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/*
* memfd.c
*
* Copyright (c) 2015 Red Hat, Inc.
*
* QEMU library functions on POSIX which are shared between QEMU and
* the QEMU tools.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/memfd.h"
#if defined CONFIG_LINUX && !defined CONFIG_MEMFD
#include <sys/syscall.h>
#include <asm/unistd.h>
static int memfd_create(const char *name, unsigned int flags)
{
#ifdef __NR_memfd_create
return syscall(__NR_memfd_create, name, flags);
#else
return -1;
#endif
}
#endif
#ifndef MFD_CLOEXEC
#define MFD_CLOEXEC 0x0001U
#endif
#ifndef MFD_ALLOW_SEALING
#define MFD_ALLOW_SEALING 0x0002U
#endif
int qemu_memfd_create(const char *name, size_t size,
unsigned int seals, Error **errp)
{
#ifdef CONFIG_LINUX
int mfd = -1;
unsigned int flags = MFD_CLOEXEC;
if (seals) {
flags |= MFD_ALLOW_SEALING;
}
mfd = memfd_create(name, flags);
if (mfd < 0) {
goto err;
}
if (ftruncate(mfd, size) == -1) {
goto err;
}
if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
goto err;
}
return mfd;
err:
if (mfd >= 0) {
close(mfd);
}
#endif
error_setg_errno(errp, errno, "failed to create memfd");
return -1;
}
/*
* This is a best-effort helper for shared memory allocation, with
* optional sealing. The helper will do his best to allocate using
* memfd with sealing, but may fallback on other methods without
* sealing.
*/
void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
int *fd, Error **errp)
{
void *ptr;
int mfd = qemu_memfd_create(name, size, seals, NULL);
/* some systems have memfd without sealing */
if (mfd == -1) {
mfd = qemu_memfd_create(name, size, 0, NULL);
}
if (mfd == -1) {
const char *tmpdir = g_get_tmp_dir();
gchar *fname;
fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir);
mfd = mkstemp(fname);
unlink(fname);
g_free(fname);
if (mfd == -1 ||
ftruncate(mfd, size) == -1) {
goto err;
}
}
ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
if (ptr == MAP_FAILED) {
goto err;
}
*fd = mfd;
return ptr;
err:
error_setg_errno(errp, errno, "failed to allocate shared memory");
if (mfd >= 0) {
close(mfd);
}
return NULL;
}
void qemu_memfd_free(void *ptr, size_t size, int fd)
{
if (ptr) {
munmap(ptr, size);
}
if (fd != -1) {
close(fd);
}
}
enum {
MEMFD_KO,
MEMFD_OK,
MEMFD_TODO
};
bool qemu_memfd_check(void)
{
static int memfd_check = MEMFD_TODO;
if (memfd_check == MEMFD_TODO) {
int fd;
void *ptr;
ptr = qemu_memfd_alloc("test", 4096, 0, &fd, NULL);
memfd_check = ptr ? MEMFD_OK : MEMFD_KO;
qemu_memfd_free(ptr, 4096, fd);
}
return memfd_check == MEMFD_OK;
}
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