mheffner

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>

static void *(*malloc_internal)(size_t size);

void __attribute__ ((constructor)) init(void);

/* Library constructor */

mheffner

$ LD_PRELOAD=./malloc_wrap.so /bin/uname
Malloc request for 34 bytes got memory: 0x1103010
Malloc request for 10 bytes got memory: 0x1103040
Linux

mheffner

$ gcc -Wall -shared -fPIC -o malloc_wrap.so malloc_wrap.c -ldl
$ LD_PRELOAD=./malloc_wrap.so /bin/uname
Malloc request for 34 bytes got memory: 0x1103010
Malloc request for 10 bytes got memory: 0x1103040
Linux

mheffner

$ ./condwait_test 
Thread exiting

mheffner

$ gcc -g3 -Wall -fPIC -shared -o condwait_wrap.so condwait_wrap.c -ldl -lpthread

$ gcc -g3 -Wall -o condwait_test condwait_test.c  -lpthread

$ ./condwait_test 
Thread exiting

$ LD_PRELOAD=./condwait_wrap.so ./condwait_test
Calling func condwait with cond: 0x600d80, mutex: 0x600dc0...^C
Exit 130

mheffner

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>

static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER;

static int okexit = 0;

mheffner

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <pthread.h>

static int (*condwait_internal)(pthread_cond_t *cond, pthread_mutex_t *mutex);

void __attribute__ ((constructor)) init(void);

mheffner

$ gdb condwait_test 

<snip LICENSE>

(gdb) b condwait_test.c:17
Breakpoint 1 at 0x400864: file condwait_test.c, line 17.
(gdb) r
Starting program: condwait_test 
[Thread debugging using libthread_db enabled]
[New Thread 0x7ffff7fd5910 (LWP 32595)]

mheffner

$ gdb condwait_test

<snip LICENSE>

(gdb) set environment LD_PRELOAD ./condwait_wrap.so
(gdb) b condwait_test.c:17
Breakpoint 1 at 0x400864: file condwait_test.c, line 17.
(gdb) r
Starting program: condwait_test 
[Thread debugging using libthread_db enabled]

mheffner

#if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_3_2)
int
__pthread_cond_wait_2_0 (cond, mutex)
     pthread_cond_2_0_t *cond;
     pthread_mutex_t *mutex;
{
  if (cond->cond == NULL)
    {
      pthread_cond_t *newcond;