1 /*
   2  * Copyright (c) 2012, 2019 SAP SE. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "asm/assembler.hpp"
  26 #include "compiler/disassembler.hpp"
  27 #include "loadlib_aix.hpp"
  28 #include "memory/allocation.hpp"
  29 #include "memory/allocation.inline.hpp"
  30 #include "misc_aix.hpp"
  31 #include "porting_aix.hpp"
  32 #include "runtime/os.hpp"
  33 #include "runtime/thread.hpp"
  34 #include "utilities/align.hpp"
  35 #include "utilities/debug.hpp"
  36 
  37 // distinguish old xlc and xlclang++, where
  38 // <ibmdemangle.h> is suggested but not found
  39 #if defined(__clang__)
  40 #define DISABLE_DEMANGLE
  41 // #include <ibmdemangle.h>
  42 #else
  43 #include <demangle.h>
  44 #endif
  45 
  46 #include <sys/debug.h>
  47 #include <pthread.h>
  48 #include <ucontext.h>
  49 
  50 //////////////////////////////////
  51 // Provide implementation for dladdr based on LoadedLibraries pool and
  52 // traceback table scan
  53 
  54 // Search traceback table in stack,
  55 // return procedure name from trace back table.
  56 #define MAX_FUNC_SEARCH_LEN 0x10000
  57 
  58 #define PTRDIFF_BYTES(p1,p2) (((ptrdiff_t)p1) - ((ptrdiff_t)p2))
  59 
  60 // Typedefs for stackslots, stack pointers, pointers to op codes.
  61 typedef unsigned long stackslot_t;
  62 typedef stackslot_t* stackptr_t;
  63 typedef unsigned int* codeptr_t;
  64 
  65 // Unfortunately, the interface of dladdr makes the implementator
  66 // responsible for maintaining memory for function name/library
  67 // name. I guess this is because most OS's keep those values as part
  68 // of the mapped executable image ready to use. On AIX, this doesn't
  69 // work, so I have to keep the returned strings. For now, I do this in
  70 // a primitive string map. Should this turn out to be a performance
  71 // problem, a better hashmap has to be used.
  72 class fixed_strings {
  73   struct node : public CHeapObj<mtInternal> {
  74     char* v;
  75     node* next;
  76   };
  77 
  78   node* first;
  79 
  80   public:
  81 
  82   fixed_strings() : first(0) {}
  83   ~fixed_strings() {
  84     node* n = first;
  85     while (n) {
  86       node* p = n;
  87       n = n->next;
  88       os::free(p->v);
  89       delete p;
  90     }
  91   }
  92 
  93   char* intern(const char* s) {
  94     for (node* n = first; n; n = n->next) {
  95       if (strcmp(n->v, s) == 0) {
  96         return n->v;
  97       }
  98     }
  99     node* p = new node;
 100     p->v = os::strdup_check_oom(s);
 101     p->next = first;
 102     first = p;
 103     return p->v;
 104   }
 105 };
 106 
 107 static fixed_strings dladdr_fixed_strings;
 108 
 109 bool AixSymbols::get_function_name (
 110     address pc0,                     // [in] program counter
 111     char* p_name, size_t namelen,    // [out] optional: function name ("" if not available)
 112     int* p_displacement,             // [out] optional: displacement (-1 if not available)
 113     const struct tbtable** p_tb,     // [out] optional: ptr to traceback table to get further
 114                                      //                 information (NULL if not available)
 115     bool demangle                    // [in] whether to demangle the name
 116   ) {
 117   struct tbtable* tb = 0;
 118   unsigned int searchcount = 0;
 119 
 120   // initialize output parameters
 121   if (p_name && namelen > 0) {
 122     *p_name = '\0';
 123   }
 124   if (p_displacement) {
 125     *p_displacement = -1;
 126   }
 127   if (p_tb) {
 128     *p_tb = NULL;
 129   }
 130 
 131   codeptr_t pc = (codeptr_t)pc0;
 132 
 133   // weed out obvious bogus states
 134   if (pc < (codeptr_t)0x1000) {
 135     trcVerbose("invalid program counter");
 136     return false;
 137   }
 138 
 139   // We see random but frequent crashes in this function since some months mainly on shutdown
 140   // (-XX:+DumpInfoAtExit). It appears the page we are reading is randomly disappearing while
 141   // we read it (?).
