Ejemplo n.º 1
0
/*
 * Function that does the real stuff.
 */
bpf_filter_func
bpf_jit_compile(struct bpf_insn *prog, u_int nins, size_t *size)
{
	bpf_bin_stream stream;
	struct bpf_insn *ins;
	int flags, fret, fpkt, fmem, fjmp, flen;
	u_int i, pass;

	/*
	 * NOTE: Do not modify the name of this variable, as it's used by
	 * the macros to emit code.
	 */
	emit_func emitm;

	flags = bpf_jit_optimize(prog, nins);
	fret = (flags & BPF_JIT_FRET) != 0;
	fpkt = (flags & BPF_JIT_FPKT) != 0;
	fmem = (flags & BPF_JIT_FMEM) != 0;
	fjmp = (flags & BPF_JIT_FJMP) != 0;
	flen = (flags & BPF_JIT_FLEN) != 0;

	if (fret)
		nins = 1;

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

	/* Allocate the reference table for the jumps. */
	if (fjmp) {
#ifdef _KERNEL
		stream.refs = malloc((nins + 1) * sizeof(u_int), M_BPFJIT,
		    M_NOWAIT | M_ZERO);
#else
		stream.refs = calloc(nins + 1, sizeof(u_int));
#endif
		if (stream.refs == NULL)
			return (NULL);
	}

	/*
	 * The first pass will emit the lengths of the instructions
	 * to create the reference table.
	 */
	emitm = emit_length;

	for (pass = 0; pass < 2; pass++) {
		ins = prog;

		/* Create the procedure header. */
		if (fmem) {
			PUSH(RBP);
			MOVrq(RSP, RBP);
			SUBib(BPF_MEMWORDS * sizeof(uint32_t), RSP);
		}
		if (flen)
			MOVrd2(ESI, R9D);
		if (fpkt) {
			MOVrq2(RDI, R8);
			MOVrd(EDX, EDI);
		}

		for (i = 0; i < nins; i++) {
			stream.bpf_pc++;

			switch (ins->code) {
			default:
#ifdef _KERNEL
				return (NULL);
#else
				abort();
#endif

			case BPF_RET|BPF_K:
				MOVid(ins->k, EAX);
				if (fmem)
					LEAVE();
				RET();
				break;

			case BPF_RET|BPF_A:
				if (fmem)
					LEAVE();
				RET();
				break;

			case BPF_LD|BPF_W|BPF_ABS:
				MOVid(ins->k, ESI);
				CMPrd(EDI, ESI);
				JAb(12);
				MOVrd(EDI, ECX);
				SUBrd(ESI, ECX);
				CMPid(sizeof(int32_t), ECX);
				if (fmem) {
					JAEb(4);
					ZEROrd(EAX);
					LEAVE();
				} else {
					JAEb(3);
					ZEROrd(EAX);
				}
				RET();
				MOVrq3(R8, RCX);
				MOVobd(RCX, RSI, EAX);
				BSWAP(EAX);
				break;

			case BPF_LD|BPF_H|BPF_ABS:
				ZEROrd(EAX);
				MOVid(ins->k, ESI);
				CMPrd(EDI, ESI);
				JAb(12);
				MOVrd(EDI, ECX);
				SUBrd(ESI, ECX);
				CMPid(sizeof(int16_t), ECX);
				if (fmem) {
					JAEb(2);
					LEAVE();
				} else
					JAEb(1);
				RET();
				MOVrq3(R8, RCX);
				MOVobw(RCX, RSI, AX);
				SWAP_AX();
				break;

			case BPF_LD|BPF_B|BPF_ABS:
				ZEROrd(EAX);
				MOVid(ins->k, ESI);
				CMPrd(EDI, ESI);
				if (fmem) {
					JBb(2);
					LEAVE();
				} else
					JBb(1);
				RET();
				MOVrq3(R8, RCX);
				MOVobb(RCX, RSI, AL);
				break;

			case BPF_LD|BPF_W|BPF_LEN:
				MOVrd3(R9D, EAX);
				break;

			case BPF_LDX|BPF_W|BPF_LEN:
				MOVrd3(R9D, EDX);
				break;

