1 /*
   2  * Copyright (c) 2012, 2013 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/debug.hpp"
  35 
  36 #include <demangle.h>
  37 #include <sys/debug.h>
  38 #include <pthread.h>
  39 #include <ucontext.h>
  40 
  41 //////////////////////////////////
  42 // Provide implementation for dladdr based on LoadedLibraries pool and
  43 // traceback table scan
  44 
  45 // Search traceback table in stack,
  46 // return procedure name from trace back table.
  47 #define MAX_FUNC_SEARCH_LEN 0x10000
  48 
  49 #define PTRDIFF_BYTES(p1,p2) (((ptrdiff_t)p1) - ((ptrdiff_t)p2))
  50 
  51 // Typedefs for stackslots, stack pointers, pointers to op codes.
  52 typedef unsigned long stackslot_t;
  53 typedef stackslot_t* stackptr_t;
  54 typedef unsigned int* codeptr_t;
  55 
  56 // Unfortunately, the interface of dladdr makes the implementator
  57 // responsible for maintaining memory for function name/library
  58 // name. I guess this is because most OS's keep those values as part
  59 // of the mapped executable image ready to use. On AIX, this doesn't
  60 // work, so I have to keep the returned strings. For now, I do this in
  61 // a primitive string map. Should this turn out to be a performance
  62 // problem, a better hashmap has to be used.
  63 class fixed_strings {
  64   struct node : public CHeapObj<mtInternal> {
  65     char* v;
  66     node* next;
  67   };
  68 
  69   node* first;
  70 
  71   public:
  72 
  73   fixed_strings() : first(0) {}
  74   ~fixed_strings() {
  75     node* n = first;
  76     while (n) {
  77       node* p = n;
  78       n = n->next;
  79       os::free(p->v);
  80       delete p;
  81     }
  82   }
  83 
  84   char* intern(const char* s) {
  85     for (node* n = first; n; n = n->next) {
  86       if (strcmp(n->v, s) == 0) {
  87         return n->v;
  88       }
  89     }
  90     node* p = new node;
  91     p->v = os::strdup_check_oom(s);
  92     p->next = first;
  93     first = p;
  94     return p->v;
  95   }
  96 };
  97 
  98 static fixed_strings dladdr_fixed_strings;
  99 
 100 bool AixSymbols::get_function_name (
 101     address pc0,                     // [in] program counter
 102     char* p_name, size_t namelen,    // [out] optional: function name ("" if not available)
 103     int* p_displacement,             // [out] optional: displacement (-1 if not available)
 104     const struct tbtable** p_tb,     // [out] optional: ptr to traceback table to get further
 105                                      //                 information (NULL if not available)
 106     bool demangle                    // [in] whether to demangle the name
 107   ) {
 108   struct tbtable* tb = 0;
 109   unsigned int searchcount = 0;
 110 
 111   // initialize output parameters
 112   if (p_name && namelen > 0) {
 113     *p_name = '\0';
 114   }
 115   if (p_displacement) {
 116     *p_displacement = -1;
 117   }
 118   if (p_tb) {
 119     *p_tb = NULL;
 120   }
 121 
 122   codeptr_t pc = (codeptr_t)pc0;
 123 
 124   // weed out obvious bogus states
 125   if (pc < (codeptr_t)0x1000) {
 126     trcVerbose("invalid program counter");
 127     return false;
 128   }
 129 
 130   // We see random but frequent crashes in this function since some months mainly on shutdown
 131   // (-XX:+DumpInfoAtExit). It appears the page we are reading is randomly disappearing while
 132   // we read it (?).
 133   // As the pc cannot be trusted to be anything sensible lets make all reads via SafeFetch. Also
 134   // bail if this is not a text address right now.
 135   if (!LoadedLibraries::find_for_text_address(pc, NULL)) {
 136     trcVerbose("not a text address");
 137     return false;
 138   }
 139 
 140   // .. (Note that is_readable_pointer returns true if safefetch stubs are not there yet;
 141   // in that case I try reading the traceback table unsafe - I rather risk secondary crashes in
 142   // error files than not having a callstack.)
