src/lib/mmap-util.c

/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "mmap-util.h"

#include <sys/stat.h>

void *mmap_file(int fd, size_t *length, int prot)
{
    struct stat st;

    if (fstat(fd, &st) < 0)
        return MAP_FAILED;

#if OFF_T_MAX > SSIZE_T_MAX
    if (st.st_size > SSIZE_T_MAX) {
        /* too large file to map into memory */
        errno = EFBIG;
        return MAP_FAILED;
    }
#endif

    *length = (size_t)st.st_size;
    if (*length == 0)
        return NULL;

    i_assert(*length > 0 && *length < SSIZE_T_MAX);

    return mmap(NULL, *length, prot, MAP_SHARED, fd, 0);
}

void *mmap_ro_file(int fd, size_t *length)
{
    return mmap_file(fd, length, PROT_READ);
}

void *mmap_rw_file(int fd, size_t *length)
{
    return mmap_file(fd, length, PROT_READ | PROT_WRITE);
}

#undef madvise
int my_madvise(void *start ATTR_UNUSED, size_t length ATTR_UNUSED,
           int advice ATTR_UNUSED)
{
#ifdef HAVE_MADVISE
    /* Ignore ENOSYS errors, which happen if the kernel hasn't implemented
       the syscall even if libc has. */
    if (madvise(start, length, advice) < 0 && errno != ENOSYS)
        return -1;
#endif
    return 0;
}

size_t mmap_get_page_size(void)
{
    static size_t size = 0;

    if (size != 0)
        return size;
    size = getpagesize();
    return size;
}