			case BPF_LD|BPF_W|BPF_IND:
				CMPrd(EDI, EDX);
				JAb(27);
				MOVid(ins->k, ESI);
				MOVrd(EDI, ECX);
				SUBrd(EDX, ECX);
				CMPrd(ESI, ECX);
				JBb(14);
				ADDrd(EDX, ESI);
				MOVrd(EDI, ECX);
				SUBrd(ESI, ECX);
				CMPid(sizeof(int32_t), ECX);
				if (fmem) {
					JAEb(4);
					ZEROrd(EAX);
					LEAVE();
				} else {
					JAEb(3);
					ZEROrd(EAX);
				}
				RET();
				MOVrq3(R8, RCX);
				MOVobd(RCX, RSI, EAX);
				BSWAP(EAX);
				break;

			case BPF_LD|BPF_H|BPF_IND:
				ZEROrd(EAX);
				CMPrd(EDI, EDX);
				JAb(27);
				MOVid(ins->k, ESI);
				MOVrd(EDI, ECX);
				SUBrd(EDX, ECX);
				CMPrd(ESI, ECX);
				JBb(14);
				ADDrd(EDX, ESI);
				MOVrd(EDI, ECX);
				SUBrd(ESI, ECX);
				CMPid(sizeof(int16_t), ECX);
				if (fmem) {
					JAEb(2);
					LEAVE();
				} else
					JAEb(1);
				RET();
				MOVrq3(R8, RCX);
				MOVobw(RCX, RSI, AX);
				SWAP_AX();
				break;

			case BPF_LD|BPF_B|BPF_IND:
				ZEROrd(EAX);
				CMPrd(EDI, EDX);
				JAEb(13);
				MOVid(ins->k, ESI);
				MOVrd(EDI, ECX);
				SUBrd(EDX, ECX);
				CMPrd(ESI, ECX);
				if (fmem) {
					JAb(2);
					LEAVE();
				} else
					JAb(1);
				RET();
				MOVrq3(R8, RCX);
				ADDrd(EDX, ESI);
				MOVobb(RCX, RSI, AL);
				break;

			case BPF_LDX|BPF_MSH|BPF_B:
				MOVid(ins->k, ESI);
				CMPrd(EDI, ESI);
				if (fmem) {
					JBb(4);
					ZEROrd(EAX);
					LEAVE();
				} else {
					JBb(3);
					ZEROrd(EAX);
				}
				RET();
				ZEROrd(EDX);
				MOVrq3(R8, RCX);
				MOVobb(RCX, RSI, DL);
				ANDib(0x0f, DL);
				SHLib(2, EDX);
				break;

			case BPF_LD|BPF_IMM:
				MOVid(ins->k, EAX);
				break;

			case BPF_LDX|BPF_IMM:
				MOVid(ins->k, EDX);
				break;

			case BPF_LD|BPF_MEM:
				MOVid(ins->k * sizeof(uint32_t), ESI);
				MOVobd(RSP, RSI, EAX);
				break;

			case BPF_LDX|BPF_MEM:
				MOVid(ins->k * sizeof(uint32_t), ESI);
				MOVobd(RSP, RSI, EDX);
				break;

			case BPF_ST:
				/*
				 * XXX this command and the following could
				 * be optimized if the previous instruction
				 * was already of this type
				 */
				MOVid(ins->k * sizeof(uint32_t), ESI);
				MOVomd(EAX, RSP, RSI);
				break;

			case BPF_STX:
				MOVid(ins->k * sizeof(uint32_t), ESI);
				MOVomd(EDX, RSP, RSI);
				break;

			case BPF_JMP|BPF_JA:
				JUMP(ins->k);
				break;

			case BPF_JMP|BPF_JGT|BPF_K:
				if (ins->jt == ins->jf) {
					JUMP(ins->jt);
					break;
				}
				CMPid(ins->k, EAX);
				JCC(JA, JBE);
				break;

			case BPF_JMP|BPF_JGE|BPF_K:
				if (ins->jt == ins->jf) {
					JUMP(ins->jt);
					break;
				}
				CMPid(ins->k, EAX);
				JCC(JAE, JB);
				break;

			case BPF_JMP|BPF_JEQ|BPF_K:
				if (ins->jt == ins->jf) {
					JUMP(ins->jt);
					break;
				}
				CMPid(ins->k, EAX);
				JCC(JE, JNE);
				break;

			case BPF_JMP|BPF_JSET|BPF_K:
				if (ins->jt == ins->jf) {
					JUMP(ins->jt);
					break;
				}
				TESTid(ins->k, EAX);
				JCC(JNE, JE);
				break;

