Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 2003-2008 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 #include <jni.h>

 #include <unistd.h>

 #include <fcntl.h>

 #include <string.h>

 #include <stdlib.h>

 #include <stddef.h>

 #include <elf.h>

 #include <link.h>

 #include "libproc_impl.h"

 #include "salibelf.h"

 // This file has the libproc implementation to read core files.

 // For live processes, refer to ps_proc.c. Portions of this is adapted

 // /modelled after Solaris libproc.so (in particular Pcore.c)

 //----------------------------------------------------------------------

 // ps_prochandle cleanup helper functions

 // close all file descriptors

 static void close_elf_files(struct ps_prochandle* ph) {

    lib_info* lib = NULL;

    // close core file descriptor

    if (ph->core->core_fd >= 0)

      close(ph->core->core_fd);

    // close exec file descriptor

    if (ph->core->exec_fd >= 0)

      close(ph->core->exec_fd);

    // close interp file descriptor

    if (ph->core->interp_fd >= 0)

      close(ph->core->interp_fd);

    // close class share archive file

    if (ph->core->classes_jsa_fd >= 0)

      close(ph->core->classes_jsa_fd);

    // close all library file descriptors

    lib = ph->libs;

    while (lib) {

       int fd = lib->fd;

       if (fd >= 0 && fd != ph->core->exec_fd) close(fd);

       lib = lib->next;

    }

 }

 // clean all map_info stuff

 static void destroy_map_info(struct ps_prochandle* ph) {

   map_info* map = ph->core->maps;

   while (map) {

      map_info* next = map->next;

      free(map);

      map = next;

   }

   if (ph->core->map_array) {

      free(ph->core->map_array);

   }

   // Part of the class sharing workaround

   map = ph->core->class_share_maps;

   while (map) {

      map_info* next = map->next;

      free(map);

      map = next;

   }

 }

 // ps_prochandle operations

 static void core_release(struct ps_prochandle* ph) {

    if (ph->core) {

       close_elf_files(ph);

       destroy_map_info(ph);

       free(ph->core);

    }

 }

 static map_info* allocate_init_map(int fd, off_t offset, uintptr_t vaddr, size_t memsz) {

    map_info* map;

    if ( (map = (map_info*) calloc(1, sizeof(map_info))) == NULL) {

       print_debug("can't allocate memory for map_info\n");

       return NULL;

    }

    // initialize map

    map->fd     = fd;

    map->offset = offset;

    map->vaddr  = vaddr;

    map->memsz  = memsz;

    return map;

 }

 // add map info with given fd, offset, vaddr and memsz

 static map_info* add_map_info(struct ps_prochandle* ph, int fd, off_t offset,

                              uintptr_t vaddr, size_t memsz) {

    map_info* map;

    if ((map = allocate_init_map(fd, offset, vaddr, memsz)) == NULL) {

       return NULL;

    }

    // add this to map list

    map->next  = ph->core->maps;

    ph->core->maps   = map;

    ph->core->num_maps++;

    return map;

 }

 // Part of the class sharing workaround

 static map_info* add_class_share_map_info(struct ps_prochandle* ph, off_t offset,

                              uintptr_t vaddr, size_t memsz) {

    map_info* map;

    if ((map = allocate_init_map(ph->core->classes_jsa_fd,

                                 offset, vaddr, memsz)) == NULL) {

       return NULL;

    }

    map->next = ph->core->class_share_maps;

    ph->core->class_share_maps = map;

 }

 // Return the map_info for the given virtual address.  We keep a sorted

 // array of pointers in ph->map_array, so we can binary search.

 static map_info* core_lookup(struct ps_prochandle *ph, uintptr_t addr)

 {

    int mid, lo = 0, hi = ph->core->num_maps - 1;

    map_info *mp;

    while (hi - lo > 1) {

      mid = (lo + hi) / 2;

       if (addr >= ph->core->map_array[mid]->vaddr)

          lo = mid;

       else

          hi = mid;

    }

    if (addr < ph->core->map_array[hi]->vaddr)

       mp = ph->core->map_array[lo];

    else

       mp = ph->core->map_array[hi];

    if (addr >= mp->vaddr && addr < mp->vaddr + mp->memsz)

       return (mp);

    // Part of the class sharing workaround

    // Unfortunately, we have no way of detecting -Xshare state.

    // Check out the share maps atlast, if we don't find anywhere.

