From e3a724edeec3836ed44675a6587a6db7b6b68dbe Mon Sep 17 00:00:00 2001 From: "David S. Miller" Date: Mon, 24 Apr 2017 15:56:21 -0700 Subject: [PATCH] sparc64: Support cbcond instructions in eBPF JIT. cbcond combines a compare with a branch into a single instruction. The limitations are: 1) Only newer chips support it 2) For immediate compares we are limited to 5-bit signed immediate values 3) The branch displacement is limited to 10-bit signed 4) We cannot use it for JSET Also, cbcond (unlike all other sparc control transfers) lacks a delay slot. Currently we don't have a useful instruction we can push into the delay slot of normal branches. So using cbcond pretty much always increases code density, and is therefore a win. Signed-off-by: David S. Miller --- arch/sparc/net/bpf_jit_comp_64.c | 238 ++++++++++++++++++++++++------- 1 file changed, 184 insertions(+), 54 deletions(-) diff --git a/arch/sparc/net/bpf_jit_comp_64.c b/arch/sparc/net/bpf_jit_comp_64.c index 43bef1ceebbf..2b2f3c3335ce 100644 --- a/arch/sparc/net/bpf_jit_comp_64.c +++ b/arch/sparc/net/bpf_jit_comp_64.c @@ -18,6 +18,16 @@ static inline bool is_simm13(unsigned int value) return value + 0x1000 < 0x2000; } +static inline bool is_simm10(unsigned int value) +{ + return value + 0x200 < 0x400; +} + +static inline bool is_simm5(unsigned int value) +{ + return value + 0x10 < 0x20; +} + static void bpf_flush_icache(void *start_, void *end_) { /* Cheetah's I-cache is fully coherent. */ @@ -39,6 +49,7 @@ static void bpf_flush_icache(void *start_, void *end_) #define SEEN_MEM 4 /* use mem[] for temporary storage */ #define S13(X) ((X) & 0x1fff) +#define S5(X) ((X) & 0x1f) #define IMMED 0x00002000 #define RD(X) ((X) << 25) #define RS1(X) ((X) << 14) @@ -46,7 +57,8 @@ static void bpf_flush_icache(void *start_, void *end_) #define OP(X) ((X) << 30) #define OP2(X) ((X) << 22) #define OP3(X) ((X) << 19) -#define COND(X) ((X) << 25) +#define COND(X) (((X) & 0xf) << 25) +#define CBCOND(X) (((X) & 0x1f) << 25) #define F1(X) OP(X) #define F2(X, Y) (OP(X) | OP2(Y)) #define F3(X, Y) (OP(X) | OP3(Y)) @@ -75,10 +87,39 @@ static void bpf_flush_icache(void *start_, void *end_) #define WDISP22(X) (((X) >> 2) & 0x3fffff) #define WDISP19(X) (((X) >> 2) & 0x7ffff) +/* The 10-bit branch displacement for CBCOND is split into two fields */ +static u32 WDISP10(u32 off) +{ + u32 ret = ((off >> 2) & 0xff) << 5; + + ret |= ((off >> (2 + 8)) & 0x03) << 19; + + return ret; +} + +#define CBCONDE CBCOND(0x09) +#define CBCONDLE CBCOND(0x0a) +#define CBCONDL CBCOND(0x0b) +#define CBCONDLEU CBCOND(0x0c) +#define CBCONDCS CBCOND(0x0d) +#define CBCONDN CBCOND(0x0e) +#define CBCONDVS CBCOND(0x0f) +#define CBCONDNE CBCOND(0x19) +#define CBCONDG CBCOND(0x1a) +#define CBCONDGE CBCOND(0x1b) +#define CBCONDGU CBCOND(0x1c) +#define CBCONDCC CBCOND(0x1d) +#define CBCONDPOS CBCOND(0x1e) +#define