/src/capstonenext/arch/BPF/BPFDisassembler.c

Source
/* Capstone Disassembly Engine */
/* BPF Backend by david942j <david942j@gmail.com>, 2019 */
/* SPDX-FileCopyrightText: 2024 Roee Toledano <roeetoledano10@gmail.com> */
/* SPDX-License-Identifier: BSD-3 */

#ifdef CAPSTONE_HAS_BPF

#include <string.h>
#include <stddef.h> // offsetof macro

#include "BPFConstants.h"
#include "BPFDisassembler.h"
#include "BPFMapping.h"
#include "../../Mapping.h"
#include "../../cs_priv.h"
#include "../../utils.h"

///< Malloc bpf_internal, also checks if code_len is large enough.
static bpf_internal *alloc_bpf_internal(const size_t code_len)
{
  bpf_internal *bpf;

  if (code_len < 8)
    return NULL;
  bpf = cs_mem_malloc(sizeof(bpf_internal));
  if (bpf == NULL)
    return NULL;
  /* default value */
  bpf->insn_size = 8;
  return bpf;
}

///< Fetch a cBPF structure from code
static bpf_internal *fetch_cbpf(MCInst *instr, const uint8_t *code,
        const size_t code_len)
{
  bpf_internal *bpf;

  bpf = alloc_bpf_internal(code_len);
  if (bpf == NULL)
    return NULL;

  bpf->op = readBytes16(instr, code);
  bpf->jt = code[2];
  bpf->jf = code[3];
  bpf->k = readBytes32(instr, code + 4);
  return bpf;
}

///< Fetch an eBPF structure from code
static bpf_internal *fetch_ebpf(MCInst *instr, const uint8_t *code,
        const size_t code_len)
{
  bpf_internal *bpf;

  bpf = alloc_bpf_internal(code_len);
  if (bpf == NULL)
    return NULL;

  bpf->op = (uint16_t)code[0];
  bpf->dst = code[1] & 0xf;
  bpf->src = (code[1] & 0xf0) >> 4;

  // eBPF has one 16-byte instruction: BPF_LD | BPF_DW | BPF_IMM,
  // in this case imm is combined with the next block's imm.
  if (bpf->op == (BPF_CLASS_LD | BPF_SIZE_DW | BPF_MODE_IMM)) {
    if (code_len < 16) {
      cs_mem_free(bpf);
      return NULL;
    }
    bpf->k = readBytes32(instr, code + 4) |
       (((uint64_t)readBytes32(instr, code + 12)) << 32);
    bpf->insn_size = 16;
  } else {
    bpf->offset = readBytes16(instr, code + 2);
    bpf->k = readBytes32(instr, code + 4);
  }
  return bpf;
}

#define CHECK_READABLE_REG(ud, reg) \
  do { \
    if (!((reg) >= BPF_REG_R0 && (reg) <= BPF_REG_R10)) \
      return false; \
  } while (0)

#define CHECK_WRITEABLE_REG(ud, reg) \
  do { \
    if (!((reg) >= BPF_REG_R0 && (reg) < BPF_REG_R10)) \
      return false; \
  } while (0)

#define CHECK_READABLE_AND_PUSH(ud, MI, r) \
  do { \
    CHECK_READABLE_REG(ud, r + BPF_REG_R0); \
    MCOperand_CreateReg0(MI, r + BPF_REG_R0); \
  } while (0)