 143 #define CHECK_POINTER_READABLE(p) \
 144   if (!MiscUtils::is_readable_pointer(p)) { \
 145     trcVerbose("pc not readable"); \
 146     return false; \
 147   }
 148 
 149   codeptr_t pc2 = (codeptr_t) pc;
 150 
 151   // Make sure the pointer is word aligned.
 152   pc2 = (codeptr_t) align_ptr_up((char*)pc2, 4);
 153   CHECK_POINTER_READABLE(pc2)
 154 
 155   // Find start of traceback table.
 156   // (starts after code, is marked by word-aligned (32bit) zeros)
 157   while ((*pc2 != NULL) && (searchcount++ < MAX_FUNC_SEARCH_LEN)) {
 158     CHECK_POINTER_READABLE(pc2)
 159     pc2++;
 160   }
 161   if (*pc2 != 0) {
 162     trcVerbose("no traceback table found");
 163     return false;
 164   }
 165   //
 166   // Set up addressability to the traceback table
 167   //
 168   tb = (struct tbtable*) (pc2 + 1);
 169 
 170   // Is this really a traceback table? No way to be sure but
 171   // some indicators we can check.
 172   if (tb->tb.lang >= 0xf && tb->tb.lang <= 0xfb) {
 173     // Language specifiers, go from 0 (C) to 14 (Objective C).
 174     // According to spec, 0xf-0xfa reserved, 0xfb-0xff reserved for ibm.
 175     trcVerbose("no traceback table found");
 176     return false;
 177   }
 178 
 179   // Existence of fields in the tbtable extension are contingent upon
 180   // specific fields in the base table.  Check for their existence so
 181   // that we can address the function name if it exists.
 182   pc2 = (codeptr_t) tb +
 183     sizeof(struct tbtable_short)/sizeof(int);
 184   if (tb->tb.fixedparms != 0 || tb->tb.floatparms != 0)
 185     pc2++;
 186 
 187   CHECK_POINTER_READABLE(pc2)
 188 
 189   if (tb->tb.has_tboff == TRUE) {
 190 
 191     // I want to know the displacement
 192     const unsigned int tb_offset = *pc2;
 193     codeptr_t start_of_procedure =
 194     (codeptr_t)(((char*)tb) - 4 - tb_offset);  // (-4 to omit leading 0000)
 195 
 196     // Weed out the cases where we did find the wrong traceback table.
 197     if (pc < start_of_procedure) {
 198       trcVerbose("no traceback table found");
 199       return false;
 200     }
 201 
 202     // return the displacement
 203     if (p_displacement) {
 204       (*p_displacement) = (int) PTRDIFF_BYTES(pc, start_of_procedure);
 205     }
 206 
 207     pc2++;
 208   } else {
 209     // return -1 for displacement
 210     if (p_displacement) {
 211       (*p_displacement) = -1;
 212     }
 213   }
 214 
 215   if (tb->tb.int_hndl == TRUE)
 216     pc2++;
 217 
 218   if (tb->tb.has_ctl == TRUE)
 219     pc2 += (*pc2) + 1; // don't care
 220 
 221   CHECK_POINTER_READABLE(pc2)
 222 
 223   //
 224   // return function name if it exists.
 225   //
 226   if (p_name && namelen > 0) {
 227     if (tb->tb.name_present) {
 228       // Copy name from text because it may not be zero terminated.
 229       const short l = MIN2<short>(*((short*)pc2), namelen - 1);
 230       // Be very careful.
 231       int i = 0; char* const p = (char*)pc2 + sizeof(short);
 232       while (i < l && MiscUtils::is_readable_pointer(p + i)) {
 233         p_name[i] = p[i];
 234         i++;
 235       }
 236       p_name[i] = '\0';
 237 
 238       // If it is a C++ name, try and demangle it using the Demangle interface (see demangle.h).
