libgcc/config/pa/linux-unwind.h

   1 /* DWARF2 EH unwinding support for PA Linux.
   2    Copyright (C) 2004-2019 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 3, or (at your option)
   9 any later version.
  10
  11 GCC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 Under Section 7 of GPL version 3, you are granted additional
  17 permissions described in the GCC Runtime Library Exception, version
  18 3.1, as published by the Free Software Foundation.
  19
  20 You should have received a copy of the GNU General Public License and
  21 a copy of the GCC Runtime Library Exception along with this program;
  22 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 <http://www.gnu.org/licenses/>.  */
  24
  25
  26 /* Do code reading to identify a signal frame, and set the frame
  27    state data appropriately.  See unwind-dw2.c for the structs.  */
  28
  29 /* Don't use this if inhibit_libc is set.
  30    The build for this target will fail trying to include missing headers. */
  31 #ifndef inhibit_libc
  32 #include <signal.h>
  33 #include <sys/ucontext.h>
  34
  35 /* Return TRUE if read access to *P is allowed.  */
  36
  37 static inline long
  38 pa32_read_access_ok (void *p)
  39 {
  40   long ret;
  41
  42   __asm__ ("proberi (%1),3,%0" : "=r" (ret) : "r" (p) :);
  43   return ret;
  44 }
  45
  46 /* Unfortunately, because of various bugs and changes to the kernel,
  47    we have several cases to deal with.
  48
  49    In 2.4, the signal trampoline is 4 words, and (CONTEXT)->ra should
  50    point directly at the beginning of the trampoline and struct rt_sigframe.
  51
  52    In <= 2.6.5-rc2-pa3, the signal trampoline is 9 words, and
  53    (CONTEXT)->ra points at the 4th word in the trampoline structure.  This
  54    is wrong, it should point at the 5th word.  This is fixed in 2.6.5-rc2-pa4.
  55
  56    To detect these cases, we first take (CONTEXT)->ra, align it to 64-bytes
  57    to get the beginning of the signal frame, and then check offsets 0, 4
  58    and 5 to see if we found the beginning of the trampoline.  This will
  59    tell us how to locate the sigcontext structure.
  60
  61    Note that with a 2.4 64-bit kernel, the signal context is not properly
  62    passed back to userspace so the unwind will not work correctly.
  63
  64    There is also a bug in various glibc versions.  The (CONTEXT)->ra
  65    for the outermost frame is not marked as undefined, so we need to
  66    check whether read access is allowed for all the accesses used in
  67    searching for the signal trampoline.  */
  68
  69 #define MD_FALLBACK_FRAME_STATE_FOR pa32_fallback_frame_state
  70
  71 static _Unwind_Reason_Code
  72 pa32_fallback_frame_state (struct _Unwind_Context *context,
  73                            _Unwind_FrameState *fs)
  74 {
  75   unsigned long sp = (unsigned long)context->ra & ~63;
  76   unsigned int *pc = (unsigned int *)sp;
  77   unsigned long off;
  78   _Unwind_Ptr new_cfa;
  79   int i;
  80   struct sigcontext *sc;
  81   struct rt_sigframe {
  82     siginfo_t info;
  83     ucontext_t uc;
  84   } *frame;
  85
  86   /* rt_sigreturn trampoline:
  87      3419000x ldi 0, %r25 or ldi 1, %r25   (x = 0 or 2)
  88      3414015a ldi __NR_rt_sigreturn, %r20
  89      e4008200 be,l 0x100(%sr2, %r0), %sr0, %r31
  90      08000240 nop  */
  91
  92   if (pa32_read_access_ok (pc)
  93       && (pc[0] == 0x34190000 || pc[0] == 0x34190002))
  94     off = 4*4;
  95   else if (pa32_read_access_ok (&pc[4])
  96            && (pc[4] == 0x34190000 || pc[4] == 0x34190002))
  97     {
  98       pc += 4;
  99       off = 10 * 4;
 100     }
 101   else if (pa32_read_access_ok (&pc[5])
 102            && (pc[5] == 0x34190000 || pc[5] == 0x34190002))
 103     {
 104       pc += 5;
 105       off = 10 * 4;
 106     }
 107   else
 108     {
 109       /* We may have to unwind through an alternate signal stack.
 110          We assume that the alignment of the alternate signal stack
 111          is BIGGEST_ALIGNMENT (i.e., that it has been allocated using
 112          malloc).  As a result, we can't distinguish trampolines
 113          used prior to 2.6.5-rc2-pa4.  However after 2.6.5-rc2-pa4,
 114          the return address of a signal trampoline will be on an odd
 115          word boundary and we can then determine the frame offset.  */
 116       sp = (unsigned long)context->ra;
 117       pc = (unsigned int *)sp;
 118       if ((sp & 4)
 119           && pa32_read_access_ok (pc)
 120           && (pc[0] == 0x34190000 || pc[0] == 0x34190002))
 121         off = 5 * 4;
 122       else
 123         return _URC_END_OF_STACK;
 124     }
 125
 126   if (!pa32_read_access_ok (&pc[3])
 127       || pc[1] != 0x3414015a
 128       || pc[2] != 0xe4008200
 129       || pc[3] != 0x08000240)
 130     return _URC_END_OF_STACK;
 131
 132   frame = (struct rt_sigframe *)(sp + off);
 133   sc = (struct sigcontext *)&frame->uc.uc_mcontext;
 134
 135   new_cfa = sc->sc_gr[30];
 136   fs->regs.cfa_how = CFA_REG_OFFSET;
 137   fs->regs.cfa_reg = 30;
 138   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 139   for (i = 1; i <= 31; i++)
 140     {
 141       fs->regs.reg[i].how = REG_SAVED_OFFSET;
 142       fs->regs.reg[i].loc.offset = (long)&sc->sc_gr[i] - new_cfa;
 143     }
 144   for (i = 4; i <= 31; i++)
 145     {
 146       /* FP regs have left and right halves */
 147       fs->regs.reg[2*i+24].how = REG_SAVED_OFFSET;
 148       fs->regs.reg[2*i+24].loc.offset
 149         = (long)&sc->sc_fr[i] - new_cfa;
 150       fs->regs.reg[2*i+24+1].how = REG_SAVED_OFFSET;
 151       fs->regs.reg[2*i+24+1].loc.offset
 152         = (long)&sc->sc_fr[i] + 4 - new_cfa;
 153     }
 154   fs->regs.reg[88].how = REG_SAVED_OFFSET;
 155   fs->regs.reg[88].loc.offset = (long) &sc->sc_sar - new_cfa;
 156   fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].how
 157     = REG_SAVED_OFFSET;
 158   fs->regs.reg[__LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__].loc.offset
 159     = (long) &sc->sc_iaoq[0] - new_cfa;
 160   fs->retaddr_column = __LIBGCC_DWARF_ALT_FRAME_RETURN_COLUMN__;
 161   fs->signal_frame = 1;
 162   return _URC_NO_REASON;
 163 }
 164 #endif /* inhibit_libc */