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1 /* Internal definitions for libdw CFI interpreter.
2    Copyright (C) 2009-2010, 2013, 2015 Red Hat, Inc.
3    This file is part of elfutils.
4 
5    This file is free software; you can redistribute it and/or modify
6    it under the terms of either
7 
8      * the GNU Lesser General Public License as published by the Free
9        Software Foundation; either version 3 of the License, or (at
10        your option) any later version
11 
12    or
13 
14      * the GNU General Public License as published by the Free
15        Software Foundation; either version 2 of the License, or (at
16        your option) any later version
17 
18    or both in parallel, as here.
19 
20    elfutils is distributed in the hope that it will be useful, but
21    WITHOUT ANY WARRANTY; without even the implied warranty of
22    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
23    General Public License for more details.
24 
25    You should have received copies of the GNU General Public License and
26    the GNU Lesser General Public License along with this program.  If
27    not, see <http://www.gnu.org/licenses/>.  */
28 
29 #ifndef _UNWINDP_H
30 #define _UNWINDP_H 1
31 
32 #include "libdwP.h"
33 #include "libelfP.h"
34 struct ebl;
35 
36 /* Cached CIE representation.  */
37 struct dwarf_cie
38 {
39   Dwarf_Off offset;	 /* Our position, as seen in FDEs' CIE_pointer.  */
40 
41   Dwarf_Word code_alignment_factor;
42   Dwarf_Sword data_alignment_factor;
43   Dwarf_Word return_address_register;
44 
45   size_t fde_augmentation_data_size;
46 
47   // play out to initial state
48   const uint8_t *initial_instructions;
49   const uint8_t *initial_instructions_end;
50 
51   const Dwarf_Frame *initial_state;
52 
53   uint8_t fde_encoding;		/* DW_EH_PE_* for addresses in FDEs.  */
54   uint8_t lsda_encoding;    /* DW_EH_PE_* for LSDA in FDE augmentation.  */
55 
56   bool sized_augmentation_data;	/* Saw 'z': FDEs have self-sized data.  */
57   bool signal_frame;		/* Saw 'S': FDE is for a signal frame.  */
58 };
59 
60 /* Cached FDE representation.  */
61 struct dwarf_fde
62 {
63   struct dwarf_cie *cie;
64 
65   /* This FDE describes PC values in [start, end).  */
66   Dwarf_Addr start;
67   Dwarf_Addr end;
68 
69   const uint8_t *instructions;
70   const uint8_t *instructions_end;
71 };
72 
73 /* This holds everything we cache about the CFI from each ELF file's
74    .debug_frame or .eh_frame section.  */
75 struct Dwarf_CFI_s
76 {
77   /* Dwarf handle we came from.  If null, this is .eh_frame data.  */
78   Dwarf *dbg;
79 #define CFI_IS_EH(cfi)	((cfi)->dbg == NULL)
80 
81   /* Data of the .debug_frame or .eh_frame section.  */
82   Elf_Data_Scn *data;
83   const unsigned char *e_ident;	/* For EI_DATA and EI_CLASS.  */
84 
85   Dwarf_Addr frame_vaddr;  /* DW_EH_PE_pcrel, address of frame section.  */
86   Dwarf_Addr textrel;		/* DW_EH_PE_textrel base address.  */
87   Dwarf_Addr datarel;		/* DW_EH_PE_datarel base address.  */
88 
89   /* Location of next unread entry in the section.  */
90   Dwarf_Off next_offset;
91 
92   /* Search tree for the CIEs, indexed by CIE_pointer (section offset).  */
93   void *cie_tree;
94 
95   /* Search tree for the FDEs, indexed by PC address.  */
96   void *fde_tree;
97 
98   /* Search tree for parsed DWARF expressions, indexed by raw pointer.  */
99   void *expr_tree;
100 
101   /* Backend hook.  */
102   struct ebl *ebl;
103 
104   /* Binary search table in .eh_frame_hdr section.  */
105   const uint8_t *search_table;
106   size_t search_table_len;
107   Dwarf_Addr search_table_vaddr;
108   size_t search_table_entries;
109   uint8_t search_table_encoding;
110 
111   /* True if the file has a byte order different from the host.  */
112   bool other_byte_order;
113 
114   /* Default rule for registers not previously mentioned
115      is same_value, not undefined.  */
116   bool default_same_value;
117 };
118 
119 
120 enum dwarf_frame_rule
121   {
122     reg_unspecified,		/* Uninitialized state.  */
123     reg_undefined,		/* DW_CFA_undefined */
124     reg_same_value,		/* DW_CFA_same_value */
125     reg_offset,			/* DW_CFA_offset_extended et al */