 142   // As the pc cannot be trusted to be anything sensible lets make all reads via SafeFetch. Also
 143   // bail if this is not a text address right now.
 144   if (!LoadedLibraries::find_for_text_address(pc, NULL)) {
 145     trcVerbose("not a text address");
 146     return false;
 147   }
 148 
 149   // .. (Note that is_readable_pointer returns true if safefetch stubs are not there yet;
 150   // in that case I try reading the traceback table unsafe - I rather risk secondary crashes in
 151   // error files than not having a callstack.)
 152 #define CHECK_POINTER_READABLE(p) \
 153   if (!os::is_readable_pointer(p)) { \
 154     trcVerbose("pc not readable"); \
 155     return false; \
 156   }
 157 
 158   codeptr_t pc2 = (codeptr_t) pc;
 159 
 160   // Make sure the pointer is word aligned.
 161   pc2 = (codeptr_t) align_up((char*)pc2, 4);
 162   CHECK_POINTER_READABLE(pc2)
 163 
 164   // Find start of traceback table.
 165   // (starts after code, is marked by word-aligned (32bit) zeros)
 166   while ((*pc2 != NULL) && (searchcount++ < MAX_FUNC_SEARCH_LEN)) {
 167     CHECK_POINTER_READABLE(pc2)
 168     pc2++;
 169   }
 170   if (*pc2 != 0) {
 171     trcVerbose("no traceback table found");
 172     return false;
 173   }
 174   //
 175   // Set up addressability to the traceback table
 176   //
 177   tb = (struct tbtable*) (pc2 + 1);
 178 
 179   // Is this really a traceback table? No way to be sure but
 180   // some indicators we can check.
 181   if (tb->tb.lang >= 0xf && tb->tb.lang <= 0xfb) {
 182     // Language specifiers, go from 0 (C) to 14 (Objective C).
 183     // According to spec, 0xf-0xfa reserved, 0xfb-0xff reserved for ibm.
 184     trcVerbose("no traceback table found");
 185     return false;
 186   }
 187 
 188   // Existence of fields in the tbtable extension are contingent upon
 189   // specific fields in the base table.  Check for their existence so
 190   // that we can address the function name if it exists.
 191   pc2 = (codeptr_t) tb +
 192     sizeof(struct tbtable_short)/sizeof(int);
 193   if (tb->tb.fixedparms != 0 || tb->tb.floatparms != 0)
 194     pc2++;
 195 
 196   CHECK_POINTER_READABLE(pc2)
 197 
 198   if (tb->tb.has_tboff == TRUE) {
 199 
 200     // I want to know the displacement
 201     const unsigned int tb_offset = *pc2;
 202     codeptr_t start_of_procedure =
 203     (codeptr_t)(((char*)tb) - 4 - tb_offset);  // (-4 to omit leading 0000)
 204 
 205     // Weed out the cases where we did find the wrong traceback table.
 206     if (pc < start_of_procedure) {
 207       trcVerbose("no traceback table found");
 208       return false;
 209     }
 210 
 211     // return the displacement
 212     if (p_displacement) {
 213       (*p_displacement) = (int) PTRDIFF_BYTES(pc, start_of_procedure);
 214     }
 215 
 216     pc2++;
 217   } else {
 218     // return -1 for displacement
 219     if (p_displacement) {
 220       (*p_displacement) = -1;
 221     }
 222   }
 223 
 224   if (tb->tb.int_hndl == TRUE)
 225     pc2++;
 226 
 227   if (tb->tb.has_ctl == TRUE)
 228     pc2 += (*pc2) + 1; // don't care
 229 
 230   CHECK_POINTER_READABLE(pc2)
 231 
 232   //
 233   // return function name if it exists.
 234   //
 235   if (p_name && namelen > 0) {
 236     if (tb->tb.name_present) {
 237       // Copy name from text because it may not be zero terminated.
 238       const short l = MIN2<short>(*((short*)pc2), namelen - 1);
 239       // Be very careful.