    // This is done this way so to avoid reading share pages

    // ahead of other normal maps. For eg. with -Xshare:off we don't

    // want to prefer class sharing data to data from core.

    mp = ph->core->class_share_maps;

    if (mp) {

       print_debug("can't locate map_info at 0x%lx, trying class share maps\n",

              addr);

    }

    while (mp) {

       if (addr >= mp->vaddr && addr < mp->vaddr + mp->memsz) {

          print_debug("located map_info at 0x%lx from class share maps\n",

                   addr);

          return (mp);

       }

       mp = mp->next;

    }

    print_debug("can't locate map_info at 0x%lx\n", addr);

    return (NULL);

 }

 //---------------------------------------------------------------

 // Part of the class sharing workaround:

 //

 // With class sharing, pages are mapped from classes[_g].jsa file.

 // The read-only class sharing pages are mapped as MAP_SHARED,

 // PROT_READ pages. These pages are not dumped into core dump.

 // With this workaround, these pages are read from classes[_g].jsa.

 // FIXME: !HACK ALERT!

 // The format of sharing achive file header is needed to read shared heap

 // file mappings. For now, I am hard coding portion of FileMapHeader here.

 // Refer to filemap.hpp.

 // FileMapHeader describes the shared space data in the file to be

 // mapped.  This structure gets written to a file.  It is not a class,

 // so that the compilers don't add any compiler-private data to it.

 // Refer to CompactingPermGenGen::n_regions in compactingPermGenGen.hpp

 #define NUM_SHARED_MAPS 4

 // Refer to FileMapInfo::_current_version in filemap.hpp

 #define CURRENT_ARCHIVE_VERSION 1

 struct FileMapHeader {

   int   _magic;              // identify file type.

   int   _version;            // (from enum, above.)

   size_t _alignment;         // how shared archive should be aligned

   struct space_info {

     int    _file_offset;     // sizeof(this) rounded to vm page size

     char*  _base;            // copy-on-write base address

     size_t _capacity;        // for validity checking

     size_t _used;            // for setting space top on read

     // 4991491 NOTICE These are C++ bool's in filemap.hpp and must match up with

     // the C type matching the C++ bool type on any given platform. For

     // Hotspot on Linux we assume the corresponding C type is char but

     // licensees on Linux versions may need to adjust the type of these fields.

     char   _read_only;       // read only space?

     char   _allow_exec;      // executable code in space?

   } _space[NUM_SHARED_MAPS]; // was _space[CompactingPermGenGen::n_regions];

   // Ignore the rest of the FileMapHeader. We don't need those fields here.

 };

 static bool read_jboolean(struct ps_prochandle* ph, uintptr_t addr, jboolean* pvalue) {

    jboolean i;

    if (ps_pdread(ph, (psaddr_t) addr, &i, sizeof(i)) == PS_OK) {

       *pvalue = i;

       return true;

    } else {

       return false;

    }

 }

 static bool read_pointer(struct ps_prochandle* ph, uintptr_t addr, uintptr_t* pvalue) {

    uintptr_t uip;

    if (ps_pdread(ph, (psaddr_t) addr, &uip, sizeof(uip)) == PS_OK) {

       *pvalue = uip;

       return true;

    } else {

       return false;

    }

 }

 // used to read strings from debuggee

 static bool read_string(struct ps_prochandle* ph, uintptr_t addr, char* buf, size_t size) {

    size_t i = 0;

    char  c = ' ';

    while (c != '\0') {

      if (ps_pdread(ph, (psaddr_t) addr, &c, sizeof(char)) != PS_OK)

          return false;

       if (i < size - 1)

          buf[i] = c;

       else // smaller buffer

          return false;

       i++; addr++;

    }

    buf[i] = '\0';

    return true;

 }

 #define USE_SHARED_SPACES_SYM "UseSharedSpaces"

 // mangled name of Arguments::SharedArchivePath

 #define SHARED_ARCHIVE_PATH_SYM "_ZN9Arguments17SharedArchivePathE"

 static bool init_classsharing_workaround(struct ps_prochandle* ph) {

    lib_info* lib = ph->libs;

    while (lib != NULL) {

       // we are iterating over shared objects from the core dump. look for

       // libjvm[_g].so.