			case BPF_JMP|BPF_JGT|BPF_X:
				if (ins->jt == ins->jf) {
					JUMP(ins->jt);
					break;
				}
				CMPrd(EDX, EAX);
				JCC(JA, JBE);
				break;

			case BPF_JMP|BPF_JGE|BPF_X:
				if (ins->jt == ins->jf) {
					JUMP(ins->jt);
					break;
				}
				CMPrd(EDX, EAX);
				JCC(JAE, JB);
				break;

			case BPF_JMP|BPF_JEQ|BPF_X:
				if (ins->jt == ins->jf) {
					JUMP(ins->jt);
					break;
				}
				CMPrd(EDX, EAX);
				JCC(JE, JNE);
				break;

			case BPF_JMP|BPF_JSET|BPF_X:
				if (ins->jt == ins->jf) {
					JUMP(ins->jt);
					break;
				}
				TESTrd(EDX, EAX);
				JCC(JNE, JE);
				break;

			case BPF_ALU|BPF_ADD|BPF_X:
				ADDrd(EDX, EAX);
				break;

			case BPF_ALU|BPF_SUB|BPF_X:
				SUBrd(EDX, EAX);
				break;

			case BPF_ALU|BPF_MUL|BPF_X:
				MOVrd(EDX, ECX);
				MULrd(EDX);
				MOVrd(ECX, EDX);
				break;

			case BPF_ALU|BPF_DIV|BPF_X:
				TESTrd(EDX, EDX);
				if (fmem) {
					JNEb(4);
					ZEROrd(EAX);
					LEAVE();
				} else {
					JNEb(3);
					ZEROrd(EAX);
				}
				RET();
				MOVrd(EDX, ECX);
				ZEROrd(EDX);
				DIVrd(ECX);
				MOVrd(ECX, EDX);
				break;

			case BPF_ALU|BPF_AND|BPF_X:
				ANDrd(EDX, EAX);
				break;

			case BPF_ALU|BPF_OR|BPF_X:
				ORrd(EDX, EAX);
				break;

			case BPF_ALU|BPF_LSH|BPF_X:
				MOVrd(EDX, ECX);
				SHL_CLrb(EAX);
				break;

			case BPF_ALU|BPF_RSH|BPF_X:
				MOVrd(EDX, ECX);
				SHR_CLrb(EAX);
				break;

			case BPF_ALU|BPF_ADD|BPF_K:
				ADD_EAXi(ins->k);
				break;

			case BPF_ALU|BPF_SUB|BPF_K:
				SUB_EAXi(ins->k);
				break;

			case BPF_ALU|BPF_MUL|BPF_K:
				MOVrd(EDX, ECX);
				MOVid(ins->k, EDX);
				MULrd(EDX);
				MOVrd(ECX, EDX);
				break;

			case BPF_ALU|BPF_DIV|BPF_K:
				MOVrd(EDX, ECX);
				ZEROrd(EDX);
				MOVid(ins->k, ESI);
				DIVrd(ESI);
				MOVrd(ECX, EDX);
				break;

			case BPF_ALU|BPF_AND|BPF_K:
				ANDid(ins->k, EAX);
				break;

			case BPF_ALU|BPF_OR|BPF_K:
				ORid(ins->k, EAX);
				break;

			case BPF_ALU|BPF_LSH|BPF_K:
				SHLib((ins->k) & 0xff, EAX);
				break;

			case BPF_ALU|BPF_RSH|BPF_K:
				SHRib((ins->k) & 0xff, EAX);
				break;

			case BPF_ALU|BPF_NEG:
				NEGd(EAX);
				break;

			case BPF_MISC|BPF_TAX:
				MOVrd(EAX, EDX);
				break;

			case BPF_MISC|BPF_TXA:
				MOVrd(EDX, EAX);
				break;
			}
			ins++;
		}

		if (pass > 0)
			continue;

		*size = stream.cur_ip;
#ifdef _KERNEL
		stream.ibuf = malloc(*size, M_BPFJIT, M_NOWAIT);
		if (stream.ibuf == NULL)
			break;
#else
		stream.ibuf = mmap(NULL, *size, PROT_READ | PROT_WRITE,
		    MAP_ANON, -1, 0);
		if (stream.ibuf == MAP_FAILED) {
			stream.ibuf = NULL;
			break;
		}
#endif

		/*
		 * Modify the reference table to contain the offsets and
		 * not the lengths of the instructions.
		 */
		if (fjmp)
			for (i = 1; i < nins + 1; i++)
				stream.refs[i] += stream.refs[i - 1];