#define CHECK_WRITABLE_AND_PUSH(ud, MI, r) \
  do { \
    CHECK_WRITEABLE_REG(ud, r + BPF_REG_R0); \
    MCOperand_CreateReg0(MI, r + BPF_REG_R0); \
  } while (0)

static bool decodeLoad(MCInst *MI, bpf_internal *bpf)
{
  if (!EBPF_MODE(MI->csh->mode)) {
    /*
     *  +-----+-----------+--------------------+
     *  | ldb |    [k]    |       [x+k]        |
     *  | ldh |    [k]    |       [x+k]        |
     *  +-----+-----------+--------------------+
     */
    if (BPF_SIZE(bpf->op) == BPF_SIZE_DW)
      return false;
    if (BPF_SIZE(bpf->op) == BPF_SIZE_B ||
        BPF_SIZE(bpf->op) == BPF_SIZE_H) {
      /* no ldx */
      if (BPF_CLASS(bpf->op) != BPF_CLASS_LD)
        return false;
      /* can only be BPF_ABS and BPF_IND */
      if (BPF_MODE(bpf->op) == BPF_MODE_ABS) {
        MCOperand_CreateImm0(MI, bpf->k);
        return true;
      } else if (BPF_MODE(bpf->op) == BPF_MODE_IND) {
        MCOperand_CreateReg0(MI, BPF_REG_X);
        MCOperand_CreateImm0(MI, bpf->k);
        return true;
      }
      return false;
    }
    /*
     *  +-----+----+------+------+-----+-------+
     *  | ld  | #k | #len | M[k] | [k] | [x+k] |
     *  +-----+----+------+------+-----+-------+
     *  | ldx | #k | #len | M[k] | 4*([k]&0xf) |
     *  +-----+----+------+------+-------------+
     */
    switch (BPF_MODE(bpf->op)) {
    default:
      break;
    case BPF_MODE_IMM:
      MCOperand_CreateImm0(MI, bpf->k);
      return true;
    case BPF_MODE_LEN:
      return true;
    case BPF_MODE_MEM:
      MCOperand_CreateImm0(MI, bpf->k);
      return true;
    }
    if (BPF_CLASS(bpf->op) == BPF_CLASS_LD) {
      if (BPF_MODE(bpf->op) == BPF_MODE_ABS) {
        MCOperand_CreateImm0(MI, bpf->k);
        return true;
      } else if (BPF_MODE(bpf->op) == BPF_MODE_IND) {
        MCOperand_CreateReg0(MI, BPF_REG_X);
        MCOperand_CreateImm0(MI, bpf->k);
        return true;
      }
    } else { /* LDX */
      if (BPF_MODE(bpf->op) == BPF_MODE_MSH) {
        MCOperand_CreateImm0(MI, bpf->k);
        return true;
      }
    }
    return false;
  }

  /* eBPF mode */
  /*
   * - IMM: lddw dst, imm64
   * - ABS: ld{w,h,b} [k]
   * - IND: ld{w,h,b} [src]
   * - MEM: ldx{w,h,b,dw} dst, [src+off]
   */
  if (BPF_CLASS(bpf->op) == BPF_CLASS_LD) {
    switch (BPF_MODE(bpf->op)) {
    case BPF_MODE_IMM:
      if (bpf->op !=
          (BPF_CLASS_LD | BPF_SIZE_DW | BPF_MODE_IMM))
        return false;
      CHECK_WRITABLE_AND_PUSH(ud, MI, bpf->dst);
      MCOperand_CreateImm0(MI, bpf->k);
      return true;
    case BPF_MODE_ABS:
      MCOperand_CreateImm0(MI, bpf->k);
      return true;
    case BPF_MODE_IND:
      CHECK_READABLE_AND_PUSH(ud, MI, bpf->src);
      return true;
    }
    return false;
  }
  /* LDX */
  if (BPF_MODE(bpf->op) == BPF_MODE_MEM) {
    CHECK_WRITABLE_AND_PUSH(ud, MI, bpf->dst);
    CHECK_READABLE_AND_PUSH(ud, MI, bpf->src);
    MCOperand_CreateImm0(MI, bpf->offset);
    return true;
  }
  return false;
}

static bool decodeStore(MCInst *MI, bpf_internal *bpf)
{
  /* in cBPF, only BPF_ST* | BPF_MEM | BPF_W is valid
   * while in eBPF:
   * - BPF_STX | BPF_XADD | BPF_{W,DW}
   * - BPF_ST* | BPF_MEM | BPF_{W,H,B,DW}
   * are valid
   */
  if (!EBPF_MODE(MI->csh->mode)) {
    /* can only store to M[] */
    if (bpf->op != (BPF_CLASS(bpf->op) | BPF_MODE_MEM | BPF_SIZE_W))
      return false;
    MCOperand_CreateImm0(MI, bpf->k);
    return true;
  }

