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#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <stdio.h>
#include "vtvmalloc.h"
#include <obstack.h>
/* Set the following macro to 1 to get internal debugging messages */
#define VTV_DEBUG 1
/* TODO: Need to protect the following variables */
static struct obstack VTV_obstack;
static unsigned long page_size = 0;
static void * current_chunk = 0;
static size_t current_chunk_size = 0;
/* TODO: Define what is the expected behavior of assert and error */
/* Handling of runtime error */
static void
VTV_error (void)
{
abort();
}
#define VTV_assert(EXPR) ((void)(!(EXPR) ? VTV_error() : (void) 0))
void
VTV_protect (void)
{
struct _obstack_chunk * ci;
ci = (struct _obstack_chunk *) current_chunk;
while (ci)
{
VTV_assert(((unsigned long)ci & (page_size - 1)) == 0);
if (mprotect(ci, (ci->limit - (char *)ci), PROT_READ) == -1)
VTV_error();
ci = ci->prev;
}
#if (VTV_DEBUG == 1)
{
int count = 0;
ci = (struct _obstack_chunk *) current_chunk;
while (ci)
{
count++;
ci = ci->prev;
}
fprintf(stderr, "VTV_protect(): protected %d pages\n", count);
}
#endif
}
void
VTV_unprotect (void)
{
struct _obstack_chunk * ci;
ci = (struct _obstack_chunk *) current_chunk;
while (ci)
{
VTV_assert(((unsigned long)ci & (page_size - 1)) == 0);
if (mprotect(ci, (ci->limit - (char *)ci), PROT_READ | PROT_WRITE) == -1)
VTV_error();
ci = ci->prev;
}
}
/* Allocates a chunk of memory that is aligned to a page boundary.
The amount of memory requested must be a multiple of the page size */
static void *
obstack_chunk_alloc (size_t size)
{
/* TODO: Why do we need to support chunk sizes less that page size? */
/* Get size to next multiple of page_size */
size = (size + (page_size - 1)) & (~(page_size - 1));
VTV_assert((size & (page_size - 1)) == 0);
void * allocated;
if ((allocated = mmap (NULL, size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0)) == 0)
VTV_error();
VTV_assert(((unsigned long) allocated & (page_size - 1)) == 0);
current_chunk = allocated;
current_chunk_size = size;
return allocated;
}
static void
obstack_chunk_free (size_t size)
{
/* Do nothing. For our purposes there should be very little de-allocation. */
}
void
VTV_malloc_init (void)
{
static int initialized = 0;
/* Make sure we only execute the main body of this function ONCE. */
if (initialized)
return;
page_size = sysconf(_SC_PAGE_SIZE);
obstack_chunk_size (&VTV_obstack) = page_size;
obstack_alignment_mask(&VTV_obstack) = sizeof(long) - 1;
/* We guarantee that the obstack alloc failed handler will never be called because
in case the allocation of the chunk fails, it will never return */
obstack_alloc_failed_handler = NULL;
obstack_init(&VTV_obstack);
initialized = 1;
}
void *
VTV_malloc (size_t size)
{
return obstack_alloc (&VTV_obstack, size);
}
void
VTV_free (void * ptr)
{
/* Do nothing. We dont care about recovering unneded memory */
}
void
VTV_malloc_stats (void)
{
int count = 0;
struct _obstack_chunk * ci = (struct _obstack_chunk *) current_chunk;
while (ci)
{
count++;
ci = ci->prev;
}
fprintf(stderr, "VTV_malloc_stats:\n Page Size = %d bytes\n Number of pages = %d\n", page_size, count);
}
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