1/* 2 * This file is part of ltrace. 3 * Copyright (C) 2012,2013 Petr Machata, Red Hat Inc. 4 * 5 * This program is free software; you can redistribute it and/or 6 * modify it under the terms of the GNU General Public License as 7 * published by the Free Software Foundation; either version 2 of the 8 * License, or (at your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, but 11 * WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 * 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, Inc., 51 Franklin St, Fifth Floor, Boston, MA 18 * 02110-1301 USA 19 */ 20 21#ifndef BACKEND_H 22#define BACKEND_H 23 24#include "forward.h" 25#include "sysdep.h" 26 27#include <gelf.h> 28 29enum process_status { 30 PS_INVALID, /* Failure. */ 31 PS_STOP, /* Job-control stop. */ 32 PS_TRACING_STOP, 33 PS_SLEEPING, 34 PS_ZOMBIE, 35 PS_OTHER, /* Necessary other states can be added as needed. */ 36}; 37 38/* 39 * This file contains documentation of back end interface. Some of 40 * these may be implemented on an OS level (i.e. they are the same 41 * e.g. on all Linux architectures), some may differ per architecture 42 * on the same OS (e.g. a way to insert a breakpoint into the process 43 * image is a likely candidate). 44 */ 45 46/* Convert a PID to a path to the corresponding binary. */ 47char *pid2name(pid_t pid); 48 49/* Given a PID, find a leader of thread group. */ 50pid_t process_leader(pid_t pid); 51 52/* Given a PID of leader thread, fill in PIDs of all the tasks. The 53 * function will initialize the pointer *RET_TASKS to a 54 * newly-allocated array, and will store number of elements in that 55 * array to *RET_N. You have to free that buffer when you don't need 56 * it anymore. */ 57int process_tasks(pid_t pid, pid_t **ret_tasks, size_t *ret_n); 58 59/* Answer whether the process PID is stopped. Returns 0 when not 60 * stopped, 1 when stopped, or -1 when there was an error. */ 61int process_stopped(pid_t pid); 62 63/* Answer a status of the task PID. See enum process_status. */ 64enum process_status process_status(pid_t pid); 65 66/* Wait for PID to be ready for tracing. */ 67int wait_for_proc(pid_t pid); 68 69/* Send a signal SIG to the task PID. */ 70int task_kill(pid_t pid, int sig); 71 72/* Called after PID is attached, but before it is continued. */ 73void trace_set_options(struct process *proc); 74 75/* Called after ltrace forks. Should attach the newly created child, 76 * in whose context this function is called. */ 77void trace_me(void); 78 79/* Called when ltrace needs to attach to PID, such as when it attaches 80 * to a running process, whose PID is given on the command line. */ 81int trace_pid(pid_t pid); 82 83/* Stop tracing PID. */ 84void untrace_pid(pid_t pid); 85 86/* The back end may need to store arbitrary data to a process. This 87 * is a place where it can initialize PROC->arch_dep. XXX this should 88 * be dropped in favor of arhc_process_init on pmachata/libs. */ 89void get_arch_dep(struct process *proc); 90 91/* Return current instruction pointer of PROC. 92 * 93 * XXX note that the IP must fit into an arch pointer. This prevents 94 * us to use 32-bit ltrace to trace 64-bit process, even on arches 95 * that would otherwise support this. Above we have a definition of 96 * arch_addr_t. This should be converted to an integral type and 97 * used for target addresses throughout. */ 98void *get_instruction_pointer(struct process *proc); 99 100/* Set instruction pointer of PROC to ADDR. XXX see above. */ 101void set_instruction_pointer(struct process *proc, void *addr); 102 103/* Return current stack pointer of PROC. XXX see above. */ 104void *get_stack_pointer(struct process *proc); 105 106/* Find and return caller address, i.e. the address where the current 107 * function returns. */ 108void *get_return_addr(struct process *proc, void *stack_pointer); 109 110/* Enable breakpoint SBP in process PROC. */ 111void enable_breakpoint(struct process *proc, struct breakpoint *sbp); 112 113/* Disable breakpoint SBP in process PROC. */ 114void disable_breakpoint(struct process *proc, struct breakpoint *sbp); 115 116/* Determine whether the event that