		/* Reset the counters. */
		stream.cur_ip = 0;
		stream.bpf_pc = 0;

		/* The second pass creates the actual code. */
		emitm = emit_code;
	}

	/*
	 * The reference table is needed only during compilation,
	 * now we can free it.
	 */
	if (fjmp)
#ifdef _KERNEL
		free(stream.refs, M_BPFJIT);
#else
		free(stream.refs);
#endif

#ifndef _KERNEL
	if (stream.ibuf != NULL &&
	    mprotect(stream.ibuf, *size, PROT_READ | PROT_EXEC) != 0) {
		munmap(stream.ibuf, *size);
		stream.ibuf = NULL;
	}
#endif

	return ((bpf_filter_func)stream.ibuf);
}
Ejemplo n.º 2
0
/*
 * Function that does the real stuff
 */
bpf_filter_func
bpf_jit_compile(struct bpf_insn *prog, u_int nins, int *mem)
{
	struct bpf_insn *ins;
	u_int i, pass;
	bpf_bin_stream stream;

	/*
	 * NOTE: do not modify the name of this variable, as it's used by
	 * the macros to emit code.
	 */
	emit_func emitm;

	/* Allocate the reference table for the jumps */
#ifdef _KERNEL
	stream.refs = (u_int *)malloc((nins + 1) * sizeof(u_int),
	    M_BPFJIT, M_NOWAIT);
#else
	stream.refs = (u_int *)malloc((nins + 1) * sizeof(u_int));
#endif
	if (stream.refs == NULL)
		return (NULL);

	/* Reset the reference table */
	for (i = 0; i < nins + 1; i++)
		stream.refs[i] = 0;

	stream.cur_ip = 0;
	stream.bpf_pc = 0;

	/*
	 * the first pass will emit the lengths of the instructions
	 * to create the reference table
	 */
	emitm = emit_length;

	pass = 0;
	for (;;) {
		ins = prog;

		/* create the procedure header */
		MOVrq2(RBX, R8);
		MOVrq(RDI, RBX);
		MOVrd2(ESI, R9D);
		MOVrd(EDX, EDI);

		for (i = 0; i < nins; i++) {
			stream.bpf_pc++;

			switch (ins->code) {
			default:
#ifdef _KERNEL
				return (NULL);
#else
				abort();
#endif

			case BPF_RET|BPF_K:
				MOVid(ins->k, EAX);
				MOVrq3(R8, RBX);
				RET();
				break;

			case BPF_RET|BPF_A:
				MOVrq3(R8, RBX);
				RET();
				break;

			case BPF_LD|BPF_W|BPF_ABS:
				MOVid(ins->k, ESI);
				CMPrd(EDI, ESI);
				JAb(12);
				MOVrd(EDI, ECX);
				SUBrd(ESI, ECX);
				CMPid(sizeof(int32_t), ECX);
				JAEb(6);
				ZEROrd(EAX);
				MOVrq3(R8, RBX);
				RET();
				MOVobd(RBX, RSI, EAX);
				BSWAP(EAX);
				break;

			case BPF_LD|BPF_H|BPF_ABS:
				ZEROrd(EAX);
				MOVid(ins->k, ESI);
				CMPrd(EDI, ESI);
				JAb(12);
				MOVrd(EDI, ECX);
				SUBrd(ESI, ECX);
				CMPid(sizeof(int16_t), ECX);
				JAEb(4);
				MOVrq3(R8, RBX);
				RET();
				MOVobw(RBX, RSI, AX);
				SWAP_AX();
				break;

			case BPF_LD|BPF_B|BPF_ABS:
				ZEROrd(EAX);
				MOVid(ins->k, ESI);
				CMPrd(EDI, ESI);
				JBb(4);
				MOVrq3(R8, RBX);
				RET();
				MOVobb(RBX, RSI, AL);
				break;

			case BPF_LD|BPF_W|BPF_LEN:
				MOVrd3(R9D, EAX);
				break;

			case BPF_LDX|BPF_W|BPF_LEN:
				MOVrd3(R9D, EDX);
				break;

