1 /****************************************************************************
2 * *
3 * GNAT COMPILER COMPONENTS *
4 * *
5 * S I G T R A M P *
6 * *
7 * Asm Implementation File *
8 * *
9 * Copyright (C) 2011-2023, Free Software Foundation, Inc. *
10 * *
11 * GNAT is free software; you can redistribute it and/or modify it under *
12 * terms of the GNU General Public License as published by the Free Soft- *
13 * ware Foundation; either version 3, or (at your option) any later ver- *
14 * sion. GNAT is distributed in the hope that it will be useful, but WITH- *
15 * OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY *
16 * or FITNESS FOR A PARTICULAR PURPOSE. *
17 * *
18 * As a special exception under Section 7 of GPL version 3, you are granted *
19 * additional permissions described in the GCC Runtime Library Exception, *
20 * version 3.1, as published by the Free Software Foundation. *
21 * *
22 * In particular, you can freely distribute your programs built with the *
23 * GNAT Pro compiler, including any required library run-time units, using *
24 * any licensing terms of your choosing. See the AdaCore Software License *
25 * for full details. *
26 * *
27 * GNAT was originally developed by the GNAT team at New York University. *
28 * Extensive contributions were provided by Ada Core Technologies Inc. *
29 * *
30 ****************************************************************************/
31
32 /**************************************************
33 * ARM-QNX version of the __gnat_sigtramp service *
34 **************************************************/
35
36 #include <signal.h>
37 #include <ucontext.h>
38
39 #include "sigtramp.h"
40 /* See sigtramp.h for a general explanation of functionality. */
41
42 /* -------------------------------------------
43 -- Prototypes for our internal asm stubs --
44 -------------------------------------------
45
46 Eventhough our symbols will remain local, the prototype claims "extern"
47 and not "static" to prevent compiler complaints about a symbol used but
48 never defined. */
49
50 /* sigtramp stub providing ARM unwinding info for common registers. */
51
52 extern void __gnat_sigtramp_common
53 (int signo, void *siginfo, void *sigcontext,
54 __sigtramphandler_t * handler, void * sc_pregs);
55
56 /* -------------------------------------
57 -- Common interface implementation --
58 -------------------------------------
59
60 We enforce optimization to minimize the overhead of the extra layer. */
61
62 void __gnat_sigtramp (int signo, void *si, void *sc,
63 __sigtramphandler_t * handler)
64 __attribute__((optimize(2)));
65
66 void __gnat_sigtramp (int signo, void *si, void *sc,
67 __sigtramphandler_t * handler)
68 {
69 mcontext_t *mcontext = &((ucontext_t *) sc)->uc_mcontext;
70
71 /* Pass MCONTEXT in the fifth position so that the assembly code can find
72 it at the same stack location as SC_PREGS. */
73 __gnat_sigtramp_common (signo, si, mcontext, handler, &mcontext->cpu);
74 }
75
76 /* asm string construction helpers. */
77
78 #define STR(TEXT) #TEXT
79 /* stringify expanded TEXT, surrounding it with double quotes. */
80
81 #define S(E) STR(E)
82 /* stringify E, which will resolve as text but may contain macros
83 still to be expanded. */
84
85 /* asm (TEXT) outputs <tab>TEXT. These facilitate the output of
86 multiline contents: */
87 #define TAB(S) "\t" S
88 #define CR(S) S "\n"
89
90 #undef TCR
91 #define TCR(S) TAB(CR(S))
92
93 /* Trampoline body block
94 --------------------- */
95
96 /* The 5 arguments passed to __gnat_sigtramp_common are located in:
97 - r0-r2: arguments to pass on to the actual handler
98 - r3: the actual handler
99 - sp: the address of the reg set to restore
100 All we have to do then is to instruct the unwinder to restore the registers
101 from the value in VSP. Unwinder instructions are executed backwards, so we
102 1- instruct to pop r2 from the VSP (.save {r2})
103 2- move the VSP to the address pointed to by r2 (.movsp r2)
104 3- restore all registers from there. (.save {r0-r15})
105 Once the unwinding instructions are set, we just need to call the handler
106 as r0-r2 are already properly set.
107 */
108 #define SIGTRAMP_BODY \
109 CR("") \
110 TCR(".save {r0-r15}") \
111 TCR(".movsp r2") \
112 TCR(".save {r2}") \
113 TCR("blx r3") \
114 TCR("# No return here.")
115
116 /* Symbol definition block
117 ----------------------- */
118
119 #define SIGTRAMP_START(SYM) \
120 CR("# " S(SYM) " unwind trampoline") \
121 TCR(".type " S(SYM) ", %function") \
122 CR("") \
123 CR(S(SYM) ":") \
124 TCR(".fnstart")
125
126 /* Symbol termination block
127 ------------------------ */
128
129 #define SIGTRAMP_END(SYM) \
130 CR(".fnend") \
131 TCR(".size " S(SYM) ", .-" S(SYM))
132
133 /*----------------------------
134 -- And now, the real code --
135 ---------------------------- */
136
137 /* Text section start. The compiler isn't aware of that switch. */
138
139 asm (".text\n"
140 TCR(".align 2"));
141
142 /* sigtramp stub for common registers. */
143
144 #define TRAMP_COMMON __gnat_sigtramp_common
145
146 asm (SIGTRAMP_START(TRAMP_COMMON));
147 asm (SIGTRAMP_BODY);
148 asm (SIGTRAMP_END(TRAMP_COMMON));