we have just seen (and that is 117 * recorded in STATUS) was a syscall. If it was, return 1. If it was 118 * a return from syscall, return 2. In both cases, set *SYSNUM to the 119 * number of said syscall. If it wasn't a syscall, return 0. If 120 * there was an error, return -1. */ 121int syscall_p(struct process *proc, int status, int *sysnum); 122 123/* Continue execution of the process with given PID. */ 124void continue_process(pid_t pid); 125 126/* Called after we received a signal SIGNUM. Should do whatever 127 * book-keeping is necessary and continue the process if 128 * necessary. */ 129void continue_after_signal(pid_t pid, int signum); 130 131/* Called after we received a system call SYSNUM. RET_P is 0 if this 132 * is system call, otherwise it's return from a system call. The 133 * callback should do whatever book-keeping is necessary and continue 134 * the process if necessary. */ 135void continue_after_syscall(struct process *proc, int sysnum, int ret_p); 136 137/* Called after we hit a breakpoint SBP. Should do whatever 138 * book-keeping is necessary and then continue the process. */ 139void continue_after_breakpoint(struct process *proc, struct breakpoint *sbp); 140 141/* Called after we received a vfork. Should do whatever book-keeping 142 * is necessary and continue the process if necessary. N.B. right 143 * now, with Linux/GNU the only back end, this is not necessary. I 144 * imagine other systems may be different. */ 145void continue_after_vfork(struct process *proc); 146 147/* Called after the process exec's. Should do whatever book-keeping 148 * is necessary and then continue the process. */ 149void continue_after_exec(struct process *proc); 150 151/* Called when trace_me or primary trace_pid fail. This may plug in 152 * any platform-specific knowledge of why it could be so. */ 153void trace_fail_warning(pid_t pid); 154 155/* A pair of functions called to initiate a detachment request when 156 * ltrace is about to exit. Their job is to undo any effects that 157 * tracing had and eventually detach process, perhaps by way of 158 * installing a process handler. 159 * 160 * OS_LTRACE_EXITING_SIGHANDLER is called from a signal handler 161 * context right after the signal was captured. It returns 1 if the 162 * request was handled or 0 if it wasn't. 163 * 164 * If the call to OS_LTRACE_EXITING_SIGHANDLER didn't handle the 165 * request, OS_LTRACE_EXITING is called when the next event is 166 * generated. Therefore it's called in "safe" context, without 167 * re-entrancy concerns, but it's only called after an even is 168 * generated. */ 169int os_ltrace_exiting_sighandler(void); 170void os_ltrace_exiting(void); 171 172/* Should copy COUNT bytes from address ADDR of process PROC to local 173 * buffer BUF. */ 174size_t umovebytes(struct process *proc, arch_addr_t addr, 175 void *buf, size_t count); 176 177/* Find out an address of symbol SYM in process PROC, and return. 178 * Returning NULL delays breakpoint insertion and enables heaps of 179 * arch-specific black magic that we should clean up some day. 180 * 181 * XXX the same points as for get_instruction_pointer apply. */ 182void *sym2addr(struct process *proc, struct library_symbol *sym); 183 184/* Obtain address of PLT entry corresponding to relocation RELA in 185 * file LTE. This is NDX-th PLT entry in the file. 186 * 187 * XXX should this return arch_addr_t? */ 188GElf_Addr arch_plt_sym_val(struct ltelf *lte, size_t ndx, GElf_Rela *rela); 189 190/* Called at some point after we have attached to PROC. This callback 191 * should insert an introspection breakpoint for handling dynamic 192 * linker library loads. */ 193int linkmap_init(struct process *proc, arch_addr_t dyn_addr); 194 195/* This should produce and return the next event of one of the traced 196 * processes. The returned pointer will not be freed by the core and 197 * should be either statically allocated, or the management should be 198 * done some other way. */ 199struct Event *next_event(void); 200 201/* Called when process PROC was removed. */ 202void process_removed(struct process *proc); 203 204/* This should extract