1/*
2            Copyright Oliver Kowalke 2009.
3   Distributed under the Boost Software License, Version 1.0.
4      (See accompanying file LICENSE_1_0.txt or copy at
5          http://www.boost.org/LICENSE_1_0.txt)
6*/
7
8/*******************************************************
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66 *                                                     *
67
68.text
69.globl _make_fcontext
70_make_fcontext:
71    ; save return address into R6
72    mflr  r6
73
74    ; first arg of make_fcontext() == top address of context-function
75    ; shift address in R3 to lower 16 byte boundary
76    clrrwi  r3, r3, 4
77
78    ; reserve space for context-data on context-stack
79    ; including 64 byte of linkage + parameter area (R1  16 == 0)
80    subi  r3, r3, 248
81
82    ; third arg of make_fcontext() == address of context-function
83    stw  r5, 176(r3)
84
85    ; set back-chain to zero
86    li   %r0, 0
87    std  %r0, 184(%r3)
88
89    ; compute address of returned transfer_t
90    addi %r0, %r3, 232
91    mr   %r4, %r0
92    std  %r4, 152(%r3)
93
94    ; load LR
95    mflr  r0
96    ; jump to label 1
97    bl  l1
98l1:
99    ; load LR into R4
100    mflr  r4
101    ; compute abs address of label finish
102    addi  r4, r4, lo16((finish - .) + 4)
103    ; restore LR
104    mtlr  r0
105    ; save address of finish as return-address for context-function
106    ; will be entered after context-function returns
107    std  r4, 168(r3)
108
109    ; restore return address from R6
110    mtlr  r6
111
112    blr  ; return pointer to context-data
113
114finish:
115    ; save return address into R0
116    mflr  r0
117    ; save return address on stack, set up stack frame
118    stw  r0, 8(r1)
119    ; allocate stack space, R1  16 == 0
120    stwu  r1, -32(r1)
121
122    ; set return value to zero
123    li  r3, 0
124    ; exit application
125    bl  __exit
126    nop
127