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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,
Ret,
Halt,
IAddRet,
IMulRet,
ISubRet,
IDivRet
};
static 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 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;
}
}
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 %lu\n",arg);
#endif
code[0]='\x48'; /* mov rbx,[rsp+ARG*8] */
code[1]='\x8b';
code[2]='\x5c';
code[3]='\x24';
code[4]=(unsigned char)arg*8;
code[5]='\x53'; /* push rbx */
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 rbx,ARG */
code[1]='\xc7';
code[2]='\xc3';
*(uint32_t*)&code[3]=(uint32_t)arg;
code[7]='\x53'; /* push rbx */
pgm+=2;
code+=8;
break;
case Put:
arg=pgm[1];
#ifdef DEBUG_JIT_INSTRUCTIONS
fprintf(stderr,"Put %lu\n",arg);
#endif
code[0]='\x5b'; /* pop rbx */
code[1]='\x48'; /* mov [rsp+ARG*8],rbx */
code[2]='\x89';
code[3]='\x5c';
code[4]='\x24';
code[5]=(unsigned char)(arg-1)*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]-(&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 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 rbx,[rsp+16] */
code[5]='\x48'; code[6]='\x8b'; code[7]='\x5c'; code[8]='\x24'; code[9]='\x10';
switch (*pgm) {
case IAddRet:
case ISubRet:
/* {add,sub} rax,rbx */
code[10]='\x48';
code[11]=*pgm==IAddRet ? '\x01' : '\x29';
code[12]='\xd8';
code+=13;
break;
case IMulRet:
/* imul rax,rbx */
code[10]='\x48'; code[11]='\x0f'; code[12]='\xaf'; code[13]='\xc3';
code+=14;
break;
case IDivRet:
/* xor rdx,rdx */
code[10]='\x48'; code[11]='\x31'; code[12]='\xd2';
/* idiv rbx */
code[13]='\x48'; code[14]='\xf7'; code[15]='\xfb';
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 %lu\n",pgm[-1]);
exit(1);
}
*code_p=code;
*pgm_p=pgm;
}
unsigned int jit(uint64_t *pgm) {
uint32_t len=*pgm++;
uint32_t i;
uint32_t *mapping=malloc(len*sizeof(uint32_t));
uint32_t code_i=0;
uint64_t *pgm_p=pgm;
for (i=0; i<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:
pgm_p+=2;
break;
default:
pgm_p+=1;
break;
}
}
char *code=mmap(NULL, code_i, PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
char *code_wr=code;
pgm_p=pgm;
for (i=0; i<len; i++)
gen_instr(code, &code_wr, &pgm_p, mapping);
mprotect(code, code_i, PROT_READ | PROT_EXEC);
int (*fun)(void) = (int(*)(void)) code;
return fun();
}
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