From: Yonghong Song <yhs@meta.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Fangrui Song <maskray@google.com>,
kernel-team@fb.com
Subject: Re: [PATCH bpf-next v2 01/15] bpf: Support new sign-extension load insns
Date: Fri, 14 Jul 2023 16:22:16 -0700 [thread overview]
Message-ID: <3c21ccc5-567b-8a12-8b82-a4fb63be5451@meta.com> (raw)
In-Reply-To: <20230714181333.lrxledwyh6f4mqri@MacBook-Pro-8.local>
On 7/14/23 11:13 AM, Alexei Starovoitov wrote:
> On Wed, Jul 12, 2023 at 11:07:24PM -0700, Yonghong Song wrote:
>>
>> @@ -1942,6 +1945,16 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
>> LDST(DW, u64)
>> #undef LDST
>>
>> +#define LDS(SIZEOP, SIZE) \
>
> LDSX ?
Ack.
>
>> + LDX_MEMSX_##SIZEOP: \
>> + DST = *(SIZE *)(unsigned long) (SRC + insn->off); \
>> + CONT;
>> +
>> + LDS(B, s8)
>> + LDS(H, s16)
>> + LDS(W, s32)
>> +#undef LDS
>
> ...
>
>> @@ -17503,7 +17580,10 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
>> if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) ||
>> insn->code == (BPF_LDX | BPF_MEM | BPF_H) ||
>> insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
>> - insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) {
>> + insn->code == (BPF_LDX | BPF_MEM | BPF_DW) ||
>> + insn->code == (BPF_LDX | BPF_MEMSX | BPF_B) ||
>> + insn->code == (BPF_LDX | BPF_MEMSX | BPF_H) ||
>> + insn->code == (BPF_LDX | BPF_MEMSX | BPF_W)) {
>> type = BPF_READ;
>> } else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) ||
>> insn->code == (BPF_STX | BPF_MEM | BPF_H) ||
>> @@ -17562,6 +17642,11 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
>> */
>> case PTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED:
>> if (type == BPF_READ) {
>> + /* it is hard to differentiate that the
>> + * BPF_PROBE_MEM is for BPF_MEM or BPF_MEMSX,
>> + * let us use insn->imm to remember it.
>> + */
>> + insn->imm = BPF_MODE(insn->code);
>
> That's a fragile approach.
> And the evidence is in this patch.
> This part of interpreter:
> LDX_PROBE_MEM_##SIZEOP: \
> bpf_probe_read_kernel(&DST, sizeof(SIZE), \
> (const void *)(long) (SRC + insn->off)); \
> DST = *((SIZE *)&DST); \
>
> wasn't updated to handle sign extension.
Thanks for catching this!
>
> How about
> #define BPF_PROBE_MEMSX 0x40 /* same as BPF_IND */
>
> and handle it in JITs and interpreter.
Good idea. Will do.
> We need a selftest for BTF style access to signed fields to make sure both
> interpreter and JIT handling of BPF_PROBE_MEMSX is tested.
Will do.
next prev parent reply other threads:[~2023-07-14 23:22 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-13 6:07 [PATCH bpf-next v2 00/15] bpf: Support new insns from cpu v4 Yonghong Song
2023-07-13 6:07 ` [PATCH bpf-next v2 01/15] bpf: Support new sign-extension load insns Yonghong Song
2023-07-14 18:13 ` Alexei Starovoitov
2023-07-14 23:22 ` Yonghong Song [this message]
2023-07-17 1:39 ` Eduard Zingerman
2023-07-19 0:15 ` Eduard Zingerman
2023-07-19 2:28 ` Yonghong Song
2023-07-13 6:07 ` [PATCH bpf-next v2 02/15] bpf: Fix sign-extension ctx member accesses Yonghong Song
2023-07-17 1:40 ` Eduard Zingerman
2023-07-19 0:40 ` Yonghong Song
2023-07-13 6:07 ` [PATCH bpf-next v2 03/15] bpf: Support new sign-extension mov insns Yonghong Song
2023-07-17 1:41 ` Eduard Zingerman
2023-07-19 1:17 ` Yonghong Song
2023-07-19 12:53 ` Eduard Zingerman
2023-07-19 15:59 ` Fangrui Song
2023-07-19 16:57 ` Eduard Zingerman
2023-07-13 6:07 ` [PATCH bpf-next v2 04/15] bpf: Support new unconditional bswap instruction Yonghong Song
2023-07-17 1:42 ` Eduard Zingerman
2023-07-19 1:22 ` Yonghong Song
2023-07-13 6:07 ` [PATCH bpf-next v2 05/15] bpf: Support new signed div/mod instructions Yonghong Song
2023-07-18 23:00 ` Eduard Zingerman
2023-07-19 2:30 ` Yonghong Song
2023-07-19 2:44 ` Alexei Starovoitov
2023-07-19 6:57 ` Yonghong Song
2023-07-13 6:07 ` [PATCH bpf-next v2 06/15] bpf: Fix jit blinding with new sdiv/smov insns Yonghong Song
2023-07-13 6:07 ` [PATCH bpf-next v2 07/15] bpf: Support new 32bit offset jmp instruction Yonghong Song
2023-07-13 6:08 ` [PATCH bpf-next v2 08/15] selftests/bpf: Add a cpuv4 test runner for cpu=v4 testing Yonghong Song
2023-07-13 6:18 ` Fangrui Song
2023-07-13 6:25 ` Yonghong Song
2023-07-13 6:08 ` [PATCH bpf-next v2 09/15] selftests/bpf: Add unit tests for new sign-extension load insns Yonghong Song
2023-07-18 23:06 ` Eduard Zingerman
2023-07-13 6:08 ` [PATCH bpf-next v2 10/15] selftests/bpf: Add unit tests for new sign-extension mov insns Yonghong Song
2023-07-13 6:08 ` [PATCH bpf-next v2 11/15] selftests/bpf: Add unit tests for new bswap insns Yonghong Song
2023-07-13 6:08 ` [PATCH bpf-next v2 12/15] selftests/bpf: Add unit tests for new sdiv/smod insns Yonghong Song
2023-07-18 23:10 ` Eduard Zingerman
2023-07-13 6:08 ` [PATCH bpf-next v2 13/15] selftests/bpf: Add unit tests for new gotol insn Yonghong Song
2023-07-13 6:08 ` [PATCH bpf-next v2 14/15] selftests/bpf: Test ldsx with more complex cases Yonghong Song
2023-07-13 6:08 ` [PATCH bpf-next v2 15/15] docs/bpf: Add documentation for new instructions Yonghong Song
2023-07-14 18:28 ` Alexei Starovoitov
2023-07-14 23:26 ` Yonghong Song
2023-07-14 23:33 ` Dave Thaler
2023-07-14 23:33 ` [Bpf] " Dave Thaler
2023-07-15 0:23 ` Alexei Starovoitov
2023-07-15 0:23 ` [Bpf] " Alexei Starovoitov
2023-07-14 23:34 ` Dave Thaler
2023-07-14 23:34 ` [Bpf] " Dave Thaler
2023-07-17 1:39 ` [PATCH bpf-next v2 00/15] bpf: Support new insns from cpu v4 Eduard Zingerman
2023-07-17 16:56 ` Alexei Starovoitov
2023-07-17 17:04 ` Eduard Zingerman
2023-07-17 21:52 ` Yonghong Song
2023-07-21 14:56 ` Jose E. Marchesi
2023-07-24 0:17 ` Jose E. Marchesi
2023-07-24 1:04 ` Jose E. Marchesi
2023-07-24 2:35 ` Yonghong Song
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