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s390/bpf: Fix optimizing out zero-extensions

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commit db7bee6538 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: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Fixes: 0546231057 ("s390/bpf: Add s390x eBPF JIT compiler backend")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ilya Leoshkevich 2021-09-06 15:04:14 +02:00 committed by Greg Kroah-Hartman
parent f7f1bac898
commit a5fc48000b
1 changed files with 30 additions and 28 deletions
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58
arch/s390/net/bpf_jit_comp.c
View file

@ -569,10 +569,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT4(0xb9080000, dst_reg, src_reg);
break;
case BPF_ALU | BPF_ADD | BPF_K: /* dst = (u32) dst + (u32) imm */
if (!imm)
break;
/* alfi %dst,imm */
EMIT6_IMM(0xc20b0000, dst_reg, imm);
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 */
@ -594,10 +594,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT4(0xb9090000, dst_reg, src_reg);
break;
case BPF_ALU | BPF_SUB | BPF_K: /* dst = (u32) dst - (u32) imm */
if (!imm)
break;
/* alfi %dst,-imm */
EMIT6_IMM(0xc20b0000, dst_reg, -imm);
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 */
@ -619,10 +619,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT4(0xb90c0000, dst_reg, src_reg);
break;
case BPF_ALU | BPF_MUL | BPF_K: /* dst = (u32) dst * (u32) imm */
if (imm == 1)
break;
/* msfi %r5,imm */
EMIT6_IMM(0xc2010000, dst_reg, imm);
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 */
@ -675,6 +675,8 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
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 */
@ -769,10 +771,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT4(0xb9820000, dst_reg, src_reg);
break;
case BPF_ALU | BPF_XOR | BPF_K: /* dst = (u32) dst ^ (u32) imm */
if (!imm)
break;
/* xilf %dst,imm */
EMIT6_IMM(0xc0070000, dst_reg, imm);
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 */
@ -793,10 +795,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
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;
/* sll %dst,imm(%r0) */
EMIT4_DISP(0x89000000, dst_reg, REG_0, imm);
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 */
@ -818,10 +820,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
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;
/* srl %dst,imm(%r0) */
EMIT4_DISP(0x88000000, dst_reg, REG_0, imm);
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 */
@ -843,10 +845,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
EMIT6_DISP_LH(0xeb000000, 0x000a, dst_reg, dst_reg, src_reg, 0);
break;
case BPF_ALU | BPF_ARSH | BPF_K: /* ((s32) dst >> imm */
if (imm == 0)
break;
/* sra %dst,imm(%r0) */
EMIT4_DISP(0x8a000000, dst_reg, REG_0, imm);
if (imm != 0) {
/* sra %dst,imm(%r0) */
EMIT4_DISP(0x8a000000, dst_reg, REG_0, imm);
}
EMIT_ZERO(dst_reg);
break;
case BPF_ALU64 | BPF_ARSH | BPF_K: /* ((s64) dst) >>= imm */