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
11extern 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 __ppc__ && !defined(__powerpc64__)
20COMPILER_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 // __ppc__ && !defined(__powerpc64__)
44