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#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
enum instr {
PushRef,
PushI,
Put,
Pop,
Call,
Jmp,
JmpTrue,
Ret,
Halt,
IAddRet,
IMulRet,
ISubRet,
IDivRet
};
static inline uint32_t instr_size(enum instr instr) {
switch (instr) {
case PushRef: return 5+1;
case PushI: return 7+1;
case Put: return 1+5;
case Pop: return 4;
case Call: return 5;
case Jmp: return 5;
case JmpTrue: return 1+3+6;
case Ret: return 1;
case Halt: return 1+1;
case IAddRet:
case ISubRet: return 5+5+3+5+1;
case IMulRet: return 5+5+4+5+1;
case IDivRet: return 5+5+3+3+5+1;
default:
fprintf(stderr,"unknown instruction %d\n",instr);
exit(1);
}
}
static inline void gen_instr(char *full_code, char **code_p, uint64_t **pgm_p, uint32_t *mapping) {
uint64_t arg;
char *code=*code_p;
uint64_t *pgm=*pgm_p;
switch (*pgm) {
case PushRef:
arg=pgm[1];
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"PushRef %ld\n",arg);
#endif
code[0]='\x48'; /* mov rcx,[rsp+ARG*8] */
code[1]='\x8b';
code[2]='\x4c';
code[3]='\x24';
code[4]=(unsigned char)arg*8;
code[5]='\x51'; /* push rcx */
pgm+=2;
code+=6;
break;
case PushI:
arg=pgm[1];
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"PushI %lu\n",arg);
#endif
code[0]='\x48'; /* mov rcx,ARG */
code[1]='\xc7';
code[2]='\xc1';
*(uint32_t*)&code[3]=(uint32_t)arg;
code[7]='\x51'; /* push rcx */
pgm+=2;
code+=8;
break;
case Put:
arg=pgm[1];
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"Put %lu\n",arg);
#endif
code[0]='\x59'; /* pop rcx */
code[1]='\x48'; /* mov [rsp+ARG*8],rcx */
code[2]='\x89';
code[3]='\x4c';
code[4]='\x24';
code[5]=(unsigned char)arg*8;
pgm+=2;
code+=6;
break;
case Pop:
arg=pgm[1];
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"Pop %lu\n",arg);
#endif
code[0]='\x48'; /* add rsp,ARG*8 */
code[1]='\x83';
code[2]='\xc4';
code[3]=(unsigned char)arg*8;
pgm+=2;
code+=4;
break;
case Call:
arg=pgm[1];
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"Call %lu -> %d\n",arg,mapping[arg]-(uint32_t)(&code[5]-full_code));
#endif
code[0]='\xe8'; /* callq ARG */
*(uint32_t*)&code[1]=mapping[arg]-(&code[5]-full_code);
pgm+=2;
code+=5;
break;
case Jmp:
arg=pgm[1];
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"Jmp %lu -> %d\n",arg,mapping[arg]-(uint32_t)(&code[5]-full_code));
#endif
code[0]='\xe9'; /* jmpq ARG */
*(uint32_t*)&code[1]=mapping[arg]-(&code[5]-full_code);
pgm+=2;
code+=5;
break;
case JmpTrue:
arg=pgm[1];
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"JmpTrue %lu -> %d\n",arg,mapping[arg]-(uint32_t)(&code[10]-full_code));
#endif
code[0]='\x59'; /* pop rcx */
code[1]='\x48'; /* test rcx,rcx */
code[2]='\x85';
code[3]='\xc9';
code[4]='\x0f'; /* jne ARG */
code[5]='\x85';
*(uint32_t*)&code[6]=mapping[arg]-(&code[10]-full_code);
pgm+=2;
code+=10;
break;
case Ret:
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"Ret\n");
#endif
code[0]='\xc3'; /* retq */
pgm++;
code+=1;
break;
case Halt:
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"Halt\n");
#endif
code[0]='\x58'; /* pop rax */
code[1]='\xc3'; /* retq */
pgm++;
code+=2;
break;
case IAddRet:
case IMulRet:
case ISubRet:
case IDivRet:
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"I<Op>Ret\n");
#endif
/* mov rax,[rsp+8] */
code[0]='\x48'; code[1]='\x8b'; code[2]='\x44'; code[3]='\x24'; code[4]='\x08';
/* mov rcx,[rsp+16] */
code[5]='\x48'; code[6]='\x8b'; code[7]='\x4c'; code[8]='\x24'; code[9]='\x10';
switch (*pgm) {
case IAddRet:
case ISubRet:
/* {add,sub} rax,rcx */
code[10]='\x48';
code[11]=*pgm==IAddRet ? '\x01' : '\x29';
code[12]='\xc8';
code+=13;
break;
case IMulRet:
/* imul rax,rcx */
code[10]='\x48'; code[11]='\x0f'; code[12]='\xaf'; code[13]='\xc1';
code+=14;
break;
case IDivRet:
/* xor rdx,rdx */
code[10]='\x48'; code[11]='\x31'; code[12]='\xd2';
/* idiv rcx */
code[13]='\x48'; code[14]='\xf7'; code[15]='\xf9';
code+=16;
break;
}
/* mov [rsp+16],rax */
code[0]='\x48'; code[1]='\x89'; code[2]='\x44'; code[3]='\x24'; code[4]='\x10';
/* retq */
code[5]='\xc3';
pgm++;
code+=6;
break;
default:
fprintf(stderr,"unknown instruction %d\n",(int)pgm[-1]);
exit(1);
}
*code_p=code;
*pgm_p=pgm;
}
void init_jit(uint64_t max_instrs, uint64_t max_code_len,
char **code_block, uint32_t **mapping) {
*code_block=mmap (NULL,max_code_len,PROT_READ | PROT_EXEC,MAP_ANONYMOUS | MAP_PRIVATE,0,0);
*mapping=malloc (max_instrs*sizeof(uint32_t));
}
char *jit_append(char *code_block, uint32_t code_len, char *code_ptr,
uint32_t *mapping, uint32_t n_instr, uint64_t *pgm, int is_main) {
uint32_t len=*pgm++;
uint32_t i;
uint32_t code_i=code_ptr-code_block;
uint64_t *pgm_p=pgm;
for (i=n_instr; i<n_instr+len; i++) {
enum instr instr=(enum instr)*pgm_p;
mapping[i]=code_i;
code_i+=instr_size(instr);
switch (instr) {
case PushRef:
case PushI:
case Put:
case Pop:
case Call:
case Jmp:
case JmpTrue:
pgm_p+=2;
break;
default:
pgm_p+=1;
break;
}
}
mprotect (code_block,code_len,PROT_WRITE);
if (is_main)
*(uint32_t*)&code_block[9]=code_ptr-code_block-13;
pgm_p=pgm;
for (i=0; i<len; i++)
gen_instr (code_block,&code_ptr,&pgm_p,mapping);
mprotect (code_block,code_len,PROT_READ | PROT_EXEC);
return code_ptr;
}
uint64_t jit_exec(char *code_block) {
return ((uint64_t(*)(void))code_block)();
}
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