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[3.249.32.32]) by smtp.gmail.com with ESMTPSA id n13-20020a5d484d000000b0031f3b04e7cdsm491358wrs.109.2023.09.07.16.05.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Sep 2023 16:05:53 -0700 (PDT) From: Puranjay Mohan To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shubham Bansal , Russell King , Mykola Lysenko , Shuah Khan , bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Cc: puranjay12@gmail.com Subject: [PATCH bpf-next v3 2/9] arm32, bpf: add support for sign-extension load instruction Date: Thu, 7 Sep 2023 23:05:43 +0000 Message-Id: <20230907230550.1417590-3-puranjay12@gmail.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230907230550.1417590-1-puranjay12@gmail.com> References: <20230907230550.1417590-1-puranjay12@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Status: No, score=-1.8 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_ENVFROM_END_DIGIT, FREEMAIL_FROM,RCVD_IN_DNSWL_BLOCKED,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net The cpuv4 added the support of an instruction that is similar to load but also sign-extends the result after the load. BPF_MEMSX | | BPF_LDX means dst = *(signed size *) (src + offset) here can be one of BPF_B, BPF_H, BPF_W. ARM32 has instructions to load a byte or a half word with sign extension into a 32bit register. As the JIT uses two 32 bit registers to simulate a 64-bit BPF register, an extra instruction is emitted to sign-extent the result up to the second register. Signed-off-by: Puranjay Mohan Reviewed-by: Russell King (Oracle) --- arch/arm/net/bpf_jit_32.c | 74 ++++++++++++++++++++++++++++++++++++++- arch/arm/net/bpf_jit_32.h | 2 ++ 2 files changed, 75 insertions(+), 1 deletion(-) diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index c03600fe86f6..1b3bd05878ab 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -333,6 +333,9 @@ static u32 arm_bpf_ldst_imm8(u32 op, u8 rt, u8 rn, s16 imm8) #define ARM_LDRD_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_LDRD_I, rt, rn, off) #define ARM_LDRH_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_LDRH_I, rt, rn, off) +#define ARM_LDRSH_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_LDRSH_I, rt, rn, off) +#define ARM_LDRSB_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_LDRSB_I, rt, rn, off) + #define ARM_STR_I(rt, rn, off) arm_bpf_ldst_imm12(ARM_INST_STR_I, rt, rn, off) #define ARM_STRB_I(rt, rn, off) arm_bpf_ldst_imm12(ARM_INST_STRB_I, rt, rn, off) #define ARM_STRD_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_STRD_I, rt, rn, off) @@ -1026,6 +1029,24 @@ static bool is_ldst_imm(s16 off, const u8 size) return -off_max <= off && off <= off_max; } +static bool is_ldst_imm8(s16 off, const u8 size) +{ + s16 off_max = 0; + + switch (size) { + case BPF_B: + off_max = 0xff; + break; + case BPF_W: + off_max = 0xfff; + break; + case BPF_H: + off_max = 0xff; + break; + } + return -off_max <= off && off <= off_max; +} + /* *(size *)(dst + off) = src */ static inline void emit_str_r(const s8 dst, const s8 src[], s16 off, struct jit_ctx *ctx, const u8 sz){ @@ -1105,6 +1126,50 @@ static inline void emit_ldx_r(const s8 dst[], const s8 src, arm_bpf_put_reg64(dst, rd, ctx); } +/* dst = *(signed size*)(src + off) */ +static inline void emit_ldsx_r(const s8 dst[], const s8 src, + s16 off, struct jit_ctx *ctx, const u8 sz){ + const s8 *tmp = bpf2a32[TMP_REG_1]; + const s8 *rd = is_stacked(dst_lo) ? tmp : dst; + s8 rm = src; + int add_off; + + if (!is_ldst_imm8(off, sz)) { + /* + * offset does not fit in the load/store immediate, + * construct an ADD instruction to apply the offset. + */ + add_off = imm8m(off); + if (add_off > 0) { + emit(ARM_ADD_I(tmp[0], src, add_off), ctx); + rm = tmp[0]; + } else { + emit_a32_mov_i(tmp[0], off, ctx); + emit(ARM_ADD_R(tmp[0], tmp[0], src), ctx); + rm = tmp[0]; + } + off = 0; + } + + switch (sz) { + case BPF_B: + /* Load a Byte with sign extension*/ + emit(ARM_LDRSB_I(rd[1], rm, off), ctx); + break; + case BPF_H: + /* Load a HalfWord with sign extension*/ + emit(ARM_LDRSH_I(rd[1], rm, off), ctx); + break; + case BPF_W: + /* Load a Word*/ + emit(ARM_LDR_I(rd[1], rm, off), ctx); + break; + } + /* Carry the sign extension to upper 32 bits */ + emit(ARM_ASR_I(rd[0], rd[1], 31), ctx); + arm_bpf_put_reg64(dst, rd, ctx); +} + /* Arithmatic Operation */ static inline void emit_ar_r(const u8 rd, const u8 rt, const u8 rm, const u8 rn, struct jit_ctx *ctx, u8 op, @@ -1603,8 +1668,15 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) case BPF_LDX | BPF_MEM | BPF_H: case BPF_LDX | BPF_MEM | BPF_B: case BPF_LDX | BPF_MEM | BPF_DW: + /* LDSX: dst = *(signed size *)(src + off) */ + case BPF_LDX | BPF_MEMSX | BPF_B: + case BPF_LDX | BPF_MEMSX | BPF_H: + case BPF_LDX | BPF_MEMSX | BPF_W: rn = arm_bpf_get_reg32(src_lo, tmp2[1], ctx); - emit_ldx_r(dst, rn, off, ctx, BPF_SIZE(code)); + if (BPF_MODE(insn->code) == BPF_MEMSX) + emit_ldsx_r(dst, rn, off, ctx, BPF_SIZE(code)); + else + emit_ldx_r(dst, rn, off, ctx, BPF_SIZE(code)); break; /* speculation barrier */ case BPF_ST | BPF_NOSPEC: diff --git a/arch/arm/net/bpf_jit_32.h b/arch/arm/net/bpf_jit_32.h index e0b593a1498d..79c7373fadce 100644 --- a/arch/arm/net/bpf_jit_32.h +++ b/arch/arm/net/bpf_jit_32.h @@ -79,9 +79,11 @@ #define ARM_INST_LDST__IMM12 0x00000fff #define ARM_INST_LDRB_I 0x05500000 #define ARM_INST_LDRB_R 0x07d00000 +#define ARM_INST_LDRSB_I 0x015000d0 #define ARM_INST_LDRD_I 0x014000d0 #define ARM_INST_LDRH_I 0x015000b0 #define ARM_INST_LDRH_R 0x019000b0 +#define ARM_INST_LDRSH_I 0x015000f0 #define ARM_INST_LDR_I 0x05100000 #define ARM_INST_LDR_R 0x07900000