1 /* simple-object.h -- simple routines to read and write object files 2 Copyright (C) 2010-2018 Free Software Foundation, Inc. 3 Written by Ian Lance Taylor, Google. 4 5 This program is free software; you can redistribute it and/or modify it 6 under the terms of the GNU General Public License as published by the 7 Free Software Foundation; either version 2, or (at your option) any 8 later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program; if not, write to the Free Software 17 Foundation, 51 Franklin Street - Fifth Floor, 18 Boston, MA 02110-1301, USA. */ 19 20 #ifndef SIMPLE_OBJECT_H 21 #define SIMPLE_OBJECT_H 22 23 #include <stddef.h> 24 #include <sys/types.h> 25 26 #ifdef HAVE_UNISTD_H 27 #include <unistd.h> 28 #endif 29 30 #ifdef __cplusplus 31 extern "C" { 32 #endif 33 34 /* This header file provides four types with associated functions. 35 They are used to read and write object files. This is a minimal 36 interface, intended to support the needs of gcc without bringing in 37 all the power and complexity of BFD. */ 38 39 /* The type simple_object_read * is used to read an existing object 40 file. */ 41 42 typedef struct simple_object_read_struct simple_object_read; 43 44 /* Create an simple_object_read given DESCRIPTOR, an open file 45 descriptor, and OFFSET, an offset within the file. The offset is 46 for use with archives, and should be 0 for an ordinary object file. 47 The descriptor must remain open until done with the returned 48 simple_object_read. SEGMENT_NAME is used on Mach-O and is required 49 on that platform: it means to only look at sections within the 50 segment with that name. It is ignored for other object file 51 formats. On error, this function returns NULL, and sets *ERRMSG to 52 an error string and sets *ERR to an errno value or 0 if there is no 53 relevant errno. */ 54 55 extern simple_object_read * 56 simple_object_start_read (int descriptor, off_t offset, 57 const char *segment_name, const char **errmsg, 58 int *err); 59 60 /* Call PFN for each section in SIMPLE_OBJECT, passing it the section 61 name, offset within the file of the section contents, and length of 62 the section contents. The offset within the file is relative to 63 the offset passed to simple_object_start_read. The DATA argument 64 to simple_object_find_sections is passed on to PFN. If PFN returns 65 0, the loop is stopped and simple_object_find_sections returns. If 66 PFN returns non-zero, the loop continues. On success this returns 67 NULL. On error it returns an error string, and sets *ERR to an 68 errno value or 0 if there is no relevant errno. */ 69 70 extern const char * 71 simple_object_find_sections (simple_object_read *simple_object, 72 int (*pfn) (void *data, const char *, 73 off_t offset, off_t length), 74 void *data, 75 int *err); 76 77 /* Look for the section NAME in SIMPLE_OBJECT. This returns 78 information for the first section NAME in SIMPLE_OBJECT. Note that 79 calling this multiple times is inefficient; use 80 simple_object_find_sections instead. 81 82 If found, return 1 and set *OFFSET to the offset in the file of the 83 section contents and set *LENGTH to the length of the section 84 contents. *OFFSET will be relative to the offset passed to 85 simple_object_start_read. 86 87 If the section is not found, and no error occurs, return 0 and set 88 *ERRMSG to NULL. 89 90 If an error occurs, return 0, set *ERRMSG to an error message, and 91 set *ERR to an errno value or 0 if there is no relevant errno. */ 92 93 extern int 94 simple_object_find_section (simple_object_read *simple_object, 95 const char *name, off_t *offset, off_t *length, 96 const char **errmsg, int *err); 97 98 /* Release all resources associated with SIMPLE_OBJECT. This does not 99 close the file descriptor. */ 100 101 extern void 102 simple_object_release_read (simple_object_read *); 103 104 /* The type simple_object_attributes holds the attributes of an object 105 file that matter for creating a file or ensuring that two files are 106 compatible. This is a set of magic numbers. */ 107 108 typedef struct simple_object_attributes_struct simple_object_attributes; 109 110 /* Fetch the attributes of