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#define _GNU_SOURCE
#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
void *(*real_malloc)(size_t sz);
void *(*real_realloc)(void *ptr, size_t sz);
void (*real_free)(void *ptr);
#define ALIGN(n, a) (((n) + (a)-1) & ~((a)-1))
#define MALLOC_BUFSIZE (128 * 1024 * 1024)
/* this is needed for optimized binaries */
static char buf[MALLOC_BUFSIZE] __attribute__((aligned(8)));
void *malloc(size_t sz)
{
static unsigned alloc_size;
void *ptr;
if (real_malloc)
return real_malloc(sz);
sz = ALIGN(sz, 8);
if (alloc_size + sz > sizeof(buf))
return NULL;
ptr = buf + alloc_size;
alloc_size += sz;
return ptr;
}
void *realloc(void *ptr, size_t size)
{
char *p;
if (real_realloc && (ptr < buf || ptr >= &buf[MALLOC_BUFSIZE]))
return real_realloc(ptr, size);
p = malloc(size);
/* using memcpy() caused segfault due to alignment */
if (ptr != NULL) {
char *q = ptr;
size_t i;
for (i = 0; i < size; i++)
p[i] = q[i];
}
return p;
}
void free(void *ptr)
{
char *p = ptr;
if (buf <= p && p < &buf[MALLOC_BUFSIZE])
return;
if (real_free)
real_free(ptr);
}
static void hook(void)
{
real_malloc = dlsym(RTLD_NEXT, "malloc");
real_realloc = dlsym(RTLD_NEXT, "realloc");
real_free = dlsym(RTLD_NEXT, "free");
}
static __attribute__((section(".preinit_array"))) void (*preinit_func_table[])(void) = {
hook,
};
int main(void)
{
fork();
free(malloc(1));
return 0;
}
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