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