closure.c

   1 #include <stdlib.h>
   2 #include <stdint.h>
   3 #include <string.h>
   4 #include <unistd.h>
   5 #include <sys/mman.h>
   6 #include "closure.h"
   7
   8 typedef struct __attribute__((packed)) {
   9         uint16_t opcode_0;
  10         void *operand_0;
  11
  12         uint16_t opcode_1;
  13         void *operand_1;
  14
  15         uint16_t opcode_2;
  16 } Closure;
  17
  18 // rdi, rsi, rdx, rcx, r8, r9
  19 static const uint16_t mov[6] = {0xbf48, 0xbe48, 0xba48, 0xb948, 0xb849, 0xb949};
  20 static size_t size;
  21
  22 __attribute__((constructor)) static void init()
  23 {
  24         size = sysconf(_SC_PAGESIZE);
  25 }
  26
  27 void *closure_create(void *self, ClosureParam *param, size_t num)
  28 {
  29         Closure *block = mmap(NULL, size, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
  30
  31         for (size_t i = 0; i < num; i++) {
  32                 if (param[i].arg >= 6)
  33                         abort(); // TODO
  34
  35                 block[i].opcode_0 = 0xb848;
  36                 block[i].operand_0 = param[i].fun;
  37
  38                 block[i].opcode_1 = mov[param[i].arg];
  39                 block[i].operand_1 = self;
  40
  41                 block[i].opcode_2 = 0xe0ff;
  42
  43                 *((void **) param[i].ptr) = &block[i];
  44         }
  45
  46         mprotect(block, size, PROT_READ | PROT_EXEC);
  47         return block;
  48 }
  49
  50 void closure_destroy(void *closure)
  51 {
  52         munmap(closure, size);
  53 }