 239       if (demangle) {
 240         char* rest;
 241         Name* const name = Demangle(p_name, rest);
 242         if (name) {
 243           const char* const demangled_name = name->Text();
 244           if (demangled_name) {
 245             strncpy(p_name, demangled_name, namelen-1);
 246             p_name[namelen-1] = '\0';
 247           }
 248           delete name;
 249         }
 250       }
 251     } else {
 252       strncpy(p_name, "<nameless function>", namelen-1);
 253       p_name[namelen-1] = '\0';
 254     }
 255   }
 256 
 257   // Return traceback table, if user wants it.
 258   if (p_tb) {
 259     (*p_tb) = tb;
 260   }
 261 
 262   return true;
 263 
 264 }
 265 
 266 bool AixSymbols::get_module_name(address pc,
 267                          char* p_name, size_t namelen) {
 268 
 269   if (p_name && namelen > 0) {
 270     p_name[0] = '\0';
 271     loaded_module_t lm;
 272     if (LoadedLibraries::find_for_text_address(pc, &lm) != NULL) {
 273       strncpy(p_name, lm.shortname, namelen);
 274       p_name[namelen - 1] = '\0';
 275       return true;
 276     }
 277   }
 278 
 279   return false;
 280 }
 281 
 282 // Special implementation of dladdr for Aix based on LoadedLibraries
 283 // Note: dladdr returns non-zero for ok, 0 for error!
 284 // Note: dladdr is not posix, but a non-standard GNU extension. So this tries to
 285 //   fulfill the contract of dladdr on Linux (see http://linux.die.net/man/3/dladdr)
 286 // Note: addr may be both an AIX function descriptor or a real code pointer
 287 //   to the entry of a function.
 288 extern "C"
 289 int dladdr(void* addr, Dl_info* info) {
 290 
 291   if (!addr) {
 292     return 0;
 293   }
 294 
 295   assert(info, "");
 296 
 297   int rc = 0;
 298 
 299   const char* const ZEROSTRING = "";
 300 
 301   // Always return a string, even if a "" one. Linux dladdr manpage
 302   // does not say anything about returning NULL
 303   info->dli_fname = ZEROSTRING;
 304   info->dli_sname = ZEROSTRING;
 305   info->dli_saddr = NULL;
 306 
 307   address p = (address) addr;
 308   loaded_module_t lm;
 309   bool found = false;
 310 
 311   enum { noclue, code, data } type = noclue;
 312 
 313   trcVerbose("dladdr(%p)...", p);
 314 
 315   // Note: input address may be a function. I accept both a pointer to
 316   // the entry of a function and a pointer to the function decriptor.
 317   // (see ppc64 ABI)
 318   found = LoadedLibraries::find_for_text_address(p, &lm);
 319   if (found) {
 320     type = code;
 321   }
 322 
 323   if (!found) {
 324     // Not a pointer into any text segment. Is it a function descriptor?
 325     const FunctionDescriptor* const pfd = (const FunctionDescriptor*) p;
 326     p = pfd->entry();
 327     if (p) {
 328       found = LoadedLibraries::find_for_text_address(p, &lm);
 329       if (found) {
 330         type = code;
 331       }
 332     }
 333   }
 334 
 335   if (!found) {
 336     // Neither direct code pointer nor function descriptor. A data ptr?
 337     p = (address)addr;
 338     found = LoadedLibraries::find_for_data_address(p, &lm);
 339     if (found) {
 340       type = data;
 341     }
 342   }
 343 
 344   // If we did find the shared library this address belongs to (either
 345   // code or data segment) resolve library path and, if possible, the
 346   // symbol name.
 347   if (found) {
 348 
 349     // No need to intern the libpath, that one is already interned one layer below.
 350     info->dli_fname = lm.path;
 351 
 352     if (type == code) {
 353 
 354       // For code symbols resolve function name and displacement. Use
 355       // displacement to calc start of function.
 356       char funcname[256] = "";
 357       int displacement = 0;
 358 
 359       if (AixSymbols::get_function_name(p, funcname, sizeof(funcname),
 360                       &displacement, NULL, true)) {
 361         if (funcname[0] != '\0') {
 362           const char* const interned = dladdr_fixed_strings.intern(funcname);
 363           info->dli_sname = interned;
 364           trcVerbose("... function name: %s ...", interned);
 365         }
 366 
 367         // From the displacement calculate the start of the function.