 240       int i = 0; char* const p = (char*)pc2 + sizeof(short);
 241       while (i < l && os::is_readable_pointer(p + i)) {
 242         p_name[i] = p[i];
 243         i++;
 244       }
 245       p_name[i] = '\0';
 246 
 247       // If it is a C++ name, try and demangle it using the Demangle interface (see demangle.h).
 248 #ifndef DISABLE_DEMANGLE
 249       if (demangle) {
 250         char* rest;
 251         Name* const name = Demangle(p_name, rest);
 252         if (name) {
 253           const char* const demangled_name = name->Text();
 254           if (demangled_name) {
 255             strncpy(p_name, demangled_name, namelen-1);
 256             p_name[namelen-1] = '\0';
 257           }
 258           delete name;
 259         }
 260       }
 261 #endif
 262     } else {
 263       strncpy(p_name, "<nameless function>", namelen-1);
 264       p_name[namelen-1] = '\0';
 265     }
 266   }
 267 
 268   // Return traceback table, if user wants it.
 269   if (p_tb) {
 270     (*p_tb) = tb;
 271   }
 272 
 273   return true;
 274 
 275 }
 276 
 277 bool AixSymbols::get_module_name(address pc,
 278                          char* p_name, size_t namelen) {
 279 
 280   if (p_name && namelen > 0) {
 281     p_name[0] = '\0';
 282     loaded_module_t lm;
 283     if (LoadedLibraries::find_for_text_address(pc, &lm) != NULL) {
 284       strncpy(p_name, lm.shortname, namelen);
 285       p_name[namelen - 1] = '\0';
 286       return true;
 287     }
 288   }
 289 
 290   return false;
 291 }
 292 
 293 // Special implementation of dladdr for Aix based on LoadedLibraries
 294 // Note: dladdr returns non-zero for ok, 0 for error!
 295 // Note: dladdr is not posix, but a non-standard GNU extension. So this tries to
 296 //   fulfill the contract of dladdr on Linux (see http://linux.die.net/man/3/dladdr)
 297 // Note: addr may be both an AIX function descriptor or a real code pointer
 298 //   to the entry of a function.
 299 extern "C"
 300 int dladdr(void* addr, Dl_info* info) {
 301 
 302   if (!addr) {
 303     return 0;
 304   }
 305 
 306   assert(info, "");
 307 
 308   int rc = 0;
 309 
 310   const char* const ZEROSTRING = "";
 311 
 312   // Always return a string, even if a "" one. Linux dladdr manpage
 313   // does not say anything about returning NULL
 314   info->dli_fname = ZEROSTRING;
 315   info->dli_sname = ZEROSTRING;
 316   info->dli_saddr = NULL;
 317 
 318   address p = (address) addr;
 319   loaded_module_t lm;
 320   bool found = false;
 321 
 322   enum { noclue, code, data } type = noclue;
 323 
 324   trcVerbose("dladdr(%p)...", p);
 325 
 326   // Note: input address may be a function. I accept both a pointer to
 327   // the entry of a function and a pointer to the function decriptor.
 328   // (see ppc64 ABI)
 329   found = LoadedLibraries::find_for_text_address(p, &lm);
 330   if (found) {
 331     type = code;
 332   }
 333 
 334   if (!found) {
 335     // Not a pointer into any text segment. Is it a function descriptor?
 336     const FunctionDescriptor* const pfd = (const FunctionDescriptor*) p;
 337     p = pfd->entry();
 338     if (p) {
 339       found = LoadedLibraries::find_for_text_address(p, &lm);
 340       if (found) {
 341         type = code;
 342       }
 343     }
 344   }
 345 
 346   if (!found) {
 347     // Neither direct code pointer nor function descriptor. A data ptr?
 348     p = (address)addr;
 349     found = LoadedLibraries::find_for_data_address(p, &lm);
 350     if (found) {
 351       type = data;
 352     }
 353   }
 354 
 355   // If we did find the shared library this address belongs to (either
 356   // code or data segment) resolve library path and, if possible, the
 357   // symbol name.
 358   if (found) {
 359 
 360     // No need to intern the libpath, that one is already interned one layer below.
