diff options
Diffstat (limited to 'arch/mips/net/bpf_jit_comp.c')
-rw-r--r-- | arch/mips/net/bpf_jit_comp.c | 1034 |
1 files changed, 1034 insertions, 0 deletions
diff --git a/arch/mips/net/bpf_jit_comp.c b/arch/mips/net/bpf_jit_comp.c new file mode 100644 index 000000000000..b17130d510d4 --- /dev/null +++ b/arch/mips/net/bpf_jit_comp.c @@ -0,0 +1,1034 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Just-In-Time compiler for eBPF bytecode on MIPS. + * Implementation of JIT functions common to 32-bit and 64-bit CPUs. + * + * Copyright (c) 2021 Anyfi Networks AB. + * Author: Johan Almbladh <johan.almbladh@gmail.com> + * + * Based on code and ideas from + * Copyright (c) 2017 Cavium, Inc. + * Copyright (c) 2017 Shubham Bansal <illusionist.neo@gmail.com> + * Copyright (c) 2011 Mircea Gherzan <mgherzan@gmail.com> + */ + +/* + * Code overview + * ============= + * + * - bpf_jit_comp.h + * Common definitions and utilities. + * + * - bpf_jit_comp.c + * Implementation of JIT top-level logic and exported JIT API functions. + * Implementation of internal operations shared by 32-bit and 64-bit code. + * JMP and ALU JIT control code, register control code, shared ALU and + * JMP/JMP32 JIT operations. + * + * - bpf_jit_comp32.c + * Implementation of functions to JIT prologue, epilogue and a single eBPF + * instruction for 32-bit MIPS CPUs. The functions use shared operations + * where possible, and implement the rest for 32-bit MIPS such as ALU64 + * operations. + * + * - bpf_jit_comp64.c + * Ditto, for 64-bit MIPS CPUs. + * + * Zero and sign extension + * ======================== + * 32-bit MIPS instructions on 64-bit MIPS registers use sign extension, + * but the eBPF instruction set mandates zero extension. We let the verifier + * insert explicit zero-extensions after 32-bit ALU operations, both for + * 32-bit and 64-bit MIPS JITs. Conditional JMP32 operations on 64-bit MIPs + * are JITed with sign extensions inserted when so expected. + * + * ALU operations + * ============== + * ALU operations on 32/64-bit MIPS and ALU64 operations on 64-bit MIPS are + * JITed in the following steps. ALU64 operations on 32-bit MIPS are more + * complicated and therefore only processed by special implementations in + * step (3). + * + * 1) valid_alu_i: + * Determine if an immediate operation can be emitted as such, or if + * we must fall back to the register version. + * + * 2) rewrite_alu_i: + * Convert BPF operation and immediate value to a canonical form for + * JITing. In some degenerate cases this form may be a no-op. + * + * 3) emit_alu_{i,i64,r,64}: + * Emit instructions for an ALU or ALU64 immediate or register operation. + * + * JMP operations + * ============== + * JMP and JMP32 operations require an JIT instruction offset table for + * translating the jump offset. This table is computed by dry-running the + * JIT without actually emitting anything. However, the computed PC-relative + * offset may overflow the 18-bit offset field width of the native MIPS + * branch instruction. In such cases, the long jump is converted into the + * following sequence. + * + * <branch> !