| 1 | /* Unexec for HP 9000 Series 800 machines. |
| 2 | |
| 3 | This file is in the public domain. |
| 4 | |
| 5 | Author: John V. Morris |
| 6 | |
| 7 | This file was written by John V. Morris at Hewlett Packard. |
| 8 | Both the author and Hewlett Packard Co. have disclaimed the |
| 9 | copyright on this file, and it is therefore in the public domain. |
| 10 | (Search for "hp9k800" in copyright.list.) |
| 11 | */ |
| 12 | |
| 13 | /* |
| 14 | Bob Desinger <hpsemc!bd@hplabs.hp.com> |
| 15 | |
| 16 | Note that the GNU project considers support for HP operation a |
| 17 | peripheral activity which should not be allowed to divert effort |
| 18 | from development of the GNU system. Changes in this code will be |
| 19 | installed when users send them in, but aside from that we don't |
| 20 | plan to think about it, or about whether other Emacs maintenance |
| 21 | might break it. |
| 22 | |
| 23 | |
| 24 | Unexec creates a copy of the old a.out file, and replaces the old data |
| 25 | area with the current data area. When the new file is executed, the |
| 26 | process will see the same data structures and data values that the |
| 27 | original process had when unexec was called. |
| 28 | |
| 29 | Unlike other versions of unexec, this one copies symbol table and |
| 30 | debug information to the new a.out file. Thus, the new a.out file |
| 31 | may be debugged with symbolic debuggers. |
| 32 | |
| 33 | If you fix any bugs in this, I'd like to incorporate your fixes. |
| 34 | Send them to uunet!hpda!hpsemc!jmorris or jmorris%hpsemc@hplabs.HP.COM. |
| 35 | |
| 36 | CAVEATS: |
| 37 | This routine saves the current value of all static and external |
| 38 | variables. This means that any data structure that needs to be |
| 39 | initialized must be explicitly reset. Variables will not have their |
| 40 | expected default values. |
| 41 | |
| 42 | Unfortunately, the HP-UX signal handler has internal initialization |
| 43 | flags which are not explicitly reset. Thus, for signals to work in |
| 44 | conjunction with this routine, the following code must executed when |
| 45 | the new process starts up. |
| 46 | |
| 47 | void _sigreturn (); |
| 48 | ... |
| 49 | sigsetreturn (_sigreturn); |
| 50 | */ |
| 51 | \f |
| 52 | #include <config.h> |
| 53 | #include "unexec.h" |
| 54 | #include "lisp.h" |
| 55 | |
| 56 | #include <stdio.h> |
| 57 | #include <fcntl.h> |
| 58 | #include <errno.h> |
| 59 | #include <a.out.h> |
| 60 | #include <dl.h> |
| 61 | |
| 62 | /* brk value to restore, stored as a global. |
| 63 | This is really used only if we used shared libraries. */ |
| 64 | static long brk_on_dump = 0; |
| 65 | |
| 66 | /* Called from main, if we use shared libraries. */ |
| 67 | int |
| 68 | run_time_remap (char *ignored) |
| 69 | { |
| 70 | brk ((char *) brk_on_dump); |
| 71 | } |
| 72 | |
| 73 | #undef roundup |
| 74 | #define roundup(x,n) (((x) + ((n) - 1)) & ~((n) - 1)) /* n is power of 2 */ |
| 75 | #define min(x,y) (((x) < (y)) ? (x) : (y)) |
| 76 | |
| 77 | /* Report a fatal error and exit. */ |
| 78 | static _Noreturn void |
| 79 | unexec_error (char const *msg) |
| 80 | { |
| 81 | perror (msg); |
| 82 | exit (1); |
| 83 | } |
| 84 | |
| 85 | /* Do an lseek and check the result. */ |
| 86 | static void |
| 87 | check_lseek (int fd, off_t offset, int whence) |
| 88 | { |
| 89 | if (lseek (fd, offset, whence) < 0) |
| 90 | unexec_error ("Cannot lseek"); |
| 91 | } |
| 92 | |
| 93 | /* Save current data space in the file, update header. */ |
| 94 | |
| 95 | static void |
| 96 | save_data_space (int file, struct header *hdr, struct som_exec_auxhdr *auxhdr, |
| 97 | int size) |
| 98 | { |
| 99 | /* Write the entire data space out to the file */ |
| 100 | if (write (file, auxhdr->exec_dmem, size) != size) |
| 101 | unexec_error ("Can't save new data space"); |
| 102 | |
| 103 | /* Update the header to reflect the new data size */ |
| 104 | auxhdr->exec_dsize = size; |
| 105 | auxhdr->exec_bsize = 0; |
| 106 | } |
| 107 | |
| 108 | /* Update the values of file pointers when something is inserted. */ |
| 109 | |
| 110 | static void |
