说明
看雪大牛罗聪写的Little C编译器，词法和语法分析分别采用lex和yacc编写。定义了一套自己的bytecode，以及写了一个虚拟机（叫模拟器更准确）去执行它。 这是一份10年前的代码！！！
https://bbs.pediy.com/thread-149966.htm
编译说明
从官网下载的flex编译不了，于是将flex和bison替换为win_flex和bison，编译通过。
https://sourceforge.net/projects/winflexbison/
运行mk.bat脚本，生成parse.c和scan.c。
WinFlexBison
lex(flex)与yacc(bison)，lex与yacc是两个在Unix下的分别作词法分析和语法分析的工具，已被移植到win平台下。
https://github.com/lexxmark/winflexbison
自定义的虚拟机操作码VM_OPER
typedef enum _OPCODE
{
emOP_NOP = 0,
emOP_SubSp,
emOP_Hlt,
emOP_Ret,
emOP_Pop,
emOP_Add_i,
emOP_Sub_i,
emOP_Mul_i,
emOP_Div_i,
emOP_Mod_i,
emOP_Jmp,
emOP_Je,
emOP_Jne,
emOP_Call,
emOP_Libcall,
emOP_Li_i,
emOP_Libp_i,
emOP_Ld_i,
emOP_Ld_b,
emOP_St_i,
emOP_St_b,
emOP_Libp_data,
emOP_And_i,
emOP_Xor_i,
emOP_Or_i,
emOP_Shl_i,
emOP_Shr_i,
emOP_Neg_i,
emOP_Not_i,
emOP_Cvt_b_i,
emOP_Cvt_b_w,
emOP_CmpEq_i,
emOP_CmpNe_i,
emOP_CmpLt_i,
emOP_CmpGt_i,
emOP_CmpLe_i,
emOP_CmpGe_i,
emOP_MAX_COUNT,
} OPCODE;
虚拟机码对应的助记符
static CONST OPER g_OperMap[] =
{
{ emOP_NOP, "nop", 1 },
{ emOP_SubSp, "subsp", 1 + sizeof_i },
{ emOP_Hlt, "hlt", 1 },
{ emOP_Ret, "ret", 1 },
{ emOP_Pop, "pop", 1 },
{ emOP_Add_i, "add_i", 1 },
{ emOP_Sub_i, "sub_i", 1 },
{ emOP_Mul_i, "mul_i", 1 },
{ emOP_Div_i, "div_i", 1 },
{ emOP_Mod_i, "mod_i", 1 },
{ emOP_Jmp, "jmp", 1 + sizeof_i },
{ emOP_Je, "je", 1 + sizeof_i },
{ emOP_Jne, "jne", 1 + sizeof_i },
{ emOP_Call, "call", 1 + sizeof_i },
{ emOP_Libcall, "libcall", 1 + sizeof_i },
{ emOP_Li_i, "li_i", 1 + sizeof_i },
{ emOP_Libp_i, "libp_i", 1 + sizeof_i },
{ emOP_Ld_i, "ld_i", 1 },
{ emOP_Ld_b, "ld_b", 1 },
{ emOP_St_i, "st_i", 1 },
{ emOP_St_b, "st_b", 1 },
{ emOP_Libp_data, "libp_data",1 },
{ emOP_And_i, "and_i", 1 },
{ emOP_Xor_i, "xor_i", 1 },
{ emOP_Or_i, "or_i", 1 },
{ emOP_Shl_i, "shl_i", 1 },
{ emOP_Shr_i, "shr_i", 1 },
{ emOP_Neg_i, "neg_i", 1 },
{ emOP_Not_i, "not_i", 1 },
{ emOP_Cvt_b_i, "cvt_b_i", 1 },
{ emOP_Cvt_b_w, "cvt_b_w", 1 },
{ emOP_CmpEq_i, "cmpeq_i", 1 },
{ emOP_CmpNe_i, "cmpne_i", 1 },
{ emOP_CmpLt_i, "cmplt_i", 1 },
{ emOP_CmpGt_i, "cmpgt_i", 1 },
{ emOP_CmpLe_i, "cmple_i", 1 },
{ emOP_CmpGe_i, "cmpge_i", 1 },
};在虚拟机中运行代码
VM_STATUS VM_Interpret(
CONST INT nCodeSize, CONST PBYTE pbyCode,
CONST INT nDataSize, CONST PBYTE pbyData,
CONST INT nStackSize, INT pStack[]
)
{
VM_STATUS VMStatus;
PINT sp;
PINT bp;
INT pc;
BYTE f;
INT a;
INT b;
#ifndef get_a
#define get_a() *(INT *)&pbyCode[pc], pc += sizeof_i
#endif
if (FALSE == VM_CheckCodeValid(nCodeSize, pbyCode))
{
VM_Printf("-----\nVM code checking not valid.");
VM_Abort(&VMStatus);
return VMStatus;
}
// VM initialize
pc = 0;
VMStatus = emVS_Running;
bp = sp = pStack + nStackSize;
while (emVS_Running == VMStatus)
{
if (sp - pStack < 0)
{
VM_Error(emVEI_Runtime_Error_Stack_Overflow);
VM_Abort(&VMStatus);
continue;
}
f = pbyCode[pc++];
switch (f)
{
case emOP_NOP:
break;
case emOP_Pop:
++sp;
break;
