On Tue, Sep 29, 2015 at 06:34:35PM +0200, marcandre.lur...@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lur...@redhat.com>
>
> Add qemu_memfd_alloc/free() helpers.
>
> The function helps to allocate and seal a memfd.
>
> Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
> ---
> include/qemu/memfd.h | 4 ++++
> util/memfd.c | 59
> ++++++++++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 61 insertions(+), 2 deletions(-)
>
> diff --git a/include/qemu/memfd.h b/include/qemu/memfd.h
> index 8b1fe6a..950fb88 100644
> --- a/include/qemu/memfd.h
> +++ b/include/qemu/memfd.h
> @@ -17,4 +17,8 @@
> #define F_SEAL_WRITE 0x0008 /* prevent writes */
> #endif
>
> +void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
> + int *fd);
> +void qemu_memfd_free(void *ptr, size_t size, int fd);
> +
> #endif /* QEMU_MEMFD_H */
> diff --git a/util/memfd.c b/util/memfd.c
> index a98d57e..3168902 100644
> --- a/util/memfd.c
> +++ b/util/memfd.c
> @@ -27,6 +27,14 @@
>
> #include "config-host.h"
>
> +#include <glib.h>
> +#include <glib/gprintf.h>
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <fcntl.h>
> +#include <sys/mman.h>
> +
> #include "qemu/memfd.h"
>
> #ifdef CONFIG_MEMFD
> @@ -44,13 +52,60 @@
> #define MFD_ALLOW_SEALING 0x0002U
> #endif
>
> -static inline int memfd_create(const char *name, unsigned int flags)
> +static int memfd_create(const char *name, unsigned int flags)
> {
> return syscall(__NR_memfd_create, name, flags);
> }
> #else /* !LINUX */
> -static inline int memfd_create(const char *name, unsigned int flags)
> +static int memfd_create(const char *name, unsigned int flags)
> {
> return -1;
> }
> #endif
> +
> +void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
> + int *fd)
> +{
> + void *ptr;
> + int mfd;
> +
> + *fd = -1;
> + mfd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC);
> + if (mfd != -1) {
> + if (ftruncate(mfd, size) == -1) {
> + perror("ftruncate");
> + close(mfd);
> + return NULL;
> + }
> +
> + if (fcntl(mfd, F_ADD_SEALS, seals) == -1) {
> + perror("fcntl");
> + close(mfd);
> + return NULL;
> + }
Why do it here? I note that you don't try to do this with the tmpfs
fallback.
> + } else {
> + perror("memfd");
> + return NULL;
> + }
> +
> + ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
> + if (ptr == MAP_FAILED) {
> + perror("mmap");
> + close(mfd);
> + return NULL;
> + }
> +
> + *fd = mfd;
> + return ptr;
> +}
> +
> +void qemu_memfd_free(void *ptr, size_t size, int fd)
> +{
> + if (ptr) {
> + munmap(ptr, size);
> + }
> +
> + if (fd != -1) {
> + close(fd);
> + }
> +}
> --
> 2.4.3
