gcc/ada/sigtramp-arm-qnx.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) 2011-2024, 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));