       const char *jvm_name = 0;

       if ((jvm_name = strstr(lib->name, "/libjvm.so")) != 0 ||

           (jvm_name = strstr(lib->name, "/libjvm_g.so")) != 0) {

          char classes_jsa[PATH_MAX];

          struct FileMapHeader header;

          size_t n = 0;

          int fd = -1, m = 0;

          uintptr_t base = 0, useSharedSpacesAddr = 0;

          uintptr_t sharedArchivePathAddrAddr = 0, sharedArchivePathAddr = 0;

          jboolean useSharedSpaces = 0;

          map_info* mi = 0;

          memset(classes_jsa, 0, sizeof(classes_jsa));

          jvm_name = lib->name;

          useSharedSpacesAddr = lookup_symbol(ph, jvm_name, USE_SHARED_SPACES_SYM);

          if (useSharedSpacesAddr == 0) {

             print_debug("can't lookup 'UseSharedSpaces' flag\n");

             return false;

          }

          // Hotspot vm types are not exported to build this library. So

          // using equivalent type jboolean to read the value of

          // UseSharedSpaces which is same as hotspot type "bool".

          if (read_jboolean(ph, useSharedSpacesAddr, &useSharedSpaces) != true) {

             print_debug("can't read the value of 'UseSharedSpaces' flag\n");

             return false;

          }

          if ((int)useSharedSpaces == 0) {

             print_debug("UseSharedSpaces is false, assuming -Xshare:off!\n");

             return true;

          }

          sharedArchivePathAddrAddr = lookup_symbol(ph, jvm_name, SHARED_ARCHIVE_PATH_SYM);

          if (sharedArchivePathAddrAddr == 0) {

             print_debug("can't lookup shared archive path symbol\n");

             return false;

          }

          if (read_pointer(ph, sharedArchivePathAddrAddr, &sharedArchivePathAddr) != true) {

             print_debug("can't read shared archive path pointer\n");

             return false;

          }

          if (read_string(ph, sharedArchivePathAddr, classes_jsa, sizeof(classes_jsa)) != true) {

             print_debug("can't read shared archive path value\n");

             return false;

          }

          print_debug("looking for %s\n", classes_jsa);

          // open the class sharing archive file

          fd = pathmap_open(classes_jsa);

          if (fd < 0) {

             print_debug("can't open %s!\n", classes_jsa);

             ph->core->classes_jsa_fd = -1;

             return false;

          } else {

             print_debug("opened %s\n", classes_jsa);

          }

          // read FileMapHeader from the file

          memset(&header, 0, sizeof(struct FileMapHeader));

          if ((n = read(fd, &header, sizeof(struct FileMapHeader)))

               != sizeof(struct FileMapHeader)) {

             print_debug("can't read shared archive file map header from %s\n", classes_jsa);

             close(fd);

             return false;

          }

          // check file magic

          if (header._magic != 0xf00baba2) {

             print_debug("%s has bad shared archive file magic number 0x%x, expecing 0xf00baba2\n",

                         classes_jsa, header._magic);

             close(fd);

             return false;

          }

          // check version

          if (header._version != CURRENT_ARCHIVE_VERSION) {

             print_debug("%s has wrong shared archive file version %d, expecting %d\n",

                         classes_jsa, header._version, CURRENT_ARCHIVE_VERSION);

             close(fd);

             return false;

          }

          ph->core->classes_jsa_fd = fd;

          // add read-only maps from classes[_g].jsa to the list of maps

          for (m = 0; m < NUM_SHARED_MAPS; m++) {

             if (header._space[m]._read_only) {

                base = (uintptr_t) header._space[m]._base;

                // no need to worry about the fractional pages at-the-end.

                // possible fractional pages are handled by core_read_data.

                add_class_share_map_info(ph, (off_t) header._space[m]._file_offset,

                          base, (size_t) header._space[m]._used);

                print_debug("added a share archive map at 0x%lx\n", base);

             }

          }

          return true;

       }

       lib = lib->next;

    }

    return true;

 }

 //---------------------------------------------------------------------------

 // functions to handle map_info

 // Order mappings based on virtual address.  We use this function as the

 // callback for sorting the array of map_info pointers.

 static int core_cmp_mapping(const void *lhsp, const void *rhsp)

 {

    const map_info *lhs = *((const map_info **)lhsp);

    const map_info *rhs = *((const map_info **)rhsp);

    if (lhs->vaddr == rhs->vaddr)

       return (0);

    return (lhs->vaddr < rhs->vaddr ? -1 : 1);

 }

 // we sort map_info by starting virtual address so that we can do

 // binary search to read from an address.

 static bool sort_map_array(struct ps_prochandle* ph) {

    size_t num_maps = ph->core->num_maps;

    map_info* map = ph->core->maps;

    int i = 0;

    // allocate map_array

    map_info** array;

    if ( (array = (map_info**) malloc(sizeof(map_info*) * num_maps)) == NULL) {

       print_debug("can't allocate memory for map array\n");

       return false;

