)
				return src;
			mem_off = insn->off;
		}
		dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
		if (dst < 0)
			return dst;
		switch (BPF_SIZE(insn->code)) {
		case BPF_B:
			emit_instr(ctx, lbu, dst, mem_off, src);
			break;
		case BPF_H:
			emit_instr(ctx, lhu, dst, mem_off, src);
			break;
		case BPF_W:
			emit_instr(ctx, lw, dst, mem_off, src);
			break;
		case BPF_DW:
			emit_instr(ctx, ld, dst, mem_off, src);
			break;
		}
		break;

	case BPF_STX | BPF_B | BPF_MEM:
	case BPF_STX | BPF_H | BPF_MEM:
	case BPF_STX | BPF_W | BPF_MEM:
	case BPF_STX | BPF_DW | BPF_MEM:
	case BPF_STX | BPF_W | BPF_XADD:
	case BPF_STX | BPF_DW | BPF_XADD:
		if (insn->dst_reg == BPF_REG_10) {
			ctx->flags |= EBPF_SEEN_FP;
			dst = MIPS_R_SP;
			mem_off = insn->off + MAX_BPF_STACK;
		} else {
			dst = ebpf_to_mips_reg(ctx, insn, dst_reg);
			if (dst < 0)
				return dst;
			mem_off = insn->off;
		}
		src = ebpf_to_mips_reg(ctx, insn, src_reg_no_fp);
		if (src < 0)
			return dst;
		if (BPF_MODE(insn->code) == BPF_XADD) {
			switch (BPF_SIZE(insn->code)) {
			case BPF_W:
				if (get_reg_val_type(ctx, this_idx, insn->src_reg) == REG_32BIT) {
					emit_instr(ctx, sll, MIPS_R_AT, src, 0);
					src = MIPS_R_AT;
				}
				emit_instr(ctx, ll, MIPS_R_T8, mem_off, dst);
				emit_instr(ctx, addu, MIPS_R_T8, MIPS_R_T8, src);
				emit_instr(ctx, sc, MIPS_R_T8, mem_off, dst);
				/*
				 * On failure back up to LL (-4
				 * instructions of 4 bytes each
				 */
				emit_instr(ctx, beq, MIPS_R_T8, MIPS_R_ZERO, -4 * 4);
				emit_instr(ctx, nop);
				break;
			case BPF_DW:
				if (get_reg_val_type(ctx, this_idx, insn->src_reg) == REG_32BIT) {
					emit_instr(ctx, daddu, MIPS_R_AT, src, MIPS_R_ZERO);
					emit_instr(ctx, dinsu, MIPS_R_AT, MIPS_R_ZERO, 32, 32);
					src = MIPS_R_AT;
				}
				emit_instr(ctx, lld, MIPS_R_T8, mem_off, dst);
				emit_instr(ctx, daddu, MIPS_R_T8, MIPS_R_T8, src);
				emit_instr(ctx, scd, MIPS_R_T8, mem_off, dst);
				emit_instr(ctx, beq, MIPS_R_T8, MIPS_R_ZERO, -4 * 4);
				emit_instr(ctx, nop);
				break;
			}
		} else { /* BPF_MEM */
			switch (BPF_SIZE(insn->code)) {
			case BPF_B:
				emit_instr(ctx, sb, src, mem_off, dst);
				break;
			case BPF_H:
				emit_instr(ctx, sh, src, mem_off, dst);
				break;
			case BPF_W:
				emit_instr(ctx, sw, src, mem_off, dst);
				break;
			case BPF_DW:
				if (get_reg_val_type(ctx, this_idx, insn->src_reg) == REG_32BIT) {
					emit_instr(ctx, daddu, MIPS_R_AT, src, MIPS_R_ZERO);
					emit_instr(ctx, dinsu, MIPS_R_AT, MIPS_R_ZERO, 32, 32);
					src = MIPS_R_AT;
				}
				emit_instr(ctx, sd, src, mem_off, dst);
				break;
			}
		}
		break;

	default:
		pr_err("NOT HANDLED %d - (%02x)\n",
		       this_idx, (unsigned int)insn->code);
		return -EINVAL;
	}
	return 1;
}

