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/* gprof-helper.c -- preload library to profile pthread-enabled programs
*
* Authors: Sam Hocevar <sam at zoy dot org>
* Daniel Jönsson <danieljo at fagotten dot org>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the Do What The Fuck You Want To
* Public License as published by Banlu Kemiyatorn. See
* http://sam.zoy.org/projects/COPYING.WTFPL for more details.
*
* Compilation example:
* gcc -shared -nostdlib -fPIC gprof-helper.c -o gprof-helper.so -lpthread -ldl
*
* Usage example:
* LD_PRELOAD=./gprof-helper.so your_program
*/
#define _GNU_SOURCE
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
#include <pthread.h>
static void * wrapper_routine(void *);
/* Original pthread function */
static int (*pthread_create_orig)(pthread_t *__restrict,
__const pthread_attr_t *__restrict,
void *(*)(void *),
void *__restrict) = NULL;
/* Library initialization function */
void _init(void)
{
pthread_create_orig = dlsym(RTLD_NEXT, "pthread_create");
fprintf(stderr, "pthreads: using profiling hooks for gprof\n");
if(pthread_create_orig == NULL)
{
char *error = dlerror();
if(error == NULL)
{
error = "pthread_create is NULL";
}
fprintf(stderr, "%s", error);
exit(EXIT_FAILURE);
}
}
/* Our data structure passed to the wrapper */
typedef struct wrapper_s
{
void * (*start_routine)(void *);
void * arg;
pthread_mutex_t lock;
pthread_cond_t wait;
struct itimerval itimer;
} wrapper_t;
/* The wrapper function in charge for setting the itimer value */
static void * wrapper_routine(void * data)
{
/* Put user data in thread-local variables */
void * (*start_routine)(void *) = ((wrapper_t*)data)->start_routine;
void * arg = ((wrapper_t*)data)->arg;
/* Set the profile timer value */
setitimer(ITIMER_PROF, &((wrapper_t*)data)->itimer, NULL);
/* Tell the calling thread that we don't need its data anymore */
pthread_mutex_lock(&((wrapper_t*)data)->lock);
pthread_cond_signal(&((wrapper_t*)data)->wait);
pthread_mutex_unlock(&((wrapper_t*)data)->lock);
/* Call the real function */
return start_routine(arg);
}
/* Our wrapper function for the real pthread_create() */
int pthread_create(pthread_t *__restrict thread,
__const pthread_attr_t *__restrict attr,
void * (*start_routine)(void *),
void *__restrict arg)
{
wrapper_t wrapper_data;
int i_return;
/* Initialize the wrapper structure */
wrapper_data.start_routine = start_routine;
wrapper_data.arg = arg;
getitimer(ITIMER_PROF, &wrapper_data.itimer);
pthread_cond_init(&wrapper_data.wait, NULL);
pthread_mutex_init(&wrapper_data.lock, NULL);
pthread_mutex_lock(&wrapper_data.lock);
/* The real pthread_create call */
i_return = pthread_create_orig(thread,
attr,
&wrapper_routine,
&wrapper_data);
/* If the thread was successfully spawned, wait for the data
* to be released */
if(i_return == 0)
{
pthread_cond_wait(&wrapper_data.wait, &wrapper_data.lock);
}
pthread_mutex_unlock(&wrapper_data.lock);
pthread_mutex_destroy(&wrapper_data.lock);
pthread_cond_destroy(&wrapper_data.wait);
return i_return;
}
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