    }

    // add maps to array

    while (map) {

       array[i] = map;

       i++;

       map = map->next;

    }

    // sort is called twice. If this is second time, clear map array

    if (ph->core->map_array) free(ph->core->map_array);

    ph->core->map_array = array;

    // sort the map_info array by base virtual address.

    qsort(ph->core->map_array, ph->core->num_maps, sizeof (map_info*),

             core_cmp_mapping);

    // print map

    if (is_debug()) {

       int j = 0;

       print_debug("---- sorted virtual address map ----\n");

       for (j = 0; j < ph->core->num_maps; j++) {

         print_debug("base = 0x%lx\tsize = %d\n", ph->core->map_array[j]->vaddr,

                                          ph->core->map_array[j]->memsz);

       }

    }

    return true;

 }

 #ifndef MIN

 #define MIN(x, y) (((x) < (y))? (x): (y))

 #endif

 static bool core_read_data(struct ps_prochandle* ph, uintptr_t addr, char *buf, size_t size) {

    ssize_t resid = size;

    int page_size=sysconf(_SC_PAGE_SIZE);

    while (resid != 0) {

       map_info *mp = core_lookup(ph, addr);

       uintptr_t mapoff;

       ssize_t len, rem;

       off_t off;

       int fd;

       if (mp == NULL)

          break;  /* No mapping for this address */

       fd = mp->fd;

       mapoff = addr - mp->vaddr;

       len = MIN(resid, mp->memsz - mapoff);

       off = mp->offset + mapoff;

       if ((len = pread(fd, buf, len, off)) <= 0)

          break;

       resid -= len;

       addr += len;

       buf = (char *)buf + len;

       // mappings always start at page boundary. But, may end in fractional

       // page. fill zeros for possible fractional page at the end of a mapping.

       rem = mp->memsz % page_size;

       if (rem > 0) {

          rem = page_size - rem;

          len = MIN(resid, rem);

          resid -= len;

          addr += len;

          // we are not assuming 'buf' to be zero initialized.

          memset(buf, 0, len);

          buf += len;

       }

    }

    if (resid) {

       print_debug("core read failed for %d byte(s) @ 0x%lx (%d more bytes)\n",

               size, addr, resid);

       return false;

    } else {

       return true;

    }

 }

 // null implementation for write

 static bool core_write_data(struct ps_prochandle* ph,

                              uintptr_t addr, const char *buf , size_t size) {

    return false;

 }

 static bool core_get_lwp_regs(struct ps_prochandle* ph, lwpid_t lwp_id,

                           struct user_regs_struct* regs) {

    // for core we have cached the lwp regs from NOTE section

    thread_info* thr = ph->threads;

    while (thr) {

      if (thr->lwp_id == lwp_id) {

        memcpy(regs, &thr->regs, sizeof(struct user_regs_struct));

        return true;

      }

      thr = thr->next;

    }

    return false;

 }

 static ps_prochandle_ops core_ops = {

    .release=  core_release,

    .p_pread=  core_read_data,

    .p_pwrite= core_write_data,

    .get_lwp_regs= core_get_lwp_regs

 };

 // read regs and create thread from NT_PRSTATUS entries from core file

 static bool core_handle_prstatus(struct ps_prochandle* ph, const char* buf, size_t nbytes) {

    // we have to read prstatus_t from buf

    // assert(nbytes == sizeof(prstaus_t), "size mismatch on prstatus_t");

    prstatus_t* prstat = (prstatus_t*) buf;

    thread_info* newthr;

    print_debug("got integer regset for lwp %d\n", prstat->pr_pid);

    // we set pthread_t to -1 for core dump

    if((newthr = add_thread_info(ph, (pthread_t) -1,  prstat->pr_pid)) == NULL)

       return false;

    // copy regs

    memcpy(&newthr->regs, prstat->pr_reg, sizeof(struct user_regs_struct));

    if (is_debug()) {

       print_debug("integer regset\n");

 #ifdef i386

       // print the regset

       print_debug("\teax = 0x%x\n", newthr->regs.eax);

       print_debug("\tebx = 0x%x\n", newthr->regs.ebx);

       print_debug("\tecx = 0x%x\n", newthr->regs.ecx);

       print_debug("\tedx = 0x%x\n", newthr->regs.edx);

       print_debug("\tesp = 0x%x\n", newthr->regs.esp);

       print_debug("\tebp = 0x%x\n", newthr->regs.ebp);

       print_debug("\tesi = 0x%x\n", newthr->regs.esi);

       print_debug("\tedi = 0x%x\n", newthr->regs.edi);

       print_debug("\teip = 0x%x\n", newthr->regs.eip);