			case BPF_LD|BPF_W|BPF_IND:
				CMPrd(EDI, EDX);
				JAb(27);
				MOVid(ins->k, ESI);
				MOVrd(EDI, ECX);
				SUBrd(EDX, ECX);
				CMPrd(ESI, ECX);
				JBb(14);
				ADDrd(EDX, ESI);
				MOVrd(EDI, ECX);
				SUBrd(ESI, ECX);
				CMPid(sizeof(int32_t), ECX);
				JAEb(6);
				ZEROrd(EAX);
				MOVrq3(R8, RBX);
				RET();
				MOVobd(RBX, RSI, EAX);
				BSWAP(EAX);
				break;

			case BPF_LD|BPF_H|BPF_IND:
				ZEROrd(EAX);
				CMPrd(EDI, EDX);
				JAb(27);
				MOVid(ins->k, ESI);
				MOVrd(EDI, ECX);
				SUBrd(EDX, ECX);
				CMPrd(ESI, ECX);
				JBb(14);
				ADDrd(EDX, ESI);
				MOVrd(EDI, ECX);
				SUBrd(ESI, ECX);
				CMPid(sizeof(int16_t), ECX);
				JAEb(4);
				MOVrq3(R8, RBX);
				RET();
				MOVobw(RBX, RSI, AX);
				SWAP_AX();
				break;

			case BPF_LD|BPF_B|BPF_IND:
				ZEROrd(EAX);
				CMPrd(EDI, EDX);
				JAEb(13);
				MOVid(ins->k, ESI);
				MOVrd(EDI, ECX);
				SUBrd(EDX, ECX);
				CMPrd(ESI, ECX);
				JAb(4);
				MOVrq3(R8, RBX);
				RET();
				ADDrd(EDX, ESI);
				MOVobb(RBX, RSI, AL);
				break;

			case BPF_LDX|BPF_MSH|BPF_B:
				MOVid(ins->k, ESI);
				CMPrd(EDI, ESI);
				JBb(6);
				ZEROrd(EAX);
				MOVrq3(R8, RBX);
				RET();
				ZEROrd(EDX);
				MOVobb(RBX, RSI, DL);
				ANDib(0x0f, DL);
				SHLib(2, EDX);
				break;

			case BPF_LD|BPF_IMM:
				MOVid(ins->k, EAX);
				break;

			case BPF_LDX|BPF_IMM:
				MOVid(ins->k, EDX);
				break;

			case BPF_LD|BPF_MEM:
				MOViq((uintptr_t)mem, RCX);
				MOVid(ins->k * 4, ESI);
				MOVobd(RCX, RSI, EAX);
				break;

			case BPF_LDX|BPF_MEM:
				MOViq((uintptr_t)mem, RCX);
				MOVid(ins->k * 4, ESI);
				MOVobd(RCX, RSI, EDX);
				break;

			case BPF_ST:
				/*
				 * XXX this command and the following could
				 * be optimized if the previous instruction
				 * was already of this type
				 */
				MOViq((uintptr_t)mem, RCX);
				MOVid(ins->k * 4, ESI);
				MOVomd(EAX, RCX, RSI);
				break;

			case BPF_STX:
				MOViq((uintptr_t)mem, RCX);
				MOVid(ins->k * 4, ESI);
				MOVomd(EDX, RCX, RSI);
				break;

			case BPF_JMP|BPF_JA:
				JMP(stream.refs[stream.bpf_pc + ins->k] -
				    stream.refs[stream.bpf_pc]);
				break;

			case BPF_JMP|BPF_JGT|BPF_K:
				if (ins->jt == 0 && ins->jf == 0)
					break;
				CMPid(ins->k, EAX);
				JCC(JA, JBE);
				break;

			case BPF_JMP|BPF_JGE|BPF_K:
				if (ins->jt == 0 && ins->jf == 0)
					break;
				CMPid(ins->k, EAX);
				JCC(JAE, JB);
				break;

			case BPF_JMP|BPF_JEQ|BPF_K:
				if (ins->jt == 0 && ins->jf == 0)
					break;
				CMPid(ins->k, EAX);
				JCC(JE, JNE);
				break;

			case BPF_JMP|BPF_JSET|BPF_K:
				if (ins->jt == 0 && ins->jf == 0)
					break;
				TESTid(ins->k, EAX);
				JCC(JNE, JE);
				break;

			case BPF_JMP|BPF_JGT|BPF_X:
				if (ins->jt == 0 && ins->jf == 0)
					break;
				CMPrd(EDX, EAX);
				JCC(JA, JBE);
				break;

			case BPF_JMP|BPF_JGE|BPF_X:
				if (ins->jt == 0 && ins->jf == 0)
					break;
				CMPrd(EDX, EAX);
				JCC(JAE, JB);
				break;

