1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Just-In-Time compiler for eBPF bytecode on 32-bit and 64-bit MIPS.
4 *
5 * Copyright (c) 2021 Anyfi Networks AB.
6 * Author: Johan Almbladh <johan.almbladh@gmail.com>
7 *
8 * Based on code and ideas from
9 * Copyright (c) 2017 Cavium, Inc.
10 * Copyright (c) 2017 Shubham Bansal <illusionist.neo@gmail.com>
11 * Copyright (c) 2011 Mircea Gherzan <mgherzan@gmail.com>
12 */
13
14 #ifndef _BPF_JIT_COMP_H
15 #define _BPF_JIT_COMP_H
16
17 /* MIPS registers */
18 #define MIPS_R_ZERO 0 /* Const zero */
19 #define MIPS_R_AT 1 /* Asm temp */
20 #define MIPS_R_V0 2 /* Result */
21 #define MIPS_R_V1 3 /* Result */
22 #define MIPS_R_A0 4 /* Argument */
23 #define MIPS_R_A1 5 /* Argument */
24 #define MIPS_R_A2 6 /* Argument */
25 #define MIPS_R_A3 7 /* Argument */
26 #define MIPS_R_A4 8 /* Arg (n64) */
27 #define MIPS_R_A5 9 /* Arg (n64) */
28 #define MIPS_R_A6 10 /* Arg (n64) */
29 #define MIPS_R_A7 11 /* Arg (n64) */
30 #define MIPS_R_T0 8 /* Temp (o32) */
31 #define MIPS_R_T1 9 /* Temp (o32) */
32 #define MIPS_R_T2 10 /* Temp (o32) */
33 #define MIPS_R_T3 11 /* Temp (o32) */
34 #define MIPS_R_T4 12 /* Temporary */
35 #define MIPS_R_T5 13 /* Temporary */
36 #define MIPS_R_T6 14 /* Temporary */
37 #define MIPS_R_T7 15 /* Temporary */
38 #define MIPS_R_S0 16 /* Saved */
39 #define MIPS_R_S1 17 /* Saved */
40 #define MIPS_R_S2 18 /* Saved */
41 #define MIPS_R_S3 19 /* Saved */
42 #define MIPS_R_S4 20 /* Saved */
43 #define MIPS_R_S5 21 /* Saved */
44 #define MIPS_R_S6 22 /* Saved */
45 #define MIPS_R_S7 23 /* Saved */
46 #define MIPS_R_T8 24 /* Temporary */
47 #define MIPS_R_T9 25 /* Temporary */
48 /* MIPS_R_K0 26 Reserved */
49 /* MIPS_R_K1 27 Reserved */
50 #define MIPS_R_GP 28 /* Global ptr */
51 #define MIPS_R_SP 29 /* Stack ptr */
52 #define MIPS_R_FP 30 /* Frame ptr */
53 #define MIPS_R_RA 31 /* Return */
54
55 /*
56 * Jump address mask for immediate jumps. The four most significant bits
57 * must be equal to PC.
58 */
59 #define MIPS_JMP_MASK 0x0fffffffUL
60
61 /* Maximum number of iterations in offset table computation */
62 #define JIT_MAX_ITERATIONS 8
63
64 /*
65 * Jump pseudo-instructions used internally
66 * for branch conversion and branch optimization.
67 */
68 #define JIT_JNSET 0xe0
69 #define JIT_JNOP 0xf0
70
71 /* Descriptor flag for PC-relative branch conversion */
72 #define JIT_DESC_CONVERT BIT(31)
73
74 /* JIT context for an eBPF program */
75 struct jit_context {
76 struct bpf_prog *program; /* The eBPF program being JITed */
77 u32 *descriptors; /* eBPF to JITed CPU insn descriptors */
78 u32 *target; /* JITed code buffer */
79 u32 bpf_index; /* Index of current BPF program insn */
80 u32 jit_index; /* Index of current JIT target insn */
81 u32 changes; /* Number of PC-relative branch conv */
82 u32 accessed; /* Bit mask of read eBPF registers */
83 u32 clobbered; /* Bit mask of modified CPU registers */
84 u32 stack_size; /* Total allocated stack size in bytes */
85 u32 saved_size; /* Size of callee-saved registers */
86 u32 stack_used; /* Stack size used for function calls */
87 };
88
89 /* Emit the instruction if the JIT memory space has been allocated */
90 #define __emit(ctx, func, ...) \
91 do { \
92 if ((ctx)->target != NULL) { \
93 u32 *p = &(ctx)->target[ctx->jit_index]; \
94 uasm_i_##func(&p, ##__VA_ARGS__); \
95 } \
96 (ctx)->jit_index++; \
97 } while (0)
98 #define emit(...) __emit(__VA_ARGS__)
99
100 /* Workaround for R10000 ll/sc errata */
101 #ifdef CONFIG_WAR_R10000_LLSC
102 #define LLSC_beqz beqzl
103 #else
104 #define LLSC_beqz beqz
105 #endif
106
107 /* Workaround for Loongson-3 ll/sc errata */
108 #ifdef CONFIG_CPU_LOONGSON3_WORKAROUNDS
109 #define LLSC_sync(ctx) emit(ctx, sync, 0)
110 #define LLSC_offset 4
111 #else
112 #define LLSC_sync(ctx)
113 #define LLSC_offset 0
114 #endif
115
116 /* Workaround for Loongson-2F jump errata */
117 #ifdef CONFIG_CPU_JUMP_WORKAROUNDS
118 #define JALR_MASK 0xffffffffcfffffffULL
119 #else
120 #define JALR_MASK (~0ULL)
121 #endif
122
123 /*
124 * Mark a BPF register as accessed, it needs to be
125 * initialized by the program if expected, e.g. FP.
