rev 9211 : 8140645: Recent Developments for AIX
Summary: Port recent developments from SAP for AIX to the OpenJDK

   1 /*
   2  * Copyright 2012, 2013 SAP AG. 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 "memory/allocation.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "runtime/os.hpp"
  29 #include "loadlib_aix.hpp"
  30 #include "porting_aix.hpp"
  31 #include "utilities/debug.hpp"
  32 
  33 // For CritSect
  34 #include "misc_aix.hpp"
  35 
  36 #include <demangle.h>
  37 #include <sys/debug.h>
  38 
  39 //////////////////////////////////
  40 // Provide implementation for dladdr based on LoadedLibraries pool and
  41 // traceback table scan (see getFuncName).
  42 
  43 // Search traceback table in stack,
  44 // return procedure name from trace back table.
  45 #define MAX_FUNC_SEARCH_LEN 0x10000
  46 // Any PC below this value is considered toast.
  47 #define MINIMUM_VALUE_FOR_PC ((unsigned int*)0x1024)
  48 
  49 #define PTRDIFF_BYTES(p1,p2) (((ptrdiff_t)p1) - ((ptrdiff_t)p2))
  50 





  51 // Trace if verbose to tty.
  52 // I use these now instead of the Xtrace system because the latter is
  53 // not available at init time, hence worthless. Until we fix this, all
  54 // tracing here is done with -XX:+Verbose.
  55 #define trcVerbose(fmt, ...) { \
  56   if (Verbose) { \
  57     fprintf(stderr, fmt, ##__VA_ARGS__); \
  58     fputc('\n', stderr); fflush(stderr); \
  59   } \
  60 }
  61 #define ERRBYE(s) { trcVerbose(s); return -1; }
  62 
  63 // Unfortunately, the interface of dladdr makes the implementator
  64 // responsible for maintaining memory for function name/library
  65 // name. I guess this is because most OS's keep those values as part
  66 // of the mapped executable image ready to use. On AIX, this doesn't
  67 // work, so I have to keep the returned strings. For now, I do this in
  68 // a primitive string map. Should this turn out to be a performance
  69 // problem, a better hashmap has to be used.
  70 class fixed_strings {
  71   struct node : public CHeapObj<mtInternal> {
  72     char* v;
  73     node* next;
  74   };
  75 
  76   node* first;
  77 
  78   public:
  79 
  80   fixed_strings() : first(0) {}
  81   ~fixed_strings() {
  82     node* n = first;
  83     while (n) {
  84       node* p = n;
  85       n = n->next;
  86       os::free(p->v);
  87       delete p;
  88     }
  89   }
  90 
  91   char* intern(const char* s) {
  92     for (node* n = first; n; n = n->next) {
  93       if (strcmp(n->v, s) == 0) {
  94         return n->v;
  95       }
  96     }
  97     node* p = new node;
  98     p->v = os::strdup_check_oom(s);
  99     p->next = first;
 100     first = p;
 101     return p->v;
 102   }
 103 };
 104 
 105 static fixed_strings dladdr_fixed_strings;
 106 
 107 // Given a code pointer, returns the function name and the displacement.
 108 // Function looks for the traceback table at the end of the function.
 109 extern "C" int getFuncName(
 110     codeptr_t pc,                    // [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     char* p_errmsg, size_t errmsglen,// [out] optional: user provided buffer for error messages
 116     bool demangle                    // [in] whether to demangle the name
 117   ) {
 118   struct tbtable* tb = 0;
 119   unsigned int searchcount = 0;
 120 
 121   // initialize output parameters
 122   if (p_name && namelen > 0) {
 123     *p_name = '\0';
 124   }
 125   if (p_errmsg && errmsglen > 0) {
 126     *p_errmsg = '\0';
 127   }
 128   if (p_displacement) {
 129     *p_displacement = -1;
 130   }
 131   if (p_tb) {
 132     *p_tb = NULL;
 133   }
 134 
 135   // weed out obvious bogus states
 136   if (pc < MINIMUM_VALUE_FOR_PC) {
 137     ERRBYE("invalid program counter");
 138   }
 139 
 140   // We see random but frequent crashes in this function since some months mainly on shutdown
 141   // (-XX:+DumpInfoAtExit). It appears the page we are reading is randomly disappearing while
 142   // we read it (?).
 143   // As the pc cannot be trusted to be anything sensible lets make all reads via SafeFetch. Also
 144   // bail if this is not a text address right now.
