1.\" Copyright (c) 2011 Kai Wang
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25.\" $Id: dwarf_expand_frame_instructions.3 3644 2018-10-15 19:55:01Z jkoshy $
26.\"
27.Dd November 9, 2011
28.Dt DWARF_EXPAND_FRAME_INSTRUCTIONS 3
29.Os
30.Sh NAME
31.Nm dwarf_expand_frame_instructions
32.Nd expand frame instructions
33.Sh LIBRARY
34.Lb libdwarf
35.Sh SYNOPSIS
36.In libdwarf.h
37.Ft int
38.Fo dwarf_expand_frame_instructions
39.Fa "Dwarf_Cie cie"
40.Fa "Dwarf_Ptr instructions"
41.Fa "Dwarf_Unsigned len"
42.Fa "Dwarf_Frame_Op **ret_ops"
43.Fa "Dwarf_Signed *ret_opcnt"
44.Fa "Dwarf_Error *error"
45.Fc
46.Sh DESCRIPTION
47Function
48.Fn dwarf_expand_frame_instructions
49translates DWARF frame instruction bytes into an array of
50.Vt Dwarf_Frame_Op
51descriptors.
52.Pp
53Argument
54.Ar cie
55should reference the CIE descriptor associated with the instructions
56to be translated.
57.Pp
58Arugment
59.Ar instructions
60should point to an array of frame instruction bytes, as
61returned by the functions
62.Xr dwarf_get_cie_info 3
63or
64.Xr dwarf_get_fde_instr_bytes 3 .
65.Pp
66Argument
67.Ar len
68should specify the number of the frame instruction bytes to be
69translated.
70.Pp
71Argument
72.Ar ret_ops
73should point to a location that will be set to a pointer to
74an array of translated
75.Vt Dwarf_Frame_Op
76descriptors.
77.Pp
78Argument
79.Ar ret_opcnt
80should point to a location that will hold the total number of the
81returned descriptors.
82.Pp
83If argument
84.Ar err
85is not NULL, it will be used to store error information in case of an
86error.
87.Ss Memory Management
88The memory area used for the descriptor array returned in argument
89.Ar ret_ops
90is allocated by
91.Lb libdwarf .
92Application code should use function
93.Xr dwarf_dealloc 3
94with type
95.Dv DW_DLA_FRAME_BLOCK
96to free the memory area when the descriptor array is no longer needed.
97.Sh RETURN VALUES
98Function
99.Fn dwarf_expand_frame_instructions
100returns
101.Dv DW_DLV_OK
102when it succeeds.
103In case of an error, it returns
104.Dv DW_DLV_ERROR
105and sets the argument
106.Ar err .
107.Sh EXAMPLES
108To retrieve and expand the frame instructions for a given FDE
109descriptor, use:
110.Bd -literal -offset indent
111Dwarf_Dbg dbg;
112Dwarf_Cie cie;
113Dwarf_Fde fde;
114Dwarf_Ptr fde_inst;
115Dwarf_Unsigned fde_instlen;
116Dwarf_Frame_Op *ops;
117Dwarf_Signed opcnt;
118Dwarf_Error de;
119
120/* ... assuming `dbg` references a valid DWARF debugging context,
121  `fde` references a valid FDE descriptor and `cie` holds the CIE
122  descriptor associated with the FDE descriptor ... */
123
124if (dwarf_get_fde_instr_bytes(fde, &fde_inst, &fde_instlen,
125    &de) != DW_DLV_OK)
126	errx(EXIT_FAILURE, "dwarf_get_fde_instr_bytes failed: %s",
127	    dwarf_errmsg(de));
128
129if (dwarf_expand_frame_instructions(cie, fde_inst, fde_instlen,
130    &ops, &opcnt, &de) != DW_DLV_OK)
131	errx(EXIT_FAILURE,
132	    "dwarf_expand_frame_instructions failed: %s",
133	    dwarf_errmsg(de));
134
135for (i = 0; i < opcnt; i++) {
136	/* ... use ops[i] ... */
137}
138
139/* Free the memory area when no longer needed. */
140dwarf_dealloc(dbg, ops, DW_DLA_FRAME_BLOCK);
141.Ed
142.Sh ERRORS
143Function
144.Fn dwarf_expand_frame_instructions
145can fail with:
146.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT"
147.It Bq Er DW_DLE_ARGUMENT
148One of the arguments
149.Ar cie ,
150.Ar instructions ,
151.Ar ret_ops
152or
153.Ar ret_opcnt
154was NULL.
155.It Bq Er DW_DLE_ARGUMENT
156Argument
157.Ar len
158was 0.
159.It Bq Er DW_DLE_MEMORY
160An out of memory condition was encountered during the execution of
161this function.
162.It Bq Er DW_DLE_FRAME_INSTR_EXEC_ERROR
163An unknown instruction was found in the instruction bytes provided
164in argument
165.Ar instructions .
166.El
167.Sh SEE ALSO
168.Xr dwarf 3 ,
169.Xr dwarf_frame_instructions_dealloc 3 ,
170.Xr dwarf_get_cie_index 3 ,
171.Xr dwarf_get_cie_info 3 ,
172.Xr dwarf_get_cie_of_fde 3 ,
173.Xr dwarf_get_fde_at_pc 3 ,
174.Xr dwarf_get_fde_info_for_all_regs 3 ,
175.Xr dwarf_get_fde_info_for_all_regs3 3 ,
176.Xr dwarf_get_fde_info_for_cfa_reg3 3 ,
177.Xr dwarf_get_fde_info_for_reg 3 ,
178.Xr dwarf_get_fde_info_for_reg3 3 ,
179.Xr dwarf_get_fde_instr_bytes 3 ,
180.Xr dwarf_get_fde_list 3 ,
181.Xr dwarf_get_fde_list_eh 3 ,
182.Xr dwarf_get_fde_n 3
183