  /* eBPF */
  if (BPF_MODE(bpf->op) == BPF_MODE_ATOMIC) {
    if (BPF_CLASS(bpf->op) != BPF_CLASS_STX)
      return false;
    if (BPF_SIZE(bpf->op) != BPF_SIZE_W &&
        BPF_SIZE(bpf->op) != BPF_SIZE_DW)
      return false;
    /* xadd [dst + off], src */
    CHECK_READABLE_AND_PUSH(ud, MI, bpf->dst);
    MCOperand_CreateImm0(MI, bpf->offset);
    CHECK_READABLE_AND_PUSH(ud, MI, bpf->src);
    return true;
  }

  if (BPF_MODE(bpf->op) != BPF_MODE_MEM)
    return false;

  /* st [dst + off], src */
  CHECK_READABLE_AND_PUSH(ud, MI, bpf->dst);
  MCOperand_CreateImm0(MI, bpf->offset);
  if (BPF_CLASS(bpf->op) == BPF_CLASS_ST)
    MCOperand_CreateImm0(MI, bpf->k);
  else
    CHECK_READABLE_AND_PUSH(ud, MI, bpf->src);
  return true;
}

static bool decodeALU(MCInst *MI, bpf_internal *bpf)
{
  /* Set MI->Operands */

  /* cBPF */
  if (!EBPF_MODE(MI->csh->mode)) {
    if (BPF_OP(bpf->op) > BPF_ALU_XOR)
      return false;
    /* cBPF's NEG has no operands */
    if (BPF_OP(bpf->op) == BPF_ALU_NEG)
      return true;
    if (BPF_SRC(bpf->op) == BPF_SRC_K)
      MCOperand_CreateImm0(MI, bpf->k);
    else /* BPF_SRC_X */
      MCOperand_CreateReg0(MI, BPF_REG_X);
    return true;
  }

  /* eBPF */

  if (BPF_OP(bpf->op) > BPF_ALU_END)
    return false;
  /* ENDian's imm must be one of 16, 32, 64 */
  if (BPF_OP(bpf->op) == BPF_ALU_END) {
    if (bpf->k != 16 && bpf->k != 32 && bpf->k != 64)
      return false;
    if (BPF_CLASS(bpf->op) == BPF_CLASS_ALU64 &&
        BPF_SRC(bpf->op) != BPF_SRC_LITTLE)
      return false;
  }

  /* - op dst, imm
   * - op dst, src
   * - neg dst
   * - le<imm> dst
   */
  /* every ALU instructions have dst op */
  CHECK_WRITABLE_AND_PUSH(ud, MI, bpf->dst);

  /* special cases */
  if (BPF_OP(bpf->op) == BPF_ALU_NEG)
    return true;
  if (BPF_OP(bpf->op) == BPF_ALU_END) {
    /* bpf->k must be one of 16, 32, 64 */
    bpf->op |= ((uint32_t)bpf->k << 4);
    return true;
  }

  /* normal cases */
  if (BPF_SRC(bpf->op) == BPF_SRC_K) {
    MCOperand_CreateImm0(MI, bpf->k);
  } else { /* BPF_SRC_X */
    CHECK_READABLE_AND_PUSH(ud, MI, bpf->src);
  }
  return true;
}

static bool decodeJump(MCInst *MI, bpf_internal *bpf)
{
  /* cBPF and eBPF are very different in class jump */
  if (!EBPF_MODE(MI->csh->mode)) {
    if (BPF_OP(bpf->op) > BPF_JUMP_JSET)
      return false;

