Hi Masami, I love your patch! Perhaps something to improve: [auto build test WARNING on stable/linux-5.4.y] url: https://github.com/0day-ci/linux/commits/Masami-Hiramatsu/Revert-ia64-kpr... base: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git linux-5.4.y config: ia64-allmodconfig (https://download.01.org/0day-ci/archive/20220115/202201151231.g2sW8oWt-lk...) compiler: ia64-linux-gcc (GCC) 11.2.0 reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # https://github.com/0day-ci/linux/commit/514059de80b018e0edcf434519ff6bf41... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Masami-Hiramatsu/Revert-ia64-kprobes-Use-generic-kretprobe-trampoline-handler/20220114-182111 git checkout 514059de80b018e0edcf434519ff6bf41b4a519b # save the config file to linux build tree mkdir build_dir COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross O=build_dir ARCH=ia64 SHELL=/bin/bash If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): arch/ia64/kernel/kprobes.c: In function 'get_kprobe_inst': arch/ia64/kernel/kprobes.c:325:22: warning: variable 'template' set but not used [-Wunused-but-set-variable] 325 | unsigned int template; | ^~~~~~~~ arch/ia64/kernel/kprobes.c: At top level: arch/ia64/kernel/kprobes.c:407:15: warning: no previous prototype for 'trampoline_probe_handler' [-Wmissing-prototypes] 407 | int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) | ^~~~~~~~~~~~~~~~~~~~~~~~ arch/ia64/kernel/kprobes.c: In function 'trampoline_probe_handler': 414 | dereference_function_descriptor(kretprobe_trampoline); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Kconfig warnings: (for reference only) WARNING: unmet direct dependencies detected for FRAME_POINTER Depends on DEBUG_KERNEL && (M68K || UML || SUPERH) || ARCH_WANT_FRAME_POINTERS Selected by - FAULT_INJECTION_STACKTRACE_FILTER && FAULT_INJECTION_DEBUG_FS && STACKTRACE_SUPPORT && !X86_64 && !MIPS && !PPC && !S390 && !MICROBLAZE && !ARM && !ARC && !X86 vim +414 arch/ia64/kernel/kprobes.c 320 321 static void __kprobes get_kprobe_inst(bundle_t *bundle, uint slot, 322 unsigned long *kprobe_inst, uint *major_opcode) 323 { 324 unsigned long kprobe_inst_p0, kprobe_inst_p1; 326 327 template = bundle->quad0.template; 328 329 switch (slot) { 330 case 0: 331 *major_opcode = (bundle->quad0.slot0 >> SLOT0_OPCODE_SHIFT); 332 *kprobe_inst = bundle->quad0.slot0; 333 break; 334 case 1: 335 *major_opcode = (bundle->quad1.slot1_p1 >> SLOT1_p1_OPCODE_SHIFT); 336 kprobe_inst_p0 = bundle->quad0.slot1_p0; 337 kprobe_inst_p1 = bundle->quad1.slot1_p1; 338 *kprobe_inst = kprobe_inst_p0 | (kprobe_inst_p1 << (64-46)); 339 break; 340 case 2: 341 *major_opcode = (bundle->quad1.slot2 >> SLOT2_OPCODE_SHIFT); 342 *kprobe_inst = bundle->quad1.slot2; 343 break; 344 } 345 } 346 347 /* Returns non-zero if the addr is in the Interrupt Vector Table */ 348 static int __kprobes in_ivt_functions(unsigned long addr) 349 { 350 return (addr >= (unsigned long)__start_ivt_text 351 && addr < (unsigned long)__end_ivt_text); 352 } 353 354 static int __kprobes valid_kprobe_addr(int template, int slot, 355 unsigned long addr) 356 { 357 if ((slot > 2) || ((bundle_encoding[template][1] == L) && slot > 1)) { 358 printk(KERN_WARNING "Attempting to insert unaligned kprobe " 359 "at 0x%lx\n", addr); 360 return -EINVAL; 361 } 362 363 if (in_ivt_functions(addr)) { 364 printk(KERN_WARNING "Kprobes can't be inserted inside " 365 "IVT functions at 0x%lx\n", addr); 366 return -EINVAL; 367 } 368 369 return 0; 370 } 371 372 