| 111 | update_file_ptrs (int file, struct header *hdr, struct som_exec_auxhdr *auxhdr, |
| 112 | unsigned int location, int offset) |
| 113 | { |
| 114 | struct subspace_dictionary_record subspace; |
| 115 | int i; |
| 116 | |
| 117 | /* Increase the overall size of the module */ |
| 118 | hdr->som_length += offset; |
| 119 | |
| 120 | /* Update the various file pointers in the header */ |
| 121 | #define update(ptr) if (ptr > location) ptr = ptr + offset |
| 122 | update (hdr->aux_header_location); |
| 123 | update (hdr->space_strings_location); |
| 124 | update (hdr->init_array_location); |
| 125 | update (hdr->compiler_location); |
| 126 | update (hdr->symbol_location); |
| 127 | update (hdr->fixup_request_location); |
| 128 | update (hdr->symbol_strings_location); |
| 129 | update (hdr->unloadable_sp_location); |
| 130 | update (auxhdr->exec_tfile); |
| 131 | update (auxhdr->exec_dfile); |
| 132 | |
| 133 | /* Do for each subspace dictionary entry */ |
| 134 | check_lseek (file, hdr->subspace_location, 0); |
| 135 | for (i = 0; i < hdr->subspace_total; i++) |
| 136 | { |
| 137 | ptrdiff_t subspace_size = sizeof subspace; |
| 138 | if (read (file, &subspace, subspace_size) != subspace_size) |
| 139 | unexec_error ("Can't read subspace record"); |
| 140 | |
| 141 | /* If subspace has a file location, update it */ |
| 142 | if (subspace.initialization_length > 0 |
| 143 | && subspace.file_loc_init_value > location) |
| 144 | { |
| 145 | subspace.file_loc_init_value += offset; |
| 146 | check_lseek (file, -subspace_size, 1); |
| 147 | if (write (file, &subspace, subspace_size) != subspace_size) |
| 148 | unexec_error ("Can't update subspace record"); |
| 149 | } |
| 150 | } |
| 151 | |
| 152 | /* Do for each initialization pointer record */ |
| 153 | /* (I don't think it applies to executable files, only relocatables) */ |
| 154 | #undef update |
| 155 | } |
| 156 | |
| 157 | /* Read in the header records from an a.out file. */ |
| 158 | |
| 159 | static void |
| 160 | read_header (int file, struct header *hdr, struct som_exec_auxhdr *auxhdr) |
| 161 | { |
| 162 | |
| 163 | /* Read the header in */ |
| 164 | check_lseek (file, 0, 0); |
| 165 | if (read (file, hdr, sizeof (*hdr)) != sizeof (*hdr)) |
| 166 | unexec_error ("Couldn't read header from a.out file"); |
| 167 | |
| 168 | if (hdr->a_magic != EXEC_MAGIC && hdr->a_magic != SHARE_MAGIC |
| 169 | && hdr->a_magic != DEMAND_MAGIC) |
| 170 | { |
| 171 | fprintf (stderr, "a.out file doesn't have valid magic number\n"); |
| 172 | exit (1); |
| 173 | } |
| 174 | |
| 175 | check_lseek (file, hdr->aux_header_location, 0); |
| 176 | if (read (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr)) |
| 177 | unexec_error ("Couldn't read auxiliary header from a.out file"); |
| 178 | } |
| 179 | |
| 180 | /* Write out the header records into an a.out file. */ |
| 181 | |
| 182 | static void |
| 183 | write_header (int file, struct header *hdr, struct som_exec_auxhdr *auxhdr) |
| 184 | { |
| 185 | /* Update the checksum */ |
| 186 | hdr->checksum = calculate_checksum (hdr); |
| 187 | |
| 188 | /* Write the header back into the a.out file */ |
| 189 | check_lseek (file, 0, 0); |
| 190 | if (write (file, hdr, sizeof (*hdr)) != sizeof (*hdr)) |
| 191 | unexec_error ("Couldn't write header to a.out file"); |
| 192 | check_lseek (file, hdr->aux_header_location, 0); |
| 193 | if (write (file, auxhdr, sizeof (*auxhdr)) != sizeof (*auxhdr)) |
| 194 | unexec_error ("Couldn't write auxiliary header to a.out file"); |
| 195 | } |
| 196 | |
| 197 | /* Calculate the checksum of a SOM header record. */ |
| 198 | |
| 199 | static int |
| 200 | calculate_checksum (struct header *hdr) |
| 201 | { |
| 202 | int checksum, i, *ptr; |
| 203 | |
| 204 | checksum = 0; ptr = (int *) hdr; |
| 205 | |
| 206 | for (i = 0; i < sizeof (*hdr) / sizeof (int) - 1; i++) |
| 207 | checksum ^= ptr[i]; |
| 208 | |
| 209 | return (checksum); |
| 210 | } |
| 211 | |
| 212 | /* Copy size bytes from the old file to the new one. */ |
| 213 | |
| 214 | static void |
| 215 | copy_file (int old, int new, int size) |
| 216 | { |
| 217 | int len; |
| 218 | int buffer[8192]; /* word aligned will be faster */ |