			case BPF_JMP|BPF_JEQ|BPF_X:
				if (ins->jt == 0 && ins->jf == 0)
					break;
				CMPrd(EDX, EAX);
				JCC(JE, JNE);
				break;

			case BPF_JMP|BPF_JSET|BPF_X:
				if (ins->jt == 0 && ins->jf == 0)
					break;
				TESTrd(EDX, EAX);
				JCC(JNE, JE);
				break;

			case BPF_ALU|BPF_ADD|BPF_X:
				ADDrd(EDX, EAX);
				break;

			case BPF_ALU|BPF_SUB|BPF_X:
				SUBrd(EDX, EAX);
				break;

			case BPF_ALU|BPF_MUL|BPF_X:
				MOVrd(EDX, ECX);
				MULrd(EDX);
				MOVrd(ECX, EDX);
				break;

			case BPF_ALU|BPF_DIV|BPF_X:
				TESTrd(EDX, EDX);
				JNEb(6);
				ZEROrd(EAX);
				MOVrq3(R8, RBX);
				RET();
				MOVrd(EDX, ECX);
				ZEROrd(EDX);
				DIVrd(ECX);
				MOVrd(ECX, EDX);
				break;

			case BPF_ALU|BPF_AND|BPF_X:
				ANDrd(EDX, EAX);
				break;

			case BPF_ALU|BPF_OR|BPF_X:
				ORrd(EDX, EAX);
				break;

			case BPF_ALU|BPF_LSH|BPF_X:
				MOVrd(EDX, ECX);
				SHL_CLrb(EAX);
				break;

			case BPF_ALU|BPF_RSH|BPF_X:
				MOVrd(EDX, ECX);
				SHR_CLrb(EAX);
				break;

			case BPF_ALU|BPF_ADD|BPF_K:
				ADD_EAXi(ins->k);
				break;

			case BPF_ALU|BPF_SUB|BPF_K:
				SUB_EAXi(ins->k);
				break;

			case BPF_ALU|BPF_MUL|BPF_K:
				MOVrd(EDX, ECX);
				MOVid(ins->k, EDX);
				MULrd(EDX);
				MOVrd(ECX, EDX);
				break;

			case BPF_ALU|BPF_DIV|BPF_K:
				MOVrd(EDX, ECX);
				ZEROrd(EDX);
				MOVid(ins->k, ESI);
				DIVrd(ESI);
				MOVrd(ECX, EDX);
				break;

			case BPF_ALU|BPF_AND|BPF_K:
				ANDid(ins->k, EAX);
				break;

			case BPF_ALU|BPF_OR|BPF_K:
				ORid(ins->k, EAX);
				break;

			case BPF_ALU|BPF_LSH|BPF_K:
				SHLib((ins->k) & 0xff, EAX);
				break;

			case BPF_ALU|BPF_RSH|BPF_K:
				SHRib((ins->k) & 0xff, EAX);
				break;

			case BPF_ALU|BPF_NEG:
				NEGd(EAX);
				break;

			case BPF_MISC|BPF_TAX:
				MOVrd(EAX, EDX);
				break;

			case BPF_MISC|BPF_TXA:
				MOVrd(EDX, EAX);
				break;
			}
			ins++;
		}

		pass++;
		if (pass == 2)
			break;

#ifdef _KERNEL
		stream.ibuf = (char *)malloc(stream.cur_ip, M_BPFJIT, M_NOWAIT);
		if (stream.ibuf == NULL) {
			free(stream.refs, M_BPFJIT);
			return (NULL);
		}
#else
		stream.ibuf = (char *)malloc(stream.cur_ip);
		if (stream.ibuf == NULL) {
			free(stream.refs);
			return (NULL);
		}
#endif

		/*
		 * modify the reference table to contain the offsets and
		 * not the lengths of the instructions
		 */
		for (i = 1; i < nins + 1; i++)
			stream.refs[i] += stream.refs[i - 1];

		/* Reset the counters */
		stream.cur_ip = 0;
		stream.bpf_pc = 0;

		/* the second pass creates the actual code */
		emitm = emit_code;
	}

	/*
	 * the reference table is needed only during compilation,
	 * now we can free it
	 */
#ifdef _KERNEL
	free(stream.refs, M_BPFJIT);
#else
	free(stream.refs);
#endif

	return ((bpf_filter_func)stream.ibuf);
}