126 */
access_reg(struct jit_context * ctx,u8 reg)127 static inline void access_reg(struct jit_context *ctx, u8 reg)
128 {
129 ctx->accessed |= BIT(reg);
130 }
131
132 /*
133 * Mark a CPU register as clobbered, it needs to be
134 * saved/restored by the program if callee-saved.
135 */
clobber_reg(struct jit_context * ctx,u8 reg)136 static inline void clobber_reg(struct jit_context *ctx, u8 reg)
137 {
138 ctx->clobbered |= BIT(reg);
139 }
140
141 /*
142 * Push registers on the stack, starting at a given depth from the stack
143 * pointer and increasing. The next depth to be written is returned.
144 */
145 int push_regs(struct jit_context *ctx, u32 mask, u32 excl, int depth);
146
147 /*
148 * Pop registers from the stack, starting at a given depth from the stack
149 * pointer and increasing. The next depth to be read is returned.
150 */
151 int pop_regs(struct jit_context *ctx, u32 mask, u32 excl, int depth);
152
153 /* Compute the 28-bit jump target address from a BPF program location */
154 int get_target(struct jit_context *ctx, u32 loc);
155
156 /* Compute the PC-relative offset to relative BPF program offset */
157 int get_offset(const struct jit_context *ctx, int off);
158
159 /* dst = imm (32-bit) */
160 void emit_mov_i(struct jit_context *ctx, u8 dst, s32 imm);
161
162 /* dst = src (32-bit) */
163 void emit_mov_r(struct jit_context *ctx, u8 dst, u8 src);
164
165 /* Validate ALU/ALU64 immediate range */
166 bool valid_alu_i(u8 op, s32 imm);
167
168 /* Rewrite ALU/ALU64 immediate operation */
169 bool rewrite_alu_i(u8 op, s32 imm, u8 *alu, s32 *val);
170
171 /* ALU immediate operation (32-bit) */
172 void emit_alu_i(struct jit_context *ctx, u8 dst, s32 imm, u8 op);
173
174 /* ALU register operation (32-bit) */
175 void emit_alu_r(struct jit_context *ctx, u8 dst, u8 src, u8 op);
176
177 /* Atomic read-modify-write (32-bit) */
178 void emit_atomic_r(struct jit_context *ctx, u8 dst, u8 src, s16 off, u8 code);
179
180 /* Atomic compare-and-exchange (32-bit) */
181 void emit_cmpxchg_r(struct jit_context *ctx, u8 dst, u8 src, u8 res, s16 off);
182
183 /* Swap bytes and truncate a register word or half word */
184 void emit_bswap_r(struct jit_context *ctx, u8 dst, u32 width);
185
186 /* Validate JMP/JMP32 immediate range */
187 bool valid_jmp_i(u8 op, s32 imm);
188
189 /* Prepare a PC-relative jump operation with immediate conditional */
190 void setup_jmp_i(struct jit_context *ctx, s32 imm, u8 width,
191 u8 bpf_op, s16 bpf_off, u8 *jit_op, s32 *jit_off);
192
193 /* Prepare a PC-relative jump operation with register conditional */
194 void setup_jmp_r(struct jit_context *ctx, bool same_reg,
195 u8 bpf_op, s16 bpf_off, u8 *jit_op, s32 *jit_off);
196
197 /* Finish a PC-relative jump operation */
198 int finish_jmp(struct jit_context *ctx, u8 jit_op, s16 bpf_off);
199
200 /* Conditional JMP/JMP32 immediate */
201 void emit_jmp_i(struct jit_context *ctx, u8 dst, s32 imm, s32 off, u8 op);
202
203 /* Conditional JMP/JMP32 register */
204 void emit_jmp_r(struct jit_context *ctx, u8 dst, u8 src, s32 off, u8 op);
205
206 /* Jump always */
207 int emit_ja(struct jit_context *ctx, s16 off);
208
209 /* Jump to epilogue */
210 int emit_exit(struct jit_context *ctx);
211
212 /*
213 * Build program prologue to set up the stack and registers.
214 * This function is implemented separately for 32-bit and 64-bit JITs.
215 */
216 void build_prologue(struct jit_context *ctx);
217
218 /*
219 * Build the program epilogue to restore the stack and registers.
220 * This function is implemented separately for 32-bit and 64-bit JITs.
221 */
222 void build_epilogue(struct jit_context *ctx, int dest_reg);
223
224 /*
225 * Convert an eBPF instruction to native instruction, i.e
226 * JITs an eBPF instruction.
227 * Returns :
228 * 0 - Successfully JITed an 8-byte eBPF instruction
229 * >0 - Successfully JITed a 16-byte eBPF instruction
230 * <0 - Failed to JIT.
231 * This function is implemented separately for 32-bit and 64-bit JITs.
232 */
233 int build_insn(const struct bpf_insn *insn, struct jit_context *ctx);
234
235 #endif /* _BPF_JIT_COMP_H */
236