    /* ja is a special case of jumps */
    if (BPF_OP(bpf->op) == BPF_JUMP_JA) {
      MCOperand_CreateImm0(MI, bpf->k);
      return true;
    }

    if (BPF_SRC(bpf->op) == BPF_SRC_K)
      MCOperand_CreateImm0(MI, bpf->k);
    else /* BPF_SRC_X */
      MCOperand_CreateReg0(MI, BPF_REG_X);
    MCOperand_CreateImm0(MI, bpf->jt);
    MCOperand_CreateImm0(MI, bpf->jf);
  } else {
    if (BPF_OP(bpf->op) > BPF_JUMP_JSLE)
      return false;

    /* JMP32 has no CALL/EXIT instruction */
    /* No operands for exit */
    if (BPF_OP(bpf->op) == BPF_JUMP_EXIT)
      return bpf->op == (BPF_CLASS_JMP | BPF_JUMP_EXIT);
    if (BPF_OP(bpf->op) == BPF_JUMP_CALL) {
      if (bpf->op == (BPF_CLASS_JMP | BPF_JUMP_CALL)) {
        MCOperand_CreateImm0(MI, bpf->k);
        return true;
      }
      if (bpf->op ==
          (BPF_CLASS_JMP | BPF_JUMP_CALL | BPF_SRC_X)) {
        CHECK_READABLE_AND_PUSH(ud, MI, bpf->k);
        return true;
      }
      return false;
    }

    /* ja is a special case of jumps */
    if (BPF_OP(bpf->op) == BPF_JUMP_JA) {
      if (BPF_SRC(bpf->op) != BPF_SRC_K)
        return false;
      if (BPF_CLASS(bpf->op) == BPF_CLASS_JMP)
        MCOperand_CreateImm0(MI, bpf->offset);
      else
        MCOperand_CreateImm0(MI, bpf->k);

      return true;
    }

    /* <j>  dst, src, +off */
    CHECK_READABLE_AND_PUSH(ud, MI, bpf->dst);
    if (BPF_SRC(bpf->op) == BPF_SRC_K)
      MCOperand_CreateImm0(MI, bpf->k);
    else
      CHECK_READABLE_AND_PUSH(ud, MI, bpf->src);
    MCOperand_CreateImm0(MI, bpf->offset);
  }
  return true;
}

static bool decodeReturn(MCInst *MI, bpf_internal *bpf)
{
  /* Here only handles the BPF_RET class in cBPF */
  switch (BPF_RVAL(bpf->op)) {
  case BPF_SRC_K:
    MCOperand_CreateImm0(MI, bpf->k);
    return true;
  case BPF_SRC_X:
    MCOperand_CreateReg0(MI, BPF_REG_X);
    return true;
  case BPF_SRC_A:
    MCOperand_CreateReg0(MI, BPF_REG_A);
    return true;
  }
  return false;
}

static bool decodeMISC(MCInst *MI, bpf_internal *bpf)
{
  uint16_t op = bpf->op ^ BPF_CLASS_MISC;
  return op == BPF_MISCOP_TAX || op == BPF_MISCOP_TXA;
}

///< 1. Check if the instruction is valid
///< 2. Set MI->opcode
///< 3. Set MI->Operands
static bool getInstruction(MCInst *MI, bpf_internal *bpf)
{
  cs_detail *detail;

  detail = MI->flat_insn->detail;
  // initialize detail
  if (detail) {
    memset(detail, 0, offsetof(cs_detail, bpf) + sizeof(cs_bpf));
  }