 368         if (displacement != -1) {
 369           info->dli_saddr = p - displacement;
 370         } else {
 371           info->dli_saddr = p;
 372         }
 373       } else {
 374 
 375         // No traceback table found. Just assume the pointer is it.
 376         info->dli_saddr = p;
 377 
 378       }
 379 
 380     } else if (type == data) {
 381 
 382       // For data symbols.
 383       info->dli_saddr = p;
 384 
 385     } else {
 386       ShouldNotReachHere();
 387     }
 388 
 389     rc = 1; // success: return 1 [sic]
 390 
 391   }
 392 
 393   // sanity checks.
 394   if (rc) {
 395     assert(info->dli_fname, "");
 396     assert(info->dli_sname, "");
 397     assert(info->dli_saddr, "");
 398   }
 399 
 400   return rc; // error: return 0 [sic]
 401 
 402 }
 403 
 404 /////////////////////////////////////////////////////////////////////////////
 405 // Native callstack dumping
 406 
 407 // Print the traceback table for one stack frame.
 408 static void print_tbtable (outputStream* st, const struct tbtable* p_tb) {
 409 
 410   if (p_tb == NULL) {
 411     st->print("<null>");
 412     return;
 413   }
 414 
 415   switch(p_tb->tb.lang) {
 416     case TB_C: st->print("C"); break;
 417     case TB_FORTRAN: st->print("FORTRAN"); break;
 418     case TB_PASCAL: st->print("PASCAL"); break;
 419     case TB_ADA: st->print("ADA"); break;
 420     case TB_PL1: st->print("PL1"); break;
 421     case TB_BASIC: st->print("BASIC"); break;
 422     case TB_LISP: st->print("LISP"); break;
 423     case TB_COBOL: st->print("COBOL"); break;
 424     case TB_MODULA2: st->print("MODULA2"); break;
 425     case TB_CPLUSPLUS: st->print("C++"); break;
 426     case TB_RPG: st->print("RPG"); break;
 427     case TB_PL8: st->print("PL8"); break;
 428     case TB_ASM: st->print("ASM"); break;
 429     case TB_HPJ: st->print("HPJ"); break;
 430     default: st->print("unknown");
 431   }
 432   st->print(" ");
 433 
 434   if (p_tb->tb.globallink) {
 435     st->print("globallink ");
 436   }
 437   if (p_tb->tb.is_eprol) {
 438     st->print("eprol ");
 439   }
 440   if (p_tb->tb.int_proc) {
 441     st->print("int_proc ");
 442   }
 443   if (p_tb->tb.tocless) {
 444     st->print("tocless ");
 445   }
 446   if (p_tb->tb.fp_present) {
 447     st->print("fp_present ");
 448   }
 449   if (p_tb->tb.int_hndl) {
 450     st->print("interrupt_handler ");
 451   }
 452   if (p_tb->tb.uses_alloca) {
 453     st->print("uses_alloca ");
 454   }
 455   if (p_tb->tb.saves_cr) {
 456     st->print("saves_cr ");
 457   }
 458   if (p_tb->tb.saves_lr) {
 459     st->print("saves_lr ");
 460   }
 461   if (p_tb->tb.stores_bc) {
 462     st->print("stores_bc ");
 463   }
 464   if (p_tb->tb.fixup) {
 465     st->print("fixup ");
 466   }
 467   if (p_tb->tb.fpr_saved > 0) {
 468     st->print("fpr_saved:%d ", p_tb->tb.fpr_saved);
 469   }
 470   if (p_tb->tb.gpr_saved > 0) {
 471     st->print("gpr_saved:%d ", p_tb->tb.gpr_saved);
 472   }
 473   if (p_tb->tb.fixedparms > 0) {
 474     st->print("fixedparms:%d ", p_tb->tb.fixedparms);
 475   }
 476   if (p_tb->tb.floatparms > 0) {
 477     st->print("floatparms:%d ", p_tb->tb.floatparms);
 478   }
 479   if (p_tb->tb.parmsonstk > 0) {
 480     st->print("parmsonstk:%d", p_tb->tb.parmsonstk);
 481   }
 482 }
 483 
 484 // Print information for pc (module, function, displacement, traceback table)
 485 // on one line.