 #endif

 #if defined(amd64) || defined(x86_64)

       // print the regset

       print_debug("\tr15 = 0x%lx\n", newthr->regs.r15);

       print_debug("\tr14 = 0x%lx\n", newthr->regs.r14);

       print_debug("\tr13 = 0x%lx\n", newthr->regs.r13);

       print_debug("\tr12 = 0x%lx\n", newthr->regs.r12);

       print_debug("\trbp = 0x%lx\n", newthr->regs.rbp);

       print_debug("\trbx = 0x%lx\n", newthr->regs.rbx);

       print_debug("\tr11 = 0x%lx\n", newthr->regs.r11);

       print_debug("\tr10 = 0x%lx\n", newthr->regs.r10);

       print_debug("\tr9 = 0x%lx\n", newthr->regs.r9);

       print_debug("\tr8 = 0x%lx\n", newthr->regs.r8);

       print_debug("\trax = 0x%lx\n", newthr->regs.rax);

       print_debug("\trcx = 0x%lx\n", newthr->regs.rcx);

       print_debug("\trdx = 0x%lx\n", newthr->regs.rdx);

       print_debug("\trsi = 0x%lx\n", newthr->regs.rsi);

       print_debug("\trdi = 0x%lx\n", newthr->regs.rdi);

       print_debug("\torig_rax = 0x%lx\n", newthr->regs.orig_rax);

       print_debug("\trip = 0x%lx\n", newthr->regs.rip);

       print_debug("\tcs = 0x%lx\n", newthr->regs.cs);

       print_debug("\teflags = 0x%lx\n", newthr->regs.eflags);

       print_debug("\trsp = 0x%lx\n", newthr->regs.rsp);

       print_debug("\tss = 0x%lx\n", newthr->regs.ss);

       print_debug("\tfs_base = 0x%lx\n", newthr->regs.fs_base);

       print_debug("\tgs_base = 0x%lx\n", newthr->regs.gs_base);

       print_debug("\tds = 0x%lx\n", newthr->regs.ds);

       print_debug("\tes = 0x%lx\n", newthr->regs.es);

       print_debug("\tfs = 0x%lx\n", newthr->regs.fs);

       print_debug("\tgs = 0x%lx\n", newthr->regs.gs);

 #endif

    }

    return true;

 }

 #define ROUNDUP(x, y)  ((((x)+((y)-1))/(y))*(y))

 // read NT_PRSTATUS entries from core NOTE segment

 static bool core_handle_note(struct ps_prochandle* ph, ELF_PHDR* note_phdr) {

    char* buf = NULL;

    char* p = NULL;

    size_t size = note_phdr->p_filesz;

    // we are interested in just prstatus entries. we will ignore the rest.

    // Advance the seek pointer to the start of the PT_NOTE data

    if (lseek(ph->core->core_fd, note_phdr->p_offset, SEEK_SET) == (off_t)-1) {

       print_debug("failed to lseek to PT_NOTE data\n");

       return false;

    }

    // Now process the PT_NOTE structures.  Each one is preceded by

    // an Elf{32/64}_Nhdr structure describing its type and size.

    if ( (buf = (char*) malloc(size)) == NULL) {

       print_debug("can't allocate memory for reading core notes\n");

       goto err;

    }

    // read notes into buffer

    if (read(ph->core->core_fd, buf, size) != size) {

       print_debug("failed to read notes, core file must have been truncated\n");

       goto err;

    }

    p = buf;

    while (p < buf + size) {

       ELF_NHDR* notep = (ELF_NHDR*) p;

       char* descdata  = p + sizeof(ELF_NHDR) + ROUNDUP(notep->n_namesz, 4);

       print_debug("Note header with n_type = %d and n_descsz = %u\n",

                                    notep->n_type, notep->n_descsz);

       if (notep->n_type == NT_PRSTATUS) {

          if (core_handle_prstatus(ph, descdata, notep->n_descsz) != true)

             return false;

       }

       p = descdata + ROUNDUP(notep->n_descsz, 4);

    }

    free(buf);

    return true;

 err:

    if (buf) free(buf);

    return false;

 }

 // read all segments from core file

 static bool read_core_segments(struct ps_prochandle* ph, ELF_EHDR* core_ehdr) {

    int i = 0;

    ELF_PHDR* phbuf = NULL;

    ELF_PHDR* core_php = NULL;

    if ((phbuf =  read_program_header_table(ph->core->core_fd, core_ehdr)) == NULL)

       return false;

    /*

     * Now iterate through the program headers in the core file.

