OpenCores
URL https://opencores.org/ocsvn/openrisc_me/openrisc_me/trunk

Subversion Repositories openrisc_me

[/] [openrisc/] [trunk/] [gnu-src/] [gcc-4.5.1/] [gcc/] [config/] [pa/] [fptr.c] - Blame information for rev 282

Details | Compare with Previous | View Log

Line No. Rev Author Line
1 282 jeremybenn
/* Subroutine for function pointer canonicalization on PA-RISC with ELF32.
2
   Copyright 2002, 2003, 2004, 2007, 2009 Free Software Foundation, Inc.
3
   Contributed by John David Anglin (dave.anglin@nrc.ca).
4
 
5
This file is part of GCC.
6
 
7
GCC is free software; you can redistribute it and/or modify it under
8
the terms of the GNU General Public License as published by the Free
9
Software Foundation; either version 3, or (at your option) any later
10
version.
11
 
12
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13
WARRANTY; without even the implied warranty of MERCHANTABILITY or
14
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
15
for more details.
16
 
17
Under Section 7 of GPL version 3, you are granted additional
18
permissions described in the GCC Runtime Library Exception, version
19
3.1, as published by the Free Software Foundation.
20
 
21
You should have received a copy of the GNU General Public License and
22
a copy of the GCC Runtime Library Exception along with this program;
23
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
24
<http://www.gnu.org/licenses/>.  */
25
 
26
 
27
/* WARNING: The code is this function depends on internal and undocumented
28
   details of the GNU linker and dynamic loader as implemented for parisc
29
   linux.  */
30
 
31
/* This MUST match the defines sysdeps/hppa/dl-machine.h and
32
   bfd/elf32-hppa.c.  */
33
#define GOT_FROM_PLT_STUB (4*4)
34
 
35
/* List of byte offsets in _dl_runtime_resolve to search for "bl" branches.
36
   The first "bl" branch instruction found MUST be a call to fixup.  See
37
   the define for TRAMPOLINE_TEMPLATE in sysdeps/hppa/dl-machine.h.  If
38
   the trampoline template is changed, the list must be appropriately
39
   updated.  The offset of -4 allows for a magic branch at the start of
40
   the template should it be necessary to change the current branch
41
   position.  */
42
#define NOFFSETS 2
43
static int fixup_branch_offset[NOFFSETS] = { 32, -4 };
44
 
45
#define GET_FIELD(X, FROM, TO) \
46
  ((X) >> (31 - (TO)) & ((1 << ((TO) - (FROM) + 1)) - 1))
47
#define SIGN_EXTEND(VAL,BITS) \
48
  ((int) ((VAL) >> ((BITS) - 1) ? (-1 << (BITS)) | (VAL) : (VAL)))
49
 
50
struct link_map;
51
typedef int (*fptr_t) (void);
52
typedef int (*fixup_t) (struct link_map *, unsigned int);
53
extern unsigned int _GLOBAL_OFFSET_TABLE_;
54
 
55
/* __canonicalize_funcptr_for_compare must be hidden so that it is not
56
   placed in the dynamic symbol table.  Like millicode functions, it
57
   must be linked into all binaries in order access the got table of
58
   that binary.  However, we don't use the millicode calling convention
59
   and the routine must be a normal function so that it can be compiled
60
   as pic code.  */
61
unsigned int __canonicalize_funcptr_for_compare (fptr_t)
62
      __attribute__ ((visibility ("hidden")));
63
 
64
unsigned int
65
__canonicalize_funcptr_for_compare (fptr_t fptr)
66
{
67
  static unsigned int fixup_plabel[2];
68
  static fixup_t fixup;
69
  unsigned int *plabel, *got;
70
 
71
  /* -1 and page 0 are special.  -1 is used in crtend to mark the end of
72
     a list of function pointers.  Also return immediately if the plabel
73
     bit is not set in the function pointer.  In this case, the function
74
     pointer points directly to the function.  */
75
  if ((int) fptr == -1 || (unsigned int) fptr < 4096 || !((int) fptr & 2))
76
    return (unsigned int) fptr;
77
 
78
  /* The function pointer points to a function descriptor (plabel).  If
79
     the plabel hasn't been resolved, the first word of the plabel points
80
     to the entry of the PLT stub just before the global offset table.
81
     The second word in the plabel contains the relocation offset for the
82
     function.  */
83
  plabel = (unsigned int *) ((unsigned int) fptr & ~3);
84
  got = (unsigned int *) (plabel[0] + GOT_FROM_PLT_STUB);
85
 
86
  /* Return the address of the function if the plabel has been resolved.  */
87
  if (got !=  &_GLOBAL_OFFSET_TABLE_)
88
    return plabel[0];
89
 
90
  /* Initialize our plabel for calling fixup if we haven't done so already.
91
     This code needs to be thread safe but we don't have to be too careful
92
     as the result is invariant.  */
93
  if (!fixup)
94
    {
95
      int i;
96
      unsigned int *iptr;
97
 
98
      /* Find the first "bl" branch in the offset search list.  This is a
99
         call to fixup or a magic branch to fixup at the beginning of the
100
         trampoline template.  The fixup function does the actual runtime
101
         resolution of function descriptors.  We only look for "bl" branches
102
         with a 17-bit pc-relative displacement.  */
103
      for (i = 0; i < NOFFSETS; i++)
104
        {
105
          iptr = (unsigned int *) (got[-2] + fixup_branch_offset[i]);
106
          if ((*iptr & 0xfc00e000) == 0xe8000000)
107
            break;
108
        }
109
 
110
      /* This should not happen... */
111
      if (i == NOFFSETS)
112
        return ~0;
113
 
114
      /* Extract the 17-bit displacement from the instruction.  */
115
      iptr += SIGN_EXTEND (GET_FIELD (*iptr, 19, 28) |
116
                           GET_FIELD (*iptr, 29, 29) << 10 |
117
                           GET_FIELD (*iptr, 11, 15) << 11 |
118
                           GET_FIELD (*iptr, 31, 31) << 16, 17);
119
 
120
      /* Build a plabel for an indirect call to fixup.  */
121
      fixup_plabel[0] = (unsigned int) iptr + 8;  /* address of fixup */
122
      fixup_plabel[1] = got[-1];                  /* ltp for fixup */
123
      fixup = (fixup_t) ((int) fixup_plabel | 3);
124
    }
125
 
126
  /* Call fixup to resolve the function address.  got[1] contains the
127
     link_map pointer and plabel[1] the relocation offset.  */
128
  fixup ((struct link_map *) got[1], plabel[1]);
129
 
130
  return plabel[0];
131
}

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.