 486 static void print_info_for_pc (outputStream* st, codeptr_t pc, char* buf,
 487                                size_t buf_size, bool demangle) {
 488   const struct tbtable* tb = NULL;
 489   int displacement = -1;
 490 
 491   if (!MiscUtils::is_readable_pointer(pc)) {
 492     st->print("(invalid)");
 493     return;
 494   }
 495 
 496   if (AixSymbols::get_module_name((address)pc, buf, buf_size)) {
 497     st->print("%s", buf);
 498   } else {
 499     st->print("(unknown module)");
 500   }
 501   st->print("::");
 502   if (AixSymbols::get_function_name((address)pc, buf, buf_size,
 503                                      &displacement, &tb, demangle)) {
 504     st->print("%s", buf);
 505   } else {
 506     st->print("(unknown function)");
 507   }
 508   if (displacement == -1) {
 509     st->print("+?");
 510   } else {
 511     st->print("+0x%x", displacement);
 512   }
 513   if (tb) {
 514     st->fill_to(64);
 515     st->print("  (");
 516     print_tbtable(st, tb);
 517     st->print(")");
 518   }
 519 }
 520 
 521 static void print_stackframe(outputStream* st, stackptr_t sp, char* buf,
 522                              size_t buf_size, bool demangle) {
 523 
 524   stackptr_t sp2 = sp;
 525 
 526   // skip backchain
 527 
 528   sp2++;
 529 
 530   // skip crsave
 531 
 532   sp2++;
 533 
 534   // retrieve lrsave. That is the only info I need to get the function/displacement
 535 
 536   codeptr_t lrsave = (codeptr_t) *(sp2);
 537   st->print (PTR64_FORMAT " - " PTR64_FORMAT " ", sp2, lrsave);
 538 
 539   if (lrsave != NULL) {
 540     print_info_for_pc(st, lrsave, buf, buf_size, demangle);
 541   }
 542 
 543 }
 544 
 545 // Function to check a given stack pointer against given stack limits.
 546 static bool is_valid_stackpointer(stackptr_t sp, stackptr_t stack_base, size_t stack_size) {
 547   if (((uintptr_t)sp) & 0x7) {
 548     return false;
 549   }
 550   if (sp > stack_base) {
 551     return false;
 552   }
 553   if (sp < (stackptr_t) ((address)stack_base - stack_size)) {
 554     return false;
 555   }
 556   return true;
 557 }
 558 
 559 // Returns true if function is a valid codepointer.
 560 static bool is_valid_codepointer(codeptr_t p) {
 561   if (!p) {
 562     return false;
 563   }
 564   if (((uintptr_t)p) & 0x3) {
 565     return false;
 566   }
 567   if (LoadedLibraries::find_for_text_address(p, NULL) == NULL) {
 568     return false;
 569   }
 570   return true;
 571 }
 572 
 573 // Function tries to guess if the given combination of stack pointer, stack base
 574 // and stack size is a valid stack frame.
 575 static bool is_valid_frame (stackptr_t p, stackptr_t stack_base, size_t stack_size) {
 576 
 577   if (!is_valid_stackpointer(p, stack_base, stack_size)) {
 578     return false;
 579   }
 580 
 581   // First check - the occurrence of a valid backchain pointer up the stack, followed by a
 582   // valid codeptr, counts as a good candidate.
 583   stackptr_t sp2 = (stackptr_t) *p;
 584   if (is_valid_stackpointer(sp2, stack_base, stack_size) && // found a valid stack pointer in the stack...
 585      ((sp2 - p) > 6) &&  // ... pointing upwards and not into my frame...
 586      is_valid_codepointer((codeptr_t)(*(sp2 + 2)))) // ... followed by a code pointer after two slots...