     * We're interested in two types of Phdrs: PT_NOTE (which

     * contains a set of saved /proc structures), and PT_LOAD (which

     * represents a memory mapping from the process's address space).

     *

     * Difference b/w Solaris PT_NOTE and Linux PT_NOTE:

     *

     *     In Solaris there are two PT_NOTE segments the first PT_NOTE (if present)

     *     contains /proc structs in the pre-2.6 unstructured /proc format. the last

     *     PT_NOTE has data in new /proc format.

     *

     *     In Solaris, there is only one pstatus (process status). pstatus contains

     *     integer register set among other stuff. For each LWP, we have one lwpstatus

     *     entry that has integer regset for that LWP.

     *

     *     Linux threads are actually 'clone'd processes. To support core analysis

     *     of "multithreaded" process, Linux creates more than one pstatus (called

     *     "prstatus") entry in PT_NOTE. Each prstatus entry has integer regset for one

     *     "thread". Please refer to Linux kernel src file 'fs/binfmt_elf.c', in particular

     *     function "elf_core_dump".

     */

     for (core_php = phbuf, i = 0; i < core_ehdr->e_phnum; i++) {

       switch (core_php->p_type) {

          case PT_NOTE:

             if (core_handle_note(ph, core_php) != true) goto err;

             break;

          case PT_LOAD: {

             if (core_php->p_filesz != 0) {

                if (add_map_info(ph, ph->core->core_fd, core_php->p_offset,

                   core_php->p_vaddr, core_php->p_filesz) == NULL) goto err;

             }

             break;

          }

       }

       core_php++;

    }

    free(phbuf);

    return true;

 err:

    free(phbuf);

    return false;

 }

 // read segments of a shared object

 static bool read_lib_segments(struct ps_prochandle* ph, int lib_fd, ELF_EHDR* lib_ehdr, uintptr_t lib_base) {

    int i = 0;

    ELF_PHDR* phbuf;

    ELF_PHDR* lib_php = NULL;

    if ((phbuf = read_program_header_table(lib_fd, lib_ehdr)) == NULL)

       return false;

    // we want to process only PT_LOAD segments that are not writable.

    // i.e., text segments. The read/write/exec (data) segments would

    // have been already added from core file segments.

    for (lib_php = phbuf, i = 0; i < lib_ehdr->e_phnum; i++) {

       if ((lib_php->p_type == PT_LOAD) && !(lib_php->p_flags & PF_W) && (lib_php->p_filesz != 0)) {

          if (add_map_info(ph, lib_fd, lib_php->p_offset, lib_php->p_vaddr + lib_base, lib_php->p_filesz) == NULL)

             goto err;

       }

       lib_php++;

    }

    free(phbuf);

    return true;

 err:

    free(phbuf);

    return false;

 }

 // process segments from interpreter (ld.so or ld-linux.so)

 static bool read_interp_segments(struct ps_prochandle* ph) {

    ELF_EHDR interp_ehdr;

    if (read_elf_header(ph->core->interp_fd, &interp_ehdr) != true) {

        print_debug("interpreter is not a valid ELF file\n");

        return false;

    }

    if (read_lib_segments(ph, ph->core->interp_fd, &interp_ehdr, ph->core->ld_base_addr) != true) {

        print_debug("can't read segments of interpreter\n");

        return false;

    }

    return true;

 }

 // process segments of a a.out

 static bool read_exec_segments(struct ps_prochandle* ph, ELF_EHDR* exec_ehdr) {

    int i = 0;

    ELF_PHDR* phbuf = NULL;

    ELF_PHDR* exec_php = NULL;

    if ((phbuf = read_program_header_table(ph->core->exec_fd, exec_ehdr)) == NULL)

       return false;

    for (exec_php = phbuf, i = 0; i < exec_ehdr->e_phnum; i++) {

       switch (exec_php->p_type) {

          // add mappings for PT_LOAD segments

          case PT_LOAD: {

             // add only non-writable segments of non-zero filesz

             if (!(exec_php->p_flags & PF_W) && exec_php->p_filesz != 0) {

                if (add_map_info(ph, ph->core->exec_fd, exec_php->p_offset, exec_php->p_vaddr, exec_php->p_filesz) == NULL) goto err;

             }

             break;