static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb) 373 { 374 unsigned int i; 375 i = atomic_add_return(1, &kcb->prev_kprobe_index); 376 kcb->prev_kprobe[i-1].kp = kprobe_running(); 377 kcb->prev_kprobe[i-1].status = kcb->kprobe_status; 378 } 379 380 static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb) 381 { 382 unsigned int i; 383 i = atomic_read(&kcb->prev_kprobe_index); 384 __this_cpu_write(current_kprobe, kcb->prev_kprobe[i-1].kp); 385 kcb->kprobe_status = kcb->prev_kprobe[i-1].status; 386 atomic_sub(1, &kcb->prev_kprobe_index); 387 } 388 389 static void __kprobes set_current_kprobe(struct kprobe *p, 390 struct kprobe_ctlblk *kcb) 391 { 392 __this_cpu_write(current_kprobe, p); 393 } 394 395 static void kretprobe_trampoline(void) 396 { 397 } 398 399 /* 400 * At this point the target function has been tricked into 401 * returning into our trampoline. Lookup the associated instance 402 * and then: 403 * - call the handler function 404 * - cleanup by marking the instance as unused 405 * - long jump back to the original return address 406 */ 407 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs) 408 { 409 struct kretprobe_instance *ri = NULL; 410 struct hlist_head *head, empty_rp; 411 struct hlist_node *tmp; 412 unsigned long flags, orig_ret_address = 0; 413 unsigned long trampoline_address = 415 416 INIT_HLIST_HEAD(&empty_rp); 417 kretprobe_hash_lock(current, &head, &flags); 418 419 /* 420 * It is possible to have multiple instances associated with a given 421 * task either because an multiple functions in the call path 422 * have a return probe installed on them, and/or more than one return 423 * return probe was registered for a target function. 424 * 425 * We can handle this because: 426 * - instances are always inserted at the head of the list 427 * - when multiple return probes are registered for the same 428 * function, the first instance's ret_addr will point to the 429 * real return address, and all the rest will point to 430 * kretprobe_trampoline 431 */ 432 hlist_for_each_entry_safe(ri, tmp, head, hlist) { 433 if (ri->task != current) 434 /* another task is sharing our hash bucket */ 435 continue; 436 437 orig_ret_address = (unsigned long)ri->ret_addr; 438 if (orig_ret_address != trampoline_address) 439 /* 440 * This is the real return address. Any other 441 * instances associated with this task are for 442 * other calls deeper on the call stack 443 */ 444 break; 445 } 446 447 regs->cr_iip = orig_ret_address; 448 449 hlist_for_each_entry_safe(ri, tmp, head, hlist) { 450 if (ri->task != current) 451 /* another task is sharing our hash bucket */ 452 continue; 453 454 if (ri->rp && ri->rp->handler) 455 ri->rp->handler(ri, regs); 456 457 orig_ret_address = (unsigned long)ri->ret_addr; 458 recycle_rp_inst(ri, &empty_rp); 459 460 if (orig_ret_address != trampoline_address) 461 /* 462 * This is the real return address. Any other 463 * instances associated with this task are for 464 * other calls deeper on the call stack 465 */ 466 break; 467 } 468 kretprobe_assert(ri, orig_ret_address, trampoline_address); 469 470 kretprobe_hash_unlock(current, &flags); 471 472 hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) { 473 hlist_del(&ri->hlist); 474 kfree(ri); 475 } 476 /* 477 * By returning a non-zero value, we are telling 478 * kprobe_handler() that we don't want the post_handler 479 * to run (and have re-enabled preemption) 480 */ 481 return 1; 482 } 483 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org