#define RVT_VISITED_MASK 0xc000000000000000ull
#define RVT_FALL_THROUGH 0x4000000000000000ull
#define RVT_BRANCH_TAKEN 0x8000000000000000ull
#define RVT_DONE (RVT_FALL_THROUGH | RVT_BRANCH_TAKEN)

static int build_int_body(struct jit_ctx *ctx)
{
	const struct bpf_prog *prog = ctx->skf;
	const struct bpf_insn *insn;
	int i, r;

	for (i = 0; i < prog->len; ) {
		insn = prog->insnsi + i;
		if ((ctx->reg_val_types[i] & RVT_VISITED_MASK) == 0) {
			/* dead instruction, don't emit it. */
			i++;
			continue;
		}

		if (ctx->target == NULL)
			ctx->offsets[i] = (ctx->offsets[i] & OFFSETS_B_CONV) | (ctx->idx * 4);

		r = build_one_insn(insn, ctx, i, prog->len);
		if (r < 0)
			return r;
		i += r;
	}
	/* epilogue offset */
	if (ctx->target == NULL)
		ctx->offsets[i] = ctx->idx * 4;

	/*
	 * All exits have an offset of the epilogue, some offsets may
	 * not have been set due to banch-around threading, so set
	 * them now.
	 */
	if (ctx->target == NULL)
		for (i = 0; i < prog->len; i++) {
			insn = prog->insnsi + i;
			if (insn->code == (BPF_JMP | BPF_EXIT))
				ctx->offsets[i] = ctx->idx * 4;
		}
	return 0;
}

/* return the last idx processed, or negative for error */
static int reg_val_propagate_range(struct jit_ctx *ctx, u64 initial_rvt,
				   int start_idx, bool follow_taken)
{
	const struct bpf_prog *prog = ctx->skf;
	const struct bpf_insn *insn;
	u64 exit_rvt = initial_rvt;
	u64 *rvt = ctx->reg_val_types;
	int idx;
	int reg;

	for (idx = start_idx; idx < prog->len; idx++) {
		rvt[idx] = (rvt[idx] & RVT_VISITED_MASK) | exit_rvt;
		insn = prog->insnsi + idx;
		switch (BPF_CLASS(insn->code)) {
		case BPF_ALU:
			switch (BPF_OP(insn->code)) {
			case BPF_ADD:
			case BPF_SUB:
			case BPF_MUL:
			case BPF_DIV:
			case BPF_OR:
			case BPF_AND:
			case BPF_LSH:
			case BPF_RSH:
			case BPF_NEG:
			case BPF_MOD:
			case BPF_XOR:
				set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
				break;
			case BPF_MOV:
				if (BPF_SRC(insn->code)) {
					set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
				} else {
					/* IMM to REG move*/
					if (insn->imm >= 0)
						set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
					else
						set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
				}
				break;
			case BPF_END:
				if (insn->imm == 64)
					set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
				else if (insn->imm == 32)
					set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
				else /* insn->imm == 16 */
					set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
				break;
			}
			rvt[idx] |= RVT_DONE;
			break;
		case BPF_ALU64:
			switch (BPF_OP(insn->code)) {
			case BPF_MOV:
				if (BPF_SRC(insn->code)) {
					/* REG to REG move*/
					set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
				} else {
					/* IMM to REG move*/
					if (insn->imm >= 0)
						set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
					else
						set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT_32BIT);
				}
				break;
			default:
				set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
			}
			rvt[idx] |= RVT_DONE;
			break;
		case BPF_LD:
			switch (BPF_SIZE(insn->code)) {
			case BPF_DW:
				if (BPF_MODE(insn->code) == BPF_IMM) {
					s64 val;

