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1/* Low-level libffi support for Altera Nios II.
2
3   Copyright (c) 2013 Mentor Graphics.
4
5   Permission is hereby granted, free of charge, to any person obtaining
6   a copy of this software and associated documentation files (the
7   ``Software''), to deal in the Software without restriction, including
8   without limitation the rights to use, copy, modify, merge, publish,
9   distribute, sublicense, and/or sell copies of the Software, and to
10   permit persons to whom the Software is furnished to do so, subject to
11   the following conditions:
12
13   The above copyright notice and this permission notice shall be
14   included in all copies or substantial portions of the Software.
15
16   THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND,
17   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
18   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
19   IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
20   CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
21   TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
22   SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
23
24/* This function is declared on the C side as
25
26   extern UINT64 ffi_call_sysv (void (*arghook) (char *, extended_cif *),
27	  		        extended_cif *ecif,
28				unsigned nbytes,
29				void (*fn) (void));
30
31   On input, the arguments appear as
32	r4 = arghook
33	r5 = ecif
34	r6 = nbytes
35	r7 = fn
36*/
37
38	.section	.text
39	.align	2
40	.global	ffi_call_sysv
41	.type	ffi_call_sysv, @function
42
43ffi_call_sysv:
44	.cfi_startproc
45
46	/* Create the stack frame, saving r16 so we can use it locally.  */
47	addi	sp, sp, -12
48	.cfi_def_cfa_offset 12
49	stw	ra, 8(sp)
50	stw	fp, 4(sp)
51	stw	r16, 0(sp)
52	.cfi_offset 31, -4
53	.cfi_offset 28, -8
54	.cfi_offset 16, -12
55	mov	fp, sp
56	.cfi_def_cfa_register 28
57	mov	r16, r7
58
59	/* Adjust the stack pointer to create the argument buffer
60	   nbytes long.  */
61	sub	sp, sp, r6
62
63	/* Call the arghook function.  */
64	mov	r2, r4		/* fn */
65	mov	r4, sp		/* argbuffer */
66	callr	r2		/* r5 already contains ecif */
67
68	/* Pop off the first 16 bytes of the argument buffer on the stack,
69	   transferring the contents to the argument registers.  */
70	ldw	r4, 0(sp)
71	ldw	r5, 4(sp)
72	ldw	r6, 8(sp)
73	ldw	r7, 12(sp)
74	addi	sp, sp, 16
75
76	/* Call the user function, which leaves its result in r2 and r3.  */
77	callr	r16
78
79	/* Pop off the stack frame.  */
80	mov	sp, fp
81	ldw	ra, 8(sp)
82	ldw	fp, 4(sp)
83	ldw	r16, 0(sp)
84	addi	sp, sp, 12
85	ret
86	.cfi_endproc
87	.size	ffi_call_sysv, .-ffi_call_sysv
88
89
90/* Closure trampolines jump here after putting the C helper address
91   in r9 and the closure pointer in r10.  The user-supplied arguments
92   to the closure are in the normal places, in r4-r7 and on the
93   stack.  Push the register arguments on the stack too and then call the
94   C helper function to deal with them.  */
95
96	.section	.text
97	.align	2
98	.global	ffi_closure_sysv
99	.type	ffi_closure_sysv, @function
100
101ffi_closure_sysv:
102	.cfi_startproc
103
104	/* Create the stack frame, pushing the register args on the stack
105	   just below the stack args.  This is the same trick illustrated
106	   in Figure 7-3 in the Nios II Processor Reference Handbook, used
107	   for variable arguments and structures passed by value.  */
108	addi	sp, sp, -20
109	.cfi_def_cfa_offset 20
110	stw	ra, 0(sp)
111	.cfi_offset 31, -20
112	stw	r4, 4(sp)
113	.cfi_offset 4, -16
114	stw	r5, 8(sp)
115	.cfi_offset 5, -12
116	stw	r6, 12(sp)
117	.cfi_offset 6, -8
118	stw	r7, 16(sp)
119	.cfi_offset 7, -4
120
121	/* Call the helper.
122	   r4 = pointer to arguments on stack
123	   r5 = closure pointer (loaded in r10 by the trampoline)
124	   r9 = address of helper function (loaded by trampoline) */
125	addi	r4, sp, 4
126	mov	r5, r10
127	callr	r9
128
129	/* Pop the stack and return.  */
130	ldw	ra, 0(sp)
131	addi	sp, sp, 20
132	.cfi_def_cfa_offset -20
133	ret
134	.cfi_endproc
135	.size	ffi_closure_sysv, .-ffi_closure_sysv
136
137