<cond> +2 Inverted PC-relative branch + * nop Delay slot + * j <offset> Unconditional absolute long jump + * nop Delay slot + * + * Since this converted sequence alters the offset table, all offsets must + * be re-calculated. This may in turn trigger new branch conversions, so + * the process is repeated until no further changes are made. Normally it + * completes in 1-2 iterations. If JIT_MAX_ITERATIONS should reached, we + * fall back to converting every remaining jump operation. The branch + * conversion is independent of how the JMP or JMP32 condition is JITed. + * + * JMP32 and JMP operations are JITed as follows. + * + * 1) setup_jmp_{i,r}: + * Convert jump conditional and offset into a form that can be JITed. + * This form may be a no-op, a canonical form, or an inverted PC-relative + * jump if branch conversion is necessary. + * + * 2) valid_jmp_i: + * Determine if an immediate operations can be emitted as such, or if + * we must fall back to the register version. Applies to JMP32 for 32-bit + * MIPS, and both JMP and JMP32 for 64-bit MIPS. + * + * 3) emit_jmp_{i,i64,r,r64}: + * Emit instructions for an JMP or JMP32 immediate or register operation. + * + * 4) finish_jmp_{i,r}: + * Emit any instructions needed to finish the jump. This includes a nop + * for the delay slot if a branch was emitted, and a long absolute jump + * if the branch was converted. + */ + +#include <linux/limits.h> +#include <linux/bitops.h> +#include <linux/errno.h> +#include <linux/filter.h> +#include <linux/bpf.h> +#include <linux/slab.h> +#include <asm/bitops.h> +#include <asm/cacheflush.h> +#include <asm/cpu-features.h> +#include <asm/isa-rev.h> +#include <asm/uasm.h> + +#include "bpf_jit_comp.h" + +/* Convenience macros for descriptor access */ +#define CONVERTED(desc) ((desc) & JIT_DESC_CONVERT) +#define INDEX(desc) ((desc) & ~JIT_DESC_CONVERT) + +/* + * Push registers on the stack, starting at a given depth from the stack + * pointer and increasing. The next depth to be written is returned. + */ +int push_regs(struct jit_context *ctx, u32 mask, u32 excl, int depth) +{ + int reg; + + for (reg = 0; reg < BITS_PER_BYTE * sizeof(mask); reg++) + if (mask & BIT(reg)) { + if ((excl & BIT(reg)) == 0) { + if (sizeof(long) == 4) + emit(ctx, sw, reg, depth, MIPS_R_SP); + else /* sizeof(long) == 8 */ + emit(ctx, sd, reg, depth, MIPS_R_SP); + } + depth += sizeof(long); + } + + ctx->stack_used = max((int)ctx->stack_used, depth); + return depth; +} + +/* + * Pop registers from the stack, starting at a given depth from the stack + * pointer and increasing. The next depth to be read is returned. + */ +int pop_regs(struct jit_context *ctx, u32 mask, u32 excl, int depth) +{ + int reg; + + for (reg = 0; reg < BITS_PER_BYTE * sizeof(mask); reg++) + if (mask & BIT(reg)) { + if ((excl & BIT(reg)) == 0) { + if (sizeof(long) == 4) + emit(ctx, lw, reg, depth, MIPS_R_SP); + else /* sizeof(long) == 8 */ + emit(ctx, ld, reg, depth, MIPS_R_SP); + } + depth += sizeof(long); + } + + return depth; +} + +/* Compute the 28-bit jump target address from a BPF program location */ +int get_target(struct jit_context *ctx, u32 loc) +{ + u32 index = INDEX(ctx->descriptors[loc]); + unsigned long pc = (unsigned long)&ctx->target[ctx->jit_index]; + unsigned long addr = (unsigned long)&ctx->target[index]; + + if (!ctx->target) + return 0; + + if ((addr ^ pc) & ~MIPS_JMP_MASK) + return -1; + + return addr & MIPS_JMP_MASK; +} + +/* Compute the PC-relative offset to relative BPF program offset */ +int get_offset(const struct jit_context *ctx, int off) +{ + return (INDEX(ctx->descriptors[ctx->bpf_index + off]) - + ctx->jit_index - 1) * sizeof(u32); +} + +/* dst = imm (register width) */ +void