 361     info->dli_fname = lm.path;
 362 
 363     if (type == code) {
 364 
 365       // For code symbols resolve function name and displacement. Use
 366       // displacement to calc start of function.
 367       char funcname[256] = "";
 368       int displacement = 0;
 369 
 370       if (AixSymbols::get_function_name(p, funcname, sizeof(funcname),
 371                       &displacement, NULL, true)) {
 372         if (funcname[0] != '\0') {
 373           const char* const interned = dladdr_fixed_strings.intern(funcname);
 374           info->dli_sname = interned;
 375           trcVerbose("... function name: %s ...", interned);
 376         }
 377 
 378         // From the displacement calculate the start of the function.
 379         if (displacement != -1) {
 380           info->dli_saddr = p - displacement;
 381         } else {
 382           info->dli_saddr = p;
 383         }
 384       } else {
 385 
 386         // No traceback table found. Just assume the pointer is it.
 387         info->dli_saddr = p;
 388 
 389       }
 390 
 391     } else if (type == data) {
 392 
 393       // For data symbols.
 394       info->dli_saddr = p;
 395 
 396     } else {
 397       ShouldNotReachHere();
 398     }
 399 
 400     rc = 1; // success: return 1 [sic]
 401 
 402   }
 403 
 404   // sanity checks.
 405   if (rc) {
 406     assert(info->dli_fname, "");
 407     assert(info->dli_sname, "");
 408     assert(info->dli_saddr, "");
 409   }
 410 
 411   return rc; // error: return 0 [sic]
 412 
 413 }
 414 
 415 /////////////////////////////////////////////////////////////////////////////
 416 // Native callstack dumping
 417 
 418 // Print the traceback table for one stack frame.
 419 static void print_tbtable (outputStream* st, const struct tbtable* p_tb) {
 420 
 421   if (p_tb == NULL) {
 422     st->print("<null>");
 423     return;
 424   }
 425 
 426   switch(p_tb->tb.lang) {
 427     case TB_C: st->print("C"); break;
 428     case TB_FORTRAN: st->print("FORTRAN"); break;
 429     case TB_PASCAL: st->print("PASCAL"); break;
 430     case TB_ADA: st->print("ADA"); break;
 431     case TB_PL1: st->print("PL1"); break;
 432     case TB_BASIC: st->print("BASIC"); break;
 433     case TB_LISP: st->print("LISP"); break;
 434     case TB_COBOL: st->print("COBOL"); break;
 435     case TB_MODULA2: st->print("MODULA2"); break;
 436     case TB_CPLUSPLUS: st->print("C++"); break;
 437     case TB_RPG: st->print("RPG"); break;
 438     case TB_PL8: st->print("PL8"); break;
 439     case TB_ASM: st->print("ASM"); break;
 440     case TB_HPJ: st->print("HPJ"); break;
 441     default: st->print("unknown");
 442   }
 443   st->print(" ");
 444 
 445   if (p_tb->tb.globallink) {
 446     st->print("globallink ");
 447   }
 448   if (p_tb->tb.is_eprol) {
 449     st->print("eprol ");
 450   }
 451   if (p_tb->tb.int_proc) {
 452     st->print("int_proc ");
 453   }
 454   if (p_tb->tb.tocless) {
 455     st->print("tocless ");
 456   }
 457   if (p_tb->tb.fp_present) {
 458     st->print("fp_present ");
 459   }
 460   if (p_tb->tb.int_hndl) {
 461     st->print("interrupt_handler ");
 462   }
 463   if (p_tb->tb.uses_alloca) {
 464     st->print("uses_alloca ");
 465   }
 466   if (p_tb->tb.saves_cr) {
 467     st->print("saves_cr ");
 468   }
 469   if (p_tb->tb.saves_lr) {
 470     st->print("saves_lr ");
 471   }
 472   if (p_tb->tb.stores_bc) {
 473     st->print("stores_bc ");
 474   }
 475   if (p_tb->tb.fixup) {
 476     st->print("fixup ");
 477   }
 478   if (p_tb->tb.fpr_saved > 0) {
 479     st->print("fpr_saved:%d ", p_tb->tb.fpr_saved);
 480   }
 481   if (p_tb->tb.gpr_saved > 0) {
 482     st->print("gpr_saved:%d ", p_tb->tb.gpr_saved);
 483   }
 484   if (p_tb->tb.fixedparms > 0) {
 485     st->print("fixedparms:%d ", p_tb->tb.fixedparms);
 486   }
 487   if (p_tb->tb.floatparms > 0) {
 488     st->print("floatparms:%d ", p_tb->tb.floatparms);
 489   }
 490   if (p_tb->tb.parmsonstk > 0) {
 491     st->print("parmsonstk:%d", p_tb->tb.parmsonstk);
 492   }
 493 }
 494 
 495 // Print information for pc (module, function, displacement, traceback table)
 496 // on one line.
