From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Daniel Borkmann <daniel@iogearbox.net>,
Johan Almbladh <johan.almbladh@anyfinetworks.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>
Cc: bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 6/9] powerpc/bpf: Fix BPF_SUB when imm == 0x80000000
Date: Mon, 04 Oct 2021 23:48:40 +0530 [thread overview]
Message-ID: <1633371242.5ghdfjua6t.naveen@linux.ibm.com> (raw)
In-Reply-To: <43626c62-9a3a-bbba-8cbc-11efb0468b4b@csgroup.eu>
Christophe Leroy wrote:
>
>
> Le 01/10/2021 à 23:14, 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>
>> ---
>> arch/powerpc/net/bpf_jit_comp64.c | 16 ++++++++--------
>> 1 file changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
>> index ffb7a2877a8469..4641a50e82d50d 100644
>> --- a/arch/powerpc/net/bpf_jit_comp64.c
>> +++ b/arch/powerpc/net/bpf_jit_comp64.c
>> @@ -333,15 +333,15 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context *
>> case BPF_ALU | BPF_SUB | BPF_K: /* (u32) dst -= (u32) imm */
>> case BPF_ALU64 | BPF_ADD | BPF_K: /* dst += 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);
>> + if (imm > -32768 && imm < 32768) {
>> + EMIT(PPC_RAW_ADDI(dst_reg, dst_reg,
>> + BPF_OP(code) == BPF_SUB ? IMM_L(-imm) : IMM_L(imm)));
>> + } else {
>> + PPC_LI32(b2p[TMP_REG_1], imm);
>> + if (BPF_OP(code) == BPF_SUB)
>> + EMIT(PPC_RAW_SUB(dst_reg, dst_reg, b2p[TMP_REG_1]));
>> + else
>> EMIT(PPC_RAW_ADD(dst_reg, dst_reg, b2p[TMP_REG_1]));
>> - }
>> }
>> goto bpf_alu32_trunc;
>
> There is now so few code common to both BPF_ADD and BPF_SUB that you
> should make them different cases.
>
> While at it, why not also use ADDIS if imm is 32 bits ? That would be an
> ADDIS/ADDI instead of LIS/ORI/ADD
Sure. I wanted to limit the change for this fix. We can do a separate
patch to optimize code generation for BPF_ADD.
- Naveen
next prev parent reply other threads:[~2021-10-04 18:19 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-01 21:14 [PATCH 0/9] powerpc/bpf: Various fixes Naveen N. Rao
2021-10-01 21:14 ` [PATCH 1/9] powerpc/lib: Add helper to check if offset is within conditional branch range Naveen N. Rao
2021-10-01 21:37 ` Song Liu
2021-10-04 18:02 ` Naveen N. Rao
2021-10-03 7:50 ` Christophe Leroy
2021-10-04 18:03 ` Naveen N. Rao
2021-10-01 21:14 ` [PATCH 2/9] powerpc/bpf: Validate branch ranges Naveen N. Rao
2021-10-01 21:45 ` Song Liu
2021-10-02 17:29 ` Johan Almbladh
2021-10-03 7:54 ` Christophe Leroy
2021-10-04 18:11 ` Naveen N. Rao
2021-10-01 21:14 ` [PATCH 3/9] powerpc/bpf: Remove unused SEEN_STACK Naveen N. Rao
2021-10-01 21:47 ` Song Liu
2021-10-02 17:30 ` Johan Almbladh
2021-10-03 7:55 ` Christophe Leroy
2021-10-04 18:11 ` Naveen N. Rao
2021-10-05 5:50 ` Christophe Leroy
2021-10-05 20:22 ` Naveen N. Rao
2021-10-01 21:14 ` [PATCH 4/9] powerpc/bpf: Handle large branch ranges with BPF_EXIT Naveen N. Rao
2021-10-01 21:53 ` Song Liu
2021-10-02 17:31 ` Johan Almbladh
2021-10-03 7:59 ` Christophe Leroy
2021-10-04 18:24 ` Naveen N. Rao
2021-10-05 5:46 ` Christophe Leroy
2022-01-07 11:46 ` Naveen N. Rao
2021-10-01 21:14 ` [PATCH 5/9] powerpc/bpf: Fix BPF_MOD when imm == 1 Naveen N. Rao
2021-10-01 21:55 ` Song Liu
2021-10-02 17:32 ` Johan Almbladh
2021-10-01 21:14 ` [PATCH 6/9] powerpc/bpf: Fix BPF_SUB when imm == 0x80000000 Naveen N. Rao
2021-10-01 22:01 ` Song Liu
2021-10-02 17:33 ` Johan Almbladh
2021-10-03 8:07 ` Christophe Leroy
2021-10-04 18:18 ` Naveen N. Rao [this message]
2021-10-05 5:40 ` Christophe Leroy
2021-10-01 21:14 ` [PATCH 7/9] powerpc/bpf: Limit 'ldbrx' to processors compliant with ISA v2.06 Naveen N. Rao
2021-10-02 17:35 ` Johan Almbladh
2021-10-01 21:14 ` [PATCH 8/9] powerpc/security: Add a helper to query stf_barrier type Naveen N. Rao
2021-10-01 21:14 ` [PATCH 9/9] powerpc/bpf: Emit stf barrier instruction sequences for BPF_NOSPEC Naveen N. Rao
2021-10-02 17:41 ` [PATCH 0/9] powerpc/bpf: Various fixes Johan Almbladh
2021-10-04 18:19 ` Naveen N. Rao
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