  MCInst_clear(MI);

  switch (BPF_CLASS(bpf->op)) {
  default: /* should never happen */
    return false;
  case BPF_CLASS_LD:
  case BPF_CLASS_LDX:
    return decodeLoad(MI, bpf);
  case BPF_CLASS_ST:
  case BPF_CLASS_STX:
    return decodeStore(MI, bpf);
  case BPF_CLASS_ALU:
    return decodeALU(MI, bpf);
  case BPF_CLASS_JMP:
    return decodeJump(MI, bpf);
  case BPF_CLASS_RET:
    /* case BPF_CLASS_JMP32: */
    if (EBPF_MODE(MI->csh->mode))
      return decodeJump(MI, bpf);
    else
      return decodeReturn(MI, bpf);
  case BPF_CLASS_MISC:
    /* case BPF_CLASS_ALU64: */
    if (EBPF_MODE(MI->csh->mode))
      return decodeALU(MI, bpf);
    else
      return decodeMISC(MI, bpf);
  }
}

// Check for regular load instructions
#define REG_LOAD_CASE(c) \
  case BPF_SIZE_##c: \
    if (BPF_CLASS(opcode) == BPF_CLASS_LD) \
      return BPF_INS_LD##c; \
    else \
      return BPF_INS_LDX##c;

static bpf_insn op2insn_ld_cbpf(unsigned opcode)
{
  switch (BPF_SIZE(opcode)) {
    REG_LOAD_CASE(W);
    REG_LOAD_CASE(H);
    REG_LOAD_CASE(B);
    REG_LOAD_CASE(DW);
  }

  return BPF_INS_INVALID;
}
#undef REG_LOAD_CASE

// Check for packet load instructions
#define PACKET_LOAD_CASE(c) \
  case BPF_SIZE_##c: \
    if (BPF_MODE(opcode) == BPF_MODE_ABS) \
      return BPF_INS_LDABS##c; \
    else if (BPF_MODE(opcode) == BPF_MODE_IND) \
      return BPF_INS_LDIND##c; \
    else \
      return BPF_INS_INVALID;

static bpf_insn op2insn_ld_ebpf(unsigned opcode)
{
  if (BPF_CLASS(opcode) == BPF_CLASS_LD) {
    switch (BPF_SIZE(opcode)) {
      PACKET_LOAD_CASE(W);
      PACKET_LOAD_CASE(H);
      PACKET_LOAD_CASE(B);
    }
  }

  // If it's not a packet load instruction, it must be a regular load instruction
  return op2insn_ld_cbpf(opcode);
}
#undef PACKET_LOAD_CASE

/* During parsing we already checked to make sure the size is D/DW and 
 * mode is STX and not ST, so we don't need to check again*/
#define ALU_CASE_REG(c) \
  case BPF_ALU_##c: \
    if (BPF_SIZE(opcode) == BPF_SIZE_W) \
      return BPF_INS_A##c; \
    else \
      return BPF_INS_A##c##64;

#define ALU_CASE_FETCH(c) \
  case BPF_ALU_##c | BPF_MODE_FETCH: \
    if (BPF_SIZE(opcode) == BPF_SIZE_W) \
      return BPF_INS_AF##c; \
    else \
      return BPF_INS_AF##c##64;

#define COMPLEX_CASE(c) \
  case BPF_ATOMIC_##c | BPF_MODE_FETCH: \
    if (BPF_SIZE(opcode) == BPF_SIZE_DW) \
      return BPF_INS_A##c##64; \
    else \
      return BPF_INS_INVALID;