          }

          // read the interpreter and it's segments

          case PT_INTERP: {

             char interp_name[BUF_SIZE];

             pread(ph->core->exec_fd, interp_name, MIN(exec_php->p_filesz, BUF_SIZE), exec_php->p_offset);

             print_debug("ELF interpreter %s\n", interp_name);

             // read interpreter segments as well

             if ((ph->core->interp_fd = pathmap_open(interp_name)) < 0) {

                print_debug("can't open runtime loader\n");

                goto err;

             }

             break;

          }

          // from PT_DYNAMIC we want to read address of first link_map addr

          case PT_DYNAMIC: {

             ph->core->dynamic_addr = exec_php->p_vaddr;

             print_debug("address of _DYNAMIC is 0x%lx\n", ph->core->dynamic_addr);

             break;

          }

       } // switch

       exec_php++;

    } // for

    free(phbuf);

    return true;

 err:

    free(phbuf);

    return false;

 }

 #define FIRST_LINK_MAP_OFFSET offsetof(struct r_debug,  r_map)

 #define LD_BASE_OFFSET        offsetof(struct r_debug,  r_ldbase)

 #define LINK_MAP_ADDR_OFFSET  offsetof(struct link_map, l_addr)

 #define LINK_MAP_NAME_OFFSET  offsetof(struct link_map, l_name)

 #define LINK_MAP_NEXT_OFFSET  offsetof(struct link_map, l_next)

 // read shared library info from runtime linker's data structures.

 // This work is done by librtlb_db in Solaris

 static bool read_shared_lib_info(struct ps_prochandle* ph) {

    uintptr_t addr = ph->core->dynamic_addr;

    uintptr_t debug_base;

    uintptr_t first_link_map_addr;

    uintptr_t ld_base_addr;

    uintptr_t link_map_addr;

    uintptr_t lib_base_diff;

    uintptr_t lib_base;

    uintptr_t lib_name_addr;

    char lib_name[BUF_SIZE];

    ELF_DYN dyn;

    ELF_EHDR elf_ehdr;

    int lib_fd;

    // _DYNAMIC has information of the form

    //         [tag] [data] [tag] [data] .....

    // Both tag and data are pointer sized.

    // We look for dynamic info with DT_DEBUG. This has shared object info.

    // refer to struct r_debug in link.h

    dyn.d_tag = DT_NULL;

    while (dyn.d_tag != DT_DEBUG) {

       if (ps_pdread(ph, (psaddr_t) addr, &dyn, sizeof(ELF_DYN)) != PS_OK) {

          print_debug("can't read debug info from _DYNAMIC\n");

          return false;

       }

       addr += sizeof(ELF_DYN);

    }

    // we have got Dyn entry with DT_DEBUG

    debug_base = dyn.d_un.d_ptr;

    // at debug_base we have struct r_debug. This has first link map in r_map field

    if (ps_pdread(ph, (psaddr_t) debug_base + FIRST_LINK_MAP_OFFSET,

                  &first_link_map_addr, sizeof(uintptr_t)) != PS_OK) {

       print_debug("can't read first link map address\n");

       return false;

    }

    // read ld_base address from struct r_debug

    if (ps_pdread(ph, (psaddr_t) debug_base + LD_BASE_OFFSET, &ld_base_addr,

                  sizeof(uintptr_t)) != PS_OK) {

       print_debug("can't read ld base address\n");

       return false;

    }

    ph->core->ld_base_addr = ld_base_addr;

    print_debug("interpreter base address is 0x%lx\n", ld_base_addr);

    // now read segments from interp (i.e ld.so or ld-linux.so)

    if (read_interp_segments(ph) != true)

       return false;

    // after adding interpreter (ld.so) mappings sort again

    if (sort_map_array(ph) != true)

       return false;

    print_debug("first link map is at 0x%lx\n", first_link_map_addr);

    link_map_addr = first_link_map_addr;

    while (link_map_addr != 0) {

       // read library base address of the .so. Note that even though <sys/link.h> calls

       // link_map->l_addr as "base address",  this is * not * really base virtual

       // address of the shared object. This is actually the difference b/w the virtual

       // address mentioned in shared object and the actual virtual base where runtime

       // linker loaded it. We use "base diff" in read_lib_segments call below.

       if (ps_pdread(ph, (psaddr_t) link_map_addr + LINK_MAP_ADDR_OFFSET,

                    &lib_base_diff, sizeof(uintptr_t)) != PS_OK) {

          print_debug("can't read shared object base address diff\n");

          return false;

       }

       // read address of the name

       if (ps_pdread(ph, (psaddr_t) link_map_addr + LINK_MAP_NAME_OFFSET,

                     &lib_name_addr, sizeof(uintptr_t)) != PS_OK) {

          print_debug("can't read address of shared object name\n");

          return false;

       }

       // read name of the shared object

       if (read_string(ph, (uintptr_t) lib_name_addr, lib_name, sizeof(lib_name)) != true) {

          print_debug("can't read shared object name\n");

          return false;

       }

       if (lib_name[0] != '\0') {

          // ignore empty lib names

          lib_fd = pathmap_open(lib_name);

          if (lib_fd < 0) {

             print_debug("can't open shared object %s\n", lib_name);

             // continue with other libraries...

