Re: [PATCH v2 04/10] powerpc/bpf: Fix BPF_SUB when imm == 0x80000000
From: Naveen N. Rao <hidden>
Date: 2021-10-07 08:48:05
Also in:
bpf
Subsystem:
bpf jit for powerpc (32-bit and 64-bit), bpf [general] (safe dynamic programs and tools), linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Hari Bathini, Christophe Leroy, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Madhavan Srinivasan, Linus Torvalds
Christophe Leroy wrote:
Le 05/10/2021 à 22:25, Naveen N. Rao a écrit :quoted
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 <redacted> --- 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 <redacted>
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);