gcc/config/pa/linux-unwind.h

   1 /* DWARF2 EH unwinding support for PA Linux.
   2    Copyright (C) 2004, 2005 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 In addition to the permissions in the GNU General Public License, the
  12 Free Software Foundation gives you unlimited permission to link the
  13 compiled version of this file with other programs, and to distribute
  14 those programs without any restriction coming from the use of this
  15 file.  (The General Public License restrictions do apply in other
  16 respects; for example, they cover modification of the file, and
  17 distribution when not linked into another program.)
  18
  19 GCC is distributed in the hope that it will be useful,
  20 but WITHOUT ANY WARRANTY; without even the implied warranty of
  21 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22 GNU General Public License for more details.
  23
  24 You should have received a copy of the GNU General Public License
  25 along with GCC; see the file COPYING.  If not, write to
  26 the Free Software Foundation, 51 Franklin Street, Fifth Floor,
  27 Boston, MA 02110-1301, USA.  */
  28
  29 /* Do code reading to identify a signal frame, and set the frame
  30    state data appropriately.  See unwind-dw2.c for the structs.  */
  31
  32 /* Don't use this if inhibit_libc is set.
  33    The build for this target will fail trying to include missing headers. */
  34 #ifndef inhibit_libc
  35 #include <signal.h>
  36 #include <sys/ucontext.h>
  37
  38 /* Unfortunately, because of various bugs and changes to the kernel,
  39    we have several cases to deal with.
  40
  41    In 2.4, the signal trampoline is 4 words, and (CONTEXT)->ra should
  42    point directly at the beginning of the trampoline and struct rt_sigframe.
  43
  44    In <= 2.6.5-rc2-pa3, the signal trampoline is 9 words, and
  45    (CONTEXT)->ra points at the 4th word in the trampoline structure.  This
  46    is wrong, it should point at the 5th word.  This is fixed in 2.6.5-rc2-pa4.
  47
  48    To detect these cases, we first take (CONTEXT)->ra, align it to 64-bytes
  49    to get the beginning of the signal frame, and then check offsets 0, 4
  50    and 5 to see if we found the beginning of the trampoline.  This will
  51    tell us how to locate the sigcontext structure.
  52
  53    Note that with a 2.4 64-bit kernel, the signal context is not properly
  54    passed back to userspace so the unwind will not work correctly.  */
  55
  56 #define MD_FALLBACK_FRAME_STATE_FOR pa32_fallback_frame_state
  57
  58 static _Unwind_Reason_Code
  59 pa32_fallback_frame_state (struct _Unwind_Context *context,
  60                            _Unwind_FrameState *fs)
  61 {
  62   unsigned long sp = (unsigned long)context->ra & ~63;
  63   unsigned int *pc = (unsigned int *)sp;
  64   unsigned long off;
  65   _Unwind_Ptr new_cfa;
  66   int i;
  67   struct sigcontext *sc;
  68   struct rt_sigframe {
  69     struct siginfo info;
  70     struct ucontext uc;
  71   } *frame;
  72
  73   /* rt_sigreturn trampoline:
  74      3419000x ldi 0, %r25 or ldi 1, %r25   (x = 0 or 2)
  75      3414015a ldi __NR_rt_sigreturn, %r20
  76      e4008200 be,l 0x100(%sr2, %r0), %sr0, %r31
  77      08000240 nop  */
  78
  79   if (pc[0] == 0x34190000 || pc[0] == 0x34190002)
  80     off = 4*4;
  81   else if (pc[4] == 0x34190000 || pc[4] == 0x34190002)
  82     {
  83       pc += 4;
  84       off = 10 * 4;
  85     }
  86   else if (pc[5] == 0x34190000 || pc[5] == 0x34190002)
  87     {
  88       pc += 5;
  89       off = 10 * 4;
  90     }
  91   else
  92     {
  93       /* We may have to unwind through an alternate signal stack.
  94          We assume that the alignment of the alternate signal stack
  95          is BIGGEST_ALIGNMENT (i.e., that it has been allocated using
  96          malloc).  As a result, we can't distinguish trampolines
  97          used prior to 2.6.5-rc2-pa4.  However after 2.6.5-rc2-pa4,
  98          the return address of a signal trampoline will be on an odd
  99          word boundary and we can then determine the frame offset.  */
 100       sp = (unsigned long)context->ra;
 101       pc = (unsigned int *)sp;
 102       if ((pc[0] == 0x34190000 || pc[0] == 0x34190002) && (sp & 4))
 103         off = 5 * 4;
 104       else
 105         return _URC_END_OF_STACK;
 106     }
 107
 108   if (pc[1] != 0x3414015a
 109       || pc[2] != 0xe4008200
 110       || pc[3] != 0x08000240)
 111     return _URC_END_OF_STACK;
 112
 113   frame = (struct rt_sigframe *)(sp + off);
 114   sc = &frame->uc.uc_mcontext;
 115
 116   new_cfa = sc->sc_gr[30];
 117   fs->regs.cfa_how = CFA_REG_OFFSET;
 118   fs->regs.cfa_reg = 30;
 119   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 120   for (i = 1; i <= 31; i++)
 121     {
 122       fs->regs.reg[i].how = REG_SAVED_OFFSET;
 123       fs->regs.reg[i].loc.offset = (long)&sc->sc_gr[i] - new_cfa;
 124     }
 125   for (i = 4; i <= 31; i++)
 126     {
 127       /* FP regs have left and right halves */
 128       fs->regs.reg[2*i+24].how = REG_SAVED_OFFSET;
 129       fs->regs.reg[2*i+24].loc.offset
 130         = (long)&sc->sc_fr[i] - new_cfa;
 131       fs->regs.reg[2*i+24+1].how = REG_SAVED_OFFSET;
 132       fs->regs.reg[2*i+24+1].loc.offset
 133         = (long)&sc->sc_fr[i] + 4 - new_cfa;
 134     }
 135   fs->regs.reg[88].how = REG_SAVED_OFFSET;
 136   fs->regs.reg[88].loc.offset = (long) &sc->sc_sar - new_cfa;
 137   fs->regs.reg[DWARF_ALT_FRAME_RETURN_COLUMN].how = REG_SAVED_OFFSET;
 138   fs->regs.reg[DWARF_ALT_FRAME_RETURN_COLUMN].loc.offset
 139     = (long) &sc->sc_iaoq[0] - new_cfa;
 140   fs->retaddr_column = DWARF_ALT_FRAME_RETURN_COLUMN;
 141   fs->signal_frame = 1;
 142   return _URC_NO_REASON;
 143 }
 144 #endif /* inhibit_libc */