ffi/trap.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3
   4 #include "../debug.h"
   5
   6 /* TODO(bernhard): use {u,}int* types */
   7
   8 #define __USE_GNU
   9 // Note by hs: my signal.h includes sys/uconctext which conflicts with
  10 // asm/ucontext - this hack kinda solves the problem for me ;-)
  11 // so feel free to blame me for that s**t
  12 #if defined __USE_XOPEN2K8
  13 #undef __USE_XOPEN2K8
  14 #define RESTORE
  15 #warning hs-hack: undefining __USE_XOPEN2K8 for signal.h
  16 #endif
  17 #include <signal.h>
  18 #ifdef RESTORE
  19 #define __USE_XOPEN2K8
  20 #endif
  21
  22 #include <sys/ucontext.h>
  23
  24 unsigned int getMethodEntry(unsigned int, unsigned int);
  25 unsigned int getStaticFieldAddr(unsigned int);
  26 unsigned int getTrapType(unsigned int, unsigned int);
  27 unsigned int mallocObject(int);
  28
  29 #ifdef DBG_TRAP
  30 #define dprintf(args...) do { printf (args); } while (0);
  31 #else
  32 #define dprintf(args...)
  33 #endif
  34
  35 void mainresult(unsigned int a)
  36 {
  37         dprintf("mainresult: 0x%08x\n", a);
  38 }
  39
  40 void staticcalltrap(int nSignal, siginfo_t *info, void *ctx)
  41 {
  42         mcontext_t *mctx = &((ucontext_t *) ctx)->uc_mcontext;
  43         unsigned int from = (unsigned int) mctx->gregs[REG_EIP] - 2;
  44         unsigned int *to_patch = (unsigned int *) (from + 1);
  45         dprintf("callertrap(mctx)  by 0x%08x\n", from);
  46         if (*to_patch != 0x90ffff90) {
  47                 dprintf("callertrap: something is wrong here. abort\n");
  48                 exit(0);
  49         }
  50         unsigned int patchme = getMethodEntry(from, 0);
  51
  52         unsigned char *insn = (unsigned char *) from;
  53         *insn = 0xe8; // call opcode
  54         dprintf(" to_patch: 0x%08x\n", (unsigned int) to_patch);
  55         dprintf("*to_patch: 0x%08x\n", *to_patch);
  56         *to_patch = patchme - (from + 5);
  57         dprintf("*to_patch: 0x%08x\n", *to_patch);
  58         mctx->gregs[REG_EIP] = (unsigned long) insn;
  59 }
  60
  61 void sigsegvtrap(int nSignal, siginfo_t *info, void *ctx)
  62 {
  63         mcontext_t *mctx = &((ucontext_t *) ctx)->uc_mcontext;
  64         unsigned int from = (unsigned int) mctx->gregs[REG_EIP];
  65         unsigned int *esp = (unsigned int *) mctx->gregs[REG_ESP];
  66
  67         /* if from is not *the* eip: get actual eip from stack storage */
  68         unsigned int from_stack = (*esp) - 3;
  69         switch(getTrapType(from, from_stack)) {
  70                 default: case 0: {
  71                         dprintf("something is wrong here: abort\n");
  72                         exit(1);
  73                 } break;
  74                 case 1: { // invokevirtual
  75                         if (from > 0) {
  76                                 dprintf("from: 0x%08x but should be 0 :-(\n", from);
  77                         }
  78                         unsigned int method_table_ptr = (unsigned int) mctx->gregs[REG_EAX];
  79                         unsigned char offset = *((unsigned char *) (*esp) - 1);
  80                         /* method entry to patch */
  81                         unsigned int *to_patch = (unsigned int*) (method_table_ptr + offset);
  82                         dprintf("invokevirtual by 0x%08x with offset 0x%08x\n", from_stack, offset);
  83                         dprintf(" to_patch: 0x%08x\n", (unsigned int) to_patch);
  84                         dprintf("*to_patch: 0x%08x\n", *to_patch);
  85                         *to_patch = getMethodEntry(from_stack, method_table_ptr);
  86                         mctx->gregs[REG_EIP] = *to_patch;
  87                         dprintf("*to_patch: 0x%08x\n", *to_patch);
  88                 } break;
  89                 case 4: { // invokeinterface
  90                         if (from > 0) {
  91                                 dprintf("from: 0x%08x but should be 0 :-(\n", from);
  92                         }
  93                         unsigned int method_table_ptr = (unsigned int) mctx->gregs[REG_EAX];
  94                         unsigned int interface_table_ptr = (unsigned int) mctx->gregs[REG_EBX];
  95                         unsigned char offset = *((unsigned char *) (*esp) - 1);
  96                         /* interface entry to patch */
  97                         unsigned int *to_patch = (unsigned int*) (interface_table_ptr + offset);
  98                         dprintf("invokeinterface by 0x%08x with offset 0x%08x\n", from_stack, offset);
  99                         dprintf(" to_patch: 0x%08x\n", (unsigned int) to_patch);
 100                         dprintf("*to_patch: 0x%08x\n", *to_patch);
 101                         *to_patch = getMethodEntry(from_stack, method_table_ptr);
 102                         mctx->gregs[REG_EIP] = *to_patch;
 103                         dprintf("*to_patch: 0x%08x\n", *to_patch);
 104                 } break;
 105                 case 2: { // static field patch
 106                         unsigned int *to_patch = (unsigned int *) (from + 2);
 107                         dprintf("staticfieldtrap by 0x%08x\n", from);
 108                         if (*to_patch != 0x00000000) {
 109                                 dprintf("staticfieldtrap: something is wrong here. abort\n");
 110                                 exit(0);
 111                         }
 112                         unsigned int patchme = getStaticFieldAddr(from);
 113
 114                         dprintf(" to_patch: 0x%08x\n", (unsigned int) to_patch);
 115                         dprintf("*to_patch: 0x%08x\n", *to_patch);
 116                         *to_patch = patchme;
 117                         dprintf("*to_patch: 0x%08x\n", *to_patch);
 118                 } break;
 119         }
 120 }
 121
 122 void register_signal(void)
 123 {
 124         struct sigaction illaction;
 125         illaction.sa_sigaction = staticcalltrap;
 126         sigemptyset(&illaction.sa_mask);
 127         illaction.sa_flags = SA_SIGINFO | SA_RESTART | SA_NODEFER;
 128         sigaction(SIGILL, &illaction, NULL);
 129
 130         struct sigaction segvaction;
 131         segvaction.sa_sigaction = sigsegvtrap;
 132         sigemptyset(&segvaction.sa_mask);
 133         segvaction.sa_flags = SA_SIGINFO | SA_RESTART | SA_NODEFER;
 134         sigaction(SIGSEGV, &segvaction, NULL);
 135 }
 136
 137 unsigned int getaddr(void)
 138 {
 139         return (unsigned int) mainresult;
 140 }
 141
 142 unsigned int getMallocObjectAddr(void)
 143 {
 144         return (unsigned int) mallocObject;
 145 }