gcc/ada/sigtramp-armvxw.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) 2013, 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.               *
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  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-VxWorks version of the __gnat_sigtramp service *
  34  ******************************************************/
  35
  36 #include "sigtramp.h"
  37 /* See sigtramp.h for a general explanation of functionality.  */
  38
  39 #include <vxWorks.h>
  40 #include <arch/../regs.h>
  41 #include <sigLib.h>
  42
  43 /* ----------------------
  44    -- General comments --
  45    ----------------------
  46
  47    Stubs are generated from toplevel asms and .cfi directives, much simpler
  48    to use and check for correctness than manual encodings of CFI byte
  49    sequences.  The general idea is to establish CFA as sigcontext->sc_pregs
  50    and state where to find the registers as offsets from there.
  51
  52    As of today, we support a single stub, providing CFI info for common
  53    registers (GPRs, LR, ...). We might need variants with support for floating
  54    point or altivec registers as well at some point.
  55
  56    Checking which variant should apply and getting at sc_pregs is simpler
  57    to express in C (we can't use offsetof in toplevel asms and hardcoding
  58    constants is not workable with the flurry of VxWorks variants), so this
  59    is the choice for our toplevel interface.
  60
  61    Note that the registers we "restore" here are those to which we have
  62    direct access through the system sigcontext structure, which includes
  63    only a partial set of the non-volatiles ABI-wise.  */
  64
  65 /* -----------------------------------------
  66    -- Protypes for our internal asm stubs --
  67    -----------------------------------------
  68
  69    SC_PREGS is always expected to be SIGCONTEXT->sc_pregs.  Eventhough our
  70    symbols will remain local, the prototype claims "extern" and not
  71    "static" to prevent compiler complaints about a symbol used but never
  72    defined.  */
  73
  74 /* sigtramp stub providing CFI info for common registers.  */
  75
  76 extern void __gnat_sigtramp_common
  77 (int signo, void *siginfo, void *sigcontext,
  78  sighandler_t * handler, void * sc_pregs);
  79
  80
  81 /* -------------------------------------
  82    -- Common interface implementation --
  83    -------------------------------------
  84
  85    We enforce optimization to minimize the overhead of the extra layer.  */
  86
  87 void __gnat_sigtramp (int signo, void *si, void *sc,
  88                       sighandler_t * handler)
  89      __attribute__((optimize(2)));
  90
  91 void __gnat_sigtramp (int signo, void *si, void *sc,
  92                       sighandler_t * handler)
  93 {
  94   struct sigcontext * sctx = (struct sigcontext *) sc;
  95
  96   __gnat_sigtramp_common (signo, si, sctx, handler, sctx->sc_pregs);
  97 }
  98
  99
 100 /* ---------------------------
 101    -- And now the asm stubs --
 102    ---------------------------
 103
 104    They all have a common structure with blocks of asm sequences queued one
 105    after the others.  Typically:
 106
 107    SYMBOL_START
 108
 109    CFI_DIRECTIVES
 110      CFI_DEF_CFA,
 111      CFI_COMMON_REGISTERS,
 112      ...
 113
 114    STUB_BODY
 115      asm code to establish frame, setup the cfa reg value,
 116      call the real signal handler, ...