 587   {
 588     return true;
 589   }
 590 
 591   return false;
 592 }
 593 
 594 // Try to relocate a stack back chain in a given stack.
 595 // Used in callstack dumping, when the backchain is broken by an overwriter
 596 static stackptr_t try_find_backchain (stackptr_t last_known_good_frame,
 597                                       stackptr_t stack_base, size_t stack_size)
 598 {
 599   if (!is_valid_stackpointer(last_known_good_frame, stack_base, stack_size)) {
 600     return NULL;
 601   }
 602 
 603   stackptr_t sp = last_known_good_frame;
 604 
 605   sp += 6; // Omit next fixed frame slots.
 606   while (sp < stack_base) {
 607     if (is_valid_frame(sp, stack_base, stack_size)) {
 608       return sp;
 609     }
 610     sp ++;
 611   }
 612 
 613   return NULL;
 614 }
 615 
 616 static void decode_instructions_at_pc(const char* header,
 617                                       codeptr_t pc, int num_before,
 618                                       int num_after, outputStream* st) {
 619   // TODO: PPC port Disassembler::decode(pc, 16, 16, st);
 620 }
 621 
 622 
 623 void AixNativeCallstack::print_callstack_for_context(outputStream* st, const ucontext_t* context,
 624                                                      bool demangle, char* buf, size_t buf_size) {
 625 
 626 #define MAX_CALLSTACK_DEPTH 50
 627 
 628   unsigned long* sp;
 629   unsigned long* sp_last;
 630   int frame;
 631 
 632   // To print the first frame, use the current value of iar:
 633   // current entry indicated by iar (the current pc)
 634   codeptr_t cur_iar = 0;
 635   stackptr_t cur_sp = 0;
 636   codeptr_t cur_rtoc = 0;
 637   codeptr_t cur_lr = 0;
 638 
 639   const ucontext_t* uc = (const ucontext_t*) context;
 640 
 641   // fallback: use the current context
 642   ucontext_t local_context;
 643   if (!uc) {
 644     st->print_cr("No context given, using current context.");
 645     if (getcontext(&local_context) == 0) {
 646       uc = &local_context;
 647     } else {
 648       st->print_cr("No context given and getcontext failed. ");
 649       return;
 650     }
 651   }
 652 
 653   cur_iar = (codeptr_t)uc->uc_mcontext.jmp_context.iar;
 654   cur_sp = (stackptr_t)uc->uc_mcontext.jmp_context.gpr[1];
 655   cur_rtoc = (codeptr_t)uc->uc_mcontext.jmp_context.gpr[2];
 656   cur_lr = (codeptr_t)uc->uc_mcontext.jmp_context.lr;
 657 
 658   // syntax used here:
 659   //  n   --------------   <-- stack_base,   stack_to
 660   //  n-1 |            |
 661   //  ... | older      |
 662   //  ... |   frames   | |
 663   //      |            | | stack grows downward
 664   //  ... | younger    | |
 665   //  ... |   frames   | V
 666   //      |            |
 667   //      |------------|   <-- cur_sp, current stack ptr
 668   //      |            |
 669   //      |  unsused   |
 670   //      |    stack   |
 671   //      |            |
 672   //      .            .
 673   //      .            .
 674   //      .            .
 675   //      .            .
 676   //      |            |
 677   //   0  --------------   <-- stack_from
 678   //
 679 
 680   // Retrieve current stack base, size from the current thread. If there is none,
 681   // retrieve it from the OS.
 682   stackptr_t stack_base = NULL;
 683   size_t stack_size = NULL;
 684   {
 685     AixMisc::stackbounds_t stackbounds;
 686     if (!AixMisc::query_stack_bounds_for_current_thread(&stackbounds)) {
 687       st->print_cr("Cannot retrieve stack bounds.");
 688       return;
 689     }
 690     stack_base = (stackptr_t)stackbounds.base;
 691     stack_size = stackbounds.size;
 692   }
 693 
 694   st->print_cr("------ current frame:");
 695   st->print("iar:  " PTR64_FORMAT " ", p2i(cur_iar));
 696   print_info_for_pc(st, cur_iar, buf, buf_size, demangle);
 697   st->cr();
 698 
 699   if (cur_iar && MiscUtils::is_readable_pointer(cur_iar)) {
 700     decode_instructions_at_pc(
 701       "Decoded instructions at iar:",
 702       cur_iar, 32, 16, st);
 703   }
 704 
 705   // Print out lr too, which may be interesting if we did jump to some bogus location;
 706   // in those cases the new frame is not built up yet and the caller location is only
 707   // preserved via lr register.
