1 /* Exception handling and frame unwind runtime interface routines.
2 Copyright (C) 2001 Free Software Foundation, Inc.
4 This file is part of GNU CC.
6 GNU CC 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)
11 GNU CC 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.
16 You should have received a copy of the GNU General Public License
17 along with GNU CC; see the file COPYING. If not, write to
18 the Free Software Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 /* @@@ Really this should be out of line, but this also causes link
22 compatibility problems with the base ABI. This is slightly better
23 than duplicating code, however. */
25 /* Pointer encodings, from dwarf2.h. */
26 #define DW_EH_PE_absptr 0x00
27 #define DW_EH_PE_omit 0xff
29 #define DW_EH_PE_uleb128 0x01
30 #define DW_EH_PE_udata2 0x02
31 #define DW_EH_PE_udata4 0x03
32 #define DW_EH_PE_udata8 0x04
33 #define DW_EH_PE_sleb128 0x09
34 #define DW_EH_PE_sdata2 0x0A
35 #define DW_EH_PE_sdata4 0x0B
36 #define DW_EH_PE_sdata8 0x0C
37 #define DW_EH_PE_signed 0x08
39 #define DW_EH_PE_pcrel 0x10
40 #define DW_EH_PE_textrel 0x20
41 #define DW_EH_PE_datarel 0x30
42 #define DW_EH_PE_funcrel 0x40
44 #define DW_EH_PE_indirect 0x80
47 /* Given an encoding, return the number of bytes the format occupies.
48 This is only defined for fixed-size encodings, and so does not
52 size_of_encoded_value (unsigned char encoding)
54 if (encoding == DW_EH_PE_omit)
57 switch (encoding & 0x07)
60 return sizeof (void *);
71 /* Given an encoding and an _Unwind_Context, return the base to which
72 the encoding is relative. This base may then be passed to
73 read_encoded_value_with_base for use when the _Unwind_Context is
77 base_of_encoded_value (unsigned char encoding, struct _Unwind_Context *context)
79 if (encoding == DW_EH_PE_omit)
82 switch (encoding & 0x70)
88 case DW_EH_PE_textrel:
89 return _Unwind_GetTextRelBase (context);
90 case DW_EH_PE_datarel:
91 return _Unwind_GetDataRelBase (context);
92 case DW_EH_PE_funcrel:
93 return _Unwind_GetRegionStart (context);
98 /* Load an encoded value from memory at P. The value is returned in VAL;
99 The function returns P incremented past the value. BASE is as given
100 by base_of_encoded_value for this encoding in the appropriate context. */
102 static const unsigned char *
103 read_encoded_value_with_base (unsigned char encoding, _Unwind_Ptr base,
104 const unsigned char *p, _Unwind_Ptr *val)
109 unsigned u2 __attribute__ ((mode (HI)));
110 unsigned u4 __attribute__ ((mode (SI)));
111 unsigned u8 __attribute__ ((mode (DI)));
112 signed s2 __attribute__ ((mode (HI)));
113 signed s4 __attribute__ ((mode (SI)));
114 signed s8 __attribute__ ((mode (DI)));
115 } __attribute__((__packed__));
117 union unaligned *u = (union unaligned *) p;
120 switch (encoding & 0x0f)
122 case DW_EH_PE_absptr:
123 result = (_Unwind_Ptr) u->ptr;
124 p += sizeof (void *);
127 case DW_EH_PE_uleb128:
129 unsigned int shift = 0;
136 result |= (_Unwind_Ptr)(byte & 0x7f) << shift;
143 case DW_EH_PE_sleb128:
145 unsigned int shift = 0;
152 result |= (_Unwind_Ptr)(byte & 0x7f) << shift;
157 if (shift < 8 * sizeof(result) && (byte & 0x40) != 0)
158 result |= -(1L << shift);
162 case DW_EH_PE_udata2:
166 case DW_EH_PE_udata4:
170 case DW_EH_PE_udata8:
175 case DW_EH_PE_sdata2:
179 case DW_EH_PE_sdata4:
183 case DW_EH_PE_sdata8:
194 result += ((encoding & 0x70) == DW_EH_PE_pcrel ? (_Unwind_Ptr)u : base);
195 if (encoding & DW_EH_PE_indirect)
196 result = *(_Unwind_Ptr *)result;
203 /* Like read_encoded_value_with_base, but get the base from the context
204 rather than providing it directly. */
206 static inline const unsigned char *
207 read_encoded_value (struct _Unwind_Context *context, unsigned char encoding,
208 const unsigned char *p, _Unwind_Ptr *val)
210 return read_encoded_value_with_base (encoding,
211 base_of_encoded_value (encoding, context),
215 /* Read an unsigned leb128 value from P, store the value in VAL, return
216 P incremented past the value. */
218 static inline const unsigned char *
219 read_uleb128 (const unsigned char *p, _Unwind_Ptr *val)
221 return read_encoded_value_with_base (DW_EH_PE_uleb128, 0, p, val);
224 /* Similar, but read a signed leb128 value. */
226 static inline const unsigned char *
227 read_sleb128 (const unsigned char *p, _Unwind_Ptr *val)
229 return read_encoded_value_with_base (DW_EH_PE_sleb128, 0, p, val);