 117
 118    SYMBOL_END
 119 */
 120
 121 /*--------------------------------
 122   -- Misc constants and helpers --
 123   -------------------------------- */
 124
 125 /* REGNO constants, dwarf column numbers for registers of interest.  */
 126
 127 #define REGNO_G_REG_OFFSET(N) (N)
 128
 129 #define REGNO_PC_OFFSET  15  /* PC_REGNUM  */
 130
 131 /* asm string construction helpers.  */
 132
 133 #define STR(TEXT) #TEXT
 134 /* stringify expanded TEXT, surrounding it with double quotes.  */
 135
 136 #define S(E) STR(E)
 137 /* stringify E, which will resolve as text but may contain macros
 138    still to be expanded.  */
 139
 140 /* asm (TEXT) outputs <tab>TEXT. These facilitate the output of
 141    multine contents:  */
 142 #define TAB(S) "\t" S
 143 #define CR(S)  S "\n"
 144
 145 #undef TCR
 146 #define TCR(S) TAB(CR(S))
 147
 148 /*------------------------------
 149   -- Stub construction blocks --
 150   ------------------------------ */
 151
 152 /* CFA setup block
 153    ---------------
 154    Only non-volatile registers are suitable for a CFA base. These are the
 155    only ones we can expect to be able retrieve from the unwinding context
 156    while walking up the chain, saved by at least the bottom-most exception
 157    propagation services. We use r8 here and set it to the value we need
 158    in stub body that follows. Any of r4-r8 should work.  */
 159
 160 #define CFA_REG 8
 161
 162 #define CFI_DEF_CFA \
 163 CR(".cfi_def_cfa " S(CFA_REG) ", 0")
 164
 165 /* Register location blocks
 166    ------------------------
 167    Rules to find registers of interest from the CFA. This should comprise
 168    all the non-volatile registers relevant to the interrupted context.  */
 169
 170 #define COMMON_CFI(REG) \
 171   ".cfi_offset " S(REGNO_##REG) "," S(REG_SET_##REG)
 172
 173 #define CFI_COMMON_REGS \
 174 CR("# CFI for common registers\n") \
 175 TCR(COMMON_CFI(G_REG_OFFSET(0)))  \
 176 TCR(COMMON_CFI(G_REG_OFFSET(1)))  \
 177 TCR(COMMON_CFI(G_REG_OFFSET(2)))  \
 178 TCR(COMMON_CFI(G_REG_OFFSET(3)))  \
 179 TCR(COMMON_CFI(G_REG_OFFSET(4)))  \
 180 TCR(COMMON_CFI(G_REG_OFFSET(5)))  \
 181 TCR(COMMON_CFI(G_REG_OFFSET(6)))  \
 182 TCR(COMMON_CFI(G_REG_OFFSET(7)))  \
 183 TCR(COMMON_CFI(G_REG_OFFSET(8)))  \
 184 TCR(COMMON_CFI(G_REG_OFFSET(9)))  \
 185 TCR(COMMON_CFI(G_REG_OFFSET(10)))  \
 186 TCR(COMMON_CFI(G_REG_OFFSET(11)))  \
 187 TCR(COMMON_CFI(G_REG_OFFSET(12)))  \
 188 TCR(COMMON_CFI(G_REG_OFFSET(13)))  \
 189 TCR(COMMON_CFI(G_REG_OFFSET(14))) \
 190 TCR(COMMON_CFI(PC_OFFSET)) \
 191 TCR(".cfi_return_column " S(REGNO_PC_OFFSET))
 192
 193 /* Trampoline body block
 194    ---------------------  */
 195
 196 #define SIGTRAMP_BODY \
 197 CR("") \
 198 TCR("# Allocate frame and save the non-volatile") \
 199 TCR("# registers we're going to modify") \
 200 TCR("mov        ip, sp") \
 201 TCR("stmfd      sp!, {r"S(CFA_REG)", fp, ip, lr, pc}") \
 202 TCR("# Setup CFA_REG = sc_pregs, that we'll retrieve as our CFA value") \
 203 TCR("ldr        r"S(CFA_REG)", [ip]") \
 204 TCR("")                 \
 205 TCR("# Call the real handler. The signo, siginfo and sigcontext") \
 206 TCR("# arguments are the same as those we received in r0, r1 and r2") \
 207 TCR("sub        fp, ip, #4") \
 208 TCR("blx        r3") \
 209 TCR("# Restore our callee-saved items, release our frame and return") \
 210 TCR("ldmfd      sp, {r"S(CFA_REG)", fp, sp, pc}")
 211
 212
 213 /* Symbol definition block
 214    -----------------------  */
 215
 216 #define SIGTRAMP_START(SYM) \
 217 CR("# " S(SYM) " cfi trampoline") \
 218 TCR(".type " S(SYM) ", %function") \
 219 CR("") \
 220 CR(S(SYM) ":") \
 221 TCR(".cfi_startproc") \
 222 TCR(".cfi_signal_frame")
 223
 224 /* Symbol termination block
 225    ------------------------  */
 226
 227 #define SIGTRAMP_END(SYM) \
 228 CR(".cfi_endproc") \
 229 TCR(".size " S(SYM) ", .-" S(SYM))
 230
 231 /*----------------------------
 232   -- And now, the real code --
 233   ---------------------------- */
 234
 235 /* Text section start.  The compiler isn't aware of that switch.  */
 236
 237 asm (".text\n"
 238      TCR(".align 2"));
 239
 240 /* sigtramp stub for common registers.  */
 241
 242 #define TRAMP_COMMON __gnat_sigtramp_common
 243
 244 asm (SIGTRAMP_START(TRAMP_COMMON));
 245 asm (CFI_DEF_CFA);
 246 asm (CFI_COMMON_REGS);
 247 asm (SIGTRAMP_BODY);
 248 asm (SIGTRAMP_END(TRAMP_COMMON));
 249
 250