SIMPLE_OBJECT. This information will 111 persist until simple_object_attributes_release is called, even if 112 SIMPLE_OBJECT is closed. On error this returns NULL, sets *ERRMSG 113 to an error message, and sets *ERR to an errno value or 0 if there 114 isn't one. */ 115 116 extern simple_object_attributes * 117 simple_object_fetch_attributes (simple_object_read *simple_object, 118 const char **errmsg, int *err); 119 120 /* Merge the FROM attributes into TO. If two objects with these 121 attributes could be linked together without error, returns NULL. 122 Otherwise, returns an error message, and sets *ERR to an errno 123 value or 0 if there isn't one. */ 124 125 extern const char * 126 simple_object_attributes_merge (simple_object_attributes *to, 127 simple_object_attributes *from, 128 int *err); 129 130 /* Release all resources associated with ATTRS. */ 131 132 extern void 133 simple_object_release_attributes (simple_object_attributes *attrs); 134 135 /* The type simple_object_write is used to create a new object file. */ 136 137 typedef struct simple_object_write_struct simple_object_write; 138 139 /* Start creating a new object file which is like ATTRS. You must 140 fetch attribute information from an existing object file before you 141 can create a new one. There is currently no support for creating 142 an object file de novo. The segment name is only used on Mach-O, 143 where it is required. It means that all sections are created 144 within that segment. It is ignored for other object file formats. 145 On error this function returns NULL, sets *ERRMSG to an error 146 message, and sets *ERR to an errno value or 0 if there isn't 147 one. */ 148 149 extern simple_object_write * 150 simple_object_start_write (simple_object_attributes *attrs, 151 const char *segment_name, 152 const char **errmsg, int *err); 153 154 /* The type simple_object_write_section is a handle for a section 155 which is being written. */ 156 157 typedef struct simple_object_write_section_struct simple_object_write_section; 158 159 /* Add a section to SIMPLE_OBJECT. NAME is the name of the new 160 section. ALIGN is the required alignment expressed as the number 161 of required low-order 0 bits (e.g., 2 for alignment to a 32-bit 162 boundary). The section is created as containing data, readable, 163 not writable, not executable, not loaded at runtime. On error this 164 returns NULL, sets *ERRMSG to an error message, and sets *ERR to an 165 errno value or 0 if there isn't one. */ 166 167 extern simple_object_write_section * 168 simple_object_write_create_section (simple_object_write *simple_object, 169 const char *name, unsigned int align, 170 const char **errmsg, int *err); 171 172 /* Add data BUFFER/SIZE to SECTION in SIMPLE_OBJECT. If COPY is 173 non-zero, the data will be copied into memory if necessary. If 174 COPY is zero, BUFFER must persist until SIMPLE_OBJECT is released. 175 On success this returns NULL. On error this returns an error 176 message, and sets *ERR to an errno value or 0 if there isn't 177 one. */ 178 179 extern const char * 180 simple_object_write_add_data (simple_object_write *simple_object, 181 simple_object_write_section *section, 182 const void *buffer, size_t size, 183 int copy, int *err); 184 185 /* Write the complete object file to DESCRIPTOR, an open file 186 descriptor. This returns NULL on success. On error this returns 187 an error message, and sets *ERR to an errno value or 0 if there 188 isn't one. */ 189 190 extern const char * 191 simple_object_write_to_file (simple_object_write *simple_object, 192 int descriptor, int *err); 193 194 /* Release all resources associated with SIMPLE_OBJECT, including any 195 simple_object_write_section's that may have been created. */ 196 197 extern void 198 simple_object_release_write (simple_object_write *); 199 200 /* Copy LTO debug sections from SRC_OBJECT to DEST. 201 If an error occurs, return the errno value in ERR and an error string. */ 202 203 extern const char * 204 simple_object_copy_lto_debug_sections (simple_object_read *src_object, 205 const char *dest, 206 int *err); 207 208 #ifdef __cplusplus 209 } 210 #endif 211 212 #endif 213