gcc/ada/sigtramp-armdroid.c

   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) 2015-2020, Free Software Foundation, Inc.        *
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  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.                                     *
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  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
  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));