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) 2015-2019, 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-Android version of the __gnat_sigtramp service *
34 ******************************************************/
35
36 #include <sys/ucontext.h>
37
38 #include "sigtramp.h"
39 /* See sigtramp.h for a general explanation of functionality. */
40
41 /* ----------------------
42 -- General comments --
43 ----------------------
44
45 Stubs are generated from toplevel asms,
46 The general idea is to establish CFA as the sigcontext
47 and state where to find the registers as offsets from there.
48
49 We support stubs for VxWorks and Android, providing unwind info for
50 common registers. We might need variants with support for floating
51 point or altivec registers as well at some point.
52
53 For Android it would be simpler to write this in Asm since there's only
54 one variant, but to keep it looking like the VxWorks stubs,
55 C is the choice for our toplevel interface.
56
57 Note that the registers we "restore" here are those to which we have
58 direct access through the system sigcontext structure, which includes
59 only a partial set of the non-volatiles ABI-wise. */
60
61 /* -----------------------------------------
62 -- Protypes for our internal asm stubs --
63 -----------------------------------------
64
65 The registers are expected to be at SIGCONTEXT + 12 (reference the
66 sicontext structure in asm/sigcontext.h which describes the first
67 3 * 4byte fields.) Even though our symbols will remain local, the
68 prototype claims "extern" and not "static" to prevent compiler complaints
69 about a symbol used but never defined. */
70
71 /* sigtramp stub providing unwind info for common registers. */
72
73 extern void __gnat_sigtramp_common
74 (int signo, void *siginfo, void *sigcontext,
75 __sigtramphandler_t * handler);
76
77 void __gnat_sigtramp (int signo, void *si, void *sc,
78 __sigtramphandler_t * handler)
79 __attribute__((optimize(2)));
80
__gnat_sigtramp(int signo,void * si,void * ucontext,__sigtramphandler_t * handler)81 void __gnat_sigtramp (int signo, void *si, void *ucontext,
82 __sigtramphandler_t * handler)
83 {
84 struct sigcontext *mcontext = &((ucontext_t *) ucontext)->uc_mcontext;
85
86 __gnat_sigtramp_common (signo, si, mcontext, handler);
87 }
88
89 /* asm string construction helpers. */
90
91 #define STR(TEXT) #TEXT
92 /* stringify expanded TEXT, surrounding it with double quotes. */
93
94 #define S(E) STR(E)
95 /* stringify E, which will resolve as text but may contain macros
96 still to be expanded. */
97
98 /* asm (TEXT) outputs <tab>TEXT. These facilitate the output of
99 multiline contents: */
100 #define TAB(S) "\t" S
101 #define CR(S) S "\n"
102
103 #undef TCR
104 #define TCR(S) TAB(CR(S))
105
106 /* Trampoline body block
107 --------------------- */
108
109 #define SIGTRAMP_BODY \
110 CR("") \
111 TCR("# Allocate frame and also save r2 which is the argument register") \
112 TCR("# containing the sigcontext, so that we can restore it during") \
113 TCR("# unwinding and thereby load the rest of the desired context.") \
114 TCR("stmfd sp!, {r2, r3, lr}") \
115 TCR("# The unwinder undo's these operations in reverse order so starting") \
116 TCR("# from bottom, restore r2 from the current vsp location, move r2 into") \
117 TCR("# the vsp, add 12 bytes to get the start of the register save area") \
118 TCR("# then restore the 15 general purpose registers of the frame which") \
119 TCR("# raised the signal.") \
120 TCR(".save {r0-r15}") \
121 TCR(".pad #12") \
122 TCR(".movsp r2") \
123 TCR(".save {r2}") \
124 TCR("# Call the real handler. The signo, siginfo and sigcontext") \
125 TCR("# arguments are the same as those we received in r0, r1 and r2.") \
126 TCR("blx r3") \
127 TCR("# Restore our callee-saved items, release our frame and return") \
128 TCR("# (should never get here!).") \
129 TCR("ldmfd sp, {r2, r3, pc}")
130
131 /* Symbol definition block
132 ----------------------- */
133
134 #define SIGTRAMP_START(SYM) \
135 CR("# " S(SYM) " unwind trampoline") \
136 TCR(".type " S(SYM) ", %function") \
137 CR("") \
138 CR(S(SYM) ":") \
139 TCR(".fnstart")
140
141 /* Symbol termination block
142 ------------------------ */
143
144 #define SIGTRAMP_END(SYM) \
145 CR(".fnend") \
146 TCR(".size " S(SYM) ", .-" S(SYM))
147
148 /*----------------------------
149 -- And now, the real code --
150 ---------------------------- */
151
152 /* Text section start. The compiler isn't aware of that switch. */
153
154 asm (".text\n"
155 TCR(".align 2"));
156
157 /* sigtramp stub for common registers. */
158
159 #define TRAMP_COMMON __gnat_sigtramp_common
160
161 asm (SIGTRAMP_START(TRAMP_COMMON));
162 asm (SIGTRAMP_BODY);
163 asm (SIGTRAMP_END(TRAMP_COMMON));
164