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__)
  44
  45 // The AArch64 compiler generates calls to __trampoline_setup() when creating
  46 // trampoline functions on the stack for use with nested functions.
  47 // This function creates a custom 36-byte trampoline function on the stack
  48 // which loads x18 with a pointer to the outer function's locals
  49 // and then jumps to the target nested function.
  50 // Note: x18 is a reserved platform register on Windows and macOS.
  51
  52 #if defined(__aarch64__) && defined(__ELF__)
  53 COMPILER_RT_ABI void __trampoline_setup(uint32_t *trampOnStack,
  54                                         int trampSizeAllocated,
  55                                         const void *realFunc, void *localsPtr) {
  56   // This should never happen, but if compiler did not allocate
  57   // enough space on stack for the trampoline, abort.
  58   if (trampSizeAllocated < 36)
  59     compilerrt_abort();
  60
  61   // create trampoline
  62   // Load realFunc into x17. mov/movk 16 bits at a time.
  63   trampOnStack[0] =
  64       0xd2800000u | ((((uint64_t)realFunc >> 0) & 0xffffu) << 5) | 0x11;
  65   trampOnStack[1] =
  66       0xf2a00000u | ((((uint64_t)realFunc >> 16) & 0xffffu) << 5) | 0x11;
  67   trampOnStack[2] =
  68       0xf2c00000u | ((((uint64_t)realFunc >> 32) & 0xffffu) << 5) | 0x11;
  69   trampOnStack[3] =
  70       0xf2e00000u | ((((uint64_t)realFunc >> 48) & 0xffffu) << 5) | 0x11;
  71   // Load localsPtr into x18
  72   trampOnStack[4] =
  73       0xd2800000u | ((((uint64_t)localsPtr >> 0) & 0xffffu) << 5) | 0x12;
  74   trampOnStack[5] =
  75       0xf2a00000u | ((((uint64_t)localsPtr >> 16) & 0xffffu) << 5) | 0x12;
  76   trampOnStack[6] =
  77       0xf2c00000u | ((((uint64_t)localsPtr >> 32) & 0xffffu) << 5) | 0x12;
  78   trampOnStack[7] =
  79       0xf2e00000u | ((((uint64_t)localsPtr >> 48) & 0xffffu) << 5) | 0x12;
  80   trampOnStack[8] = 0xd61f0220; // br x17
  81
  82   // Clear instruction cache.
  83   __clear_cache(trampOnStack, &trampOnStack[9]);
  84 }
  85 #endif // defined(__aarch64__) && !defined(__APPLE__) && !defined(_WIN64)