CBCONDVC CBCOND(0x1f) + +#define CBCONDGEU CBCONDCC +#define CBCONDLU CBCONDCS + #define ANNUL (1 << 29) #define XCC (1 << 21) #define BRANCH (F2(0, 1) | XCC) +#define CBCOND_OP (F2(0, 3) | XCC) #define BA (BRANCH | CONDA) #define BG (BRANCH | CONDG) @@ -351,6 +392,22 @@ static void emit_branch(unsigned int br_opc, unsigned int from_idx, unsigned int emit(br_opc | WDISP22(off << 2), ctx); } +static void emit_cbcond(unsigned int cb_opc, unsigned int from_idx, unsigned int to_idx, + const u8 dst, const u8 src, struct jit_ctx *ctx) +{ + unsigned int off = to_idx - from_idx; + + emit(cb_opc | WDISP10(off << 2) | RS1(dst) | RS2(src), ctx); +} + +static void emit_cbcondi(unsigned int cb_opc, unsigned int from_idx, unsigned int to_idx, + const u8 dst, s32 imm, struct jit_ctx *ctx) +{ + unsigned int off = to_idx - from_idx; + + emit(cb_opc | IMMED | WDISP10(off << 2) | RS1(dst) | S5(imm), ctx); +} + #define emit_read_y(REG, CTX) emit(RD_Y | RD(REG), CTX) #define emit_write_y(REG, CTX) emit(WR_Y | IMMED | RS1(REG) | S13(0), CTX) @@ -358,7 +415,7 @@ static void emit_branch(unsigned int br_opc, unsigned int from_idx, unsigned int emit(SUBCC | RS1(R1) | RS2(R2) | RD(G0), CTX) #define emit_cmpi(R1, IMM, CTX) \ - emit(SUBCC | IMMED | RS1(R1) | S13(IMM) | RD(G0), CTX); + emit(SUBCC | IMMED | RS1(R1) | S13(IMM) | RD(G0), CTX) #define emit_btst(R1, R2, CTX) \ emit(ANDCC | RS1(R1) | RS2(R2) | RD(G0), CTX) @@ -366,6 +423,117 @@ static void emit_branch(unsigned int br_opc, unsigned int from_idx, unsigned int #define emit_btsti(R1, IMM, CTX) \ emit(ANDCC | IMMED | RS1(R1) | S13(IMM) | RD(G0), CTX) +static int emit_compare_and_branch(const u8 code, const u8 dst, u8 src, + const s32 imm, bool is_imm, int branch_dst, + struct jit_ctx *ctx) +{ + bool use_cbcond = (sparc64_elf_hwcap & AV_SPARC_CBCOND) != 0; + const u8 tmp = bpf2sparc[TMP_REG_1]; + + branch_dst = ctx->offset[branch_dst]; + + if (!is_simm10(branch_dst - ctx->idx) || + BPF_OP(code) == BPF_JSET) + use_cbcond = false; + + if (is_imm) { + bool fits = true; + + if (use_cbcond) { + if (!is_simm5(imm)) + fits = false; + } else if (!is_simm13(imm)) { + fits = false; + } + if (!fits) { + ctx->tmp_1_used = true; + emit_loadimm_sext(imm, tmp, ctx); + src = tmp; + is_imm = false; + } + } + + if (!use_cbcond) { + u32 br_opcode; + + if (BPF_OP(code) == BPF_JSET) { + if (is_imm) + emit_btsti(dst, imm, ctx); + else + emit_btst(dst, src, ctx); + } else { + if (is_imm) + emit_cmpi(dst, imm, ctx); + else + emit_cmp(dst, src, ctx); + } + switch (BPF_OP(code)) { + case BPF_JEQ: + br_opcode = BE; + break; + case BPF_JGT: + br_opcode = BGU; + break; + case BPF_JGE: + br_opcode = BGEU; + break; + case BPF_JSET: + case BPF_JNE: + br_opcode = BNE; + break; + case BPF_JSGT: + br_opcode = BG; + break; + case BPF_JSGE: + br_opcode = BGE; + break; + default: + /* Make sure we dont leak kernel