 497 static void print_info_for_pc (outputStream* st, codeptr_t pc, char* buf,
 498                                size_t buf_size, bool demangle) {
 499   const struct tbtable* tb = NULL;
 500   int displacement = -1;
 501 
 502   if (!os::is_readable_pointer(pc)) {
 503     st->print("(invalid)");
 504     return;
 505   }
 506 
 507   if (AixSymbols::get_module_name((address)pc, buf, buf_size)) {
 508     st->print("%s", buf);
 509   } else {
 510     st->print("(unknown module)");
 511   }
 512   st->print("::");
 513   if (AixSymbols::get_function_name((address)pc, buf, buf_size,
 514                                      &displacement, &tb, demangle)) {
 515     st->print("%s", buf);
 516   } else {
 517     st->print("(unknown function)");
 518   }
 519   if (displacement == -1) {
 520     st->print("+?");
 521   } else {
 522     st->print("+0x%x", displacement);
 523   }
 524   if (tb) {
 525     st->fill_to(64);
 526     st->print("  (");
 527     print_tbtable(st, tb);
 528     st->print(")");
 529   }
 530 }
 531 
 532 static void print_stackframe(outputStream* st, stackptr_t sp, char* buf,
 533                              size_t buf_size, bool demangle) {
 534 
 535   stackptr_t sp2 = sp;
 536 
 537   // skip backchain
 538 
 539   sp2++;
 540 
 541   // skip crsave
 542 
 543   sp2++;
 544 
 545   // retrieve lrsave. That is the only info I need to get the function/displacement
 546 
 547   codeptr_t lrsave = (codeptr_t) *(sp2);
 548   st->print (PTR64_FORMAT " - " PTR64_FORMAT " ", sp2, lrsave);
 549 
 550   if (lrsave != NULL) {
 551     print_info_for_pc(st, lrsave, buf, buf_size, demangle);
 552   }
 553 
 554 }
 555 
 556 // Function to check a given stack pointer against given stack limits.
 557 static bool is_valid_stackpointer(stackptr_t sp, stackptr_t stack_base, size_t stack_size) {
 558   if (((uintptr_t)sp) & 0x7) {
 559     return false;
 560   }
 561   if (sp > stack_base) {
 562     return false;
 563   }
 564   if (sp < (stackptr_t) ((address)stack_base - stack_size)) {
 565     return false;
 566   }
 567   return true;
 568 }
 569 
 570 // Returns true if function is a valid codepointer.
 571 static bool is_valid_codepointer(codeptr_t p) {
 572   if (!p) {
 573     return false;
 574   }
 575   if (((uintptr_t)p) & 0x3) {
 576     return false;
 577   }
 578   if (LoadedLibraries::find_for_text_address(p, NULL) == NULL) {
 579     return false;
 580   }
 581   return true;
 582 }
 583 
 584 // Function tries to guess if the given combination of stack pointer, stack base
 585 // and stack size is a valid stack frame.
 586 static bool is_valid_frame (stackptr_t p, stackptr_t stack_base, size_t stack_size) {
 587 
 588   if (!is_valid_stackpointer(p, stack_base, stack_size)) {
 589     return false;
 590   }
 591 
 592   // First check - the occurrence of a valid backchain pointer up the stack, followed by a
 593   // valid codeptr, counts as a good candidate.
