Commit dcff1035 authored by Marc-André Lureau's avatar Marc-André Lureau Committed by Eduardo Habkost
Browse files

memfd: split qemu_memfd_alloc() 



Add a function to only create a memfd, without mmap. The function is
used in the following memory backend.

Signed-off-by: default avatarMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: default avatarPhilippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20171023141815.17709-2-marcandre.lureau@redhat.com>
Signed-off-by: default avatarEduardo Habkost <ehabkost@redhat.com>
parent 3e5bdc65

include/qemu/memfd.h

+1 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#define F_SEAL_WRITE    0x0008  /* prevent writes */

#endif



int qemu_memfd_create(const char *name, size_t size, unsigned int seals);

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);

util/memfd.c

+36 −25
Original line number Diff line number Diff line
@@ -53,45 +53,56 @@ static int memfd_create(const char *name, unsigned int flags) 
#define MFD_ALLOW_SEALING 0x0002U

#endif



/*

 * 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)

int qemu_memfd_create(const char *name, size_t size, unsigned int seals)

{

    void *ptr;

    int mfd = -1;



    *fd = -1;



#ifdef CONFIG_LINUX

    unsigned int flags = MFD_CLOEXEC;



    if (seals) {

        mfd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC);

        flags |= MFD_ALLOW_SEALING;

    }



    if (mfd == -1) {

        /* some systems have memfd without sealing */

        mfd = memfd_create(name, MFD_CLOEXEC);

        seals = 0;

    mfd = memfd_create(name, flags);

    if (mfd < 0) {

        return -1;

    }

#endif



    if (mfd != -1) {

    if (ftruncate(mfd, size) == -1) {

        perror("ftruncate");

        close(mfd);

            return NULL;

        return -1;

    }



    if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {

        perror("fcntl");

        close(mfd);

            return NULL;

        return -1;

    }

    } else {

#endif



    return mfd;

}



/*

 * 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)

{

    void *ptr;

    int mfd = qemu_memfd_create(name, size, seals);



    /* some systems have memfd without sealing */

    if (mfd == -1) {

        mfd = qemu_memfd_create(name, size, 0);

    }



    if (mfd == -1) {

        const char *tmpdir = g_get_tmp_dir();

        gchar *fname;