 145   if (!LoadedLibraries::find_for_text_address(pc, NULL)) {
 146     ERRBYE("not a text address");
 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 (!MiscUtils::is_readable_pointer(p)) { \
 154     ERRBYE("pc not readable"); \
 155   }
 156 
 157   codeptr_t pc2 = pc;
 158 
 159   // make sure the pointer is word aligned.
 160   pc2 = (codeptr_t) align_ptr_up((char*)pc2, 4);
 161   CHECK_POINTER_READABLE(pc2)
 162 
 163   // Find start of traceback table.
 164   // (starts after code, is marked by word-aligned (32bit) zeros)
 165   while ((*pc2 != NULL) && (searchcount++ < MAX_FUNC_SEARCH_LEN)) {
 166     CHECK_POINTER_READABLE(pc2)
 167     pc2++;
 168   }
 169   if (*pc2 != 0) {
 170     ERRBYE("no traceback table found");
 171   }
 172   //
 173   // Set up addressability to the traceback table
 174   //
 175   tb = (struct tbtable*) (pc2 + 1);
 176 
 177   // Is this really a traceback table? No way to be sure but
 178   // some indicators we can check.
 179   if (tb->tb.lang >= 0xf && tb->tb.lang <= 0xfb) {
 180     // Language specifiers, go from 0 (C) to 14 (Objective C).
 181     // According to spec, 0xf-0xfa reserved, 0xfb-0xff reserved for ibm.
 182     ERRBYE("no traceback table found");
 183   }
 184 
 185   // Existence of fields in the tbtable extension are contingent upon
 186   // specific fields in the base table.  Check for their existence so
 187   // that we can address the function name if it exists.
 188   pc2 = (codeptr_t) tb +
 189     sizeof(struct tbtable_short)/sizeof(int);
 190   if (tb->tb.fixedparms != 0 || tb->tb.floatparms != 0)
 191     pc2++;
 192 
 193   CHECK_POINTER_READABLE(pc2)
 194 
 195   if (tb->tb.has_tboff == TRUE) {
 196 
 197     // I want to know the displacement
 198     const unsigned int tb_offset = *pc2;
 199     codeptr_t start_of_procedure =
 200     (codeptr_t)(((char*)tb) - 4 - tb_offset);  // (-4 to omit leading 0000)
 201 
 202     // Weed out the cases where we did find the wrong traceback table.
 203     if (pc < start_of_procedure) {
 204       ERRBYE("no traceback table found");
 205     }
 206 
 207     // return the displacement
 208     if (p_displacement) {
 209       (*p_displacement) = (int) PTRDIFF_BYTES(pc, start_of_procedure);
 210     }
 211 
 212     pc2++;
 213   } else {
 214     // return -1 for displacement
 215     if (p_displacement) {
 216       (*p_displacement) = -1;
 217     }
 218   }
 219 
 220   if (tb->tb.int_hndl == TRUE)
 221     pc2++;
 222 
 223   if (tb->tb.has_ctl == TRUE)
 224     pc2 += (*pc2) + 1; // don't care
 225 
 226   CHECK_POINTER_READABLE(pc2)
 227 
 228   //
 229   // return function name if it exists.
 230   //
 231   if (p_name && namelen > 0) {
 232     if (tb->tb.name_present) {
 233       // copy name from text because it may not be zero terminated.
 234       // 256 is good enough for most cases; do not use large buffers here.
 235       char buf[256];
 236       const short l = MIN2<short>(*((short*)pc2), sizeof(buf) - 1);
 237       // be very careful.
 238       int i = 0; char* const p = (char*)pc2 + sizeof(short);
 239       while (i < l && MiscUtils::is_readable_pointer(p + i)) {
 240         buf[i] = p[i];
 241         i++;
 242       }
 243       buf[i] = '\0';
 244 
 245       p_name[0] = '\0';
 246 
 247       // If it is a C++ name, try and demangle it using the Demangle interface (see demangle.h).
 248       if (demangle) {
 249         char* rest;
 250         Name* const name = Demangle(buf, rest);
 251         if (name) {
 252           const char* const demangled_name = name->Text();
 253           if (demangled_name) {
 254             strncpy(p_name, demangled_name, namelen-1);
 255             p_name[namelen-1] = '\0';
 256           }
 257           delete name;
 258         }
 259       }
 260 
 261       // Fallback: if demangling did not work, just provide the unmangled name.