#define CASE(c) \
  case BPF_SIZE_##c: \
    if (BPF_CLASS(opcode) == BPF_CLASS_ST) \
      return BPF_INS_ST##c; \
    else \
      return BPF_INS_STX##c;

static bpf_insn op2insn_st(unsigned opcode, const uint32_t imm)
{
  /*
   * - BPF_STX | ALU atomic operations | BPF_{W,DW}
   * - BPF_STX | Complex atomic operations | BPF_{DW}
   * - BPF_ST* | BPF_MEM | BPF_{W,H,B,DW}
   */

  if (BPF_MODE(opcode) == BPF_MODE_ATOMIC) {
    switch (imm) {
      ALU_CASE_REG(ADD);
      ALU_CASE_REG(OR);
      ALU_CASE_REG(AND);
      ALU_CASE_REG(XOR);
      ALU_CASE_FETCH(ADD);
      ALU_CASE_FETCH(OR);
      ALU_CASE_FETCH(AND);
      ALU_CASE_FETCH(XOR);
      COMPLEX_CASE(XCHG);
      COMPLEX_CASE(CMPXCHG);
    default: // Reached if complex atomic operation is used without fetch modifier
      return BPF_INS_INVALID;
    }
  }

  /* should be BPF_MEM */
  switch (BPF_SIZE(opcode)) {
    CASE(W);
    CASE(H);
    CASE(B);
    CASE(DW);
  }

  return BPF_INS_INVALID;
}
#undef CASE

#define CASE(c) \
  case BPF_ALU_##c: \
    CASE_IF(c)

#define CASE_IF(c) \
  do { \
    if (BPF_CLASS(opcode) == BPF_CLASS_ALU) \
      return BPF_INS_##c; \
    else \
      return BPF_INS_##c##64; \
  } while (0)

static bpf_insn op2insn_alu(unsigned opcode, const uint16_t off,
          const bool is_ebpf)
{
  /* Endian is a special case */
  if (BPF_OP(opcode) == BPF_ALU_END) {
    if (BPF_CLASS(opcode) == BPF_CLASS_ALU64) {
      switch (opcode ^ BPF_CLASS_ALU64 ^ BPF_ALU_END ^
        BPF_SRC_LITTLE) {
      case (16 << 4):
        return BPF_INS_BSWAP16;
      case (32 << 4):
        return BPF_INS_BSWAP32;
      case (64 << 4):
        return BPF_INS_BSWAP64;
      default:
        return BPF_INS_INVALID;
      }
    }

    switch (opcode ^ BPF_CLASS_ALU ^ BPF_ALU_END) {
    case BPF_SRC_LITTLE | (16 << 4):
      return BPF_INS_LE16;
    case BPF_SRC_LITTLE | (32 << 4):
      return BPF_INS_LE32;
    case BPF_SRC_LITTLE | (64 << 4):
      return BPF_INS_LE64;
    case BPF_SRC_BIG | (16 << 4):
      return BPF_INS_BE16;
    case BPF_SRC_BIG | (32 << 4):
      return BPF_INS_BE32;
    case BPF_SRC_BIG | (64 << 4):
      return BPF_INS_BE64;
    }
    return BPF_INS_INVALID;
  }

  switch (BPF_OP(opcode)) {
    CASE(ADD);
    CASE(SUB);
    CASE(MUL);
    CASE(OR);
    CASE(AND);
    CASE(LSH);
    CASE(RSH);
    CASE(NEG);
    CASE(XOR);
    CASE(ARSH);
  case BPF_ALU_DIV:
    if (!is_ebpf || off == 0)
      CASE_IF(DIV);
    else if (off == 1)
      CASE_IF(SDIV);
    else
      return BPF_INS_INVALID;
  case BPF_ALU_MOD:
    if (!is_ebpf || off == 0)
      CASE_IF(MOD);
    else if (off == 1)
      CASE_IF(SMOD);
    else
      return BPF_INS_INVALID;
  case BPF_ALU_MOV:
    /* BPF_CLASS_ALU can have: mov, mov8s, mov16s
     * BPF_CLASS_ALU64 can have: mov, mov8s, mov16s, mov32s
     * */
    if (off == 0)
      CASE_IF(MOV);
    else if (off == 8)
      CASE_IF(MOVSB);
    else if (off == 16)
      CASE_IF(MOVSH);
    else if (off == 32 && BPF_CLASS(opcode) == BPF_CLASS_ALU64)
      return BPF_INS_MOVSW64;
    else
      return BPF_INS_INVALID;
  }

  return BPF_INS_INVALID;
}
#undef CASE_IF
#undef CASE

#define BPF_CALLX (BPF_CLASS_JMP | BPF_JUMP_CALL | BPF_SRC_X)