emit_mov_i(struct jit_context *ctx, u8 dst, s32 imm) +{ + if (imm >= -0x8000 && imm <= 0x7fff) { + emit(ctx, addiu, dst, MIPS_R_ZERO, imm); + } else { + emit(ctx, lui, dst, (s16)((u32)imm >> 16)); + emit(ctx, ori, dst, dst, (u16)(imm & 0xffff)); + } + clobber_reg(ctx, dst); +} + +/* dst = src (register width) */ +void emit_mov_r(struct jit_context *ctx, u8 dst, u8 src) +{ + emit(ctx, ori, dst, src, 0); + clobber_reg(ctx, dst); +} + +/* Validate ALU immediate range */ +bool valid_alu_i(u8 op, s32 imm) +{ + switch (BPF_OP(op)) { + case BPF_NEG: + case BPF_LSH: + case BPF_RSH: + case BPF_ARSH: + /* All legal eBPF values are valid */ + return true; + case BPF_ADD: + /* imm must be 16 bits */ + return imm >= -0x8000 && imm <= 0x7fff; + case BPF_SUB: + /* -imm must be 16 bits */ + return imm >= -0x7fff && imm <= 0x8000; + case BPF_AND: + case BPF_OR: + case BPF_XOR: + /* imm must be 16 bits unsigned */ + return imm >= 0 && imm <= 0xffff; + case BPF_MUL: + /* imm must be zero or a positive power of two */ + return imm == 0 || (imm > 0 && is_power_of_2(imm)); + case BPF_DIV: + case BPF_MOD: + /* imm must be an 17-bit power of two */ + return (u32)imm <= 0x10000 && is_power_of_2((u32)imm); + } + return false; +} + +/* Rewrite ALU immediate operation */ +bool rewrite_alu_i(u8 op, s32 imm, u8 *alu, s32 *val) +{ + bool act = true; + + switch (BPF_OP(op)) { + case BPF_LSH: + case BPF_RSH: + case BPF_ARSH: + case BPF_ADD: + case BPF_SUB: + case BPF_OR: + case BPF_XOR: + /* imm == 0 is a no-op */ + act = imm != 0; + break; + case BPF_MUL: + if (imm == 1) { + /* dst * 1 is a no-op */ + act = false; + } else if (imm == 0) { + /* dst * 0 is dst & 0 */ + op = BPF_AND; + } else { + /* dst * (1 << n) is dst << n */ + op = BPF_LSH; + imm = ilog2(abs(imm)); + } + break; + case BPF_DIV: + if (imm == 1) { + /* dst / 1 is a no-op */ + act = false; + } else { + /* dst / (1 << n) is dst >> n */ + op = BPF_RSH; + imm = ilog2(imm); + } + break; + case BPF_MOD: + /* dst % (1 << n) is dst & ((1 << n) - 1) */ + op = BPF_AND; + imm--; + break; + } + + *alu = op; + *val = imm; + return act; +} + +/* ALU immediate operation (32-bit) */ +void emit_alu_i(struct jit_context *ctx, u8 dst, s32 imm, u8 op) +{ + switch (BPF_OP(op)) { + /* dst = -dst */ + case BPF_NEG: + emit(ctx, subu, dst, MIPS_R_ZERO, dst); + break; + /* dst = dst & imm */ + case BPF_AND: + emit(ctx, andi, dst, dst, (u16)imm); + break; + /* dst = dst | imm */ + case BPF_OR: + emit(ctx, ori, dst, dst, (u16)imm); + break; + /* dst = dst ^ imm */ + case BPF_XOR: + emit(ctx, xori, dst, dst, (u16)imm); + break; + /* dst = dst << imm */ + case BPF_LSH: + emit(ctx, sll, dst, dst, imm); + break; + /* dst = dst >> imm */ + case BPF_RSH: + emit(ctx, srl, dst, dst, imm); + break; + /* dst = dst >> imm (arithmetic) */ + case BPF_ARSH: + emit(ctx, sra, dst, dst, imm); + break; + /* dst = dst + imm */ + case BPF_ADD: + emit(ctx, addiu, dst, dst, imm); + break; + /* dst = dst - imm */ + case BPF_SUB: + emit(ctx, addiu, dst, dst, -imm); + break; + } + clobber_reg(ctx, dst); +} + +/* ALU register operation (32-bit) */ +void emit_alu_r(struct jit_context *ctx, u8 dst, u8 src, u8 op) +{ + switch (BPF_OP(op)) { + /* dst = dst & src */ + case BPF_AND: + emit(ctx, and, dst, dst, src); + break; + /* dst = dst | src */ + case BPF_OR: + emit(ctx, or, dst, dst, src); + break; + /* dst = dst ^ src */ + case BPF_XOR: + emit(ctx, xor, dst, dst, src); + break; + /* dst = dst << src */ + case BPF_LSH: + emit(ctx, sllv, dst, dst, src); + break; + /* dst = dst >> src */ + case BPF_RSH: + emit(ctx, srlv, dst, dst, src); + break; + /* dst = dst >> src (arithmetic) */ + case BPF_ARSH: + emit(ctx, srav, dst, dst, src); + break; + /* dst = dst + src */ + case BPF_ADD: + emit(ctx, addu, dst, dst, src); + break; + /* dst = dst - src */ + case BPF_SUB: + emit(ctx, subu, dst, dst, src); + break; + /* dst = dst * src */ + case BPF_MUL: + if (cpu_has_mips32r1 || cpu_has_mips32r6) { + emit(ctx, mul, dst, dst, src); + } else { + emit(ctx, multu, dst, src); + emit(ctx, mflo, dst); + } + break; + /* dst = dst / src */ + case BPF_DIV: + if (cpu_has_mips32r6) { + emit(ctx, divu_r6, dst, dst, src); + } else { + emit(ctx, divu, dst, src); + emit(ctx, mflo, dst); + } + break; + /* dst = dst % src */ + case BPF_MOD: + if (cpu_has_mips32r6) { + emit(ctx, modu, dst, dst, src); + } else { + emit(ctx, divu, dst, src); + emit(ctx, mfhi, dst); + } + break; + } + clobber_reg(ctx, dst); +} + +/* Atomic read-modify-write (32-bit) */ +void emit_atomic_r(struct jit_context *ctx, u8 dst, u8 src, s16 off, u8 code) +{ + LLSC_sync(ctx); + emit(ctx, ll, MIPS_R_T9, off, dst); + switch (code) { + case BPF_ADD: + case BPF_ADD | BPF_FETCH: + emit(ctx, addu, MIPS_R_T8, MIPS_R_T9, src); + break; + case BPF_AND: + case BPF_AND | BPF_FETCH: + emit(ctx, and, MIPS_R_T8, MIPS_R_T9, src); + break; + case BPF_OR: + case BPF_OR | BPF_FETCH: + emit(ctx, or, MIPS_R_T8, MIPS_R_T9, src); + break; + case BPF_XOR: + case BPF_XOR | BPF_FETCH: + emit(ctx, xor, MIPS_R_T8, MIPS_R_T9, src); + break; + case BPF_XCHG: + emit(ctx, move, MIPS_R_T8, src); + break; + } + emit(ctx, sc, MIPS_R_T8, off, dst); + emit(ctx, LLSC_beqz, MIPS_R_T8, -16 - LLSC_offset); + emit(ctx, nop); /* Delay slot */ + + if (code & BPF_FETCH) { + emit(ctx, move, src, MIPS_R_T9); + clobber_reg(ctx, src); + } +} + +/* Atomic compare-and-exchange (32-bit) */ +void emit_cmpxchg_r(struct jit_context *ctx, u8 dst, u8 src, u8 res, s16 off) +{ + LLSC_sync(ctx); + emit(ctx, ll, MIPS_R_T9, off, dst); + emit(ctx, bne, MIPS_R_T9, res, 12); + emit(ctx, move, MIPS_R_T8, src); /* Delay slot */ + emit(ctx, sc, MIPS_R_T8, off, dst); + emit(ctx, LLSC_beqz, MIPS_R_T8, -20 - LLSC_offset); + emit(ctx, move, res, MIPS_R_T9); /* Delay slot */ + clobber_reg(ctx, res); +} + +/* Swap bytes and truncate a register word or half word */ +void emit_bswap_r(struct jit_context *ctx, u8 dst, u32 width) +{ + u8 tmp = MIPS_R_T8; + u8 msk = MIPS_R_T9; + + switch (width) { + /* Swap bytes in a word */ + case 32: + if (cpu_has_mips32r2 || cpu_has_mips32r6) { + emit(ctx, wsbh, dst, dst); + emit(ctx, rotr, dst, dst, 16); + } else { + emit(ctx, sll, tmp, dst, 16); /* tmp = dst << 16 */ + emit(ctx, srl, dst, dst, 16); /* dst = dst >> 16 */ + emit(ctx, or, dst, dst, tmp); /* dst = dst | tmp */ + + emit(ctx, lui, msk, 0xff); /* msk = 0x00ff0000 */ + emit(ctx, ori, msk, msk, 0xff); /* msk = msk | 0xff */ + + emit(ctx, and, tmp, dst, msk); /* tmp = dst & msk */ + emit(ctx, sll, tmp, tmp, 8); /* tmp = tmp << 8 */ + emit(ctx, srl, dst, dst, 8); /* dst = dst >> 8 */ + emit(ctx, and, dst, dst, msk); /* dst = dst & msk */ + emit(ctx, or, dst, dst, tmp); /* reg = dst | tmp */ + } + break; + /* Swap bytes in a half word */ + case 16: + if (cpu_has_mips32r2 || cpu_has_mips32r6) { + emit(ctx, wsbh, dst, dst); + emit(ctx, andi, dst, dst, 