 262       if (p_name[0] == '\0') {
 263         strncpy(p_name, buf, namelen-1);
 264         p_name[namelen-1] = '\0';
 265       }
 266 
 267     } else {
 268       strncpy(p_name, "<nameless function>", namelen-1);
 269       p_name[namelen-1] = '\0';
 270     }
 271   }
 272   // Return traceback table, if user wants it.
 273   if (p_tb) {
 274     (*p_tb) = tb;
 275   }
 276 
 277   return 0;
 278 }
 279 
 280 // Special implementation of dladdr for Aix based on LoadedLibraries
 281 // Note: dladdr returns non-zero for ok, 0 for error!
 282 // Note: dladdr is not posix, but a non-standard GNU extension. So this tries to
 283 //   fulfill the contract of dladdr on Linux (see http://linux.die.net/man/3/dladdr)
 284 // Note: addr may be both an AIX function descriptor or a real code pointer
 285 //   to the entry of a function.
 286 extern "C"
 287 int dladdr(void* addr, Dl_info* info) {
 288 
 289   if (!addr) {
 290     return 0;
 291   }
 292 
 293   assert(info, "");
 294 
 295   int rc = 0;
 296 
 297   const char* const ZEROSTRING = "";
 298 
 299   // Always return a string, even if a "" one. Linux dladdr manpage
 300   // does not say anything about returning NULL
 301   info->dli_fname = ZEROSTRING;
 302   info->dli_sname = ZEROSTRING;
 303   info->dli_saddr = NULL;
 304 
 305   address p = (address) addr;
 306   loaded_module_t lm;
 307   bool found = false;
 308 
 309   enum { noclue, code, data } type = noclue;
 310 
 311   trcVerbose("dladdr(%p)...", p);
 312 
 313   // Note: input address may be a function. I accept both a pointer to
 314   // the entry of a function and a pointer to the function decriptor.
 315   // (see ppc64 ABI)
 316   found = LoadedLibraries::find_for_text_address(p, &lm);
 317   if (found) {
 318     type = code;
 319   }
 320 
 321   if (!found) {
 322     // Not a pointer into any text segment. Is it a function descriptor?
 323     const FunctionDescriptor* const pfd = (const FunctionDescriptor*) p;
 324     p = pfd->entry();
 325     if (p) {
 326       found = LoadedLibraries::find_for_text_address(p, &lm);
 327       if (found) {
 328         type = code;
 329       }
 330     }
 331   }
 332 
 333   if (!found) {
 334     // Neither direct code pointer nor function descriptor. A data ptr?
 335     p = (address)addr;
 336     found = LoadedLibraries::find_for_data_address(p, &lm);
 337     if (found) {
 338       type = data;
 339     }
 340   }
 341 
 342   // If we did find the shared library this address belongs to (either
 343   // code or data segment) resolve library path and, if possible, the
 344   // symbol name.
 345   if (found) {
 346 
 347     // No need to intern the libpath, that one is already interned one layer below.
 348     info->dli_fname = lm.path;


 349 
 350     if (type == code) {
 351 
 352       // For code symbols resolve function name and displacement. Use
 353       // displacement to calc start of function.
 354       char funcname[256] = "";
 355       int displacement = 0;
 356 
 357       if (getFuncName((codeptr_t) p, funcname, sizeof(funcname), &displacement,
 358                       NULL, NULL, 0, false) == 0) {
 359         if (funcname[0] != '\0') {
 360           const char* const interned = dladdr_fixed_strings.intern(funcname);
 361           info->dli_sname = interned;
 362           trcVerbose("... function name: %s ...", interned);
 363         }
 364 
 365         // From the displacement calculate the start of the function.
 366         if (displacement != -1) {
 367           info->dli_saddr = p - displacement;
 368         } else {
 369           info->dli_saddr = p;
 370         }
 371       } else {
 372 
 373         // No traceback table found. Just assume the pointer is it.
 374         info->dli_saddr = p;
 375 
 376       }
 377 
 378     } else if (type == data) {
 379 
 380       // For data symbols.
 381       info->dli_saddr = p;
 382 
 383     } else {
 384       ShouldNotReachHere();
 385     }
 386 
 387     rc = 1; // success: return 1 [sic]
 388 
 389   }
 390 
 391   // sanity checks.
 392   if (rc) {
 393     assert(info->dli_fname, "");
 394     assert(info->dli_sname, "");
 395     assert(info->dli_saddr, "");
 396   }
 397 
 398   return rc; // error: return 0 [sic]
 399 
 400 }
 401 
--- EOF ---