					val = (s64)((u32)insn->imm | ((u64)(insn + 1)->imm << 32));
					if (val > 0 && val <= S32_MAX)
						set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
					else if (val >= S32_MIN && val <= S32_MAX)
						set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT_32BIT);
					else
						set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
					rvt[idx] |= RVT_DONE;
					idx++;
				} else {
					set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
				}
				break;
			case BPF_B:
			case BPF_H:
				set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
				break;
			case BPF_W:
				if (BPF_MODE(insn->code) == BPF_IMM)
					set_reg_val_type(&exit_rvt, insn->dst_reg,
							 insn->imm >= 0 ? REG_32BIT_POS : REG_32BIT);
				else
					set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
				break;
			}
			rvt[idx] |= RVT_DONE;
			break;
		case BPF_LDX:
			switch (BPF_SIZE(insn->code)) {
			case BPF_DW:
				set_reg_val_type(&exit_rvt, insn->dst_reg, REG_64BIT);
				break;
			case BPF_B:
			case BPF_H:
				set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT_POS);
				break;
			case BPF_W:
				set_reg_val_type(&exit_rvt, insn->dst_reg, REG_32BIT);
				break;
			}
			rvt[idx] |= RVT_DONE;
			break;
		case BPF_JMP:
			switch (BPF_OP(insn->code)) {
			case BPF_EXIT:
				rvt[idx] = RVT_DONE | exit_rvt;
				rvt[prog->len] = exit_rvt;
				return idx;
			case BPF_JA:
				rvt[idx] |= RVT_DONE;
				idx += insn->off;
				break;
			case BPF_JEQ:
			case BPF_JGT:
			case BPF_JGE:
			case BPF_JLT:
			case BPF_JLE:
			case BPF_JSET:
			case BPF_JNE:
			case BPF_JSGT:
			case BPF_JSGE:
			case BPF_JSLT:
			case BPF_JSLE:
				if (follow_taken) {
					rvt[idx] |= RVT_BRANCH_TAKEN;
					idx += insn->off;
					follow_taken = false;
				} else {
					rvt[idx] |= RVT_FALL_THROUGH;
				}
				break;
			case BPF_CALL:
				set_reg_val_type(&exit_rvt, BPF_REG_0, REG_64BIT);
				/* Upon call return, argument registers are clobbered. */
				for (reg = BPF_REG_0; reg <= BPF_REG_5; reg++)
					set_reg_val_type(&exit_rvt, reg, REG_64BIT);

				rvt[idx] |= RVT_DONE;
				break;
			default:
				WARN(1, "Unhandled BPF_JMP case.\n");
				rvt[idx] |= RVT_DONE;
				break;
			}
			break;
		default:
			rvt[idx] |= RVT_DONE;
			break;
		}
	}
	return idx;
}

/*
 * Track the value range (i.e. 32-bit vs. 64-bit) of each register at
 * each eBPF insn.  This allows unneeded sign and zero extension
 * operations to be omitted.
 *
 * Doesn't handle yet confluence of control paths with conflicting
 * ranges, but it is good enough for most sane code.
 */
static int reg_val_propagate(struct jit_ctx *ctx)
{
	const struct bpf_prog *prog = ctx->skf;
	u64 exit_rvt;
	int reg;
	int i;

	/*
	 * 11 registers * 3 bits/reg leaves top bits free for other
	 * uses.  Bit-62..63 used to see if we have visited an insn.
	 */
	exit_rvt = 0;

	/* Upon entry, argument registers are 64-bit. */
	for (reg = BPF_REG_1; reg <= BPF_REG_5; reg++)
		set_reg_val_type(&exit_rvt, reg, REG_64BIT);

	/*
	 * First follow all conditional branches on the fall-through
	 * edge of control flow..
	 */
	reg_val_propagate_range(ctx, exit_rvt, 0, false);
restart_search:
	/*
	 * Then repeatedly find the first conditional branch where
	 * both edges of control flow have not been taken, and follow
	 * the branch taken edge.  We will end up restarting the
	 * search once per conditional branch insn.
	 */
	for (i = 0; i < prog->len; i++) {
		u64 rvt = ctx->reg_val_types[i];

		if ((rvt & RVT_VISITED_MASK) == RVT_DONE ||
		    (rvt & RVT_VISITED_MASK) == 0)
			continue;
		if ((rvt & RVT_VISITED_MASK) == RVT_FALL_THROUGH) {
			reg_val_propagate_range(ctx, rvt & ~RVT_VISITED_MASK, i, true);
		} else { /* RVT_BRANCH_TAKEN */
			WARN(1, "Unexpected RVT_BRANCH_TAKEN case.\n");
			reg_val_propagate_range(ctx, rvt & ~RVT_VISITED_MASK, i, false);
		}
		goto restart_search;
	}
	/*
	 * Eventually all conditional branches have been followed on
	 * both branches and we are done.  Any insn that has not been
	 * visited at this point is dead.
	 */

	return 0;
}

static void jit_fill_hole(void *area, unsigned int size)
{
	u32 *p;

