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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Just-In-Time compiler for eBPF bytecode on 32-bit and 64-bit MIPS.
*
* 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>
*/
#ifndef _BPF_JIT_COMP_H
#define _BPF_JIT_COMP_H
/* MIPS registers */
#define MIPS_R_ZERO 0 /* Const zero */
#define MIPS_R_AT 1 /* Asm temp */
#define MIPS_R_V0 2 /* Result */
#define MIPS_R_V1 3 /* Result */
#define MIPS_R_A0 4 /* Argument */
#define MIPS_R_A1 5 /* Argument */
#define MIPS_R_A2 6 /* Argument */
#define MIPS_R_A3 7 /* Argument */
#define MIPS_R_A4 8 /* Arg (n64) */
#define MIPS_R_A5 9 /* Arg (n64) */
#define MIPS_R_A6 10 /* Arg (n64) */
#define MIPS_R_A7 11 /* Arg (n64) */
#define MIPS_R_T0 8 /* Temp (o32) */
#define MIPS_R_T1 9 /* Temp (o32) */
#define MIPS_R_T2 10 /* Temp (o32) */
#define MIPS_R_T3 11 /* Temp (o32) */
#define MIPS_R_T4 12 /* Temporary */
#define MIPS_R_T5 13 /* Temporary */
#define MIPS_R_T6 14 /* Temporary */
#define MIPS_R_T7 15 /* Temporary */
#define MIPS_R_S0 16 /* Saved */
#define MIPS_R_S1 17 /* Saved */
#define MIPS_R_S2 18 /* Saved */
#define MIPS_R_S3 19 /* Saved */
#define MIPS_R_S4 20 /* Saved */
#define MIPS_R_S5 21 /* Saved */
#define MIPS_R_S6 22 /* Saved */
#define MIPS_R_S7 23 /* Saved */
#define MIPS_R_T8 24 /* Temporary */
#define MIPS_R_T9 25 /* Temporary */
/* MIPS_R_K0 26 Reserved */
/* MIPS_R_K1 27 Reserved */
#define MIPS_R_GP 28 /* Global ptr */
#define MIPS_R_SP 29 /* Stack ptr */
#define MIPS_R_FP 30 /* Frame ptr */
#define MIPS_R_RA 31 /* Return */
/*
* Jump address mask for immediate jumps. The four most significant bits
* must be equal to PC.
*/
#define MIPS_JMP_MASK 0x0fffffffUL
/* Maximum number of iterations in offset table computation */
#define JIT_MAX_ITERATIONS 8
/*
* Jump pseudo-instructions used internally
* for branch conversion and branch optimization.
*/
#define JIT_JNSET 0xe0
#define JIT_JNOP 0xf0
/* Descriptor flag for PC-relative branch conversion */
#define JIT_DESC_CONVERT BIT(31)
/* JIT context for an eBPF program */
struct jit_context {
struct bpf_prog *program; /* The eBPF program being JITed */
u32 *descriptors; /* eBPF to JITed CPU insn descriptors */
u32 *target; /* JITed code buffer */
u32 bpf_index; /* Index of current BPF program insn */
u32 jit_index; /* Index of current JIT target insn */
u32 changes; /* Number of PC-relative branch conv */
u32 accessed; /* Bit mask of read eBPF registers */
u32 clobbered; /* Bit mask of modified CPU registers */
u32 stack_size; /* Total allocated stack size in bytes */
u32 saved_size; /* Size of callee-saved registers */
u32 stack_used; /* Stack size used for function calls */
};
/* Emit the instruction if the JIT memory space has been allocated */
#define emit(ctx, func, ...) \
do { \
if ((ctx)->target != NULL) { \
u32 *p = &(ctx)->target[ctx->jit_index]; \
uasm_i_##func(&p, ##__VA_ARGS__); \
} \
(ctx)->jit_index++; \
} while (0)
/*
* Mark a BPF register as accessed, it needs to be
* initialized by the program if expected, e.g. FP.
*/
static inline void access_reg(struct jit_context *ctx, u8 reg)
{
ctx->accessed |= BIT(reg);
}
/*
* Mark a CPU register as clobbered, it needs to be
* saved/restored by the program if callee-saved.
*/
static inline void clobber_reg(struct jit_context *ctx, u8 reg)
{
ctx->clobbered |= BIT(reg);
}
/*
* 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);
/*
* 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);
/* Compute the 28-bit jump target address from a BPF program location */
int get_target(struct jit_context *ctx, u32 loc);
/* Compute the PC-relative offset to relative BPF program offset */
int get_offset(const struct jit_context *ctx, int off);
/* dst = imm (32-bit) */
void emit_mov_i(struct jit_context *ctx, u8 dst, s32 imm);
/* dst = src (32-bit) */
void emit_mov_r(struct jit_context *ctx, u8 dst, u8 src);
/* Validate ALU/ALU64 immediate range */
bool valid_alu_i(u8 op, s32 imm);
/* Rewrite ALU/ALU64 immediate operation */
bool rewrite_alu_i(u8 op, s32 imm, u8 *alu, s32 *val);
/* ALU immediate operation (32-bit) */
void emit_alu_i(struct jit_context *ctx, u8 dst, s32 imm, u8 op);
/* ALU register operation (32-bit) */
void emit_alu_r(struct jit_context *ctx, u8 dst, u8 src, u8 op);
/* Atomic read-modify-write (32-bit) */
void emit_atomic_r(struct jit_context *ctx, u8 dst, u8 src, s16 off, u8 code);
/* Atomic compare-and-exchange (32-bit) */
void emit_cmpxchg_r(struct jit_context *ctx, u8 dst, u8 src, u8 res, s16 off);
/* Swap bytes and truncate a register word or half word */
void emit_bswap_r(struct jit_context *ctx, u8 dst, u32 width);
/* Validate JMP/JMP32 immediate range */
bool valid_jmp_i(u8 op, s32 imm);
/* 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);
/* 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);
/* Finish a PC-relative jump operation */
int finish_jmp(struct jit_context *ctx, u8 jit_op, s16 bpf_off);
/* Conditional JMP/JMP32 immediate */
void emit_jmp_i(struct jit_context *ctx, u8 dst, s32 imm, s32 off, u8 op);
/* Conditional JMP/JMP32 register */
void emit_jmp_r(struct jit_context *ctx, u8 dst, u8 src, s32 off, u8 op);
/* Jump always */
int emit_ja(struct jit_context *ctx, s16 off);
/* Jump to epilogue */
int emit_exit(struct jit_context *ctx);
/*
* Build program prologue to set up the stack and registers.
* This function is implemented separately for 32-bit and 64-bit JITs.
*/
void build_prologue(struct jit_context *ctx);
/*
* Build the program epilogue to restore the stack and registers.
* This function is implemented separately for 32-bit and 64-bit JITs.
*/
void build_epilogue(struct jit_context *ctx, int dest_reg);
/*
* Convert an eBPF instruction to native instruction, i.e
* JITs an eBPF instruction.
* Returns :
* 0 - Successfully JITed an 8-byte eBPF instruction
* >0 - Successfully JITed a 16-byte eBPF instruction
* <0 - Failed to JIT.
* This function is implemented separately for 32-bit and 64-bit JITs.
*/
int build_insn(const struct bpf_insn *insn, struct jit_context *ctx);
#endif /* _BPF_JIT_COMP_H */
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