#define CASE(c) \
  case BPF_JUMP_##c: \
    if (BPF_CLASS(opcode) == BPF_CLASS_JMP) \
      return BPF_INS_##c; \
    else \
      return BPF_INS_##c##32;

#define SPEC_CASE(c) \
  case BPF_JUMP_##c: \
    if (BPF_CLASS(opcode) == BPF_CLASS_JMP) \
      return BPF_INS_##c; \
    else \
      return BPF_INS_INVALID;

static bpf_insn op2insn_jmp(unsigned opcode)
{
  if (opcode == BPF_CALLX) {
    return BPF_INS_CALLX;
  }

  switch (BPF_OP(opcode)) {
  case BPF_JUMP_JA:
    if (BPF_CLASS(opcode) == BPF_CLASS_JMP)
      return BPF_INS_JA;
    else
      return BPF_INS_JAL;
    CASE(JEQ);
    CASE(JGT);
    CASE(JGE);
    CASE(JSET);
    CASE(JNE);
    CASE(JSGT);
    CASE(JSGE);
    SPEC_CASE(CALL);
    SPEC_CASE(EXIT);
    CASE(JLT);
    CASE(JLE);
    CASE(JSLT);
    CASE(JSLE);
  }

  return BPF_INS_INVALID;
}
#undef SPEC_CASE
#undef CASE
#undef BPF_CALLX

#ifndef CAPSTONE_DIET

static void update_regs_access(MCInst *MI, cs_detail *detail, bpf_insn insn_id,
             unsigned int opcode)
{
  if (insn_id == BPF_INS_INVALID)
    return;
  /*
   * In eBPF mode, only these instructions have implicit registers access:
   * - legacy ld{w,h,b,dw} * // w: r0
   * - exit // r: r0
   */
  if (EBPF_MODE(MI->csh->mode)) {
    switch (insn_id) {
    default:
      break;
    case BPF_INS_LDABSW:
    case BPF_INS_LDABSH:
    case BPF_INS_LDABSB:
    case BPF_INS_LDINDW:
    case BPF_INS_LDINDH:
    case BPF_INS_LDINDB:
    case BPF_INS_LDDW:
      if (BPF_MODE(opcode) == BPF_MODE_ABS ||
          BPF_MODE(opcode) == BPF_MODE_IND)
        map_add_implicit_write(MI, BPF_REG_R0);
      break;
    case BPF_INS_EXIT:
      map_add_implicit_read(MI, BPF_REG_R0);
      break;
    }
    return;
  }

  /* cBPF mode */
  switch (BPF_CLASS(opcode)) {
  default:
    break;
  case BPF_CLASS_LD:
    map_add_implicit_write(MI, BPF_REG_A);
    break;
  case BPF_CLASS_LDX:
    map_add_implicit_write(MI, BPF_REG_X);
    break;
  case BPF_CLASS_ST:
    map_add_implicit_read(MI, BPF_REG_A);
    break;
  case BPF_CLASS_STX:
    map_add_implicit_read(MI, BPF_REG_X);
    break;
  case BPF_CLASS_ALU:
    map_add_implicit_read(MI, BPF_REG_A);
    map_add_implicit_write(MI, BPF_REG_A);
    break;
  case BPF_CLASS_JMP:
    if (insn_id != BPF_INS_JA) // except the unconditional jump
      map_add_implicit_read(MI, BPF_REG_A);
    break;
  /* case BPF_CLASS_RET: */
  case BPF_CLASS_MISC:
    if (insn_id == BPF_INS_TAX) {
      map_add_implicit_read(MI, BPF_REG_A);
      map_add_implicit_write(MI, BPF_REG_X);
    } else {
      map_add_implicit_read(MI, BPF_REG_X);
      map_add_implicit_write(MI, BPF_REG_A);
    }
    break;
  }
}
#endif