information to the + * user. + */ + return -EFAULT; + } + emit_branch(br_opcode, ctx->idx, branch_dst, ctx); + emit_nop(ctx); + } else { + u32 cbcond_opcode; + + switch (BPF_OP(code)) { + case BPF_JEQ: + cbcond_opcode = CBCONDE; + break; + case BPF_JGT: + cbcond_opcode = CBCONDGU; + break; + case BPF_JGE: + cbcond_opcode = CBCONDGEU; + break; + case BPF_JNE: + cbcond_opcode = CBCONDNE; + break; + case BPF_JSGT: + cbcond_opcode = CBCONDG; + break; + case BPF_JSGE: + cbcond_opcode = CBCONDGE; + break; + default: + /* Make sure we dont leak kernel information to the + * user. + */ + return -EFAULT; + } + cbcond_opcode |= CBCOND_OP; + if (is_imm) + emit_cbcondi(cbcond_opcode, ctx->idx, branch_dst, + dst, imm, ctx); + else + emit_cbcond(cbcond_opcode, ctx->idx, branch_dst, + dst, src, ctx); + } + return 0; +} + static void load_skb_regs(struct jit_ctx *ctx, u8 r_skb) { const u8 r_headlen = bpf2sparc[SKB_HLEN_REG]; @@ -765,44 +933,15 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) case BPF_JMP | BPF_JGE | BPF_X: case BPF_JMP | BPF_JNE | BPF_X: case BPF_JMP | BPF_JSGT | BPF_X: - case BPF_JMP | BPF_JSGE | BPF_X: { - u32 br_opcode; + case BPF_JMP | BPF_JSGE | BPF_X: + case BPF_JMP | BPF_JSET | BPF_X: { + int err; - emit_cmp(dst, src, ctx); -emit_cond_jmp: - switch (BPF_OP(code)) { - case BPF_JEQ: - br_opcode = BE; - break; - case BPF_JGT: - br_opcode = BGU; - break; - case BPF_JGE: - br_opcode = BGEU; - break; - case BPF_JSET: - case BPF_JNE: - br_opcode = BNE; - break; - case BPF_JSGT: - br_opcode = BG; - break; - case BPF_JSGE: - br_opcode = BGE; - break; - default: - /* Make sure we dont leak kernel information to the - * user. - */ - return -EFAULT; - } - emit_branch(br_opcode, ctx->idx, ctx->offset[i + off], ctx); - emit_nop(ctx); + err = emit_compare_and_branch(code, dst, src, 0, false, i + off, ctx); + if (err) + return err; break; } - case BPF_JMP | BPF_JSET | BPF_X: - emit_btst(dst, src, ctx); - goto emit_cond_jmp; /* IF (dst COND imm) JUMP off */ case BPF_JMP | BPF_JEQ | BPF_K: case BPF_JMP | BPF_JGT | BPF_K: @@ -810,23 +949,14 @@ emit_cond_jmp: case BPF_JMP | BPF_JNE | BPF_K: case BPF_JMP | BPF_JSGT | BPF_K: case BPF_JMP | BPF_JSGE | BPF_K: - if (is_simm13(imm)) { - emit_cmpi(dst, imm, ctx); - } else { - ctx->tmp_1_used = true; - emit_loadimm_sext(imm, bpf2sparc[TMP_REG_1], ctx); - emit_cmp(dst, bpf2sparc[TMP_REG_1], ctx); - } - goto emit_cond_jmp; - case BPF_JMP | BPF_JSET | BPF_K: - if (is_simm13(imm)) { - emit_btsti(dst, imm, ctx); - } else { - ctx->tmp_1_used = true; - emit_loadimm_sext(imm, bpf2sparc[TMP_REG_1], ctx); - emit_btst(dst, bpf2sparc[TMP_REG_1], ctx); - } - goto emit_cond_jmp; + case BPF_JMP | BPF_JSET | BPF_K: { + int err; + + err = emit_compare_and_branch(code, dst, 0, imm, true, i + off, ctx); + if (err) + return err; + break; + } /* function call */ case BPF_JMP | BPF_CALL: -- 2.30.2