	/* We are guaranteed to have aligned memory. */
	for (p = area; size >= sizeof(u32); size -= sizeof(u32))
		uasm_i_break(&p, BRK_BUG); /* Increments p */
}

struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
	struct bpf_prog *orig_prog = prog;
	bool tmp_blinded = false;
	struct bpf_prog *tmp;
	struct bpf_binary_header *header = NULL;
	struct jit_ctx ctx;
	unsigned int image_size;
	u8 *image_ptr;

	if (!bpf_jit_enable || !cpu_has_mips64r2)
		return prog;

	tmp = bpf_jit_blind_constants(prog);
	/* If blinding was requested and we failed during blinding,
	 * we must fall back to the interpreter.
	 */
	if (IS_ERR(tmp))
		return orig_prog;
	if (tmp != prog) {
		tmp_blinded = true;
		prog = tmp;
	}

	memset(&ctx, 0, sizeof(ctx));

	preempt_disable();
	switch (current_cpu_type()) {
	case CPU_CAVIUM_OCTEON:
	case CPU_CAVIUM_OCTEON_PLUS:
	case CPU_CAVIUM_OCTEON2:
	case CPU_CAVIUM_OCTEON3:
		ctx.use_bbit_insns = 1;
		break;
	default:
		ctx.use_bbit_insns = 0;
	}
	preempt_enable();

	ctx.offsets = kcalloc(prog->len + 1, sizeof(*ctx.offsets), GFP_KERNEL);
	if (ctx.offsets == NULL)
		goto out_err;

	ctx.reg_val_types = kcalloc(prog->len + 1, sizeof(*ctx.reg_val_types), GFP_KERNEL);
	if (ctx.reg_val_types == NULL)
		goto out_err;

	ctx.skf = prog;

	if (reg_val_propagate(&ctx))
		goto out_err;

	/*
	 * First pass discovers used resources and instruction offsets
	 * assuming short branches are used.
	 */
	if (build_int_body(&ctx))
		goto out_err;

	/*
	 * If no calls are made (EBPF_SAVE_RA), then tail call count
	 * in $v1, else we must save in n$s4.
	 */
	if (ctx.flags & EBPF_SEEN_TC) {
		if (ctx.flags & EBPF_SAVE_RA)
			ctx.flags |= EBPF_SAVE_S4;
		else
			ctx.flags |= EBPF_TCC_IN_V1;
	}

	/*
	 * Second pass generates offsets, if any branches are out of
	 * range a jump-around long sequence is generated, and we have
	 * to try again from the beginning to generate the new
	 * offsets.  This is done until no additional conversions are
	 * necessary.
	 */
	do {
		ctx.idx = 0;
		ctx.gen_b_offsets = 1;
		ctx.long_b_conversion = 0;
		if (gen_int_prologue(&ctx))
			goto out_err;
		if (build_int_body(&ctx))
			goto out_err;
		if (build_int_epilogue(&ctx, MIPS_R_RA))
			goto out_err;
	} while (ctx.long_b_conversion);

	image_size = 4 * ctx.idx;

	header = bpf_jit_binary_alloc(image_size, &image_ptr,
				      sizeof(u32), jit_fill_hole);
	if (header == NULL)
		goto out_err;

	ctx.target = (u32 *)image_ptr;

	/* Third pass generates the code */
	ctx.idx = 0;
	if (gen_int_prologue(&ctx))
		goto out_err;
	if (build_int_body(&ctx))
		goto out_err;
	if (build_int_epilogue(&ctx, MIPS_R_RA))
		goto out_err;

	/* Update the icache */
	flush_icache_range((unsigned long)ctx.target,
			   (unsigned long)(ctx.target + ctx.idx * sizeof(u32)));

	if (bpf_jit_enable > 1)
		/* Dump JIT code */
		bpf_jit_dump(prog->len, image_size, 2, ctx.target);

	bpf_jit_binary_lock_ro(header);
	prog->bpf_func = (void *)ctx.target;
	prog->jited = 1;
	prog->jited_len = image_size;
out_normal:
	if (tmp_blinded)
		bpf_jit_prog_release_other(prog, prog == orig_prog ?
					   tmp : orig_prog);
	kfree(ctx.offsets);
	kfree(ctx.reg_val_types);

	return prog;

out_err:
	prog = orig_prog;
	if (header)
		bpf_jit_binary_free(header);
	goto out_normal;
}