static bool setFinalOpcode(MCInst *MI, const bpf_internal *bpf)
{
  bpf_insn id = BPF_INS_INVALID;
#ifndef CAPSTONE_DIET
  cs_detail *detail;

  detail = get_detail(MI);
#endif

  const uint16_t opcode = bpf->op;
  switch (BPF_CLASS(opcode)) {
  default: // will never happen
    break;
  case BPF_CLASS_LD:
  case BPF_CLASS_LDX:
    if (EBPF_MODE(MI->csh->mode))
      id = op2insn_ld_ebpf(opcode);
    else
      id = op2insn_ld_cbpf(opcode);
    add_group(MI, BPF_GRP_LOAD);
    break;
  case BPF_CLASS_ST:
  case BPF_CLASS_STX:
    id = op2insn_st(opcode, bpf->k);
    add_group(MI, BPF_GRP_STORE);
    break;
  case BPF_CLASS_ALU:
    id = op2insn_alu(opcode, bpf->offset, EBPF_MODE(MI->csh->mode));
    add_group(MI, BPF_GRP_ALU);
    break;
  case BPF_CLASS_JMP:
    id = op2insn_jmp(opcode);
#ifndef CAPSTONE_DIET
    if (id == BPF_INS_CALL || id == BPF_INS_CALLX)
      add_group(MI, BPF_GRP_CALL);
    else if (id == BPF_INS_EXIT)
      add_group(MI, BPF_GRP_RETURN);
    else
      add_group(MI, BPF_GRP_JUMP);
#endif
    break;
  case BPF_CLASS_RET:
    /* case BPF_CLASS_JMP32: */
    if (EBPF_MODE(MI->csh->mode)) {
      id = op2insn_jmp(opcode);
      add_group(MI, BPF_GRP_JUMP);
    } else {
      id = BPF_INS_RET;
      add_group(MI, BPF_GRP_RETURN);
    }
    break;
  // BPF_CLASS_MISC and BPF_CLASS_ALU64 have exactly same value
  case BPF_CLASS_MISC:
    /* case BPF_CLASS_ALU64: */
    if (EBPF_MODE(MI->csh->mode)) {
      // ALU64 in eBPF
      id = op2insn_alu(opcode, bpf->offset, true);
      add_group(MI, BPF_GRP_ALU);
    } else {
      if (BPF_MISCOP(opcode) == BPF_MISCOP_TXA)
        id = BPF_INS_TXA;
      else
        id = BPF_INS_TAX;
      add_group(MI, BPF_GRP_MISC);
    }
    break;
  }

  if (id == BPF_INS_INVALID)
    return false;

  MCInst_setOpcodePub(MI, id);
#undef PUSH_GROUP

#ifndef CAPSTONE_DIET
  if (detail) {
    update_regs_access(MI, detail, id, opcode);
  }
#endif
  return true;
}

bool BPF_getInstruction(csh ud, const uint8_t *code, size_t code_len,
      MCInst *instr, uint16_t *size, uint64_t address,
      void *info)
{
  bpf_internal *bpf;

  if (EBPF_MODE(instr->csh->mode))
    bpf = fetch_ebpf(instr, code, code_len);
  else
    bpf = fetch_cbpf(instr, code, code_len);
  if (bpf == NULL)
    return false;
  if (!getInstruction(instr, bpf) || !setFinalOpcode(instr, bpf)) {
    cs_mem_free(bpf);
    return false;
  }
  MCInst_setOpcode(instr, bpf->op);

  *size = bpf->insn_size;
  cs_mem_free(bpf);

  return true;
}

#endif

Coverage Report

Created: 2026-01-12 07:13