lib/trampoline_setup.c

   1 /* ===----- trampoline_setup.c - Implement __trampoline_setup -------------===
   2  *
   3  *                     The LLVM Compiler Infrastructure
   4  *
   5  * This file is dual licensed under the MIT and the University of Illinois Open
   6  * Source Licenses. See LICENSE.TXT for details.
   7  *
   8  * ===----------------------------------------------------------------------===
   9  */
  10
  11 #include "int_lib.h"
  12
  13 extern void __clear_cache(void* start, void* end);
  14
  15 /*
  16  * The ppc compiler generates calls to __trampoline_setup() when creating
  17  * trampoline functions on the stack for use with nested functions.
  18  * This function creates a custom 40-byte trampoline function on the stack
  19  * which loads r11 with a pointer to the outer function's locals
  20  * and then jumps to the target nested function.
  21  */
  22
  23 #if __ppc__ && !defined(__powerpc64__)
  24 void __trampoline_setup(uint32_t* trampOnStack, int trampSizeAllocated,
  25                                 const void* realFunc, void* localsPtr)
  26 {
  27     /* should never happen, but if compiler did not allocate */
  28     /* enough space on stack for the trampoline, abort */
  29     if ( trampSizeAllocated < 40 )
  30         compilerrt_abort();
  31
  32     /* create trampoline */
  33     trampOnStack[0] = 0x7c0802a6;    /* mflr r0 */
  34     trampOnStack[1] = 0x4800000d;    /* bl Lbase */
  35     trampOnStack[2] = (uint32_t)realFunc;
  36     trampOnStack[3] = (uint32_t)localsPtr;
  37     trampOnStack[4] = 0x7d6802a6;    /* Lbase: mflr r11 */
  38     trampOnStack[5] = 0x818b0000;    /* lwz    r12,0(r11) */
  39     trampOnStack[6] = 0x7c0803a6;    /* mtlr r0 */
  40     trampOnStack[7] = 0x7d8903a6;    /* mtctr r12 */
  41     trampOnStack[8] = 0x816b0004;    /* lwz    r11,4(r11) */
  42     trampOnStack[9] = 0x4e800420;    /* bctr */
  43
  44     /* clear instruction cache */
  45     __clear_cache(trampOnStack, &trampOnStack[10]);
  46 }
  47 #endif /* __ppc__ && !defined(__powerpc64__) */