1 /* Helper functions for form handling.
2    Copyright (C) 2003-2009, 2014 Red Hat, Inc.
3    This file is part of elfutils.
4    Written by Ulrich Drepper <drepper@redhat.com>, 2003.
5 
6    This file is free software; you can redistribute it and/or modify
7    it under the terms of either
8 
9      * the GNU Lesser General Public License as published by the Free
10        Software Foundation; either version 3 of the License, or (at
11        your option) any later version
12 
13    or
14 
15      * the GNU General Public License as published by the Free
16        Software Foundation; either version 2 of the License, or (at
17        your option) any later version
18 
19    or both in parallel, as here.
20 
21    elfutils is distributed in the hope that it will be useful, but
22    WITHOUT ANY WARRANTY; without even the implied warranty of
23    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
24    General Public License for more details.
25 
26    You should have received copies of the GNU General Public License and
27    the GNU Lesser General Public License along with this program.  If
28    not, see <http://www.gnu.org/licenses/>.  */
29 
30 #ifdef HAVE_CONFIG_H
31 # include <config.h>
32 #endif
33 
34 #include <dwarf.h>
35 #include <string.h>
36 
37 #include "libdwP.h"
38 
39 
40 size_t
41 internal_function
__libdw_form_val_compute_len(struct Dwarf_CU * cu,unsigned int form,const unsigned char * valp)42 __libdw_form_val_compute_len (struct Dwarf_CU *cu, unsigned int form,
43 			      const unsigned char *valp)
44 {
45   const unsigned char *startp = valp;
46   const unsigned char *endp = cu->endp;
47   Dwarf_Word u128;
48   size_t result;
49 
50   /* NB: This doesn't cover constant form lengths, which are
51      already handled by the inlined __libdw_form_val_len.  */
52   switch (form)
53     {
54     case DW_FORM_addr:
55       result = cu->address_size;
56       break;
57 
58     case DW_FORM_ref_addr:
59       result = cu->version == 2 ? cu->address_size : cu->offset_size;
60       break;
61 
62     case DW_FORM_strp:
63     case DW_FORM_sec_offset:
64     case DW_FORM_GNU_ref_alt:
65     case DW_FORM_GNU_strp_alt:
66       result = cu->offset_size;
67       break;
68 
69     case DW_FORM_block1:
70       if (unlikely ((size_t) (endp - startp) < 1))
71 	goto invalid;
72       result = *valp + 1;
73       break;
74 
75     case DW_FORM_block2:
76       if (unlikely ((size_t) (endp - startp) < 2))
77 	goto invalid;
78       result = read_2ubyte_unaligned (cu->dbg, valp) + 2;
79       break;
80 
81     case DW_FORM_block4:
82       if (unlikely ((size_t) (endp - startp) < 4))
83 	goto invalid;
84       result = read_4ubyte_unaligned (cu->dbg, valp) + 4;
85       break;
86 
87     case DW_FORM_block:
88     case DW_FORM_exprloc:
89       get_uleb128 (u128, valp, endp);
90       result = u128 + (valp - startp);
91       break;
92 
93     case DW_FORM_string:
94       {
95 	const unsigned char *endstrp = memchr (valp, '\0',
96 					       (size_t) (endp - startp));
97 	if (unlikely (endstrp == NULL))
98 	  goto invalid;
99 	result = (size_t) (endstrp - startp) + 1;
100 	break;
101       }
102 
103     case DW_FORM_sdata:
104     case DW_FORM_udata:
105     case DW_FORM_ref_udata:
106       get_uleb128 (u128, valp, endp);
107       result = valp - startp;
108       break;
109 
110     case DW_FORM_indirect:
111       get_uleb128 (u128, valp, endp);
112       // XXX Is this really correct?
113       result = __libdw_form_val_len (cu, u128, valp);
114       if (result != (size_t) -1)
115 	result += valp - startp;
116       else
117         return (size_t) -1;
118       break;
119 
120     default:
121       goto invalid;
122     }
123 
124   if (unlikely (result > (size_t) (endp - startp)))
125     {
126     invalid:
127       __libdw_seterrno (DWARF_E_INVALID_DWARF);
128       result = (size_t) -1;
129     }
130 
131   return result;
132 }
133