 594   stackptr_t sp2 = (stackptr_t) *p;
 595   if (is_valid_stackpointer(sp2, stack_base, stack_size) && // found a valid stack pointer in the stack...
 596      ((sp2 - p) > 6) &&  // ... pointing upwards and not into my frame...
 597      is_valid_codepointer((codeptr_t)(*(sp2 + 2)))) // ... followed by a code pointer after two slots...
 598   {
 599     return true;
 600   }
 601 
 602   return false;
 603 }
 604 
 605 // Try to relocate a stack back chain in a given stack.
 606 // Used in callstack dumping, when the backchain is broken by an overwriter
 607 static stackptr_t try_find_backchain (stackptr_t last_known_good_frame,
 608                                       stackptr_t stack_base, size_t stack_size)
 609 {
 610   if (!is_valid_stackpointer(last_known_good_frame, stack_base, stack_size)) {
 611     return NULL;
 612   }
 613 
 614   stackptr_t sp = last_known_good_frame;
 615 
 616   sp += 6; // Omit next fixed frame slots.
 617   while (sp < stack_base) {
 618     if (is_valid_frame(sp, stack_base, stack_size)) {
 619       return sp;
 620     }
 621     sp ++;
 622   }
 623 
 624   return NULL;
 625 }
 626 
 627 static void decode_instructions_at_pc(const char* header,
 628                                       codeptr_t pc, int num_before,
 629                                       int num_after, outputStream* st) {
 630   // TODO: PPC port Disassembler::decode(pc, 16, 16, st);
 631 }
 632 
 633 
 634 void AixNativeCallstack::print_callstack_for_context(outputStream* st, const ucontext_t* context,
 635                                                      bool demangle, char* buf, size_t buf_size) {
 636 
 637 #define MAX_CALLSTACK_DEPTH 50
 638 
 639   unsigned long* sp;
 640   unsigned long* sp_last;
 641   int frame;
 642 
 643   // To print the first frame, use the current value of iar:
 644   // current entry indicated by iar (the current pc)
 645   codeptr_t cur_iar = 0;
 646   stackptr_t cur_sp = 0;
 647   codeptr_t cur_rtoc = 0;
 648   codeptr_t cur_lr = 0;
 649 
 650   const ucontext_t* uc = (const ucontext_t*) context;
 651 
 652   // fallback: use the current context
 653   ucontext_t local_context;
 654   if (!uc) {
 655     st->print_cr("No context given, using current context.");
 656     if (getcontext(&local_context) == 0) {
 657       uc = &local_context;
 658     } else {
 659       st->print_cr("No context given and getcontext failed. ");
 660       return;
 661     }
 662   }
 663 
 664   cur_iar = (codeptr_t)uc->uc_mcontext.jmp_context.iar;
 665   cur_sp = (stackptr_t)uc->uc_mcontext.jmp_context.gpr[1];
 666   cur_rtoc = (codeptr_t)uc->uc_mcontext.jmp_context.gpr[2];
 667   cur_lr = (codeptr_t)uc->uc_mcontext.jmp_context.lr;
 668 
 669   // syntax used here:
 670   //  n   --------------   <-- stack_base,   stack_to
 671   //  n-1 |            |
 672   //  ... | older      |
 673   //  ... |   frames   | |
 674   //      |            | | stack grows downward
 675   //  ... | younger    | |
 676   //  ... |   frames   | V
 677   //      |            |
 678   //      |------------|   <-- cur_sp, current stack ptr
 679   //      |            |
 680   //      |  unsused   |
 681   //      |    stack   |
 682   //      |            |
 683   //      .            .
 684   //      .            .
 685   //      .            .
 686   //      .            .
 687   //      |            |
 688   //   0  --------------   <-- stack_from
 689   //
 690 
 691   // Retrieve current stack base, size from the current thread. If there is none,
 692   // retrieve it from the OS.