entry point address and interpreter (dynamic 205 * linker) bias if possible. Returns 0 if there were no errors, -1 206 * otherwise. Sets *ENTRYP and *INTERP_BIASP to non-zero values if 207 * the corresponding value is known, or zero otherwise; this is not 208 * done for pointers that are NULL. */ 209int process_get_entry(struct process *proc, 210 arch_addr_t *entryp, 211 arch_addr_t *interp_biasp); 212 213 214/* Optional callbacks 215 * 216 * Some callbacks are only available if backend (arch.h) has a certain 217 * define. If such a define is not present, default implementation 218 * (most often doing nothing at all) us used instead. This is used 219 * for gradual extensions of ltrace, so that backends that are not 220 * fully up to date, or that don't need certain functionality, keep 221 * working, while other backends take advantage of the optional 222 * features. */ 223 224/* The following callbacks have to be implemented in backend if arch.h 225 * defines ARCH_HAVE_LTELF_DATA. Those are used to init and destroy 226 * LTE->arch. arch_elf_init returns 0 on success or a negative value 227 * on failure. */ 228int arch_elf_init(struct ltelf *lte, struct library *lib); 229void arch_elf_destroy(struct ltelf *lte); 230 231/* The following callbacks have to be implemented in OS backend if 232 * os.h defines OS_HAVE_BREAKPOINT_DATA. Those are used to init, 233 * destroy, and clone SBP->os. os_breakpoint_init and 234 * os_breakpoint_clone return 0 on success or a negative value on 235 * failure. */ 236int os_breakpoint_init(struct process *proc, struct breakpoint *sbp); 237void os_breakpoint_destroy(struct breakpoint *sbp); 238int os_breakpoint_clone(struct breakpoint *retp, struct breakpoint *sbp); 239 240/* The following callbacks have to be implemented in backend if arch.h 241 * defines ARCH_HAVE_BREAKPOINT_DATA. Those are used to init, 242 * destroy, and clone SBP->arch. arch_breakpoint_init and 243 * arch_breakpoint_clone return 0 on success or a negative value on 244 * failure. */ 245int arch_breakpoint_init(struct process *proc, struct breakpoint *sbp); 246void arch_breakpoint_destroy(struct breakpoint *sbp); 247int arch_breakpoint_clone(struct breakpoint *retp, struct breakpoint *sbp); 248 249/* The following callbacks have to be implemented in OS backend if 250 * os.h defines OS_HAVE_LIBRARY_DATA. Those are used to init, destroy 251 * and clone LIB->os. os_library_init and os_library_clone return 0 252 * on success or a negative value on failure. */ 253int os_library_init(struct library *lib); 254void os_library_destroy(struct library *lib); 255int os_library_clone(struct library *retp, struct library *lib); 256 257/* The following callbacks have to be implemented in backend if arch.h 258 * defines ARCH_HAVE_LIBRARY_DATA. Those are used to init, destroy 259 * and clone LIB->arch. arch_library_init and arch_library_clone 260 * return 0 on success or a negative value on failure. */ 261int arch_library_init(struct library *lib); 262void arch_library_destroy(struct library *lib); 263int arch_library_clone(struct library *retp, struct library *lib); 264 265/* The following callbacks have to be implemented in OS backend if 266 * os.h defines OS_HAVE_LIBRARY_SYMBOL_DATA. Those are used to init, 267 * destroy and clone LIBSYM->os. os_library_symbol_init and 268 * os_library_symbol_clone return 0 on success or a negative value on 269 * failure. */ 270int os_library_symbol_init(struct library_symbol *libsym); 271void os_library_symbol_destroy(struct library_symbol *libsym); 272int os_library_symbol_clone(struct library_symbol *retp, 273 struct library_symbol *libsym); 274 275/* The following callbacks have to be implemented in backend if arch.h 276 * defines ARCH_HAVE_LIBRARY_SYMBOL_DATA. Those are used to init, 277 * destroy and clone LIBSYM->arch. arch_library_symbol_init and 278 * arch_library_symbol_clone return 0 on success or a negative value 279 * on failure. */ 280int arch_library_symbol_init(struct library_symbol *libsym); 281void arch_library_symbol_destroy(struct library_symbol *libsym); 282int arch_library_symbol_clone(struct library_symbol *retp, 