0xffff); + } else { + emit(ctx, andi, tmp, dst, 0xff00); /* t = d & 0xff00 */ + emit(ctx, srl, tmp, tmp, 8); /* t = t >> 8 */ + emit(ctx, andi, dst, dst, 0x00ff); /* d = d & 0x00ff */ + emit(ctx, sll, dst, dst, 8); /* d = d << 8 */ + emit(ctx, or, dst, dst, tmp); /* d = d | t */ + } + break; + } + clobber_reg(ctx, dst); +} + +/* Validate jump immediate range */ +bool valid_jmp_i(u8 op, s32 imm) +{ + switch (op) { + case JIT_JNOP: + /* Immediate value not used */ + return true; + case BPF_JEQ: + case BPF_JNE: + /* No immediate operation */ + return false; + case BPF_JSET: + case JIT_JNSET: + /* imm must be 16 bits unsigned */ + return imm >= 0 && imm <= 0xffff; + case BPF_JGE: + case BPF_JLT: + case BPF_JSGE: + case BPF_JSLT: + /* imm must be 16 bits */ + return imm >= -0x8000 && imm <= 0x7fff; + case BPF_JGT: + case BPF_JLE: + case BPF_JSGT: + case BPF_JSLE: + /* imm + 1 must be 16 bits */ + return imm >= -0x8001 && imm <= 0x7ffe; + } + return false; +} + +/* Invert a conditional jump operation */ +static u8 invert_jmp(u8 op) +{ + switch (op) { + case BPF_JA: return JIT_JNOP; + case BPF_JEQ: return BPF_JNE; + case BPF_JNE: return BPF_JEQ; + case BPF_JSET: return JIT_JNSET; + case BPF_JGT: return BPF_JLE; + case BPF_JGE: return BPF_JLT; + case BPF_JLT: return BPF_JGE; + case BPF_JLE: return BPF_JGT; + case BPF_JSGT: return BPF_JSLE; + case BPF_JSGE: return BPF_JSLT; + case BPF_JSLT: return BPF_JSGE; + case BPF_JSLE: return BPF_JSGT; + } + return 0; +} + +/* Prepare a PC-relative jump operation */ +static void setup_jmp(struct jit_context *ctx, u8 bpf_op, + s16 bpf_off, u8 *jit_op, s32 *jit_off) +{ + u32 *descp = &ctx->descriptors[ctx->bpf_index]; + int op = bpf_op; + int offset = 0; + + /* Do not compute offsets on the first pass */ + if (INDEX(*descp) == 0) + goto done; + + /* Skip jumps never taken */ + if (bpf_op == JIT_JNOP) + goto done; + + /* Convert jumps always taken */ + if (bpf_op == BPF_JA) + *descp |= JIT_DESC_CONVERT; + + /* + * Current ctx->jit_index points to the start of the branch preamble. + * Since the preamble differs among different branch conditionals, + * the current index cannot be used to compute the branch offset. + * Instead, we use the offset table value for the next instruction, + * which gives the index immediately after the branch delay slot. + */ + if (!CONVERTED(*descp)) { + int target = ctx->bpf_index + bpf_off + 1; + int origin = ctx->bpf_index + 1; + + offset = (INDEX(ctx->descriptors[target]) - + INDEX(ctx->descriptors[origin]) + 1) * sizeof(u32); + } + + /* + * The PC-relative branch offset field on MIPS is 18 bits signed, + * so if the computed offset is larger than this we generate a an + * absolute jump that we skip with an inverted conditional branch. + */ + if (CONVERTED(*descp) || offset < -0x20000 || offset > 0x1ffff) { + offset = 3 * sizeof(u32); + op = invert_jmp(bpf_op); + ctx->changes += !CONVERTED(*descp); + *descp |= JIT_DESC_CONVERT; + } + +done: + *jit_off = offset; + *jit_op = op; +} + +/* Prepare a PC-relative jump operation with immediate conditional */ +void setup_jmp_i(struct jit_context *ctx, s32 imm, u8 width, + u8 bpf_op, s16 bpf_off, u8 *jit_op, s32 *jit_off) +{ + bool always = false; + bool never = false; + + switch (bpf_op) { + case BPF_JEQ: + case BPF_JNE: + break; + case BPF_JSET: + case BPF_JLT: + never = imm == 0; + break; + case BPF_JGE: + always = imm == 0; + break; + case BPF_JGT: + never = (u32)imm == U32_MAX; + break; + case BPF_JLE: + always = (u32)imm == U32_MAX; + break; + case BPF_JSGT: + never = imm == S32_MAX && width == 32; + break; + case BPF_JSGE: + always = imm == S32_MIN && width == 32; + break; + case BPF_JSLT: + never = imm == S32_MIN && width == 32; + break; + case BPF_JSLE: + always = imm == S32_MAX && width == 32; + break; + } + + if (never) + bpf_op = JIT_JNOP; + if (always) + bpf_op = BPF_JA; + setup_jmp(ctx, bpf_op, bpf_off, jit_op, jit_off); +} + +/* Prepare a PC-relative jump operation with register conditional */ +void setup_jmp_r(struct jit_context *ctx, bool same_reg, + u8 bpf_op, s16 bpf_off, u8 *jit_op, s32 *jit_off) +{ + switch (bpf_op) { + case BPF_JSET: + break; + case BPF_JEQ: + case BPF_JGE: + case BPF_JLE: + case BPF_JSGE: + case BPF_JSLE: + if (same_reg) + bpf_op = BPF_JA; + break; + case BPF_JNE: + case BPF_JLT: + case BPF_JGT: + case BPF_JSGT: + case BPF_JSLT: + if (same_reg) + bpf_op = JIT_JNOP; + break; + } + setup_jmp(ctx, bpf_op, bpf_off, jit_op, jit_off); +} + +/* Finish a PC-relative jump operation */ +int finish_jmp(struct jit_context *ctx, u8 jit_op, s16 bpf_off) +{ + /* Emit conditional branch delay slot */ + if (jit_op != JIT_JNOP) + emit(ctx, nop); + /* + * Emit an absolute long jump with delay slot, + * if the PC-relative branch was converted. + */ + if (CONVERTED(ctx->descriptors[ctx->bpf_index])) { + int target = get_target(ctx, ctx->bpf_index + bpf_off + 1); + + if (target < 0) + return -1; + emit(ctx, j, target); + emit(ctx, nop); + } + return 0; +} + +/* Jump immediate (32-bit) */ +void emit_jmp_i(struct jit_context *ctx, u8 dst, s32 imm, s32 off, u8 op) +{ + switch (op) { + /* No-op, used internally for branch optimization */ + case JIT_JNOP: + break; + /* PC += off if dst & imm */ + case BPF_JSET: + emit(ctx, andi, MIPS_R_T9, dst, (u16)imm); + emit(ctx, bnez, MIPS_R_T9, off); + break; + /* PC += off if (dst & imm) == 0 (not in BPF, used for long jumps) */ + case JIT_JNSET: + emit(ctx, andi, MIPS_R_T9, dst, (u16)imm); + emit(ctx, beqz, MIPS_R_T9, off); + break; + /* PC += off if dst > imm */ + case BPF_JGT: + emit(ctx, sltiu, MIPS_R_T9, dst, imm + 1); + emit(ctx, beqz, MIPS_R_T9, off); + break; + /* PC += off if dst >= imm */ + case BPF_JGE: + emit(ctx, sltiu, MIPS_R_T9, dst, imm); + emit(ctx, beqz, MIPS_R_T9, off); + break; + /* PC += off if dst < imm */ + case BPF_JLT: + emit(ctx, sltiu, MIPS_R_T9, dst, imm); + emit(ctx, bnez, MIPS_R_T9, off); + break; + /* PC += off if dst <= imm */ + case BPF_JLE: + emit(ctx, sltiu, MIPS_R_T9, dst, imm + 1); + emit(ctx, bnez, MIPS_R_T9, off); + break; + /* PC += off if dst > imm (signed) */ + case BPF_JSGT: + emit(ctx, slti, MIPS_R_T9, dst, imm + 1); + emit(ctx, beqz, MIPS_R_T9, off); + break; + /* PC += off if dst >= imm (signed) */ + case BPF_JSGE: + emit(ctx, slti, MIPS_R_T9, dst, imm); + emit(ctx, beqz, MIPS_R_T9, off); + break; + /* PC += off if dst < imm (signed) */ + case BPF_JSLT: + emit(ctx, slti, MIPS_R_T9, dst, imm); + emit(ctx, bnez, MIPS_R_T9, off); + break; + /* PC += off if dst <= imm (signed) */ + case BPF_JSLE: + emit(ctx, slti, MIPS_R_T9, dst, imm + 1); + emit(ctx, bnez, MIPS_R_T9, off); + break; + } +} + +/* Jump register (32-bit) */ +void emit_jmp_r(struct jit_context *ctx, u8 dst, u8 src, s32 off, u8 op) +{ + switch (op) { + /* No-op, used internally for branch optimization */ + case JIT_JNOP: + break; + /* PC += off if dst == src */ + case BPF_JEQ: + emit(ctx, beq, dst, src, off); + break; + /* PC += off if dst != src */ + case BPF_JNE: + emit(ctx, bne, dst, src, off); + break; + /* PC += off if dst & src */ + case BPF_JSET: + emit(ctx, and, MIPS_R_T9, dst, src); + emit(ctx, bnez, MIPS_R_T9, off); + break; + /* PC += off if (dst & imm) == 0 (not in BPF, used for long jumps) */ + case JIT_JNSET: + emit(ctx, and, MIPS_R_T9, dst, src); + emit(ctx, beqz, MIPS_R_T9, off); + break; + /* PC += off if dst > src */ + case BPF_JGT: + emit(ctx, sltu, MIPS_R_T9, src, dst); + emit(ctx, bnez, MIPS_R_T9, off); + break; + /* PC += off if dst >= src */ + case BPF_JGE: + emit(ctx, sltu, MIPS_R_T9, dst, src); + emit(ctx, beqz, MIPS_R_T9, off); + break; + /* PC += off if dst < src */ + case BPF_JLT: + emit(ctx, sltu, MIPS_R_T9, dst, src); + emit(ctx, bnez, MIPS_R_T9, off); + break; + /* PC += off if dst <= src */ + case BPF_JLE: + emit(ctx, sltu, MIPS_R_T9, src, dst); + emit(ctx, beqz, MIPS_R_T9, off); + break; + /* PC += off if dst > src (signed) */ + case BPF_JSGT: + emit(ctx, slt, MIPS_R_T9, src, dst); + emit(ctx, bnez, MIPS_R_T9, off); + break; + /* PC += off if dst >= src (signed) */ + case BPF_JSGE: + emit(ctx, slt, MIPS_R_T9, dst, src); + emit(ctx, beqz, MIPS_R_T9, off); + break; + /* PC += off if dst < src (signed) */ + case BPF_JSLT: + emit(ctx, slt, MIPS_R_T9, dst, src); + emit(ctx, bnez, MIPS_R_T9, off); + break; + /* PC += off if dst <= src (signed) */ + case BPF_JSLE: + emit(ctx, slt, MIPS_R_T9, src, dst); + emit(ctx, beqz, MIPS_R_T9, off); + break; + } +} + +/* Jump always */ +int emit_ja(struct jit_context *ctx, s16 off) +{ + int target = get_target(ctx, ctx->bpf_index + off + 1); + + if (target < 0) + return -1; + emit(ctx, j, target); + emit(ctx, nop); + return 0; +} + +/* Jump to epilogue */ +int emit_exit(struct jit_context *ctx) +{ + int target = get_target(ctx, ctx->program->len); + + if (target < 0) + return -1; + emit(ctx, j, target); + emit(ctx, nop); + return 0; +} + +/* Build the program body from eBPF bytecode */ +static int build_body(struct jit_context *ctx) +{ + const struct bpf_prog *prog = ctx->program; + unsigned int i; + + ctx->stack_used = 0; + for (i = 0; i < prog->len; i++) { + const struct bpf_insn *insn = &prog->insnsi[i]; + u32 *descp = &ctx->descriptors[i]; + int ret; + + access_reg(ctx, insn->src_reg); + access_reg(ctx, insn->dst_reg); + + ctx->bpf_index = i; + if (ctx->target == NULL) { + ctx->changes += INDEX(*descp) != ctx->jit_index; + *descp &= JIT_DESC_CONVERT; + *descp |= ctx->jit_index; + } + + ret = build_insn(insn, ctx); + if (ret < 0) + return ret; + + if (ret > 0) { + i++; + if (ctx->target == NULL) + descp[1] = ctx->jit_index; + } + } + + /* Store the end offset, where the epilogue begins */ + ctx->descriptors[prog->len] = ctx->jit_index; + return 0; +} + +/* Set the branch conversion flag on all instructions */ +static void set_convert_flag(struct jit_context *ctx, bool enable) +{ + const struct bpf_prog *prog = ctx->program; + u32 flag = enable ? JIT_DESC_CONVERT : 0; + unsigned int i; + + for (i = 0; i <= prog->len; i++) + ctx->descriptors[i] = INDEX(ctx->descriptors[i]) | flag; +} + +static void jit_fill_hole(void *area, unsigned int size) +{ + u32 *p; + + /* We are guaranteed to have aligned memory. */ + for (p = area; size >= sizeof(u32); size -= sizeof(u32)) + uasm_i_break(&p, BRK_BUG); /* Increments p */ +} + +bool