126     reg_val_offset,		/* DW_CFA_val_offset et al */
127     reg_register,		/* DW_CFA_register */
128     reg_expression,		/* DW_CFA_expression */
129     reg_val_expression,		/* DW_CFA_val_expression */
130   };
131 
132 /* This describes what we know about an individual register.  */
133 struct dwarf_frame_register
134 {
135   enum dwarf_frame_rule rule:3;
136 
137   /* The meaning of the value bits depends on the rule:
138 
139 	Rule			Value
140 	----			-----
141 	undefined		unused
142 	same_value		unused
143 	offset(N)		N	(register saved at CFA + value)
144 	val_offset(N)		N	(register = CFA + value)
145 	register(R)		R	(register = register #value)
146 	expression(E)		section offset of DW_FORM_block containing E
147 					(register saved at address E computes)
148 	val_expression(E)	section offset of DW_FORM_block containing E
149 					(register = value E computes)
150   */
151   Dwarf_Sword value:(sizeof (Dwarf_Sword) * 8 - 3);
152 };
153 
154 /* This holds instructions for unwinding frame at a particular PC location
155    described by an FDE.  */
156 struct Dwarf_Frame_s
157 {
158   /* This frame description covers PC values in [start, end).  */
159   Dwarf_Addr start;
160   Dwarf_Addr end;
161 
162   Dwarf_CFI *cache;
163 
164   /* Previous state saved by DW_CFA_remember_state, or .cie->initial_state,
165      or NULL in an initial_state pseudo-frame.  */
166   Dwarf_Frame *prev;
167 
168   /* The FDE that generated this frame state.  This points to its CIE,
169      which has the return_address_register and signal_frame flag.  */
170   struct dwarf_fde *fde;
171 
172   /* The CFA is unknown, is R+N, or is computed by a DWARF expression.
173      A bogon in the CFI can indicate an invalid/incalculable rule.
174      We store that as cfa_invalid rather than barfing when processing it,
175      so callers can ignore the bogon unless they really need that CFA.  */
176   enum { cfa_undefined, cfa_offset, cfa_expr, cfa_invalid } cfa_rule;
177   union
178   {
179     Dwarf_Op offset;
180     Dwarf_Block expr;
181   } cfa_data;
182   /* We store an offset rule as a DW_OP_bregx operation.  */
183 #define cfa_val_reg	cfa_data.offset.number
184 #define cfa_val_offset	cfa_data.offset.number2
185 
186   size_t nregs;
187   struct dwarf_frame_register regs[];
188 };
189 
190 
191 /* Clean up the data structure and all it points to.  */
192 extern void __libdw_destroy_frame_cache (Dwarf_CFI *cache)
193   __nonnull_attribute__ (1) internal_function;
194 
195 /* Enter a CIE encountered while reading through for FDEs.  */
196 extern void __libdw_intern_cie (Dwarf_CFI *cache, Dwarf_Off offset,
197 				const Dwarf_CIE *info)
198   __nonnull_attribute__ (1, 3) internal_function;
199 
200 /* Look up a CIE_pointer for random access.  */
201 extern struct dwarf_cie *__libdw_find_cie (Dwarf_CFI *cache, Dwarf_Off offset)
202   __nonnull_attribute__ (1) internal_function;
203 
204 
205 /* Look for an FDE covering the given PC address.  */
206 extern struct dwarf_fde *__libdw_find_fde (Dwarf_CFI *cache,
207 					   Dwarf_Addr address)
208   __nonnull_attribute__ (1) internal_function;
209 
210 /* Look for an FDE by its offset in the section.  */
211 extern struct dwarf_fde *__libdw_fde_by_offset (Dwarf_CFI *cache,
212 						Dwarf_Off offset)
213   __nonnull_attribute__ (1) internal_function;
214 
215 /* Process the FDE that contains the given PC address,
216    to yield the frame state when stopped there.
217    The return value is a DWARF_E_* error code.  */
218 extern int __libdw_frame_at_address (Dwarf_CFI *cache, struct dwarf_fde *fde,
219 				     Dwarf_Addr address, Dwarf_Frame **frame)
220   __nonnull_attribute__ (1, 2, 4) internal_function;
221 
222 
223 /* Dummy struct for memory-access.h macros.  */
224 #define BYTE_ORDER_DUMMY(var, e_ident)					      \
225   const struct { bool other_byte_order; } var =				      \
226     { ((BYTE_ORDER == LITTLE_ENDIAN && e_ident[EI_DATA] == ELFDATA2MSB)       \
227        || (BYTE_ORDER == BIG_ENDIAN && e_ident[EI_DATA] == ELFDATA2LSB)) }
228 
229 
230 INTDECL (dwarf_next_cfi)
231 INTDECL (dwarf_getcfi)
232 INTDECL (dwarf_getcfi_elf)
233 INTDECL (dwarf_cfi_end)
234 INTDECL (dwarf_cfi_addrframe)
235 
236 #endif	/* unwindP.h */
237