 693   stackptr_t stack_base = NULL;
 694   size_t stack_size = NULL;
 695   {
 696     AixMisc::stackbounds_t stackbounds;
 697     if (!AixMisc::query_stack_bounds_for_current_thread(&stackbounds)) {
 698       st->print_cr("Cannot retrieve stack bounds.");
 699       return;
 700     }
 701     stack_base = (stackptr_t)stackbounds.base;
 702     stack_size = stackbounds.size;
 703   }
 704 
 705   st->print_cr("------ current frame:");
 706   st->print("iar:  " PTR64_FORMAT " ", p2i(cur_iar));
 707   print_info_for_pc(st, cur_iar, buf, buf_size, demangle);
 708   st->cr();
 709 
 710   if (cur_iar && os::is_readable_pointer(cur_iar)) {
 711     decode_instructions_at_pc(
 712       "Decoded instructions at iar:",
 713       cur_iar, 32, 16, st);
 714   }
 715 
 716   // Print out lr too, which may be interesting if we did jump to some bogus location;
 717   // in those cases the new frame is not built up yet and the caller location is only
 718   // preserved via lr register.
 719   st->print("lr:   " PTR64_FORMAT " ", p2i(cur_lr));
 720   print_info_for_pc(st, cur_lr, buf, buf_size, demangle);
 721   st->cr();
 722 
 723   if (cur_lr && os::is_readable_pointer(cur_lr)) {
 724     decode_instructions_at_pc(
 725       "Decoded instructions at lr:",
 726       cur_lr, 32, 16, st);
 727   }
 728 
 729   // Check and print sp.
 730   st->print("sp:   " PTR64_FORMAT " ", p2i(cur_sp));
 731   if (!is_valid_stackpointer(cur_sp, stack_base, stack_size)) {
 732     st->print("(invalid) ");
 733     goto cleanup;
 734   } else {
 735     st->print("(base - 0x%X) ", PTRDIFF_BYTES(stack_base, cur_sp));
 736   }
 737   st->cr();
 738 
 739   // Check and print rtoc.
 740   st->print("rtoc: "  PTR64_FORMAT " ", p2i(cur_rtoc));
 741   if (cur_rtoc == NULL || cur_rtoc == (codeptr_t)-1 ||
 742       !os::is_readable_pointer(cur_rtoc)) {
 743     st->print("(invalid)");
 744   } else if (((uintptr_t)cur_rtoc) & 0x7) {
 745     st->print("(unaligned)");
 746   }
 747   st->cr();
 748 
 749   st->print_cr("|---stackaddr----|   |----lrsave------|:   <function name>");
 750 
 751   ///
 752   // Walk callstack.
 753   //
 754   // (if no context was given, use the current stack)
 755   sp = (unsigned long*)(*(unsigned long*)cur_sp); // Stack pointer
 756   sp_last = cur_sp;
 757 
 758   frame = 0;
 759 
 760   while (frame < MAX_CALLSTACK_DEPTH) {
 761 
 762     // Check sp.
 763     bool retry = false;
 764     if (sp == NULL) {
 765       // The backchain pointer was NULL. This normally means the end of the chain. But the
 766       // stack might be corrupted, and it may be worth looking for the stack chain.
 767       if (is_valid_stackpointer(sp_last, stack_base, stack_size) && (stack_base - 0x10) > sp_last) {
 768         // If we are not within <guess> 0x10 stackslots of the stack base, we assume that this
 769         // is indeed not the end of the chain but that the stack was corrupted. So lets try to
 770         // find the end of the chain.
 771         st->print_cr("*** back chain pointer is NULL - end of stack or broken backchain ? ***");
 772         retry = true;
 773       } else {
 774         st->print_cr("*** end of backchain ***");
 775         goto end_walk_callstack;
 776       }
 777     } else if (!is_valid_stackpointer(sp, stack_base, stack_size)) {
 778       st->print_cr("*** stack pointer invalid - backchain corrupted (" PTR_FORMAT ") ***", p2i(sp));
 779       retry = true;
 780     } else if (sp < sp_last) {
 781       st->print_cr("invalid stack pointer: " PTR_FORMAT " (not monotone raising)", p2i(sp));
 782       retry = true;
 783     }
 784 
 785     // If backchain is broken, try to recover, by manually scanning the stack for a pattern
 786     // which looks like a valid stack.