bpf_jit_needs_zext(void) +{ + return true; +} + +struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) +{ + struct bpf_prog *tmp, *orig_prog = prog; + struct bpf_binary_header *header = NULL; + struct jit_context ctx; + bool tmp_blinded = false; + unsigned int tmp_idx; + unsigned int image_size; + u8 *image_ptr; + int tries; + + /* + * If BPF JIT was not enabled then we must fall back to + * the interpreter. + */ + if (!prog->jit_requested) + return orig_prog; + /* + * If constant blinding was enabled and we failed during blinding + * then we must fall back to the interpreter. Otherwise, we save + * the new JITed code. + */ + tmp = bpf_jit_blind_constants(prog); + if (IS_ERR(tmp)) + return orig_prog; + if (tmp != prog) { + tmp_blinded = true; + prog = tmp; + } + + memset(&ctx, 0, sizeof(ctx)); + ctx.program = prog; + + /* + * Not able to allocate memory for descriptors[], then + * we must fall back to the interpreter + */ + ctx.descriptors = kcalloc(prog->len + 1, sizeof(*ctx.descriptors), + GFP_KERNEL); + if (ctx.descriptors == NULL) + goto out_err; + + /* First pass discovers used resources */ + if (build_body(&ctx) < 0) + goto out_err; + /* + * Second pass computes instruction offsets. + * If any PC-relative branches are out of range, a sequence of + * a PC-relative branch + a jump is generated, and we have to + * try again from the beginning to generate the new offsets. + * This is done until no additional conversions are necessary. + * The last two iterations are done with all branches being + * converted, to guarantee offset table convergence within a + * fixed number of iterations. + */ + ctx.jit_index = 0; + build_prologue(&ctx); + tmp_idx = ctx.jit_index; + + tries = JIT_MAX_ITERATIONS; + do { + ctx.jit_index = tmp_idx; + ctx.changes = 0; + if (tries == 2) + set_convert_flag(&ctx, true); + if (build_body(&ctx) < 0) + goto out_err; + } while (ctx.changes > 0 && --tries > 0); + + if (WARN_ONCE(ctx.changes > 0, "JIT offsets failed to converge")) + goto out_err; + + build_epilogue(&ctx, MIPS_R_RA); + + /* Now we know the size of the structure to make */ + image_size = sizeof(u32) * ctx.jit_index; + header = bpf_jit_binary_alloc(image_size, &image_ptr, + sizeof(u32), jit_fill_hole); + /* + * Not able to allocate memory for the structure then + * we must fall back to the interpretation + */ + if (header == NULL) + goto out_err; + + /* Actual pass to generate final JIT code */ + ctx.target = (u32 *)image_ptr; + ctx.jit_index = 0; + + /* + * If building the JITed code fails somehow, + * we fall back to the interpretation. + */ + build_prologue(&ctx); + if (build_body(&ctx) < 0) + goto out_err; + build_epilogue(&ctx, MIPS_R_RA); + + /* Populate line info meta data */ + set_convert_flag(&ctx, false); + bpf_prog_fill_jited_linfo(prog, &ctx.descriptors[1]); + + /* Set as read-only exec and flush instruction cache */ + bpf_jit_binary_lock_ro(header); + flush_icache_range((unsigned long)header, + (unsigned long)&ctx.target[ctx.jit_index]); + + if (bpf_jit_enable > 1) + bpf_jit_dump(prog->len, image_size, 2, ctx.target); + + prog->bpf_func = (void *)ctx.target; + prog->jited = 1; + prog->jited_len = image_size; + +out: + if (tmp_blinded) + bpf_jit_prog_release_other(prog, prog == orig_prog ? + tmp : orig_prog); + kfree(ctx.descriptors); + return prog; + +out_err: + prog = orig_prog; + if (header) + bpf_jit_binary_free(header); + goto out; +} |