| 219 | |
| 220 | for (; size > 0; size -= len) |
| 221 | { |
| 222 | len = min (size, sizeof (buffer)); |
| 223 | if (read (old, buffer, len) != len) |
| 224 | unexec_error ("Read failure on a.out file"); |
| 225 | if (write (new, buffer, len) != len) |
| 226 | unexec_error ("Write failure in a.out file"); |
| 227 | } |
| 228 | } |
| 229 | |
| 230 | /* Copy the rest of the file, up to EOF. */ |
| 231 | |
| 232 | static void |
| 233 | copy_rest (int old, int new) |
| 234 | { |
| 235 | int buffer[4096]; |
| 236 | int len; |
| 237 | |
| 238 | /* Copy bytes until end of file or error */ |
| 239 | while ((len = read (old, buffer, sizeof (buffer))) > 0) |
| 240 | if (write (new, buffer, len) != len) break; |
| 241 | |
| 242 | if (len != 0) |
| 243 | unexec_error ("Unable to copy the rest of the file"); |
| 244 | } |
| 245 | |
| 246 | #ifdef DEBUG |
| 247 | static void |
| 248 | display_header (struct header *hdr, struct som_exec_auxhdr *auxhdr) |
| 249 | { |
| 250 | /* Display the header information (debug) */ |
| 251 | printf ("\n\nFILE HEADER\n"); |
| 252 | printf ("magic number %d \n", hdr->a_magic); |
| 253 | printf ("text loc %.8x size %d \n", auxhdr->exec_tmem, auxhdr->exec_tsize); |
| 254 | printf ("data loc %.8x size %d \n", auxhdr->exec_dmem, auxhdr->exec_dsize); |
| 255 | printf ("entry %x \n", auxhdr->exec_entry); |
| 256 | printf ("Bss segment size %u\n", auxhdr->exec_bsize); |
| 257 | printf ("\n"); |
| 258 | printf ("data file loc %d size %d\n", |
| 259 | auxhdr->exec_dfile, auxhdr->exec_dsize); |
| 260 | printf ("som_length %d\n", hdr->som_length); |
| 261 | printf ("unloadable sploc %d size %d\n", |
| 262 | hdr->unloadable_sp_location, hdr->unloadable_sp_size); |
| 263 | } |
| 264 | #endif /* DEBUG */ |
| 265 | |
| 266 | |
| 267 | /* Create a new a.out file, same as old but with current data space */ |
| 268 | void |
| 269 | unexec (const char *new_name, /* name of the new a.out file to be created */ |
| 270 | const char *old_name) /* name of the old a.out file */ |
| 271 | { |
| 272 | int old, new; |
| 273 | int old_size, new_size; |
| 274 | struct header hdr; |
| 275 | struct som_exec_auxhdr auxhdr; |
| 276 | long i; |
| 277 | |
| 278 | /* For the greatest flexibility, should create a temporary file in |
| 279 | the same directory as the new file. When everything is complete, |
| 280 | rename the temp file to the new name. |
| 281 | This way, a program could update its own a.out file even while |
| 282 | it is still executing. If problems occur, everything is still |
| 283 | intact. NOT implemented. */ |
| 284 | |
| 285 | /* Open the input and output a.out files. */ |
| 286 | old = emacs_open (old_name, O_RDONLY, 0); |
| 287 | if (old < 0) |
| 288 | unexec_error (old_name); |
| 289 | new = emacs_open (new_name, O_CREAT | O_RDWR | O_TRUNC, 0777); |
| 290 | if (new < 0) |
| 291 | unexec_error (new_name); |
| 292 | |
| 293 | /* Read the old headers. */ |
| 294 | read_header (old, &hdr, &auxhdr); |
| 295 | |
| 296 | brk_on_dump = (long) sbrk (0); |
| 297 | |
| 298 | /* Decide how large the new and old data areas are. */ |
| 299 | old_size = auxhdr.exec_dsize; |
| 300 | /* I suspect these two statements are separate |
| 301 | to avoid a compiler bug in hpux version 8. */ |
| 302 | i = (long) sbrk (0); |
| 303 | new_size = i - auxhdr.exec_dmem; |
| 304 | |
| 305 | /* Copy the old file to the new, up to the data space. */ |
| 306 | check_lseek (old, 0, 0); |
| 307 | copy_file (old, new, auxhdr.exec_dfile); |
| 308 | |
| 309 | /* Skip the old data segment and write a new one. */ |
| 310 | check_lseek (old, old_size, 1); |
| 311 | save_data_space (new, &hdr, &auxhdr, new_size); |
| 312 | |
| 313 | /* Copy the rest of the file. */ |
| 314 | copy_rest (old, new); |
| 315 | |
| 316 | /* Update file pointers since we probably changed size of data area. */ |
| 317 | update_file_ptrs (new, &hdr, &auxhdr, auxhdr.exec_dfile, new_size-old_size); |
| 318 | |
| 319 | /* Save the modified header. */ |
| 320 | write_header (new, &hdr, &auxhdr); |
| 321 | |
| 322 | /* Close the binary file. */ |
| 323 | emacs_close (old); |
| 324 | emacs_close (new); |
| 325 | } |