 787     if (retry) {
 788       st->print_cr("trying to recover and find backchain...");
 789       sp = try_find_backchain(sp_last, stack_base, stack_size);
 790       if (sp) {
 791         st->print_cr("found something which looks like a backchain at " PTR64_FORMAT ", after 0x%x bytes... ",
 792             p2i(sp), PTRDIFF_BYTES(sp, sp_last));
 793       } else {
 794         st->print_cr("did not find a backchain, giving up.");
 795         goto end_walk_callstack;
 796       }
 797     }
 798 
 799     // Print stackframe.
 800     print_stackframe(st, sp, buf, buf_size, demangle);
 801     st->cr();
 802     frame ++;
 803 
 804     // Next stack frame and link area.
 805     sp_last = sp;
 806     sp = (unsigned long*)(*sp);
 807   }
 808 
 809   // Prevent endless loops in case of invalid callstacks.
 810   if (frame == MAX_CALLSTACK_DEPTH) {
 811     st->print_cr("...(stopping after %d frames.", MAX_CALLSTACK_DEPTH);
 812   }
 813 
 814 end_walk_callstack:
 815 
 816   st->print_cr("-----------------------");
 817 
 818 cleanup:
 819 
 820   return;
 821 
 822 }
 823 
 824 
 825 bool AixMisc::query_stack_bounds_for_current_thread(stackbounds_t* out) {
 826 
 827   // Information about this api can be found (a) in the pthread.h header and
 828   // (b) in http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.aix.basetechref/doc/basetrf1/pthread_getthrds_np.htm
 829   //
 830   // The use of this API to find out the current stack is kind of undefined.
 831   // But after a lot of tries and asking IBM about it, I concluded that it is safe
 832   // enough for cases where I let the pthread library create its stacks. For cases
 833   // where I create an own stack and pass this to pthread_create, it seems not to
 834   // work (the returned stack size in that case is 0).
 835 
 836   pthread_t tid = pthread_self();
 837   struct __pthrdsinfo pinfo;
 838   char dummy[1]; // Just needed to satisfy pthread_getthrds_np.
 839   int dummy_size = sizeof(dummy);
 840 
 841   memset(&pinfo, 0, sizeof(pinfo));
 842 
 843   const int rc = pthread_getthrds_np(&tid, PTHRDSINFO_QUERY_ALL, &pinfo,
 844                                      sizeof(pinfo), dummy, &dummy_size);
 845 
 846   if (rc != 0) {
 847     fprintf(stderr, "pthread_getthrds_np failed (%d)\n", rc);
 848     fflush(stdout);
 849     return false;
 850   }
 851 
 852   // The following may happen when invoking pthread_getthrds_np on a pthread
 853   // running on a user provided stack (when handing down a stack to pthread
 854   // create, see pthread_attr_setstackaddr).
 855   // Not sure what to do then.
 856   if (pinfo.__pi_stackend == NULL || pinfo.__pi_stackaddr == NULL) {
 857     fprintf(stderr, "pthread_getthrds_np - invalid values\n");
 858     fflush(stdout);
 859     return false;
 860   }
 861 
 862   // Note: we get three values from pthread_getthrds_np:
 863   //       __pi_stackaddr, __pi_stacksize, __pi_stackend
 864   //
 865   // high addr    ---------------------                                                           base, high
 866   //
 867   //    |         pthread internal data, like ~2K
 868   //    |
 869   //    |         ---------------------   __pi_stackend   (usually not page aligned, (xxxxF890))
 870   //    |
 871   //    |
 872   //    |
 873   //    |
 874   //    |
 875   //    |
 876   //    |          ---------------------   (__pi_stackend - __pi_stacksize)
 877   //    |
 878   //    |          padding to align the following AIX guard pages, if enabled.
 879   //    |
 880   //    V          ---------------------   __pi_stackaddr                                        low, base - size
 881   //
 882   // low addr      AIX guard pages, if enabled (AIXTHREAD_GUARDPAGES > 0)
 883   //
 884 
 885   out->base = (address)pinfo.__pi_stackend;
 886   address low = (address)pinfo.__pi_stackaddr;
 887   out->size = out->base - low;
 888   return true;
 889 
 890 }
 891 
 892 
 893 
 894