283 struct library_symbol *libsym); 284 285/* The following callbacks have to be implemented in OS backend if 286 * os.h defines OS_HAVE_PROCESS_DATA. The protocol is same as for, 287 * respectively, arch_process_init, arch_process_destroy, 288 * arch_process_clone and arch_process_exec. */ 289int os_process_init(struct process *proc); 290void os_process_destroy(struct process *proc); 291int os_process_clone(struct process *retp, struct process *proc); 292int os_process_exec(struct process *proc); 293 294/* The following callbacks have to be implemented in backend if arch.h 295 * defines ARCH_HAVE_PROCESS_DATA. Those are used to init, destroy 296 * and clone PROC->arch. arch_process_exec is called to update 297 * PROC->arch in case that PROC underwent an exec. See notes at 298 * process_init, process_destroy, process_clone and process_exec in 299 * proc.h. */ 300int arch_process_init(struct process *proc); 301void arch_process_destroy(struct process *proc); 302int arch_process_clone(struct process *retp, struct process *proc); 303int arch_process_exec(struct process *proc); 304 305/* The following callback has to be implemented in backend if arch.h 306 * defines ARCH_HAVE_GET_SYM_INFO. 307 * 308 * This is called for every PLT relocation RELA in ELF file LTE (which 309 * is named FILENAME), that ltrace is about to add. The corresponding 310 * PLT entry is for SYM_INDEX-th relocation in the file. This call is 311 * supposed to initialize SYM and RELA. It returns 0 if there were no 312 * errors and given symbol should be used, 1 if the symbol should not 313 * be used, or a negative value if there were errors. */ 314int arch_get_sym_info(struct ltelf *lte, const char *filename, size_t sym_index, 315 GElf_Rela *rela, GElf_Sym *sym); 316 317enum plt_status { 318 PLT_FAIL, 319 PLT_OK, 320 PLT_DEFAULT, 321}; 322 323/* The following callback has to be implemented in OS backend if os.h 324 * defines OS_HAVE_ADD_PLT_ENTRY. 325 * 326 * This is called for every PLT relocation R in ELF file LTE, that 327 * ltrace is about to add to a library constructed in process PROC. 328 * The corresponding PLT entry is for symbol called NAME, and it's 329 * I-th relocation in the file. 330 * 331 * If this function returns PLT_DEFAULT, PLT address is obtained by 332 * calling arch_plt_sym_val, and symbol is allocated. If PLT_OK or 333 * PLT_DEFAULT are returned, the chain of symbols passed back in RET 334 * is added to library under construction. */ 335enum plt_status os_elf_add_plt_entry(struct process *proc, struct ltelf *lte, 336 const char *name, GElf_Rela *rela, 337 size_t i, struct library_symbol **ret); 338 339/* Like os_elf_add_plt_entry, but tied to ARCH_HAVE_ADD_PLT_ENTRY in 340 * arch.h. The arch callback is called first. If it returns 341 * PLT_DEFAULT, the os callback is called next. */ 342enum plt_status arch_elf_add_plt_entry(struct process *proc, struct ltelf *lte, 343 const char *name, GElf_Rela *rela, 344 size_t i, struct library_symbol **ret); 345 346/* The following callback has to be implemented in OS backend if os.h 347 * defines OS_HAVE_ADD_FUNC_ENTRY. 348 * 349 * This is called for every symbol in ltrace is about to add to the 350 * library constructed for LTE in process PROC. 351 * 352 * If this function returns PLT_DEFAULT, then if there is a 353 * pre-existing symbol, its name may be updated if the newly-found 354 * name is shorter. Otherwise a new symbol is created. 355 * 356 * If PLT_OK or PLT_DEFAULT are returned, the chain of symbols passed 357 * back in RET is added to library under construction. */ 358enum plt_status os_elf_add_func_entry(struct process *proc, struct ltelf *lte, 359 const GElf_Sym *sym, 360 arch_addr_t addr, const char *name, 361 struct library_symbol **ret); 362 363/* Like os_elf_add_func_entry, but tied to ARCH_HAVE_ADD_FUNC_ENTRY in 364 * arch.h. The arch callback is called first. If it returns 365 * PLT_DEFAULT, the os callback is called next. */ 366enum plt_status arch_elf_add_func_entry(struct process *proc, struct ltelf *lte, 367 const GElf_Sym *sym, 368 arch_addr_t addr, const char *name, 369 struct library_symbol **ret); 370 371/* This callback needs to be implemented if arch.h defines 372 * ARCH_HAVE_DYNLINK_DONE. It is called after the dynamic linker is 373 * done with the process start-up. */ 374void arch_dynlink_done(struct process *proc); 375 376/* This callback needs to be implemented if arch.h defines 377 * ARCH_HAVE_SYMBOL_RET. It is called after a traced call returns. */ 378void arch_symbol_ret(struct process *proc, struct library_symbol *libsym); 379 380 381/* This callback needs to be implemented if arch.h defines 382 * ARCH_HAVE_FIND_DL_DEBUG. 