case emOP_SubSp:
a = get_a();
sp = (PINT)((INT)sp - a);
break;
case emOP_Hlt:
VMStatus = emVS_Halt;
break;
case emOP_Add_i:
++sp;
sp[0] += sp[-1];
break;
case emOP_Sub_i:
++sp;
sp[0] -= sp[-1];
break;
case emOP_Mul_i:
++sp;
sp[0] *= sp[-1];
break;
case emOP_Div_i:
++sp;
if (0 == sp[-1])
{
VM_Error(emVEI_Runtime_Error_Divided_By_Zero);
VM_Abort(&VMStatus);
continue;
}
sp[0] /= sp[-1];
break;
case emOP_Mod_i:
++sp;
if (0 == sp[-1])
{
VM_Error(emVEI_Runtime_Error_Divided_By_Zero);
VM_Abort(&VMStatus);
continue;
}
sp[0] %= sp[-1];
break;
case emOP_And_i:
++sp;
sp[0] &= sp[-1];
break;
case emOP_Xor_i:
++sp;
sp[0] ^= sp[-1];
break;
case emOP_Or_i:
++sp;
sp[0] |= sp[-1];
break;
case emOP_Shl_i:
++sp;
sp[0] <<= sp[-1];
break;
case emOP_Shr_i:
++sp;
sp[0] >>= sp[-1];
break;
case emOP_Neg_i:
sp[0] = -sp[0];
break;
case emOP_Not_i:
sp[0] = ~sp[0];
break;
case emOP_Cvt_b_i:
sp[0] = (CHAR)sp[0];
break;
case emOP_Cvt_b_w:
sp[0] = (SHORT)sp[0];
break;
case emOP_CmpEq_i:
++sp;
sp[0] = sp[0] == sp[-1];
break;
case emOP_CmpNe_i:
++sp;
sp[0] = sp[0] != sp[-1];
break;
case emOP_CmpLt_i:
++sp;
sp[0] = sp[0] < sp[-1];
break;
case emOP_CmpGt_i:
++sp;
sp[0] = sp[0] > sp[-1];
break;
case emOP_CmpLe_i:
++sp;
sp[0] = sp[0] <= sp[-1];
break;
case emOP_CmpGe_i:
++sp;
sp[0] = sp[0] >= sp[-1];
break;
case emOP_Jmp:
a = get_a();
pc = a;
break;
case emOP_Je:
a = get_a();
if (sp[0] == 0)
pc = a;
++sp;
break;
case emOP_Jne:
a = get_a();
if (sp[0] != 0)
pc = a;
++sp;
break;
case emOP_Libcall:
a = get_a(); // function index
--sp;
LibCall(bp, sp, a);
b = sp[0]; // return value
++sp;
sp[0] = b; // return value
break;
case emOP_Call:
b = sp[0]; // li_i XXXXXXXX, means function's offset
a = get_a(); // get param-size
Push_i(pc); // return pc
Push_i((INT)bp); // bp
Push_i(a); // param-size
bp = sp; // mov ebp, esp
pc = b; // set pc to new position
break;
case emOP_Ret:
a = sp[0]; // return value
sp = bp; // mov esp, ebp
b = Pop_i(); // param-size
bp = (PINT)Pop_i(); // pop ebp
pc = Pop_i(); // restore return position
sp = (PINT)((INT)sp + b); // eat up param's space
sp[0] = a; // return value
break;
case emOP_Li_i:
a = get_a();
Push_i(a);
break;
case emOP_Libp_i:
a = get_a();
Push_i((INT)bp - a);
break;
case emOP_Ld_i:
sp[0] = *((INT *)sp[0]);
break;
case emOP_Ld_b:
sp[0] = *((CHAR *)sp[0]);
break;
case emOP_St_i:
*((INT *)sp[0]) = sp[1];
++sp;
break;
case emOP_St_b:
*((BYTE *)sp[0]) = sp[1] & 0xff;
++sp;
break;
case emOP_Libp_data:
sp[0] = (INT)&pbyData[sp[0]];
break;
default:
break;
} // switch
} // while
return VMStatus;
}lib.c
lib.c中定义了作者实现的虚拟机函数。
//
// Lib-call define
//
typedef enum _LIB_CALL_INDEX
{
emLCI_printnum = 0,
emLCI_printstr,
emLCI_strcpy,
emLCI_strcat,
emLCI_strlen,
emLCI_DeleteFile,
emLCI_MAX_COUNT,
} LIB_CALL_INDEX;
其他资料
编译原理
《lex和yacc从入门到精通》
flex: the fast lexical analyser
应用
程序的关键算法的加密保护，增加破解难度。