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[v2,04/10] powerpc/bpf: Fix BPF_SUB when imm == 0x80000000

Message ID fc4b1276eb10761fd7ce0814c8dd089da2815251.1633464148.git.naveen.n.rao@linux.vnet.ibm.com (mailing list archive)
State Accepted
Headers show
Series powerpc/bpf: Various fixes | expand
Related show

Commit Message

Naveen N. Rao Oct. 5, 2021, 8:25 p.m. UTC 
We aren't handling subtraction involving an immediate value of
0x80000000 properly. Fix the same.

Fixes: 156d0e290e969c ("powerpc/ebpf/jit: Implement JIT compiler for extended BPF")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
Changelog:
- Split up BPF_ADD and BPF_SUB cases per Christophe's comments

 arch/powerpc/net/bpf_jit_comp64.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

Comments

Christophe Leroy Oct. 6, 2021, 4:55 a.m. UTC | #1 
Le 05/10/2021 à 22:25, Naveen N. Rao a écrit :
> We aren't handling subtraction involving an immediate value of
> 0x80000000 properly. Fix the same.
> 
> Fixes: 156d0e290e969c ("powerpc/ebpf/jit: Implement JIT compiler for extended BPF")
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> ---
> Changelog:
> - Split up BPF_ADD and BPF_SUB cases per Christophe's comments
> 
>   arch/powerpc/net/bpf_jit_comp64.c | 27 +++++++++++++++++----------
>   1 file changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
> index d67f6d62e2e1ff..6626e6c17d4ed2 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -330,18 +330,25 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>   			EMIT(PPC_RAW_SUB(dst_reg, dst_reg, src_reg));
>   			goto bpf_alu32_trunc;
>   		case BPF_ALU | BPF_ADD | BPF_K: /* (u32) dst += (u32) imm */
> -		case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */
>   		case BPF_ALU64 | BPF_ADD | BPF_K: /* dst += imm */
> +			if (!imm) {
> +				goto bpf_alu32_trunc;
> +			} else if (imm >= -32768 && imm < 32768) {
> +				EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(imm)));
> +			} else {
> +				PPC_LI32(b2p[TMP_REG_1], imm);
> +				EMIT(PPC_RAW_ADD(dst_reg, dst_reg, b2p[TMP_REG_1]));
> +			}
> +			goto bpf_alu32_trunc;
> +		case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */
>   		case BPF_ALU64 | BPF_SUB | BPF_K: /* dst -= imm */
> -			if (BPF_OP(code) == BPF_SUB)
> -				imm = -imm;
> -			if (imm) {
> -				if (imm >= -32768 && imm < 32768)
> -					EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(imm)));
> -				else {
> -					PPC_LI32(b2p[TMP_REG_1], imm);
> -					EMIT(PPC_RAW_ADD(dst_reg, dst_reg, b2p[TMP_REG_1]));
> -				}
> +			if (!imm) {
> +				goto bpf_alu32_trunc;
> +			} else if (imm > -32768 && imm < 32768) {

Why do you exclude imm == 32768 ?


Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>



> +				EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(-imm)));
> +			} else {
> +				PPC_LI32(b2p[TMP_REG_1], imm);
> +				EMIT(PPC_RAW_SUB(dst_reg, dst_reg, b2p[TMP_REG_1]));
>   			}
>   			goto bpf_alu32_trunc;
>   		case BPF_ALU | BPF_MUL | BPF_X: /* (u32) dst *= (u32) src */
>
Naveen N. Rao Oct. 7, 2021, 8:47 a.m. UTC | #2 
Christophe Leroy wrote:
> 
> 
> Le 05/10/2021 à 22:25, Naveen N. Rao a écrit :
>> We aren't handling subtraction involving an immediate value of
>> 0x80000000 properly. Fix the same.
>> 
>> Fixes: 156d0e290e969c ("powerpc/ebpf/jit: Implement JIT compiler for extended BPF")
>> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
>> ---
>> Changelog:
>> - Split up BPF_ADD and BPF_SUB cases per Christophe's comments
>> 
>>   arch/powerpc/net/bpf_jit_comp64.c | 27 +++++++++++++++++----------
>>   1 file changed, 17 insertions(+), 10 deletions(-)
>> 
>> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
>> index d67f6d62e2e1ff..6626e6c17d4ed2 100644
>> --- a/arch/powerpc/net/bpf_jit_comp64.c
>> +++ b/arch/powerpc/net/bpf_jit_comp64.c
>> @@ -330,18 +330,25 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>>   			EMIT(PPC_RAW_SUB(dst_reg, dst_reg, src_reg));
>>   			goto bpf_alu32_trunc;
>>   		case BPF_ALU | BPF_ADD | BPF_K: /* (u32) dst += (u32) imm */
>> -		case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */
>>   		case BPF_ALU64 | BPF_ADD | BPF_K: /* dst += imm */
>> +			if (!imm) {
>> +				goto bpf_alu32_trunc;
>> +			} else if (imm >= -32768 && imm < 32768) {
>> +				EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(imm)));
>> +			} else {
>> +				PPC_LI32(b2p[TMP_REG_1], imm);
>> +				EMIT(PPC_RAW_ADD(dst_reg, dst_reg, b2p[TMP_REG_1]));
>> +			}
>> +			goto bpf_alu32_trunc;
>> +		case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */
>>   		case BPF_ALU64 | BPF_SUB | BPF_K: /* dst -= imm */
>> -			if (BPF_OP(code) == BPF_SUB)
>> -				imm = -imm;
>> -			if (imm) {
>> -				if (imm >= -32768 && imm < 32768)
>> -					EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(imm)));
>> -				else {
>> -					PPC_LI32(b2p[TMP_REG_1], imm);
>> -					EMIT(PPC_RAW_ADD(dst_reg, dst_reg, b2p[TMP_REG_1]));
>> -				}
>> +			if (!imm) {
>> +				goto bpf_alu32_trunc;
>> +			} else if (imm > -32768 && imm < 32768) {
> 
> Why do you exclude imm == 32768 ?
> 
> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>

Good catch -- that was from an earlier version where this was shared 
across BPF_ADD and BPF_SUB. I missed updating this section before 
posting.

Michael, please consider squashing in the below diff into this patch.

Thanks!
- Naveen


---
diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index f5a804d8c95bc1..0fdc1ff86e4f1c 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -368,7 +368,7 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
 		case BPF_ALU64 | BPF_SUB | BPF_K: /* dst -= imm */
 			if (!imm) {
 				goto bpf_alu32_trunc;
-			} else if (imm > -32768 && imm < 32768) {
+			} else if (imm > -32768 && imm <= 32768) {
 				EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(-imm)));
 			} else {
 				PPC_LI32(b2p[TMP_REG_1], imm);
diff mbox series

Patch

diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index d67f6d62e2e1ff..6626e6c17d4ed2 100644
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -330,18 +330,25 @@  int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
 			EMIT(PPC_RAW_SUB(dst_reg, dst_reg, src_reg));
 			goto bpf_alu32_trunc;
 		case BPF_ALU | BPF_ADD | BPF_K: /* (u32) dst += (u32) imm */
-		case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */
 		case BPF_ALU64 | BPF_ADD | BPF_K: /* dst += imm */
+			if (!imm) {
+				goto bpf_alu32_trunc;
+			} else if (imm >= -32768 && imm < 32768) {
+				EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(imm)));
+			} else {
+				PPC_LI32(b2p[TMP_REG_1], imm);
+				EMIT(PPC_RAW_ADD(dst_reg, dst_reg, b2p[TMP_REG_1]));
+			}
+			goto bpf_alu32_trunc;
+		case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */
 		case BPF_ALU64 | BPF_SUB | BPF_K: /* dst -= imm */
-			if (BPF_OP(code) == BPF_SUB)
-				imm = -imm;
-			if (imm) {
-				if (imm >= -32768 && imm < 32768)
-					EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(imm)));
-				else {
-					PPC_LI32(b2p[TMP_REG_1], imm);
-					EMIT(PPC_RAW_ADD(dst_reg, dst_reg, b2p[TMP_REG_1]));
-				}
+			if (!imm) {
+				goto bpf_alu32_trunc;
+			} else if (imm > -32768 && imm < 32768) {
+				EMIT(PPC_RAW_ADDI(dst_reg, dst_reg, IMM_L(-imm)));
+			} else {
+				PPC_LI32(b2p[TMP_REG_1], imm);
+				EMIT(PPC_RAW_SUB(dst_reg, dst_reg, b2p[TMP_REG_1]));
 			}
 			goto bpf_alu32_trunc;
 		case BPF_ALU | BPF_MUL | BPF_X: /* (u32) dst *= (u32) src */