          } else {

             if (read_elf_header(lib_fd, &elf_ehdr)) {

                lib_base = lib_base_diff + find_base_address(lib_fd, &elf_ehdr);

                print_debug("reading library %s @ 0x%lx [ 0x%lx ]\n",

                            lib_name, lib_base, lib_base_diff);

                // while adding library mappings we need to use "base difference".

                if (! read_lib_segments(ph, lib_fd, &elf_ehdr, lib_base_diff)) {

                   print_debug("can't read shared object's segments\n");

                   close(lib_fd);

                   return false;

                }

                add_lib_info_fd(ph, lib_name, lib_fd, lib_base);

                // Map info is added for the library (lib_name) so

                // we need to re-sort it before calling the p_pdread.

                if (sort_map_array(ph) != true)

                   return false;

             } else {

                print_debug("can't read ELF header for shared object %s\n", lib_name);

                close(lib_fd);

                // continue with other libraries...

             }

          }

       }

       // read next link_map address

       if (ps_pdread(ph, (psaddr_t) link_map_addr + LINK_MAP_NEXT_OFFSET,

                         &link_map_addr, sizeof(uintptr_t)) != PS_OK) {

          print_debug("can't read next link in link_map\n");

          return false;

       }

    }

    return true;

 }

 // the one and only one exposed stuff from this file

 struct ps_prochandle* Pgrab_core(const char* exec_file, const char* core_file) {

    ELF_EHDR core_ehdr;

    ELF_EHDR exec_ehdr;

    ELF_EHDR lib_ehdr;

    struct ps_prochandle* ph = (struct ps_prochandle*) calloc(1, sizeof(struct ps_prochandle));

    if (ph == NULL) {

       print_debug("can't allocate ps_prochandle\n");

       return NULL;

    }

    if ((ph->core = (struct core_data*) calloc(1, sizeof(struct core_data))) == NULL) {

       free(ph);

       print_debug("can't allocate ps_prochandle\n");

       return NULL;

    }

    // initialize ph

    ph->ops = &core_ops;

    ph->core->core_fd   = -1;

    ph->core->exec_fd   = -1;

    ph->core->interp_fd = -1;

    // open the core file

    if ((ph->core->core_fd = open(core_file, O_RDONLY)) < 0) {

       print_debug("can't open core file\n");

       goto err;

    }

    // read core file ELF header

    if (read_elf_header(ph->core->core_fd, &core_ehdr) != true || core_ehdr.e_type != ET_CORE) {

       print_debug("core file is not a valid ELF ET_CORE file\n");

       goto err;

    }

    if ((ph->core->exec_fd = open(exec_file, O_RDONLY)) < 0) {

       print_debug("can't open executable file\n");

       goto err;

    }

    if (read_elf_header(ph->core->exec_fd, &exec_ehdr) != true || exec_ehdr.e_type != ET_EXEC) {

       print_debug("executable file is not a valid ELF ET_EXEC file\n");

       goto err;

    }

    // process core file segments

    if (read_core_segments(ph, &core_ehdr) != true)

       goto err;

    // process exec file segments

    if (read_exec_segments(ph, &exec_ehdr) != true)

       goto err;

    // exec file is also treated like a shared object for symbol search

    if (add_lib_info_fd(ph, exec_file, ph->core->exec_fd,

                        (uintptr_t)0 + find_base_address(ph->core->exec_fd, &exec_ehdr)) == NULL)

       goto err;

    // allocate and sort maps into map_array, we need to do this

    // here because read_shared_lib_info needs to read from debuggee

    // address space

    if (sort_map_array(ph) != true)

       goto err;

    if (read_shared_lib_info(ph) != true)

       goto err;

    // sort again because we have added more mappings from shared objects

    if (sort_map_array(ph) != true)

       goto err;

    if (init_classsharing_workaround(ph) != true)

       goto err;

    return ph;

 err:

    Prelease(ph);

    return NULL;

 }