383 * It is called by generic code to find the address of the dynamic 384 * linkers debug structure. 385 * DYN_ADDR holds the address of the dynamic section. 386 * If the debug area is found, return 0 and fill in the address in *RET. 387 * If the debug area is not found, return a negative value. */ 388int arch_find_dl_debug(struct process *proc, arch_addr_t dyn_addr, 389 arch_addr_t *ret); 390 391/* This is called to obtain a list of directories to search when 392 * loading config files. The callback sets *RETP to a pointer to the 393 * first element of a NULL-terminated array of directory names. It's 394 * legitimate to set *RETP to NULL to indicate there are no 395 * directories. The function returns 0 on success or a negative value 396 * on a failure. 397 * 398 * If PRIVATE is set, the list in *RETP should contain only user's own 399 * directories (presumably under HOME if there's any such thing on the 400 * given OS). Otherwise only system directories should be reported. 401 * 402 * The directories don't have to exist. Directories passed in -F are 403 * handled separately by the caller and this callback shouldn't 404 * concern itself with it. */ 405int os_get_config_dirs(int private, const char ***retp); 406 407/* This is called to obtain list of legacy config files to import, if 408 * any. A reference to initialized vector of char* is passed in. 409 * 410 * This returns 0 on success, in which case strings from *RETP (if 411 * any) are interpreted as files names. These files belong to the 412 * caller and will eventually be freed. 413 * 414 * Returns a negative value for failure, in which case *RETP contents 415 * are not consulted in any way. */ 416int os_get_ltrace_conf_filenames(struct vect *retp); 417 418/* If arch.h defines ARCH_HAVE_FETCH_ARG, the following callbacks have 419 * to be implemented: arch_fetch_arg_init, arch_fetch_arg_clone, 420 * arch_fetch_arg_done, arch_fetch_arg_next and arch_fetch_retval. 421 * See fetch.h for details. */ 422 423/* If arch.h defines both ARCH_HAVE_FETCH_ARG and 424 * ARCH_HAVE_FETCH_PACK, the following callbacks have to be 425 * implemented: arch_fetch_param_pack_start, 426 * arch_fetch_param_pack_end. See fetch.h for details. */ 427 428enum sw_singlestep_status { 429 SWS_FAIL, 430 SWS_OK, 431 SWS_HW, 432}; 433struct sw_singlestep_data; 434 435/* The following callback has to be implemented in backend if arch.h 436 * defines ARCH_HAVE_SW_SINGLESTEP. 437 * 438 * This is called before the OS backend requests hardware singlestep. 439 * arch_sw_singlestep should consider whether a singlestep needs to be 440 * done in software. If not, it returns SWS_HW. Otherwise it needs 441 * to add one or several breakpoints by calling ADD_CB. When it is 442 * done, it continues the process as appropriate, and answers either 443 * SWS_OK, or SWS_FAIL, depending on how it went. 444 * 445 * PROC is the process that should perform the singlestep, BP the 446 * breakpoint that we are singlestepping over. ADD_CB is a callback 447 * to request adding breakpoints that should trap the process after 448 * it's continued. The arguments to ADD_CB are the address where the 449 * breakpoint should be added, and DATA. ADD_CB returns 0 on success 450 * or a negative value on failure. It is expected that 451 * arch_sw_singlestep returns SWS_FAIL if ADD_CB returns error. */ 452enum sw_singlestep_status arch_sw_singlestep(struct process *proc, 453 struct breakpoint *bp, 454 int (*add_cb)(arch_addr_t addr, 455 struct sw_singlestep_data *), 456 struct sw_singlestep_data *data); 457 458#endif /* BACKEND_H */ 459