1/* ===----- trampoline_setup.c - Implement __trampoline_setup -------------===
2 *
3 *                     The LLVM Compiler Infrastructure
4 *
5 * This file is distributed under the University of Illinois Open Source
6 * License. See LICENSE.TXT for details.
7 *
8 * ===----------------------------------------------------------------------===
9 */
10
11#include <stdint.h>
12#include <stdlib.h>
13
14extern void __clear_cache(void* start, void* end);
15
16/*
17 * The ppc compiler generates calls to __trampoline_setup() when creating
18 * trampoline functions on the stack for use with nested functions.
19 * This function creates a custom 40-byte trampoline function on the stack
20 * which loads r11 with a pointer to the outer function's locals
21 * and then jumps to the target nested function.
22 */
23
24#if __ppc__
25void __trampoline_setup(uint32_t* trampOnStack, int trampSizeAllocated,
26                                const void* realFunc, void* localsPtr)
27{
28    /* should never happen, but if compiler did not allocate */
29    /* enough space on stack for the trampoline, abort */
30    if ( trampSizeAllocated < 40 )
31        abort();
32
33    /* create trampoline */
34    trampOnStack[0] = 0x7c0802a6;    /* mflr r0 */
35    trampOnStack[1] = 0x4800000d;    /* bl Lbase */
36    trampOnStack[2] = (uint32_t)realFunc;
37    trampOnStack[3] = (uint32_t)localsPtr;
38    trampOnStack[4] = 0x7d6802a6;    /* Lbase: mflr r11 */
39    trampOnStack[5] = 0x818b0000;    /* lwz    r12,0(r11) */
40    trampOnStack[6] = 0x7c0803a6;    /* mtlr r0 */
41    trampOnStack[7] = 0x7d8903a6;    /* mtctr r12 */
42    trampOnStack[8] = 0x816b0004;    /* lwz    r11,4(r11) */
43    trampOnStack[9] = 0x4e800420;    /* bctr */
44
45    /* clear instruction cache */
46    __clear_cache(trampOnStack, &trampOnStack[10]);
47}
48#endif /* __ppc__ */
49