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/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
/* @UNSAFE: whole file */
#include "lib.h"
#include "mmap-util.h"
#include <fcntl.h>
#ifndef MAP_ANONYMOUS
# ifdef MAP_ANON
# define MAP_ANONYMOUS MAP_ANON
# else
# define MAP_ANONYMOUS 0
# endif
#endif
#ifndef HAVE_LINUX_MREMAP
#include <sys/mman.h>
#define MMAP_SIGNATURE 0xdeadbeef
#define PAGE_ALIGN(size) \
(((size) + (size_t)page_size-1) & ~(size_t)(page_size-1))
struct anon_header {
unsigned int signature;
size_t size;
};
static int page_size = 0;
static int header_size = 0;
static int zero_fd = -1;
static void movable_mmap_init(void)
{
#if MAP_ANONYMOUS == 0
/* mmap()ing /dev/zero should be the same with some platforms */
zero_fd = open("/dev/zero", O_RDWR);
if (zero_fd == -1)
i_fatal("Can't open /dev/zero for creating anonymous mmap: %m");
fd_close_on_exec(zero_fd, TRUE);
#endif
page_size = getpagesize();
header_size = page_size;
}
void *mmap_anon(size_t length)
{
struct anon_header *hdr;
void *base;
if (header_size == 0)
movable_mmap_init();
/* we need extra page to store the pieces which construct
the full mmap. also allocate only page-aligned mmap sizes. */
length = PAGE_ALIGN(length + header_size);
base = mmap(NULL, length, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, zero_fd, 0);
if (base == MAP_FAILED)
return MAP_FAILED;
/* initialize the header */
hdr = base;
hdr->signature = MMAP_SIGNATURE;
hdr->size = length - header_size;
return (char *) hdr + header_size;
}
static void *mremap_move(struct anon_header *hdr, size_t new_size)
{
void *new_base;
char *p;
size_t block_size, old_size;
new_base = mmap_anon(new_size);
if (new_base == MAP_FAILED)
return MAP_FAILED;
/* If we're moving large memory areas, it takes less memory to
copy the memory pages in smaller blocks. */
old_size = hdr->size;
block_size = 1024*1024;
p = (char *) hdr + header_size + hdr->size;
do {
if (block_size > old_size)
block_size = old_size;
p -= block_size;
old_size -= block_size;
memcpy((char *) new_base + old_size, p, block_size);
if (munmap((void *) p, block_size) < 0)
i_panic("munmap() failed: %m");
} while (old_size != 0);
if (munmap((void *) hdr, header_size) < 0)
i_panic("munmap() failed: %m");
return new_base;
}
void *mremap_anon(void *old_address, size_t old_size ATTR_UNUSED,
size_t new_size, unsigned long flags)
{
struct anon_header *hdr;
if (old_address == NULL || old_address == MAP_FAILED) {
errno = EINVAL;
return MAP_FAILED;
}
hdr = (struct anon_header *) ((char *) old_address - header_size);
if (hdr->signature != MMAP_SIGNATURE)
i_panic("movable_mremap(): Invalid old_address");
new_size = PAGE_ALIGN(new_size);
if (new_size > hdr->size) {
/* grow */
if ((flags & MREMAP_MAYMOVE) == 0) {
errno = ENOMEM;
return MAP_FAILED;
}
return mremap_move(hdr, new_size);
}
if (new_size < hdr->size) {
/* shrink */
if (munmap((void *) ((char *) hdr + header_size + new_size),
hdr->size - new_size) < 0)
i_panic("munmap() failed: %m");
hdr->size = new_size;
}
return old_address;
}
int munmap_anon(void *start, size_t length ATTR_UNUSED)
{
struct anon_header *hdr;
if (start == NULL || start == MAP_FAILED) {
errno = EINVAL;
return -1;
}
hdr = (struct anon_header *) ((char *) start - header_size);
if (hdr->signature != MMAP_SIGNATURE)
i_panic("movable_munmap(): Invalid address");
if (munmap((void *) hdr, hdr->size + header_size) < 0)
i_panic("munmap() failed: %m");
return 0;
}
#else
void *mmap_anon(size_t length)
{
return mmap(NULL, length, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
}
void *mremap_anon(void *old_address, size_t old_size, size_t new_size,
unsigned long flags)
{
return mremap(old_address, old_size, new_size, flags);
}
int munmap_anon(void *start, size_t length)
{
return munmap(start, length);
}
#endif
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