 708   st->print("lr:   " PTR64_FORMAT " ", p2i(cur_lr));
 709   print_info_for_pc(st, cur_lr, buf, buf_size, demangle);
 710   st->cr();
 711 
 712   if (cur_lr && MiscUtils::is_readable_pointer(cur_lr)) {
 713     decode_instructions_at_pc(
 714       "Decoded instructions at lr:",
 715       cur_lr, 32, 16, st);
 716   }
 717 
 718   // Check and print sp.
 719   st->print("sp:   " PTR64_FORMAT " ", p2i(cur_sp));
 720   if (!is_valid_stackpointer(cur_sp, stack_base, stack_size)) {
 721     st->print("(invalid) ");
 722     goto cleanup;
 723   } else {
 724     st->print("(base - 0x%X) ", PTRDIFF_BYTES(stack_base, cur_sp));
 725   }
 726   st->cr();
 727 
 728   // Check and print rtoc.
 729   st->print("rtoc: "  PTR64_FORMAT " ", p2i(cur_rtoc));
 730   if (cur_rtoc == NULL || cur_rtoc == (codeptr_t)-1 ||
 731       !MiscUtils::is_readable_pointer(cur_rtoc)) {
 732     st->print("(invalid)");
 733   } else if (((uintptr_t)cur_rtoc) & 0x7) {
 734     st->print("(unaligned)");
 735   }
 736   st->cr();
 737 
 738   st->print_cr("|---stackaddr----|   |----lrsave------|:   <function name>");
 739 
 740   ///
 741   // Walk callstack.
 742   //
 743   // (if no context was given, use the current stack)
 744   sp = (unsigned long*)(*(unsigned long*)cur_sp); // Stack pointer
 745   sp_last = cur_sp;
 746 
 747   frame = 0;
 748 
 749   while (frame < MAX_CALLSTACK_DEPTH) {
 750 
 751     // Check sp.
 752     bool retry = false;
 753     if (sp == NULL) {
 754       // The backchain pointer was NULL. This normally means the end of the chain. But the
 755       // stack might be corrupted, and it may be worth looking for the stack chain.
 756       if (is_valid_stackpointer(sp_last, stack_base, stack_size) && (stack_base - 0x10) > sp_last) {
 757         // If we are not within <guess> 0x10 stackslots of the stack base, we assume that this
 758         // is indeed not the end of the chain but that the stack was corrupted. So lets try to
 759         // find the end of the chain.
 760         st->print_cr("*** back chain pointer is NULL - end of stack or broken backchain ? ***");
 761         retry = true;
 762       } else {
 763         st->print_cr("*** end of backchain ***");
 764         goto end_walk_callstack;
 765       }
 766     } else if (!is_valid_stackpointer(sp, stack_base, stack_size)) {
 767       st->print_cr("*** stack pointer invalid - backchain corrupted (" PTR_FORMAT ") ***", p2i(sp));
 768       retry = true;
 769     } else if (sp < sp_last) {
 770       st->print_cr("invalid stack pointer: " PTR_FORMAT " (not monotone raising)", p2i(sp));
 771       retry = true;
 772     }
 773 
 774     // If backchain is broken, try to recover, by manually scanning the stack for a pattern
 775     // which looks like a valid stack.
