compiler-rt/lib/builtins/trampoline_setup.c

   1 //===----- trampoline_setup.c - Implement __trampoline_setup -------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "int_lib.h"
  10
  11 extern void __clear_cache(void *start, void *end);
  12
  13 // The ppc compiler generates calls to __trampoline_setup() when creating
  14 // trampoline functions on the stack for use with nested functions.
  15 // This function creates a custom 40-byte trampoline function on the stack
  16 // which loads r11 with a pointer to the outer function's locals
  17 // and then jumps to the target nested function.
  18
  19 #if __powerpc__ && !defined(__powerpc64__)
  20 COMPILER_RT_ABI void __trampoline_setup(uint32_t *trampOnStack,
  21                                         int trampSizeAllocated,
  22                                         const void *realFunc, void *localsPtr) {
  23   // should never happen, but if compiler did not allocate
  24   // enough space on stack for the trampoline, abort
  25   if (trampSizeAllocated < 40)
  26     compilerrt_abort();
  27
  28   // create trampoline
  29   trampOnStack[0] = 0x7c0802a6; // mflr r0
  30   trampOnStack[1] = 0x4800000d; // bl Lbase
  31   trampOnStack[2] = (uint32_t)realFunc;
  32   trampOnStack[3] = (uint32_t)localsPtr;
  33   trampOnStack[4] = 0x7d6802a6; // Lbase: mflr r11
  34   trampOnStack[5] = 0x818b0000; // lwz    r12,0(r11)
  35   trampOnStack[6] = 0x7c0803a6; // mtlr r0
  36   trampOnStack[7] = 0x7d8903a6; // mtctr r12
  37   trampOnStack[8] = 0x816b0004; // lwz    r11,4(r11)
  38   trampOnStack[9] = 0x4e800420; // bctr
  39
  40   // clear instruction cache
  41   __clear_cache(trampOnStack, &trampOnStack[10]);
  42 }
  43 #endif // __powerpc__ && !defined(__powerpc64__)