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 __powerpc__ && !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 // __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__)
53COMPILER_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)
86

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source code of compiler-rt/lib/builtins/trampoline_setup.c