 776     if (retry) {
 777       st->print_cr("trying to recover and find backchain...");
 778       sp = try_find_backchain(sp_last, stack_base, stack_size);
 779       if (sp) {
 780         st->print_cr("found something which looks like a backchain at " PTR64_FORMAT ", after 0x%x bytes... ",
 781             p2i(sp), PTRDIFF_BYTES(sp, sp_last));
 782       } else {
 783         st->print_cr("did not find a backchain, giving up.");
 784         goto end_walk_callstack;
 785       }
 786     }
 787 
 788     // Print stackframe.
 789     print_stackframe(st, sp, buf, buf_size, demangle);
 790     st->cr();
 791     frame ++;
 792 
 793     // Next stack frame and link area.
 794     sp_last = sp;
 795     sp = (unsigned long*)(*sp);
 796   }
 797 
 798   // Prevent endless loops in case of invalid callstacks.
 799   if (frame == MAX_CALLSTACK_DEPTH) {
 800     st->print_cr("...(stopping after %d frames.", MAX_CALLSTACK_DEPTH);
 801   }
 802 
 803 end_walk_callstack:
 804 
 805   st->print_cr("-----------------------");
 806 
 807 cleanup:
 808 
 809   return;
 810 
 811 }
 812 
 813 
 814 bool AixMisc::query_stack_bounds_for_current_thread(stackbounds_t* out) {
 815 
 816   // Information about this api can be found (a) in the pthread.h header and
 817   // (b) in http://publib.boulder.ibm.com/infocenter/pseries/v5r3/index.jsp?topic=/com.ibm.aix.basetechref/doc/basetrf1/pthread_getthrds_np.htm
 818   //
 819   // The use of this API to find out the current stack is kind of undefined.
 820   // But after a lot of tries and asking IBM about it, I concluded that it is safe
 821   // enough for cases where I let the pthread library create its stacks. For cases
 822   // where I create an own stack and pass this to pthread_create, it seems not to
 823   // work (the returned stack size in that case is 0).
 824 
 825   pthread_t tid = pthread_self();
 826   struct __pthrdsinfo pinfo;
 827   char dummy[1]; // Just needed to satisfy pthread_getthrds_np.
 828   int dummy_size = sizeof(dummy);
 829 
 830   memset(&pinfo, 0, sizeof(pinfo));
 831 
 832   const int rc = pthread_getthrds_np(&tid, PTHRDSINFO_QUERY_ALL, &pinfo,
 833                                      sizeof(pinfo), dummy, &dummy_size);
 834 
 835   if (rc != 0) {
 836     fprintf(stderr, "pthread_getthrds_np failed (%d)\n", rc);
 837     fflush(stdout);
 838     return false;
 839   }
 840 
 841   // The following may happen when invoking pthread_getthrds_np on a pthread
 842   // running on a user provided stack (when handing down a stack to pthread
 843   // create, see pthread_attr_setstackaddr).
 844   // Not sure what to do then.
 845   if (pinfo.__pi_stackend == NULL || pinfo.__pi_stackaddr == NULL) {
 846     fprintf(stderr, "pthread_getthrds_np - invalid values\n");
 847     fflush(stdout);
 848     return false;
 849   }
 850 
 851   // Note: we get three values from pthread_getthrds_np:
 852   //       __pi_stackaddr, __pi_stacksize, __pi_stackend
 853   //
 854   // high addr    ---------------------                                                           base, high
 855   //
 856   //    |         pthread internal data, like ~2K
 857   //    |
 858   //    |         ---------------------   __pi_stackend   (usually not page aligned, (xxxxF890))
 859   //    |
 860   //    |
 861   //    |
 862   //    |
 863   //    |
 864   //    |
 865   //    |          ---------------------   (__pi_stackend - __pi_stacksize)
 866   //    |
 867   //    |          padding to align the following AIX guard pages, if enabled.
 868   //    |
 869   //    V          ---------------------   __pi_stackaddr                                        low, base - size
 870   //
 871   // low addr      AIX guard pages, if enabled (AIXTHREAD_GUARDPAGES > 0)
 872   //
 873 
 874   out->base = (address)pinfo.__pi_stackend;
 875   address low = (address)pinfo.__pi_stackaddr;
 876   out->size = out->base - low;
 877   return true;
 878 
 879 }
 880 
 881 
 882 
 883