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Commit c22cf384 authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Greg Kroah-Hartman
Browse files

s390/bpf: Fix optimizing out zero-extensions 



commit db7bee653859ef7179be933e7d1384644f795f26 upstream.

Currently the JIT completely removes things like `reg32 += 0`,
however, the BPF_ALU semantics requires the target register to be
zero-extended in such cases.

Fix by optimizing out only the arithmetic operation, but not the
subsequent zero-extension.

Reported-by: default avatarJohan Almbladh <johan.almbladh@anyfinetworks.com>
Fixes: 05462310 ("s390/bpf: Add s390x eBPF JIT compiler backend")
Reviewed-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2a4bf15a

arch/s390/net/bpf_jit_comp.c

+26 −24
Original line number Diff line number Diff line
@@ -591,10 +591,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i 
		EMIT4(0xb9080000, dst_reg, src_reg);

		break;

	case BPF_ALU | BPF_ADD | BPF_K: /* dst = (u32) dst + (u32) imm */

		if (!imm)

			break;

		if (imm != 0) {

			/* alfi %dst,imm */

			EMIT6_IMM(0xc20b0000, dst_reg, imm);

		}

		EMIT_ZERO(dst_reg);

		break;

	case BPF_ALU64 | BPF_ADD | BPF_K: /* dst = dst + imm */
@@ -616,10 +616,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i 
		EMIT4(0xb9090000, dst_reg, src_reg);

		break;

	case BPF_ALU | BPF_SUB | BPF_K: /* dst = (u32) dst - (u32) imm */

		if (!imm)

			break;

		if (imm != 0) {

			/* alfi %dst,-imm */

			EMIT6_IMM(0xc20b0000, dst_reg, -imm);

		}

		EMIT_ZERO(dst_reg);

		break;

	case BPF_ALU64 | BPF_SUB | BPF_K: /* dst = dst - imm */
@@ -646,10 +646,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i 
		EMIT4(0xb90c0000, dst_reg, src_reg);

		break;

	case BPF_ALU | BPF_MUL | BPF_K: /* dst = (u32) dst * (u32) imm */

		if (imm == 1)

			break;

		if (imm != 1) {

			/* msfi %r5,imm */

			EMIT6_IMM(0xc2010000, dst_reg, imm);

		}

		EMIT_ZERO(dst_reg);

		break;

	case BPF_ALU64 | BPF_MUL | BPF_K: /* dst = dst * imm */
@@ -710,6 +710,8 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i 
			if (BPF_OP(insn->code) == BPF_MOD)

				/* lhgi %dst,0 */

				EMIT4_IMM(0xa7090000, dst_reg, 0);

			else

				EMIT_ZERO(dst_reg);

			break;

		}

		/* lhi %w0,0 */
@@ -802,10 +804,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i 
		EMIT4(0xb9820000, dst_reg, src_reg);

		break;

	case BPF_ALU | BPF_XOR | BPF_K: /* dst = (u32) dst ^ (u32) imm */

		if (!imm)

			break;

		if (imm != 0) {

			/* xilf %dst,imm */

			EMIT6_IMM(0xc0070000, dst_reg, imm);

		}

		EMIT_ZERO(dst_reg);

		break;

	case BPF_ALU64 | BPF_XOR | BPF_K: /* dst = dst ^ imm */
@@ -826,10 +828,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i 
		EMIT6_DISP_LH(0xeb000000, 0x000d, dst_reg, dst_reg, src_reg, 0);

		break;

	case BPF_ALU | BPF_LSH | BPF_K: /* dst = (u32) dst << (u32) imm */

		if (imm == 0)

			break;

		if (imm != 0) {

			/* sll %dst,imm(%r0) */

			EMIT4_DISP(0x89000000, dst_reg, REG_0, imm);

		}

		EMIT_ZERO(dst_reg);

		break;

	case BPF_ALU64 | BPF_LSH | BPF_K: /* dst = dst << imm */
@@ -851,10 +853,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, int i 
		EMIT6_DISP_LH(0xeb000000, 0x000c, dst_reg, dst_reg, src_reg, 0);

		break;

	case BPF_ALU | BPF_RSH | BPF_K: /* dst = (u32) dst >> (u32) imm */

		if (imm == 0)

			break;

		if (imm != 0) {

			/* srl %dst,imm(%r0) */

			EMIT4_DISP(0x88000000, dst_reg, REG_0, imm);

		}

		EMIT_ZERO(dst_reg);

		break;

	case BPF_ALU64 | BPF_RSH | BPF_K: /* dst = dst >> imm */