Java example source code file (ps_core.c)
The ps_core.c Java example source code
/*
* Copyright (c) 2003, 2013, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.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_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_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 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.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.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.
#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.
// We assume the corresponding C type is char but licensees
// 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];
// 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, (char *)&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"
#define LIBJVM_NAME "/libjvm.so"
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.so.
const char *jvm_name = 0;
if ((jvm_name = strstr(lib->name, LIBJVM_NAME)) != 0) {
char classes_jsa[PATH_MAX];
struct FileMapHeader header;
int fd = -1;
int m = 0;
size_t n = 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.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 = %zu\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/BSD 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;
int page_size = sysconf(_SC_PAGE_SIZE);
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)) {
uintptr_t target_vaddr = lib_php->p_vaddr + lib_base;
map_info *existing_map = core_lookup(ph, target_vaddr);
if (existing_map == NULL){
if (add_map_info(ph, lib_fd, lib_php->p_offset,
target_vaddr, lib_php->p_memsz) == NULL) {
goto err;
}
} else {
// Coredump stores value of p_memsz elf field
// rounded up to page boundary.
if ((existing_map->memsz != page_size) &&
(existing_map->fd != lib_fd) &&
(ROUNDUP(existing_map->memsz, page_size) != ROUNDUP(lib_php->p_memsz, page_size))) {
print_debug("address conflict @ 0x%lx (existing map size = %ld, size = %ld, flags = %d)\n",
target_vaddr, existing_map->memsz, lib_php->p_memsz, lib_php->p_flags);
goto err;
}
/* replace PT_LOAD segment with library segment */
print_debug("overwrote with new address mapping (memsz %ld -> %ld)\n",
existing_map->memsz, ROUNDUP(lib_php->p_memsz, page_size));
existing_map->fd = lib_fd;
existing_map->offset = lib_php->p_offset;
existing_map->memsz = ROUNDUP(lib_php->p_memsz, page_size);
}
}
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 or ld-elf.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
lib_name[0] = '\0';
if (lib_name_addr != 0 &&
read_string(ph, (uintptr_t) lib_name_addr, lib_name, sizeof(lib_name)) != true) {
print_debug("can't read shared object name\n");
// don't let failure to read the name stop opening the file. If something is really wrong
// it will fail later.
}
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;
}
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